Signal processing method, signal processing device, radiation detection device, and computer program

Abstract

Provided are a signal processing method, a signal processing device, a radiation detection device, and a computer program that allow sufficient elimination of a sum peak from a spectrum of radiation.　This signal processing method for processing a signal containing an answering wave to be generated in response to detection of radiation executes correction processing including: measuring a feature amount corresponding to a time for which the answering wave or an answering wave group formed by a plurality of answering waves continues; counting, for each wave height, the number of the answering waves or the answering wave groups containing the measured feature amount within a predetermined first range containing the feature amount of a single answering wave; and deducting a specific value from the counted number in accordance with the answering wave or the answering wave group not containing the feature amount within the first range.

Description

[Technical Field]

[0001] The present invention relates to a signal processing method, a signal processing device, a radiation detection device, and a computer program for processing signals generated by the detection of radiation. [Background technology]

[0002] A radiation detection device for detecting radiation such as X-rays comprises a radiation detector and a signal processing device that processes the signal output by the radiation detector. The radiation detector is constructed using semiconductor radiation detection elements and generates a response wave, such as a step wave or pulse wave, each time radiation is detected. The signal processing device measures the amplitude of the response wave. The amplitude of the response wave corresponds to the energy of the radiation.

[0003] Response waves spread and have a width with a certain time constant. When multiple adjacent response waves overlap, the wave height of the response wave may change. In this case, the energy of the radiation is measured incorrectly, and a peak with an incorrect energy, a so-called sum peak, is generated in the radiation spectrum. Conventionally, techniques have been used to suppress the generation of sum peaks by not counting the radiation when multiple response waves overlap. Patent Document 1 discloses an example of such a technique. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Patent No. 6550376 [Overview of the Initiative] [Problems that the invention aims to solve]

[0005] Conventionally, various methods have been developed to detect the overlap of multiple response waves. However, if multiple response waves completely overlap, it is impossible to detect the overlap. For this reason, conventional techniques cannot adequately remove the sum peak from the radiation spectrum.

[0006] The present invention has been made in view of these circumstances, and its object is to provide a signal processing method, a signal processing device, a radiation detection device, and a computer program that enable sufficient removal of a sump peak from the spectrum of radiation. [Means for solving the problem]

[0007] The signal processing method according to the present invention is a method for processing a signal that includes a response wave generated in response to the detection of radiation, characterized in that it measures a feature quantity corresponding to the duration of a response wave, or a group of response waves consisting of multiple response waves, counts the number of response waves or groups of response waves in which the measured feature quantity is included in a predetermined first range that includes the feature quantity of a single response wave, and performs a correction process to subtract a specific value from the counted number for response waves or groups of response waves in which the feature quantity is not included in the first range.

[0008] In one embodiment of the present invention, feature quantities corresponding to the duration of a response wave or group of response waves are measured, and response waves or groups of response waves whose feature quantities fall within a first range containing the feature quantities of a single response wave are counted by wave height, while response waves or groups of response waves whose feature quantities do not fall within the first range are not counted. Furthermore, a specific value is subtracted from the counted number depending on the response wave or group of response waves whose feature quantities do not fall within the first range. Simply not counting response wave groups whose feature quantities do not fall within the first range would result in incorrectly counting response wave groups whose feature quantities do fall within the first range as a single response wave. By subtracting a specific value from the counted number, numbers that are presumed to have been incorrectly counted are removed.

[0009] In the signal processing method according to the present invention, the specific value is the number of response wave groups including a feature amount in the first range that exists at a predetermined ratio with respect to the response wave groups not including the feature amount in the first range.

[0010] In one embodiment of the present invention, in the correction process, the number of response wave groups including a feature amount in the first range is subtracted from the number of response waves or response wave groups in which the response waves or response wave groups including a feature amount in the first range are counted. The response wave groups including a feature amount in the first range statistically exist at a predetermined ratio with respect to the response wave groups not including a feature in the first range. Therefore, by subtracting a value corresponding to the number of response wave groups not including a feature in the first range and the predetermined ratio, the estimated number of response wave groups including a feature amount in the first range can be subtracted. Thereby, the influence of the response wave groups having a feature amount equivalent to that of a single response wave can be reduced as much as possible, and the count number of response waves corresponding to the detection of radiation can be made closer to the true value.

[0011] The signal processing method according to the present invention determines whether or not the measured feature amount is included in the first range, and when the measured feature amount is included in the first range, counts the response waves or response wave groups by wave height, and when the measured feature amount is not included in the first range, does not count the response waves or response wave groups, and is characterized by performing the correction process.

[0012] In one embodiment of the present invention, each time it is determined that no feature amount is included in the first range, the number of response waves or response wave groups in which the response waves or response wave groups including a feature amount in the first range are counted is corrected. The correction is performed quickly, and the count number of response waves corresponding to the detection of radiation can be made closer to the true value.

[0013] In the signal processing method according to the present invention, response waves or groups of response waves in which a feature amount is included in the first range are counted by wave height, and response waves or groups of response waves in which a feature amount is not included in the first range are not counted, thereby generating a first count number. Response waves or groups of response waves in which a feature amount is included in a second range corresponding to a predetermined time range exceeding the time range corresponding to the first range are counted by wave height, thereby generating a second count number. In the correction process, the first count number is corrected by adding a value obtained by multiplying the second count number by a predetermined correction coefficient to the first count number. The correction coefficient is determined based on the ratio between the probability that the feature amount of the response wave group is included in the second range and the probability that the feature amount of the response wave group is included in the first range.

[0014] In one aspect of the present invention, a first count number obtained by counting response waves or groups of response waves in which a feature amount is included in a first range is generated, and a second count number obtained by counting groups of response waves in which a feature amount is included in a second range corresponding to a predetermined time range exceeding the time range corresponding to the first range is generated. The first count number is corrected by adding a number obtained by multiplying the second count number by a correction coefficient to the first count number. The correction coefficient is determined based on the ratio between the probability that the feature amount of the response wave group is included in the second range and the probability that the feature amount of the response wave group is included in the first range, so that the estimated number of response wave groups in which a feature amount is included in the first range can be subtracted from the first count number by the correction process. By using this correction coefficient, the correction process is performed.

[0015] In the signal processing method according to the present invention, a plurality of the second ranges and the correction coefficients corresponding to the respective second ranges are determined. In the correction process, the correction coefficient corresponding to the second range in which the measured feature amount is included is used.

[0016] In one embodiment of the present invention, a plurality of second ranges and correction coefficients corresponding to the second ranges are defined. If the number of response waves included in the response wave group is different, the distribution of the features will be different, and the second range in which the features are included will be different. In addition, the probability that the features of the response wave group are included in the first range will be different. By using correction coefficients corresponding to different second ranges, the first count is corrected according to the number of response wave groups in which the second range in which the features are included is different.

[0017] The signal processing method according to the present invention is characterized by generating a first spectrum representing the relationship between the first count and the wave height, and generating a second spectrum representing the relationship between the corrected value of the first count and the wave height.

[0018] In one embodiment of the present invention, a first spectrum based on a first count number and a second spectrum based on a number corrected from the first count number are generated. The number corrected from the first count number is the number obtained by subtracting a number statistically estimated for the number of response wave groups whose features are included in the first range from the number of response waves or response wave groups whose features are included in the first range. As a radiation spectrum, a second spectrum is generated in which the occurrence of a sum peak caused by a response wave group having features equivalent to those of a single response wave is suppressed. Furthermore, the first spectrum, which includes a sum peak, and the second spectrum can be compared.

[0019] The signal processing method according to the present invention is characterized by calculating a subtraction value for each wave height by subtracting a corrected value from the first count, assigning a plurality of divided values ​​obtained by dividing the subtraction value at one wave height to a plurality of wave heights lower than the first wave height, the divided values ​​being values ​​proportional to the corrected value of the first count at the assigned wave height, generating the plurality of divided values ​​for the subtraction value at each wave height, and further correcting the first count by adding the divided values ​​to the corrected value of the first count at the assigned wave height.

[0020] In one embodiment of the present invention, a subtraction value is calculated at each wave height corresponding to the number of response wave groups in which the feature quantity is included in a first range, and multiple division values ​​are assigned to multiple lower wave heights by dividing the subtraction value. The sum of the multiple division values ​​becomes the subtraction value, and the division values ​​are proportional to the corrected value of the first count at each wave height. The first count is further corrected by adding the division values ​​to the corrected value of the first count at the assigned wave height. As a result, the counts of the multiple response waves included in the response wave group increase in proportion to the number of response wave groups in which the feature quantity is included in a first range. The intensity of the peaks included in the spectrum of radiation from which the thumb peak has been removed is recovered by the amount of the intensity of the thumb peak caused by the response wave group in which the feature quantity is included in a first range.

[0021] The signal processing method according to the present invention is characterized in that the feature quantity is the time width of a response wave or a group of response waves.

[0022] In one embodiment of the present invention, the feature quantity is the time width of the response wave. By utilizing the time width, the response wave or group of response waves can be characterized.

[0023] The signal processing method according to the present invention is characterized in that the feature quantity is the length of time from the beginning of the first response wave included in the response wave group to the end of the last response wave included in the response wave group.

[0024] In one embodiment of the present invention, the feature quantity is the length of time from the beginning of the first response wave to the end of the last response wave included in the response wave group. By using this length of time as the feature quantity, the response wave group can also be characterized, and correction processing can be performed to reduce the influence of the response wave group having feature quantities equivalent to those of a single response wave.

[0025] The signal processing method according to the present invention is characterized in that the response wave is a step wave or a pulse wave.

[0026] In one embodiment of the present invention, a radiation detector that generates step waves in response to radiation detection is used to reduce the influence of a group of step waves having feature quantities equivalent to those of a single step wave on radiation detection. Alternatively, a radiation detector that generates pulse waves in response to radiation detection is used to reduce the influence of a group of pulse waves having feature quantities equivalent to those of a single pulse wave on radiation detection.

[0027] The signal processing device according to the present invention is characterized by comprising: a feature quantity measurement unit that measures a feature quantity corresponding to the duration of a response wave generated in response to the detection of radiation, or a group of response waves consisting of multiple response waves; a determination unit that determines whether or not the measured feature quantity is included in a predetermined first range that includes the feature quantity of a single response wave; and a correction unit that counts the number of response waves or groups of response waves in which the feature quantity is included in the first range, by wave height, and subtracts a specific value from the counted number according to the response waves or groups of response waves in which the feature quantity is not included in the first range.

[0028] In one embodiment of the present invention, the signal processing device measures the feature quantities of a response wave or a group of response waves, counts the response wave or group of response waves by wave height if the feature quantities are included in a first range, and does not count the response wave or group of response waves if the feature quantities are not included in the first range. Furthermore, the signal processing device subtracts a specific value from the counted number depending on the response wave or group of response waves in which the feature quantities are not included in the first range. In this way, the signal processing device can minimize the influence of a group of response waves having feature quantities equivalent to those of a single response wave, and bring the count of response waves corresponding to radiation detection closer to the true value.

[0029] The radiation detection device according to the present invention is characterized by comprising: a radiation detector that generates a response wave in response to incident radiation; a feature measurement unit that measures a feature amount corresponding to the duration of the generated response wave or response wave group when the radiation detector generates a response wave or a group of response waves consisting of multiple response waves; a determination unit that determines whether or not the measured feature amount is included in a predetermined first range that includes the feature amount of a single response wave; and a correction unit that counts the number of response waves or response wave groups in which the feature amount is included in the first range, by wave height, and subtracts a specific value from the counted number according to the response waves or response wave groups in which the feature amount is not included in the first range.

[0030] In one embodiment of the present invention, the radiation detection device detects radiation and generates a response wave, measures the characteristic quantities of the response wave or group of response waves, counts the response wave or group of response waves by wave height if the characteristic quantities are included in a first range, and does not count the response wave or group of response waves if the characteristic quantities are not included in the first range. Furthermore, the radiation detection device subtracts a specific value from the counted number depending on the response wave or group of response waves in which the characteristic quantities are not included in the first range. In this way, the radiation detection device can minimize the influence of a group of response waves having characteristic quantities equivalent to those of a single response wave, and bring the count of response waves corresponding to radiation detection closer to the true value.

[0031] The radiation detection device according to the present invention is further characterized by comprising: a first spectrum generation unit that generates a first spectrum representing the relationship between a first count number, obtained by counting the number of response waves or response wave groups containing a feature quantity in the first range for each wave height, and wave height; and a second spectrum generation unit that generates a second spectrum representing the relationship between a value obtained by correcting the first count number by the correction unit and wave height.

[0032] In one embodiment of the present invention, the radiation detection device generates a first spectrum based on a first count number and a second spectrum based on a number corrected from the first count number. The number corrected from the first count number is the number obtained by subtracting the number of response wave groups whose features are included in the first range, which is statistically estimated from the number of response waves or response wave groups whose features are included in the first range. As a result, a second spectrum is generated in which the occurrence of a sum peak caused by a response wave group having features equivalent to those of a single response wave is suppressed.

[0033] The computer program according to the present invention is characterized in that, when a feature quantity corresponding to the duration of a response wave or a group of response waves consisting of multiple response waves generated in response to the detection of radiation is included in a predetermined first range that includes the feature quantity of a single response wave, the program obtains a first count number generated by counting response waves or groups of response waves by wave height, obtains a second count number obtained by counting response waves or groups of response waves by wave height that include the feature quantity in a second range corresponding to a predetermined time range that exceeds the time range corresponding to the first range, and causes the computer to perform the following process: subtract from the first count number the number of response wave groups that include the feature quantity in the first range according to the second count number.

[0034] In one embodiment of the present invention, a computer following a computer program generates a first count number, which is the number of response waves or response wave groups containing the feature quantity in a first range, and a second count number, which is the number of response wave groups containing the feature quantity in a second range. The first count number is then corrected according to the second count number. The first count number can also be corrected by having the computer generate the first and second count numbers without the signal processing device performing the count, thereby generating a spectrum in which the occurrence of sum peaks is suppressed. [Effects of the Invention]

[0035] The present invention offers excellent effects, such as the ability to generate a radiation spectrum with sufficient removal of the peak. [Brief explanation of the drawing]

[0036] [Figure 1] This is a block diagram showing an example of the functional configuration of a radiation detection device. [Figure 2] This is a block diagram showing an example of the internal configuration of an analytical instrument. [Figure 3] This is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to Embodiment 1. [Figure 4] This is a schematic characteristic diagram showing examples of step waves and their derivative waveforms. [Figure 5] This is a schematic characteristic diagram showing examples of step waves and their derivative waveforms when the interval between events is short. [Figure 6] This is a schematic characteristic diagram illustrating an example of a trapezoidal wave. [Figure 7] This is a schematic characteristic diagram showing the probability distribution of the time width of a single step wave. [Figure 8] This is a schematic characteristic diagram showing the probability distribution of the time width of a single step wave and the probability distribution of the time width of a double step wave group. [Figure 9] This flowchart shows the procedure for processing performed by the signal processing device according to Embodiment 1. [Figure 10] This is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to an embodiment. [Figure 11] This flowchart shows the procedure for processing performed by the signal processing device according to Embodiment 2. [Figure 12] This flowchart shows the procedure for processing performed by the analytical apparatus according to Embodiment 2. [Figure 13] This is a schematic characteristic diagram showing examples of the first and second spectra. [Figure 14] This is a schematic characteristic diagram showing the probability distribution of the time width of a single step wave, the probability distribution of the time width of a double step wave group, the probability distribution of the time width of a triple step wave group, and the probability distribution of the time width of a quadruple step wave group. [Figure 15] This is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to Embodiment 3. [Figure 16]This flowchart shows the procedure for processing performed by the signal processing device according to Embodiment 3. [Figure 17] This is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to Embodiment 4. [Figure 18] This flowchart shows the procedure for processing performed by the signal processing device and analyzer according to Embodiment 4. [Figure 19] This is a schematic characteristic diagram showing examples of multiple step waves separated from each other and their derivative waveforms. [Figure 20] This is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to Embodiment 5. [Figure 21] This is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to Embodiment 6. [Figure 22] This is a schematic characteristic diagram showing an example of a pulse wave. [Figure 23] This is a schematic characteristic diagram showing an example of a pulse wave when the interval between events is short. [Figure 24] This is a block diagram showing the functional configuration of a radiation detector and a signal processing device according to Embodiment 7. [Figure 25] This is a schematic graph showing examples of step wave groups, trapezoidal waves, and waveforms obtained by differentiating trapezoidal waves. [Figure 26] This is a schematic characteristic diagram showing an example of a spectrum illustrating the relationship between the first spectrum, the second spectrum, and the second count number and wave height. [Figure 27] This flowchart shows an example of the procedure for the process performed by the analyzer according to Embodiment 8 to recover the radiation count. [Modes for carrying out the invention]

[0037] The present invention will be described in detail below with reference to drawings illustrating its embodiments. <Embodiment 1> Figure 1 is a block diagram showing an example of the functional configuration of a radiation detection device 10. The radiation detection device 10 is, for example, a fluorescent X-ray analyzer. The radiation detection device 10 comprises an irradiation unit 42 that irradiates the sample 6 with radiation such as electron beams or X-rays, a sample stage 5 on which the sample 6 is placed, and a radiation detector 1. Radiation is irradiated from the irradiation unit 42 to the sample 6, generating radiation such as fluorescent X-rays in the sample 6, and the radiation detector 1 detects the radiation generated from the sample 6. In the figure, radiation is indicated by arrows. Note that the radiation detection device 10 may also be configured to hold the sample 6 by a method other than placing it on the sample stage 5.

[0038] The radiation detector 1 is connected to a signal processing device 2 and a voltage application unit 43 that applies the voltage necessary for radiation detection to the radiation detection element of the radiation detector 1. The signal processing device 2 is connected to an analysis device 3. The signal processing device 2, analysis device 3, voltage application unit 43, and irradiation unit 42 are connected to a control unit 41. The control unit 41 controls the operation of the signal processing device 2, analysis device 3, voltage application unit 43, and irradiation unit 42. The analysis device 3 is connected to a display unit 44 such as a liquid crystal display or an EL display (Electroluminescent Display). The control unit 41 may be configured to receive user input and control each part of the radiation detection device 10 according to the received input.

[0039] Figure 2 is a block diagram showing an example of the internal configuration of the analysis device 3. The analysis device 3 is a computer such as a personal computer. The analysis device 3 comprises a calculation unit 31, a memory 32, a drive unit 33, a storage unit 34, and an operation unit 35. The analysis device 3 is also connected to a display unit 44 and a signal processing unit 2. The calculation unit 31 is configured using, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), or a multi-core CPU. The calculation unit 31 may also be configured using a quantum computer. The memory 32 stores temporary data generated in connection with calculations. The memory 32 is, for example, RAM (Random Access Memory). The drive unit 33 reads information from a recording medium 30 such as an optical disc or portable memory.

[0040] The storage unit 34 is non-volatile and is, for example, a hard disk or a non-volatile semiconductor memory. The operation unit 35 accepts input of information such as text by receiving operations from the user. The operation unit 35 is, for example, a touch panel, a keyboard, or a pointing device.

[0041] The arithmetic unit 31 causes the drive unit 33 to read the computer program 341 recorded on the recording medium 30, and stores the read computer program 341 in the storage unit 34. The arithmetic unit 31 executes the necessary processing for the analysis device 3 according to the computer program 341. The computer program 341 may be downloaded from outside the analysis device 3. Alternatively, the computer program 341 may be pre-stored in the storage unit 34. In these cases, the analysis device 3 does not need to have a drive unit 33. The analysis device 3 may be composed of multiple computers. Alternatively, the control unit 41 and the analysis device 3 may be composed of the same computer.

[0042] Figure 3 is a block diagram showing the functional configuration of the radiation detector 1 and the signal processing device 2 according to Embodiment 1. In Figure 3, the signal flow is indicated by arrows. The radiation detector 1 comprises a radiation detection element 11 and a preamplifier 12. The radiation detection element 11 generates an electric charge corresponding to the energy of the incident radiation and outputs a current signal corresponding to the generated charge. For example, the radiation detection element 11 is a semiconductor radiation detection element such as a silicon drift type radiation detection element. The preamplifier 12 converts the current signal output by the radiation detection element 11 into a voltage signal and generates a step wave. The step wave corresponds to a response wave. The radiation detector 1 outputs a signal including the step wave generated by the preamplifier 12. In this way, the radiation detector 1 generates a step wave.

[0043] Figure 4 is a schematic characteristic diagram showing an example of a step wave and its differential waveform. The upper panel shows the signal consisting of the step wave, and the lower panel shows the differential signal. In the figure, the horizontal axis represents time, the vertical axis in the upper panel represents the signal value, and the vertical axis in the lower panel represents the differential value. Each time radiation is incident on the radiation detection element 11 and an event occurs in which the radiation detection element 11 detects radiation, the radiation detector 1 outputs a step wave in which the signal value increases in one step. One step wave is generated in response to one event, in which the signal value increases in one step. If multiple events occur, a signal containing multiple step waves is output. The signal value increases each time an event occurs. The height of the step in which the signal value increases is defined as the wave height of the step wave. The wave height of the step wave corresponds to the energy of the detected radiation. The radiation detection device 10 determines the energy of the radiation according to the wave height of the step wave.

[0044] The differential signal of a step wave is a signal in which the signal value rises from a predetermined signal reference to a peak value, and then falls back down to the signal reference. The signal reference is, for example, zero. The integral of the differential signal is the wave height of the step wave. A step wave has a time width, which is the duration of the step wave. Hereafter, a point in time will be referred to as a single point. As shown in Figure 4, tangents to the differential waveform are generated at two points where the differential value of the step wave is a predetermined threshold, and the distance (length of time) between the two points where the two tangents intersect the horizontal axis (the straight line representing the signal reference) is defined as the time width of the step wave. The time width of the step wave corresponds to the duration of the step wave. The time width differs depending on the step wave and characterizes the step wave. The signal processing device 2 may also use the distance between the two points where the differential value of the step wave is a predetermined threshold as the time width of the step wave. The signal processing device 2 may also use the time width of the step wave obtained by other methods.

[0045] Figure 5 is a schematic characteristic diagram showing an example of a step wave and its derivative waveform when the interval between events is short. The upper panel shows the signal consisting of a step wave, and the lower panel shows the derivative signal. In the figure, the horizontal axis represents time, the vertical axis in the upper panel represents the signal value, and the vertical axis in the lower panel represents the derivative value. In the example shown in Figure 5, the interval between events is shorter than in the example shown in Figure 4. A group of step waves is generated, consisting of multiple step waves that are close together and overlap each other. A group of step waves corresponds to a group of response waves. A group of step waves consists of multiple step waves contained between one point where the derivative value is a predetermined threshold and the next point where the derivative value is a predetermined threshold. For example, a group of step waves is generated when the interval between two events is less than or equal to the time width of a single step wave, that is, when the interval between adjacent step waves is less than or equal to the time width of a single step wave.

[0046] As shown in Figure 5, a group of step waves is grouped together as a single step, and the height of the step in which the signal value increases due to the group of step waves is defined as the wave height of the group of step waves. The wave height of the group of step waves does not correspond to the energy of the detected radiation. Also, as shown in Figure 5, tangents to the differential waveform are generated at two points where the differential value of the group of step waves is a predetermined threshold, and the distance (length of time) between the two points where the two tangents intersect the horizontal axis is defined as the time width of the group of step waves. The time width of the group of step waves is the length of time from the beginning of the first step wave included in the group to the end of the last step wave, and corresponds to the duration of the group of step waves.

[0047] The duration of a step wave group tends to be longer than that of a single step wave. However, if the interval between two events is very short, the two step waves are very close together, and the duration of a step wave group consisting of two step waves becomes approximately the same as that of a single step wave. A step wave group with a duration equivalent to that of a single step wave cannot be distinguished from a single step wave based on its duration alone. Therefore, signals that appear to consist of a single step wave may actually consist of a step wave group containing multiple step waves. If the wave height of a step wave group is mistakenly measured as the wave height of a single step wave, the energy of the radiation will be measured incorrectly according to the wave height.

[0048] The signal output by the radiation detector 1 is input to the signal processing device 2. The signal processing device 2 executes a signal processing method. As shown in Figure 3, the signal processing device 2 is equipped with an A / D (analog / digital) converter 21. The A / D converter 21 receives a signal containing a step wave from the radiation detector 1 and performs A / D conversion on the signal containing the step wave. The A / D converter 21 receives a continuous signal, samples the signal, and performs A / D conversion on the values ​​obtained by the sampling to generate discrete signal values. The signal output by the A / D converter 21 consists of multiple discrete signal values. The time interval between the signal values ​​is constant.

[0049] The A / D conversion unit 21 is connected to a trapezoidal shaping unit 221 and a differentiation unit 231. The trapezoidal shaping unit 221 and the differentiation unit 231 receive signals from the A / D conversion unit 21. Between the A / D conversion unit 21 and the trapezoidal shaping unit 221 and the differentiation unit 231, a conversion unit that converts the signal to cancel out waveform distortion due to signal delay and a noise reduction unit that removes noise from the signal may also be connected.

[0050] The trapezoidal shaping unit 221 is configured using a trapezoidal shaping filter. The trapezoidal shaping unit 221 converts a step wave or group of step waves contained in the signal into a trapezoidal wave by shaping the waveform of the input signal with a trapezoidal shaping filter. Figure 6 is a schematic characteristic diagram showing an example of a trapezoidal wave. In the figure, the horizontal axis represents time, and the vertical axis represents the signal value after conversion. The trapezoidal wave shown in Figure 6 is a trapezoidal wave converted from a step wave. The shape of the trapezoidal wave is a trapezoid with a constant height. The shape of the trapezoidal wave converted from a group of step waves may not have a constant height. The height from a predetermined signal reference to the maximum value of the trapezoidal wave is defined as the wave height of the trapezoidal wave. The wave height of the trapezoidal wave converted from a step wave or group of step waves corresponds to the wave height of the step wave or group of step waves. A wave height measuring unit 222 is connected to the trapezoidal shaping unit 221.

[0051] The differentiation unit 231 performs an operation that approximates the derivative by calculating the difference. For example, the differentiation unit 231 is configured using a processor. The differentiation unit 231 calculates the difference between two adjacent signal values ​​included in the input signal. In this way, the differentiation unit 231 approximately differentiates the step wave or group of step waves included in the signal. The signal processing device 2 uses the difference value calculated by the differentiation unit 231 as an approximate derivative value, uses a signal consisting of multiple difference values ​​as an approximate derivative signal, and uses the waveform of a signal consisting of multiple difference values ​​as an approximate derivative waveform. Note that the differentiation unit 231 may calculate the derivative value using a method other than the method of using the difference value as an approximate derivative value, such as dividing the difference value by the interval between signals.

[0052] A feature measurement unit 232 is connected to the differentiation unit 231. For example, the feature measurement unit 232 is configured using a processor that performs calculations. The feature measurement unit 232 measures a feature corresponding to the duration of the staircase wave or group of staircase waves. In this embodiment, the feature measurement unit 232 measures the time width of the staircase wave or group of staircase waves as a feature. The feature measurement unit 232 receives a signal from the differentiation unit 231 and measures the time width of the staircase wave or group of staircase waves from the differential waveform of the staircase wave or group of staircase waves contained in the signal. As explained with reference to Figures 4 and 5, the feature measurement unit 232 generates tangents to the differential waveform at two points where the differential value is a predetermined threshold, and measures the time width of the staircase wave or group of staircase waves by calculating the distance between the two points where the two tangents intersect the horizontal axis.

[0053] A processing unit 24 is connected to the wave height measurement unit 222 and the feature measurement unit 232. The processing unit 24 is configured using elements that perform calculations. For example, the processing unit 24 is configured using an FPGA (field-programmable gate array). The processing unit 24 receives the wave height as input from the wave height measurement unit 222 and the time width of a step wave or a group of step waves as input from the feature measurement unit 232. The processing unit 24 determines whether the time width measured by the feature measurement unit 232 is included in a predetermined first range that includes the time width of a single step wave.

[0054] Figure 7 is a schematic characteristic diagram showing the probability distribution of the time width of a single step wave. The horizontal axis in the figure represents the time width, and the values ​​listed on the horizontal axis are values ​​where the average value of the time width of a single step wave is set to 1. The vertical axis represents probability. Figure 7 schematically shows an ideal probability distribution. The time width of a single step wave is distributed around the mean value. An upper limit is set for the time width that a single step wave can take, and the range of time widths from zero to the upper limit is defined as the first range. The first range is set so that it includes the values ​​that the time width of a single step wave can take. The processing unit 24 determines that the time width is included in the first range if the measured time width is less than or equal to the predetermined upper limit. The processing unit 24 may also determine that the time width is included in the first range if the time width is less than the upper limit. If the time width is not included in the first range, the measured time width is the time width of a group of step waves, not the time width of a single step wave. Mistakenly counting a group of step waves as a single step wave can cause sum peaking. Alternatively, a lower limit may be set for the time width of a single step wave, and the range from the lower limit to the upper limit may be defined as the first range. The processing unit 24 stores information in advance for identifying the first range.

[0055] A counting unit 25 is connected to the processing unit 24. The counting unit 25 counts step waves for each wave height. For example, the counting unit 25 is a multi-channel analyzer. In a multi-channel analyzer, each of the multiple channels is associated with a wave height. The counting unit 25 may be configured to count pulse waves for all wave heights, or it may be configured to count pulse waves only for specific wave heights.

[0056] If the time width measured by the feature measurement unit 232 falls within the first range, the processing unit 24 instructs the counting unit 25 to increment the count by +1 for the wave height measured by the wave height measurement unit 222. The counting unit 25 performs the count according to the input instruction. If the time width measured by the feature measurement unit 232 does not fall within the first range, the processing unit 24 does not instruct the counting unit 25 to count. As a result, the counting unit 25 does not count step wave groups whose time widths do not fall within the first range. In this way, it is prevented that step wave groups having a time width larger than that of a single step wave will be mistakenly counted as a single step wave. However, as mentioned above, there are step wave groups that have a time width equivalent to that of a single step wave. The count number when the time width falls within the first range includes the number of step waves whose time width falls within the first range and the number of step wave groups whose time width falls within the first range.

[0057] The processing unit 24 further performs processing to reduce the influence of a group of step waves having a time width equivalent to that of a single step wave. Only a group of step waves consisting of two overlapping step waves is considered. Hereafter, a group of two overlapping step waves will be referred to as a double step wave group. Figure 8 is a schematic characteristic diagram showing the probability distribution of the time width of a single step wave and the probability distribution of the time width of a double step wave group. The upper panel shows the probability distribution of the time width of a single step wave, and the lower panel shows the probability distribution of the time width of a double step wave group. The horizontal axis in the figure represents the time width, and the values ​​on the horizontal axis are values ​​where the average value of the time width of a single step wave is set to 1. The vertical axis represents probability. Figure 8 schematically shows an ideal probability distribution.

[0058] As described above, the time width of a single step wave is distributed around the mean value. The time width of a double step wave group is distributed from the same lower limit as the time width of a single step wave to approximately twice the mean value of the time width of a single step wave. If the time width of the double step wave group exceeds twice the mean value of the time width of a single step wave, the two step waves separate. Therefore, the upper limit of the time width of the double step wave group is close to twice the mean value of the time width of a single step wave. Since the incidence of radiation on the radiation detection element 11 can be considered random, the probability that the next radiation will occur after the previous radiation has occurred is constant regardless of the interval between radiation incidences. Therefore, the probability distribution of the time width of the double step wave group is approximately uniform.

[0059] As shown in Figure 8, within a double step wave group, there exists a step wave group with a time width equivalent to that of a single step wave. That is, there exists a step wave group whose time width falls within the first range. Therefore, simply not counting step wave groups whose time width does not fall within the first range will result in mistakenly counting step wave groups whose time width falls within the first range as a single step wave. Mistakenly counting step wave groups whose time width falls within the first range as a single step wave causes sum peaking.

[0060] Set an upper limit for the time width of the double step wave group. Set a second range corresponding to a predetermined time range that exceeds the time range corresponding to the first range and up to the set upper limit. The second range is set so that it includes the values ​​that the time width of the double step wave group can take that are not included in the first range. There may be a gap between the first range and the second range. The upper limit for the time width of the double step wave group may be unlimited.

[0061] If a group of step waves whose time width falls within the second range occurs, then a group of step waves whose time width falls within the first range should also occur with a certain probability. If the number of step wave groups whose time width falls within the second range is obtained, the number of step wave groups whose time width falls within the first range can be statistically estimated based on the ratio of the probability of a step wave group whose time width falls within the first range occurring to the probability of a step wave group whose time width falls within the second range occurring. Let a1 be the integral value of the probability distribution of the time width of the double step wave group within the first range, and a2 be the integral value within the second range. The ratio of the probability of a step wave group whose time width falls within the first range occurring to the probability of a step wave group whose time width falls within the second range occurring is (a1 / a2). For each step wave group whose time width falls within the second range, the number of step wave groups whose time width falls within the first range is estimated to be (a1 / a2).

[0062] The processing unit 24 pre-stores information for identifying the second range and a correction count value k2 = (-a1 / a2). The value of k2 is predetermined by setting the first and second ranges and calculating it based on the probability distribution of the time width of the double step wave group. A theoretical probability distribution may be used to determine k2, or a probability distribution obtained from experiments using standard samples may be used.

[0063] If the time width measured by the feature measurement unit 232 does not fall within the first range, the processing unit 24 instructs the counting unit 25 to count k2 for the wave height measured by the wave height measurement unit 222. The processing unit 24 may also determine whether the time width falls within the second range and, if so, instruct the counting unit 25 to count k2. The counting unit 25 performs the count according to the input instruction. Since the value of k2 is negative, the count by the counting unit 25 decreases. One step wave group is detected whose time width falls within the second range. TaThe number of step wave groups whose time widths fall within the first range, which are presumed to be detected in this case, is (a1 / a2). Therefore, by counting k2=(-a1 / a2), the estimated number of step wave groups whose time widths fall within the first range is subtracted from the number of step waves or step wave groups whose time widths fall within the first range. In this way, the influence of step wave groups having time widths equivalent to those of a single step wave is reduced in the count of single step waves.

[0064] The signal processing unit 2 outputs data showing the relationship between the wave height of the step wave and the count number counted by the counting unit 25. The count number corresponds to the number of times the radiation detector 1 detected radiation having energy corresponding to the wave height of the step wave.

[0065] The analyzer 3 receives data output by the signal processing device 2. The analyzer 3 generates a spectrum of radiation detected by the radiation detector 1 based on the relationship between the step wave amplitude and the count. The calculation unit 31 performs the necessary processing according to the computer program 341. The analyzer 3 may further perform further processing, such as elemental analysis of the radiation source, based on the generated radiation spectrum. For example, the radiation detector 1 detects fluorescent X-rays, and the analyzer 3 performs qualitative or quantitative analysis of the elements contained in the sample based on the fluorescent X-ray spectrum. The display unit 44 displays the spectrum generated by the analyzer 3 and the analysis results from the analyzer 3. The signal processing device 2 may also have a function to generate radiation spectra.

[0066] The following describes the processing flow performed by the signal processing device 2. Figure 9 is a flowchart showing the processing steps performed by the signal processing device 2 according to Embodiment 1. Hereinafter, steps will be abbreviated as S. When radiation is incident on the radiation detection element 11, the radiation detector 1 generates a step wave corresponding to the energy of the radiation and outputs a signal including the step wave. The signal processing device 2 receives the signal including the step wave from the radiation detector 1 (S11). The A / D conversion unit 21 performs A / D conversion on the input signal (S12).

[0067] Wave height measurement and feature measurement are performed on the A / D converted signal (S13). In S13, the trapezoidal shaping unit 221 converts the waveform of the A / D converted signal into a trapezoidal wave, and the wave height measurement unit 222 measures the wave height of the trapezoidal wave, thereby measuring the wave height of the step wave or step wave group contained in the signal. In addition, the differentiation unit 231 differentiates the A / D converted signal, and the feature measurement unit 232 measures the time width (feature) of the step wave or step wave group contained in the signal.

[0068] The processing unit 24 determines whether the time width (feature) measured by the feature measurement unit 232 falls within the first range (S14). If the time width (feature) falls within the first range (S14: YES), the processing unit 24 instructs the counting unit 25 to perform a +1 count, and the counting unit 25 counts +1 for the wave height measured by the wave height measurement unit 222 (S15). The counting unit 25, which is a multi-channel analyzer, records the count for each channel, and in S15, +1 is added to the count recorded in the channel associated with the wave height. The processing in S14 and S15 counts the number of step waves or step wave groups whose time width falls within the first range. The count includes the number of single step waves counted and the number of step wave groups whose time width falls within the first range counted.

[0069] If the time width (feature) is not included in the first range (S14: NO), the processing unit 24 instructs the counting unit 25 to count k2, and the counting unit 25 counts k2 for the wave height measured by the wave height measurement unit 222 without adding +1 (S16). That is, the counting unit 25 corrects the count by adding k2 to the count recorded in the channel associated with the wave height. Alternatively, if the time width is not included in the first range, the processing unit 24 may determine whether the time width (feature) is included in the second range, and if the time width is included in the second range, it may instruct the counting unit 25 to count k2, and the counting unit 25 may count k2. The processing unit 24 corresponds to the determination unit and the correction unit.

[0070] After processing S15 or S16 is completed, the signal processing device 2 terminates its processing. The signal processing device 2 repeatedly executes processing S11 to S16. If the time width is not included in the first range, the measured time width is the time width of the step wave group, and the measured wave height is the wave height of the step wave group and does not correspond to the energy of the radiation. By not performing a +1 count when the time width is not included in the first range, it is prevented from mistakenly counting a step wave group whose time width is not included in the first range as a single step wave. Furthermore, by counting k2, the number of step wave groups whose time width is included in the first range, which is statistically estimated to exist in a specific ratio to the number of step wave groups whose time width is included in the second range, is subtracted from the count. This reduces the influence of step wave groups having a time width equivalent to that of a single step wave in the count of single step waves.

[0071] The signal processing device 2 outputs data showing the relationship between the wave height of the step wave and the count number counted by the counting unit 25. The analysis device 3 receives the data output by the signal processing device 2 as input. The calculation unit 31 of the analysis device 3 generates a spectrum of radiation detected by the radiation detector 1 based on the input data. The count number that forms the basis of the spectrum is the number obtained by subtracting the number of step wave groups whose time width is included in the first range from the number of step waves or step wave groups whose time width is included in the first range, which is statistically estimated based on the number of step wave groups whose time width is not included in the first range. As a result, the influence of step wave groups having a time width equivalent to that of a single step wave is reduced as much as possible, and the count number of step waves corresponding to radiation detection approaches the true value. In the spectrum, the occurrence of a thumb peak caused by a step wave group having a time width equivalent to that of a single step wave is suppressed. Conventionally, it was difficult to remove the number of step wave groups whose time width is included in the first range from the count number counted by the counting unit 25. In this embodiment, the radiation detection device 10 can generate a spectrum with thumb peaks sufficiently removed.

[0072] In this embodiment, the time width is used as a feature quantity corresponding to the duration of the step wave or group of step waves. However, the signal processing device 2 may also use the slope of the step wave as a feature quantity. For example, tangents to the differential waveform are generated at two points where the differential value of the step wave is a predetermined threshold. The point in time when the two tangents intersect the horizontal axis is the midpoint of these two points is determined, and the slope of the step wave at this point is used as a feature quantity. The longer the time width of the step wave, the smaller the slope of the step wave, and the shorter the time width of the step wave, the larger the slope of the step wave. Therefore, the slope of a step wave or group of step waves can be used as a feature quantity corresponding to the duration of the step wave or group of step waves.

[0073] In the configuration where slope is used as a feature, the feature measurement unit 232 measures the slope of the step wave or step wave group. For example, the feature measurement unit 232 obtains the differential value of the step wave or step wave group as the slope at the point where the two tangents of the differential waveform intersect the horizontal axis at the midpoint of two points. The processing unit 24 uses the slope of the step wave or step wave group as a feature and performs processing. Alternatively, the maximum value of the slope of the step wave or step wave group may be used as a feature. For example, the feature measurement unit 232 obtains the maximum value of the differential value of the step wave or step wave group as the maximum value of the slope, and the processing unit 24 uses the maximum value of the slope as a feature. In these configurations as well, the signal processing device 2 reduces the influence of a step wave group having a time width equivalent to that of a single step wave with respect to the number of single step waves counted. Similarly, the signal processing device 2 can generate a spectrum with sufficient thumb peak removal.

[0074] <Embodiment 2> Embodiment 2 shows a configuration in which step waves with different ranges of feature quantities are counted separately. The configuration of the parts of the radiation detection device 10 other than the signal processing device 2 is the same as in Embodiment 1. Figure 10 is a block diagram showing the functional configuration of the radiation detector 1 and the signal processing device 2 according to Embodiment 2. The radiation detector 1 is the same as in Embodiment 1. The A / D conversion unit 21, trapezoidal shaping unit 221, and wave height measurement unit 222 of the signal processing device 2 are the same as in Embodiment 1.

[0075] The differentiation unit 231 and the feature measurement unit 232 are connected to the integration unit 233. The integration unit 233 is configured using an integration circuit. The integration unit 233 may also be configured using a processor that performs integration calculations. Integral section 233 The integrator integrates the signal by multiplying two adjacent signal values ​​contained in the input signal. The integrator 233 receives the differentiated signal from the derivative 231 and the time width (feature) from the feature measurement unit 232. The integrator 233 calculates the wave height of the step wave or step wave group by integrating the differentiated signal from the derivative 231 over the time width input from the feature measurement unit 232.

[0076] As the time width of the step wave group increases, it becomes longer than the holding time of the trapezoidal shaping filter used by the trapezoidal shaping unit 221. When measuring the wave height of a signal by calculating the wave height of the trapezoidal wave, the wave height of a signal that rises over a longer period than the holding time cannot be accurately determined, and a smaller value than the actual value is calculated. For this reason, for step wave groups with a time width longer than that of a single step wave, the calculation by the integration unit 233 yields a more accurate wave height than the measurement by the wave height measurement unit 222. However, since the calculation by the integration unit 233 is more susceptible to noise, for a single step wave, the measurement by the wave height measurement unit 222 yields a more accurate wave height.

[0077] The integration unit 233 is connected to the processing unit 24. The processing unit 24 is connected to a first counting unit 251 and a second counting unit 252. The first counting unit 251 and the second counting unit 252 count step waves by wave height. For example, the first counting unit 251 and the second counting unit 252 are a multi-channel analyzer. The first counting unit 251 and the second counting unit 252 may be configured to count pulse waves for all wave heights, or they may be configured to count pulse waves only for specific wave heights.

[0078] The processing unit 24 receives wave height input from the wave height measurement unit 222, time width of a step wave or group of step waves input from the feature measurement unit 232, and wave height input from the integration unit 233. The processing unit 24 stores information in advance to identify the first range and the second range. If the time width measured by the feature measurement unit 232 is included in the first range, the processing unit 24 instructs the first counting unit 251 to add +1 to the wave height measured by the wave height measurement unit 222. The first counting unit 251 performs the count according to the input instruction. If the time width measured by the feature measurement unit 232 is not included in the first range, the processing unit 24 does not input an instruction for counting to the first counting unit 251, but instead instructs the second counting unit 252 to add +1 to the wave height calculated by the integration unit 233. The second counting unit 252 performs the count according to the input instruction. The count number calculated by the second counting unit 252 corresponds to the second count number.

[0079] The signal processing device 2 outputs data showing the relationship between the wave height of a step wave or group of step waves and the count number counted by the first counting unit 251, and data showing the relationship between the wave height of a group of step waves and the count number counted by the second counting unit 252. The count number counted by the first counting unit 251 is the number of step waves or group of step waves whose time width is included in the first range. The count number counted by the second counting unit 252 is the number of step waves whose time width is not included in the first range.

[0080] Figure 11 is a flowchart showing the processing steps performed by the signal processing device 2 according to Embodiment 2. The signal processing device 2 receives a signal including a step wave from the radiation detector 1 (S21), and the A / D conversion unit 21 performs A / D conversion on the input signal (S22). Wave height measurement and feature measurement are performed on the A / D converted signal (S23). In S23, the trapezoidal shaping unit 221 converts the signal waveform into a trapezoidal wave, and the wave height measurement unit 222 measures the wave height of the step wave or step wave group. The differentiation unit 231 differentiates the signal, the feature measurement unit 232 measures the time width (feature) of the step wave or step wave group, and the integration unit 233 calculates the wave height of the step wave or step wave group by integrating the differentiated signal.

[0081] The processing unit 24 determines whether the time width (feature) measured by the feature measurement unit 232 falls within the first range (S24). If the time width (feature) falls within the first range (S24: YES), the processing unit 24 instructs the first count unit 251 to perform a +1 count, and the first count unit 251 counts +1 for the wave height measured by the wave height measurement unit 222 (S25). In S25, the first count unit 251 adds +1 to the count recorded in the channel associated with the wave height measured by the wave height measurement unit 222. If the time width (feature) does not fall within the first range (S24: NO), the processing unit 24 instructs the second count unit 252 to perform a +1 count, and the second count unit 252 counts +1 for the wave height calculated by the integration unit 233 (S26). In S26, the second counting unit 252 adds +1 to the count recorded in the channel associated with the wave height calculated by the integrating unit 233. Alternatively, if the time width is not included in the first range, the processing unit 24 may determine whether the time width (feature) is included in the second range, and if the time width is included in the second range, it may instruct the second counting unit 252 to perform a count of +1, and the second counting unit 252 may perform the count. The count counted by the first counting unit 251 corresponds to the first count, and the count counted by the second counting unit 252 corresponds to the second count.

[0082] After processing S25 or S26 is completed, the signal processing device 2 terminates its processing. The signal processing device 2 repeatedly executes processing S21 to S26. The signal processing device 2 outputs data showing the relationship between the wave height of the step wave or step wave group and the number of counts counted by the first counting unit 251, and data showing the relationship between the wave height of the step wave group and the number of counts counted by the second counting unit 252. The analyzer 3 receives the data output by the signal processing device 2 as input and stores the data in the storage unit 34.

[0083] Figure 12 is a flowchart showing the procedure of processing performed by the analyzer 3 according to Embodiment 2. The calculation unit 31 performs the following processing according to the computer program 341. The analyzer 3 generates a first spectrum (S31) that shows the relationship between the count number counted by the first count unit 251 and the wave height. In S31, the calculation unit 31 generates the first spectrum based on the count number counted by the first count unit 251 and the wave height, which are included in the data stored in the storage unit 34. In the first spectrum, signals caused by step wave groups with time widths not included in the first range have been removed, but signals caused by step wave groups with time widths included in the first range have not been removed. Therefore, the first spectrum still contains a thumb peak. The processing in S31 corresponds to the first spectrum generation unit.

[0084] The analyzer 3 calculates a corrected count number by correcting the count number counted by the first counting unit 251 (S32). In S32, the corrected count number is calculated by subtracting a value estimated to be the number of step wave groups whose time width is included in the first range, according to the number of step wave groups whose time width is included in the second range, from the count number counted by the first counting unit 251. In S32, the calculation unit 31 calculates the corrected count number I using the following equation (1), with I1 being the count number counted by the first counting unit 251 and I2 being the count number counted by the second counting unit 252. C Calculate. I C =I1+k2I2…(1)

[0085] The value of the correction coefficient k2 is determined based on the setting of the first and second ranges, and the probability distribution of the time widths of the double step wave groups. As shown in Figure 8, the ratio of the probability of a step wave group occurring whose time width is included in the first range to the probability of a step wave group occurring whose time width is included in the second range is (a1 / a2). If the number of step wave groups whose time width is included in the second range is N, then the number of step wave groups whose time width is included in the first range is statistically estimated to be (a1 / a2)N. If the value of the correction coefficient k2 is k2 = (-a1 / a2), then by adding the value obtained by multiplying the number of step wave groups whose time width is included in the second range by the correction coefficient k2 to the number of step waves or step wave groups whose time width is included in the first range, the estimated number of step wave groups whose time width is included in the first range can be subtracted from the number of step waves or step wave groups whose time width is included in the first range. Thus, the value of the correction coefficient k2 is determined as k2 = (-a1 / a2). The value of the correction coefficient k2 is the same as the correction count value k2 in Embodiment 1. The value of the correction coefficient k2 is stored in the storage unit 34 beforehand. The calculation unit 31 calculates the correction count number I according to equation (1) using the correction coefficient k2. C By calculating this, the count number counted by the first count unit 251 is corrected. The corrected count number corresponds to the value obtained by correcting the first count number. Through this correction, the number of step waves or step wave groups having a time width included in the first range is subtracted from the number of step waves or step wave groups having a time width included in the first range, which is a statistically estimated value. The processing in S31 and S32 corresponds to the correction unit.

[0086] The calculation unit 31 calculates the correction count I C A second spectrum is generated that shows the relationship between the first and second steps and the wave height (S33). The second spectrum has the influence of a group of step waves having a time width equivalent to that of a single step wave removed. The processing in S33 corresponds to the second spectrum generation unit. The calculation unit 31 displays the generated first and second spectra on the display unit 44 (S34). The analyzer 3 then completes the processing.

[0087] Figure 13 is a schematic characteristic diagram showing examples of the first and second spectra. The first spectrum is shown in the upper panel, and the second spectrum is shown in the lower panel. The horizontal axis in the figure represents the wave height of the step wave. The vertical axis in the upper panel represents the count number by the first counting unit 251, and the vertical axis in the lower panel represents the corrected count number I C This shows the following. The wave height of the step wave corresponds to the energy of the radiation incident on the radiation detection element 11. The count for each energy is the number of radiation particles with each respective energy counted. Figure 13 shows an example in which radiation is irradiated from the irradiation unit 42 onto a sample 6 containing the elements manganese, copper, and tin, and the radiation generated from the sample 6 is detected by the radiation detector 1 to generate the first spectrum and the second spectrum.

[0088] The count number from the first counting unit 251 is the number of step waves or step wave groups whose time width falls within the first range, and includes the number of step wave groups whose time width falls within the first range. Therefore, the first spectrum includes a sum peak caused by a step wave group having a time width equivalent to that of a single step wave. Corrected count number I C This is the number obtained by subtracting the number of step wave groups whose time width is included in the first range from the number of step waves or step wave groups whose time width is included in the first range, which is statistically estimated based on the number of step wave groups whose time width is included in the second range. As a result, in the second spectrum, the generation of sump peaks caused by step wave groups having a time width equivalent to that of a single step wave is suppressed. As shown in Figure 13, in the second spectrum, the number of peaks is reduced compared to the first spectrum, and sump peaks are removed to some extent. In this way, the radiation detector 10 is able to generate a second spectrum as a radiation spectrum in which sump peaks have been sufficiently removed.

[0089] As described above, in Embodiment 2, the radiation detection device 10 generates a first spectrum including a sum peak and a second spectrum from which the sum peak has been removed. By comparing the two spectra, the effect of the sum peak on the spectrum can be confirmed. After comparing the first and second spectra, it is possible to select which spectrum to use for elemental analysis. Alternatively, a composite spectrum can be created by combining the first spectrum for a certain energy range and the second spectrum for another energy range, and elemental analysis can be performed using the composite spectrum. In Embodiment 2 as well, the signal processing device 2 may use the slope of the step wave as a feature quantity.

[0090] <Embodiment 3> In Embodiments 1 and 2, only step wave groups consisting of two superimposed step waves were considered. However, Embodiment 3 shows an embodiment that takes into account step wave groups consisting of three or more superimposed step waves. Embodiment 3 mainly shows examples that take into account step wave groups consisting of three and four superimposed step waves in addition to step wave groups consisting of two superimposed step waves. Hereinafter, a step wave group consisting of three superimposed step waves will be referred to as a triple step wave group, and a step wave group consisting of four superimposed step waves will be referred to as a quadruple step wave group.

[0091] Figure 14 is a schematic characteristic diagram showing the probability distributions of the time width of a single step wave, a double step wave group, a triple step wave group, and a quadruple step wave group. From top to bottom, the first figure shows the probability distribution of the time width of a single step wave, the second shows the probability distribution of the time width of a double step wave group, the third shows the probability distribution of the time width of a triple step wave group, and the fourth shows the probability distribution of the time width of a quadruple step wave group. The horizontal axis in the figure represents the time width, and the values ​​on the horizontal axis are set to 1, with the average time width of a single step wave being the baseline. The vertical axis represents probability. Figure 14 schematically shows an ideal probability distribution.

[0092] As described in Embodiment 1, the time width of a single step wave is distributed around the mean value, and the probability distribution of the time width of a double step wave group is approximately uniform. The time width of a triple step wave group is distributed from the same lower limit as the time width of a single step wave to around three times the mean value of the time width of a single step wave. Because the third step wave that overlaps each of the uniformly distributed double step wave groups is also uniformly distributed, the probability distribution of the time width of the triple step wave group is approximately triangular, as shown in Figure 14.

[0093] The time width of a quadruple step wave group is distributed from the same lower limit as the time width of a single step wave to approximately four times the average value of the time width of a single step wave. Because the fourth step wave, which overlaps each of the three triangular step wave groups, exhibits a uniform distribution, the probability distribution of the time width of the quadruple step wave group is as shown in Figure 14. A similar probability distribution of the time width can be obtained for step wave groups with five or more overlapping step waves. The more overlapping step waves there are, the closer the probability distribution of the time width of the step wave group approaches a normal distribution.

[0094] As shown in Figure 14, even within a group of three or more overlapping step waves, there are groups of step waves that have a time width equivalent to that of a single step wave. That is, there are groups of step waves whose time width falls within the first range. Mistakenly counting these groups of three or more overlapping step waves with a time width within the first range as a single step wave causes sum peaking.

[0095] For groups of step waves consisting of three or more overlapping step waves, a second range is set for each. Each second range exceeds the time range corresponding to the first range. For a group of three overlapping step waves, an upper limit is set for the time width of the group of three overlapping step waves, and a second range is set corresponding to a predetermined time range from a predetermined value exceeding the upper limit of the time width of a group of two overlapping step waves to the set upper limit. For a group of four overlapping step waves, an upper limit is set for the time width of the group of four overlapping step waves, and a second range is set corresponding to a predetermined time range from a predetermined value exceeding the upper limit of the time width of a group of three overlapping step waves to the set upper limit. Similarly, a second range can be set for groups of five or more overlapping step waves.

[0096] The second ranges for double, triple, and quadruple step wave groups are distinct from each other and do not overlap. The second range for one step wave group is set to a range that does not include the time width of other step wave groups that overlap with fewer step waves than the number of step waves contained in that step wave group. For example, as shown in Figure 14, the second range for a triple step wave group is the range from twice to three times the average value of the time width of a single step wave, and the second range for a quadruple step wave group is the range from three times to four times the average value of the time width of a single step wave. There may be gaps between multiple second ranges. The upper limit of the time width that can be taken by the step wave group with the largest number of overlapping step waves may be unlimited. For example, when considering up to quadruple step wave groups, the upper limit of the time width that can be taken by a quadruple step wave group may be unlimited.

[0097] As shown in Figure 14, the second range for a double step wave group that includes a time width may include not only double step wave groups, but also triple step wave groups and quadruple step wave groups. Similarly, the second range for a triple step wave group that includes a time width may include not only triple step wave groups, but also quadruple step wave groups. In other words, the second range differs depending on the minimum number of step waves that can be included in the step wave group.

[0098] Let b1 be the integral value within the first range of the probability distribution of the time width of a triple step wave group, and let b2 be the integral value within the second range. The ratio of the probability of a triple step wave group occurring whose time width falls within the first range to the probability of a triple step wave group occurring whose time width falls within the second range is (b1 / b2). Also, let b3 be the integral value within the second range of the probability distribution of the time width of a triple step wave group relating to a double step wave group.

[0099] Let the integral value within the first range of the probability distribution of the time width of the quadruple staircase wave group be c1, and the integral value within the second range be c2. The ratio of the probability of occurrence of a quadruple staircase wave group whose time width is included in the first range to the probability of occurrence of a quadruple staircase wave group whose time width is included in the second range is (c1 / c2). Also, let the integral value within the second range related to the double staircase wave group in the probability distribution of the time width of the quadruple staircase wave group be c3, and the integral value within the second range related to the triple staircase wave group in the probability distribution of the time width of the quadruple staircase wave group be c4.

[0100] Let the count number of the staircase wave or staircase wave group whose time width is included in the first range before correction be I1, the count number of the staircase wave group whose time width is included in the second range related to the double staircase wave group be I2, the count number of the staircase wave group whose time width is included in the second range related to the triple staircase wave group be I3, and the count number of the staircase wave group whose time width is included in the second range related to the quadruple staircase wave group be I4. Let the number obtained by subtracting the estimated number of the staircase wave group whose time width is included in the first range from the count number I1 before correction be the corrected count number I C Let it be. The corrected count number I C is calculated by the following formula (2) with k2, k3, and k4 as correction coefficients. I C = I1 + k2I2 + k3I3 + k4I4 …(2)

[0101] As described above, the staircase wave group whose time width is included in the second range related to the double staircase wave group includes the double staircase wave group, the triple staircase wave group, and the quadruple staircase wave group. Also, the staircase wave group whose time width is included in the second range related to the triple staircase wave group includes the triple staircase wave group and the quadruple staircase wave group. Let the number of double staircase wave groups whose time width is included in the second range related to the double staircase wave group be I2’, the number of triple staircase wave groups whose time width is included in the second range related to the triple staircase wave group be I3’, and the number of quadruple staircase wave groups whose time width is included in the second range related to the quadruple staircase wave group be I4’. The corrected count number I C is calculated by the following formula (3). I C = I1 + (-a1 / a2)I2’ + (-b1 / b2)I3’ + (-c1 / c2)I4’ …(3)

[0102] If we consider up to quadruple step wave groups, then I4'=I4. The number of quadruple step wave groups whose second range includes a time width is (c4 / c2)I4, so I3'=I3-(c4 / c2)I4. Also, the number of quadruple step wave groups whose second range includes a time width is (c3 / c2)I4, and the number of triple step wave groups whose second range includes a time width is (b3 / b2)I3'. Therefore, I2' is expressed by equation (4) below. I2' = I2 - (b3 / b2)I3' - (c3 / c2)I4 =I2-(b3 / b2){I3-(c4 / c2)I4}-(c3 / c2)I4 =I2-(b3 / b2)I3+{(b3 / b2)(c4 / c2)-(c3 / c2)}I4…(4)

[0103] Substituting I3' and I2' into equation (3) yields equation (5) below. I C =I1+(-a1 / a2)I2+{(a1 / a2)(b3 / b2)-(b1 / b2)}I3+[(a1 / a2){(c3 / c2)-(b3 / b2)(c4 / c2)}+(b1 / b2)(c4 / c2)-(c1 / c2)] …(5)

[0104] Comparing equation (2) and equation (5), the correction coefficients k2, k3, and k4 can be determined as shown in equations (6), (7), and (8) below. k2 = (-a1 / a2) …(6) k3={(a1 / a2)(b3 / b2)-(b1 / b2)} …(7) k4=[(a1 / a2){(c3 / c2)-(b3 / b2)(c4 / c2)}+(b1 / b2)(c4 / c2)-(c1 / c2)] …(8) Similarly, a correction factor can be determined when considering a group of step waves consisting of five or more overlapping step waves.

[0105] The configuration of the parts of the radiation detection device 10 other than the signal processing device 2 is the same as in Embodiments 1 and 2. Figure 15 is a block diagram showing the functional configuration of the radiation detector 1 and the signal processing device 2 according to Embodiment 3. The radiation detector 1 is the same as in Embodiments 1 and 2. The A / D conversion unit 21, trapezoidal shaping unit 221, wave height measurement unit 222, differentiation unit 231, feature quantity measurement unit 232, and integration unit 233 of the signal processing device 2 are the same as in Embodiment 2.

[0106] The processing unit 24 is connected to a first counting unit 251, a second counting unit 252, a third counting unit 253, and a fourth counting unit 254. The first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254 count step waves according to wave height. For example, the first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254 are a multi-channel analyzer. The first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254 may be configured to count pulse waves for all wave heights, or they may be configured to count pulse waves only for specific wave heights.

[0107] The processing unit 24 receives wave height input from the wave height measurement unit 222, time width of a step wave or step wave group input from the feature quantity measurement unit 232, and wave height input from the integration unit 233. The processing unit 24 stores information in advance for identifying a first range and multiple second ranges. If the time width measured by the feature quantity measurement unit 232 is included in the first range, the processing unit 24 inputs an instruction to the first count unit 251 to add +1 to the wave height measured by the wave height measurement unit 222. If the time width is included in the second range relating to a double step wave group, the processing unit 24 inputs an instruction to the second count unit 252 to add +1 to the wave height calculated by the integration unit 233. If the time width is included in the second range relating to a triple step wave group, the processing unit 24 inputs an instruction to the third count unit 253 to add +1 to the wave height calculated by the integration unit 233. If the time width falls within the second range relating to the quadruple step wave group, the processing unit 24 instructs the fourth counting unit 254 to increment the wave height calculated by the integrating unit 233 by +1. The first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254 perform the count according to the input instruction.

[0108] The signal processing device 2 outputs data showing the relationship between the wave height of a step wave or group of step waves and the counts counted by the first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254. The counts counted by the first counting unit 251 are the number of step waves or groups of step waves whose time width is included in the first range. The counts counted by the second counting unit 252 are the number of step wave groups whose time width is included in the second range relating to double step wave groups. The counts counted by the third counting unit 253 are the number of step wave groups whose time width is included in the second range relating to triple step wave groups. The counts counted by the fourth counting unit 254 are the number of step wave groups whose time width is included in the second range relating to quadruple step wave groups.

[0109] Figure 16 is a flowchart showing the processing steps performed by the signal processing device 2 according to Embodiment 3. The signal processing device 2 receives a signal including a step wave from the radiation detector 1 (S41), and the A / D conversion unit 21 performs A / D conversion on the input signal (S42). Wave height measurement and feature measurement are performed on the A / D converted signal (S43). In S43, the trapezoidal shaping unit 221 converts the signal waveform into a trapezoidal wave, and the wave height measurement unit 222 measures the wave height of the step wave or step wave group. The differentiation unit 231 differentiates the signal, the feature measurement unit 232 measures the time width (feature) of the step wave or step wave group, and the integration unit 233 calculates the wave height of the step wave or step wave group by integrating the differentiated signal.

[0110] The processing unit 24 determines whether the time width (feature) measured by the feature measurement unit 232 falls within the first range (S44). If the time width (feature) falls within the first range (S44: YES), the processing unit 24 instructs the first count unit 251 to perform a +1 count, and the first count unit 251 counts +1 for the wave height measured by the wave height measurement unit 222 (S45). In S45, the first count unit 251 adds +1 to the count recorded in the channel associated with the wave height measured by the wave height measurement unit 222. If the time width (feature) does not fall within the first range (S44: NO), the processing unit 24 determines the second range in which the time width (feature) falls (S46). For example, in S46, the processing unit 24 determines which of the following second ranges—the second range relating to a double step wave group, the second range relating to a triple step wave group, and the second range relating to a quadruple step wave group—contains the time width. The processing unit 24 instructs the counting unit corresponding to the second range containing the time width to perform a +1 count, and the counting unit then counts +1 for the wave height calculated by the integrating unit 233 (S47).

[0111] As mentioned above, S47If the time width falls within the second range corresponding to a double step wave group, the second counting unit 252 adds +1 to the wave height calculated by the integrating unit 233. That is, the second counting unit 252 adds +1 to the count recorded in the channel corresponding to the wave height calculated by the integrating unit 233. If the time width falls within the second range corresponding to a triple step wave group, the third counting unit 253 adds +1 to the wave height calculated by the integrating unit 233. That is, the third counting unit 253 adds +1 to the count recorded in the channel corresponding to the wave height calculated by the integrating unit 233. If the time width falls within the second range corresponding to a quadruple step wave group, the fourth counting unit 254 adds +1 to the wave height calculated by the integrating unit 233. That is, the fourth counting unit 254 adds +1 to the count recorded in the channel corresponding to the wave height calculated by the integrating unit 233. The processing unit 24 may also perform a process to prevent any of the counting units from counting if the time width does not fall within any of the second ranges. The processing unit 24 corresponds to the determination unit. The count counted by the first counting unit 251 corresponds to the first count. The count counts counted by the second counting unit 252, the third counting unit 253, and the fourth counting unit 254 correspond to the second count.

[0112] After processing S45 or S47 is completed, the signal processing device 2 terminates its processing. The signal processing device 2 repeatedly executes processing S41 to S47. The signal processing device 2 outputs data showing the relationship between the wave height of the step wave or step wave group and the counts counted by the first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254. The analysis device 3 receives the data output by the signal processing device 2 as input and stores the data in the storage unit 34.

[0113] The analyzer 3 executes the processes in S31 to S34. In S32, the calculation unit 31 sets the number of counts in the first counting unit 251 as I1, the number of counts in the second counting unit 252 as I2, the number of counts in the third counting unit 253 as I3, and the number of counts in the fourth counting unit 254 as I4, and uses equation (2) to set the corrected count number I CThe correction coefficients k2, k3, and k4 included in equation (2) are expressed by equations (6), (7), and (8). The specific values ​​of the correction coefficients k2, k3, and k4 are stored in the storage unit 34 beforehand. The calculation unit 31 uses the correction coefficients stored in the storage unit 34 to calculate the correction count I C By calculating the corrected count I1 in the first count unit 251, the count I1 is corrected. In S33, the calculation unit 31 calculates the corrected count I C A second spectrum is generated based on this. Through the processing in S31 to S34, the analyzer 3 generates the first and second spectra as shown in Figure 13 and displays them on the display unit 44.

[0114] Multiple second ranges are predetermined and do not overlap with each other. Each second range is determined according to the minimum number of step waves that can be included in the step wave group. The values ​​of the correction coefficients k2, k3, and k4 are predetermined according to the multiple second ranges. The values ​​of the correction coefficients k2, k3, and k4 may be determined theoretically, or they may be determined by experiments performed by the radiation detector 10 using standard samples. The values ​​of the correction coefficients k2, k3, and k4 are constants specific to the radiation detector 10, regardless of the measurement conditions or differences in the sample 6. Therefore, if the correction coefficients are determined during the manufacture of the radiation detector 10 and stored, the radiation detector 10 can continuously perform the correction process.

[0115] In Embodiment 3, the radiation detection device 10 also generates a second spectrum. Correction count I CThis is the number obtained by statistically inferring the number of step wave groups whose time widths are included in one of several second ranges, and subtracting the number of step wave groups whose time widths are included in the first range and in which 2 to 4 step waves overlap from the number of step waves or step wave groups whose time widths are included in the first range. As a result, the influence of step wave groups having a time width equivalent to that of a single step wave is reduced as much as possible, and the step wave count corresponding to radiation detection approaches the true value. In the second spectrum, the generation of sum peaks caused by step wave groups having a time width equivalent to that of a single step wave is further suppressed. The radiation detection device 10 can generate a second spectrum that is more accurate as a radiation spectrum by removing sum peaks. In Embodiment 3 as well, it is possible to compare the first spectrum including sum peaks with the second spectrum from which sum peaks have been removed. It is also possible to use a composite spectrum obtained by combining the first spectrum for a certain energy range with the second spectrum for another energy range.

[0116] The signal processing device 2 may also be configured to consider a group of step waves in which five or more step waves overlap. In this configuration as well, the signal processing device 2 includes a counting unit corresponding to the number of step waves included in the group of step waves, a second range is set according to the number of step waves included in the group of step waves, and counting is performed in the counting unit corresponding to the second range which includes the time width (feature quantity). The analyzer 3 uses a correction coefficient determined according to the number of step waves included in the group of step waves to calculate the corrected count number I C The signal processing device 2 calculates the second spectrum and generates a second spectrum. In this configuration as well, the radiation detection device 10 can further remove the sum peak and generate a more accurate second spectrum. In Embodiment 3, the signal processing device 2 may also use the slope of the step wave as a feature quantity. Alternatively, the signal processing device 2 may correct the count not only when the feature quantity is included in the second range relating to a double step wave group, but also when the feature quantity is included in the second range relating to a step wave group in which three or more step waves overlap, as configured in Embodiment 1.

[0117] <Embodiment 4> Embodiment 4 shows a configuration in which radiation counting is performed by the analysis device 3. The configuration of the parts of the radiation detection device 10 other than the signal processing device 2 is the same as in Embodiments 1 to 3. Figure 17 is a block diagram showing the functional configuration of the radiation detector 1 and the signal processing device 2 according to Embodiment 4. The radiation detector 1 is the same as in Embodiments 1 to 3. The A / D conversion unit 21, trapezoidal shaping unit 221, wave height measurement unit 222, differential unit 231, feature quantity measurement unit 232, and integral unit 233 of the signal processing device 2 are the same as in Embodiments 2 and 3.

[0118] The signal processing device 2 does not have a counting unit. The processing unit 24 receives the wave height from the wave height measurement unit 222, the time width of a step wave or group of step waves from the feature quantity measurement unit 232, and the wave height from the integration unit 233. The processing unit 24 stores information in advance to identify the first range and each of the second ranges. The processing unit 24 determines the range that includes the time width. The processing unit 24 inputs the information including the range determination result and the wave height to the analysis device 3. The analysis device 3 performs a count according to the range that includes the time width, according to the information input from the processing unit 24.

[0119] Figure 18 is a flowchart showing the processing steps performed by the signal processing device 2 and analysis device 3 according to Embodiment 4. The signal processing device 2 receives a signal including a step wave from the radiation detector 1 (S51), and the A / D conversion unit 21 performs A / D conversion on the input signal (S52). Wave height measurement and feature measurement are performed on the A / D converted signal (S53). In S53, the trapezoidal shaping unit 221 converts the signal waveform into a trapezoidal wave, and the wave height measurement unit 222 measures the wave height of the step wave or step wave group. The differentiation unit 231 differentiates the signal, the feature measurement unit 232 measures the time width (feature) of the step wave or step wave group, and the integration unit 233 calculates the wave height of the step wave or step wave group by integrating the differentiated signal.

[0120] The processing unit 24 determines the range in which the time width (feature) measured by the feature measurement unit 232 is included (S54). In S54, the processing unit 24 determines whether the time width is included in the first range, and if the time width is not included in the first range, it determines the second range in which the time width is included. For example, the processing unit 24 determines which of the following second ranges is included in the time width: the second range for a double step wave group, the second range for a triple step wave group, and the second range for a quadruple step wave group. The processing in S54 corresponds to the determination unit.

[0121] The processing unit 24 then outputs information including the determination results for wave height and range, and the analysis device 3 receives the outputted information (S55). In S55, if the time width is included in the first range, the processing unit 24 inputs information to the analysis device 3 including the wave height measured by the wave height measurement unit 222 and the determination result indicating that the time width is included in the first range. If the time width is included in either of the second ranges, the processing unit 24 inputs information to the analysis device 3 including the wave height calculated by the integration unit 233 and the determination result indicating the second range in which the time width is included. The analysis device 3 stores the input information in the storage unit 34.

[0122] The analysis device 3 counts the number of items corresponding to the range in which the time width (feature) is contained, categorized by wave height (S56). The analysis device 3 stores the number of items corresponding to the range in which the time width is contained, categorized by wave height, in the storage unit 34. For example, the analysis device 3 stores in the storage unit 34 the number of items corresponding to the counts in the first count unit 251, second count unit 252, third count unit 253, and fourth count unit 254 in Embodiment 3, in association with the wave height. In S56, the calculation unit 31 identifies the range in which the time width is contained according to the judgment result contained in the input information, and adds +1 to the number corresponding to the identified range, which is stored in association with the wave height contained in the information. The processing in S56 corresponds to the correction unit.

[0123] The number stored in the memory unit 34 by the analyzer 3 is the number of step waves or step wave groups counted by wave height and by the range in which the time width is included. For example, the number stored in the memory unit 34 by the analyzer 3 includes the number of step waves or step wave groups whose time width is included in the first range counted by wave height, the number of step wave groups included in the second range relating to double step wave groups whose time width is included by wave height, the number of step wave groups included in the second range relating to triple step wave groups whose time width is included by wave height, and the number of step wave groups included in the second range relating to quadruple step wave groups whose time width is included by wave height. The number of step waves or step wave groups whose time width is included in the first range corresponds to the first count number. The number of step wave groups whose time width is included in any of the second ranges corresponds to the second count number. After the processing in S56 is completed, the analyzer 3 terminates processing. The signal processing device 2 and the analyzer 3 repeatedly execute the processing in S51 to S56.

[0124] The analyzer 3 performs the processes S31 to S34. In S31, the calculation unit 31 generates a first spectrum based on the number of step waves or step wave groups whose time width is included in the first range, counted by wave height. In S32, for example, the calculation unit 31 uses equation (2) to calculate a corrected count number I based on the number stored in the storage unit 34 that corresponds to the range in which the time width is included. C The following is calculated. The values ​​of the correction coefficients k2, k3, and k4 are stored in the storage unit 34 beforehand. Correction count I C This is the number obtained by subtracting the number of step wave groups whose time width is included in the first range from the number of step waves or step wave groups whose time width is included in the first range, which is statistically estimated based on the number of step wave groups whose time width is included in the second range. In S33, the calculation unit 31 calculates the corrected count I C A second spectrum is generated based on this. Through the processing in S31 to S34, the analyzer 3 generates the first and second spectra as shown in Figure 13 and displays them on the display unit 44.

[0125] In Embodiment 4, the radiation detection device 10 also generates a second spectrum in which the influence of a group of step waves having a time width equivalent to that of a single step wave is reduced. This makes it possible for the radiation detection device 10 to generate a second spectrum as the radiation spectrum in which the sum peak has been sufficiently removed. In Embodiment 4, too, it is possible to compare the first spectrum including the sum peak with the second spectrum from which the sum peak has been removed. Furthermore, it is also possible to use a composite spectrum obtained by combining the first spectrum for a certain energy range with the second spectrum for another energy range.

[0126] In Embodiment 4, the radiation detection device 10 may also use the slope of the step wave as a feature quantity. Alternatively, similar to Embodiment 1, the radiation detection device 10 may correct the number of step waves or step wave groups in which the feature quantity is included in the first range whenever it is determined that the feature quantity is not included in the first range.

[0127] In embodiments 1 to 4, the radiation detection device 10 may be configured to correct the time width, which is a feature quantity, according to the wave height. In this configuration, the time width of the step wave corresponding to a single event is corrected to be constant regardless of the wave height. For example, the processing unit 24 corrects the wave height by dividing the time width by the wave height. The larger the wave height of the step wave, the larger the time width of the step wave tends to be. By correcting the time width, step waves or groups of step waves can be classified without being affected by the magnitude of the wave height. Alternatively, the radiation detection device 10 may be configured in which a first range or a second range is defined according to the wave height. In this configuration as well, step waves or groups of step waves can be classified without being affected by the magnitude of the wave height.

[0128] <Embodiment 5> Embodiment 5 shows a configuration in which the duration of a step wave or a group of step waves is used as a feature quantity. Figure 19 is a schematic characteristic diagram showing an example of multiple step waves that are spaced apart from each other and their differential waveforms. The upper panel shows the signal consisting of step waves, and the lower panel shows the differential signal. In the figure, the horizontal axis represents time, the vertical axis in the upper panel represents the signal value, and the vertical axis in the lower panel represents the differential value. The multiple step waves shown in Figure 19 are sufficiently spaced apart and do not overlap. Even multiple step waves that are spaced apart in this way are considered to be a single group of step waves.

[0129] The height of the step in which the signal value increases due to the step wave group is defined as the wave height of the step wave group. Furthermore, tangents to the differential waveform are generated at the point where the differential value of the step wave group first reaches a predetermined threshold and at the point where the differential value reaches the threshold last. The length of time between the two points where the two tangents intersect the horizontal axis is defined as the duration of the step wave group. The duration of the step wave group is the time from the beginning of the first step wave included in the step wave group to the end of the last step wave, and corresponds to the duration of the step wave group. Let L be the upper limit of the time between adjacent step waves included in a step wave group. In Embodiment 5, a step wave group consists of multiple step waves whose time between adjacent step waves is less than or equal to the upper limit L. A step wave group may contain three or more points where the differential value reaches a predetermined threshold. If the time from the point where the differential value of one step wave reaches the threshold last to the point where the differential value of the next step wave reaches the threshold first exceeds the upper limit L, these two step waves are considered to belong to different step wave groups. The duration of a single step wave is equivalent to its time width.

[0130] The incidence of radiation onto the radiation detection element 11 can be considered random, and the probability distribution of duration can be obtained theoretically or experimentally. Similar to embodiments 1 to 4, the range containing the duration of a single step wave is defined as the first range. If a group of step waves with a duration longer than the upper limit of the first range occurs, a group of step waves with a duration included in the first range should also occur with a certain probability. The range of possible values ​​for durations not included in the first range is divided into multiple second ranges. A correction coefficient for correcting the number of step waves or groups of step waves with durations included in the first range can be obtained from the ratio of the probability of a group of step waves with a duration included in any of the second ranges occurring to the probability of a group of step waves with a duration included in the first range occurring.

[0131] The configuration of the parts of the radiation detection device 10 other than the signal processing device 2 is the same as in Embodiments 1 to 4. Figure 20 is a block diagram showing the functional configuration of the radiation detector 1 and the signal processing device 2 according to Embodiment 5. The radiation detector 1 is the same as in Embodiments 1 to 4. The A / D conversion unit 21, trapezoidal shaping unit 221, wave height measurement unit 222, and differentiation unit 231 of the signal processing device 2 are the same as in Embodiment 3.

[0132] The signal processing device 2 includes an interface unit 234. The interface unit 234 is connected to the analyzer 3. The interface unit 234 receives an upper limit L of the time between adjacent step waves included in a step wave group from the analyzer 3. When the counting rate of radiation is high, the number of step waves included in the signal increases, and it is desirable for the upper limit L to be small. When the counting rate of radiation is low, the number of step waves included in the signal decreases, and it is desirable for the upper limit L to be large. The interface unit 234 receives an upper limit L from the analyzer 3 according to the counting rate. For example, the user operates the operation unit 35 to input the upper limit L to the analyzer 3, and the upper limit L is input from the analyzer 3 to the interface unit 234. The upper limit L may also be input after the radiation measurement is performed and the counting rate is confirmed. The interface unit 234 may also receive the upper limit L from the control unit 41.

[0133] The interface unit 234 inputs an upper limit value L to the feature measurement unit 232 and the processing unit 24. The feature measurement unit 232 receives a signal from the differentiation unit 231 and measures the duration of a step wave or step wave group from the differential waveform of the step wave or step wave group contained in the signal. As explained with reference to Figure 19, the feature measurement unit 232 generates tangents to the differential waveform at the point where the differential value of the step wave group first reaches a predetermined threshold and at the point where the differential value last reaches a threshold, and measures the duration of the step wave or step wave group by calculating the length of time between the two points where the two tangents intersect the horizontal axis. The feature measurement unit 232 calculates the duration so that the time between adjacent step waves included in the step wave group does not exceed the upper limit value L input from the interface unit 234. For example, the feature measurement unit 232 measures the duration from the first step wave to the last step wave, measures the time elapsed since the last step wave, and determines the duration if the time elapsed while the next step wave cannot be obtained exceeds the upper limit value L.

[0134] The feature measurement unit 232 inputs the measured duration to the integration unit 233 and the processing unit 24. The integration unit 233 calculates the wave height of the step wave or step wave group by integrating the differential signal from the differential unit 231 over the duration input from the feature measurement unit 232. The integration unit 233 inputs the wave height to the processing unit 24.

[0135] The processing unit 24 is connected to a first counting unit 251, a second counting unit 252, a third counting unit 253, and a fourth counting unit 254. The processing unit 24 stores multiple second ranges corresponding to the upper limit value L. For example, for each of the multiple upper limit values ​​L, multiple different second ranges are stored. The multiple second ranges for each upper limit value L are associated one-to-one with the second counting unit 252, the third counting unit 253, and the fourth counting unit 254. The processing unit 24 determines the multiple second ranges to be used in processing according to the upper limit value L input from the interface unit 234.

[0136] The processing unit 24 instructs the first counting unit 251 to add +1 to the wave height measured by the wave height measurement unit 222 if the duration measured by the feature measurement unit 232 falls within the first range. If the duration does not fall within the first range, the processing unit 24 determines the second range in which the duration falls and instructs the counting unit corresponding to the second range in which the duration falls to add +1 to the wave height calculated by the integration unit 233. The first counting unit 251, second counting unit 252, third counting unit 253, and fourth counting unit 254 perform counts according to the input instructions. The signal processing device 2 outputs data showing the relationship between the wave height of the step wave or step wave group and the counts counted by the first counting unit 251, second counting unit 252, third counting unit 253, and fourth counting unit 254.

[0137] The signal processing device 2 executes the processes in S41 to S47. In S43, the duration of the step wave or step wave group is measured as a feature. The signal processing device 2 repeatedly executes the processes in S41 to S47. The signal processing device 2 outputs data showing the relationship between the wave height of the step wave or step wave group and the counts counted by the first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254. The analysis device 3 receives the data output by the signal processing device 2 as input and stores the data in the storage unit 34.

[0138] The analyzer 3 stores multiple correction coefficients in the storage unit 34 for each of the multiple upper limit values ​​L. The analyzer 3 executes the processes S31 to S34. In S32, the calculation unit 31 determines the correction coefficient to be used according to the same upper limit value L as the upper limit value L input to the signal processing device 2, and uses the determined correction coefficient to correct the number of corrections I, similar to Embodiment 3. C The calculation unit 31 calculates the calculated correction count I. C A second spectrum is generated based on this. Through the processing in S31 to S34, the analyzer 3 generates the first and second spectra as shown in Figure 13 and displays them on the display unit 44.

[0139] In Embodiment 5, the radiation detection device 10 also generates a second spectrum in which the influence of a group of step waves having a duration equivalent to the duration of a single step wave is reduced. Correction count I C This is the number obtained by subtracting the number of step wave groups whose duration is included in the first range from the number of step waves or step wave groups whose duration is included in the first range, which is statistically estimated based on the number of step wave groups whose duration is included in the second range. As a result, the radiation detection device 10 can generate a second spectrum as the radiation spectrum in which the sum peak has been sufficiently removed.

[0140] In addition, similar to Embodiment 1, the radiation detection device 10 may correct the number of step waves or step wave groups whose duration falls within the first range whenever it is determined that the duration does not fall within the first range. Alternatively, similar to Embodiment 4, the radiation detection device 10 may perform radiation counting using the analyzer 3.

[0141] <Embodiment 6> Embodiments 1 to 5 show a configuration in which a step wave is used as the response wave. Embodiment 6 shows a configuration in which a pulse wave is used as the response wave. The configuration of the parts of the radiation detection device 10 other than the radiation detector 1 and the signal processing device 2 is the same as in Embodiments 1 to 5. Figure 21 is a block diagram showing the functional configuration of the radiation detector 1 and the signal processing device 2 according to Embodiment 6. The radiation detection element 11 is an element that generates a pulse wave having a pulse height corresponding to the energy of the radiation each time an event occurs in which radiation is incident and radiation is detected. For example, the radiation detection element 11 is a proportional counter. For example, the radiation detection element 11 may be a combination of a scintillator and a photomultiplier tube. The pulse wave corresponds to the response wave. The preamplifier 12 amplifies the pulse wave generated by the radiation detection element 11. The radiation detector 1 outputs a signal including the pulse wave. In this way, the radiation detector 1 generates a pulse wave.

[0142] Figure 22 is a schematic characteristic diagram showing an example of a pulse wave. In the figure, the horizontal axis represents time, and the vertical axis represents the signal value. A pulse wave is a signal in which the signal value rises from a predetermined signal reference to a peak value, and then falls back to the signal reference. The signal reference is, for example, zero. Each time radiation is incident on the radiation detection element 11 and an event occurs in which the radiation detection element 11 detects radiation, the radiation detector 1 outputs a pulse wave in which the signal value rises once and then falls. One pulse wave is generated for each event. If multiple events occur, a signal containing multiple pulse waves is output. The height from the signal reference to the peak of the pulse wave is defined as the pulse height. The pulse height corresponds to the energy of the detected radiation.

[0143] As shown in Figure 22, tangents to the pulse wave are generated at two points where the signal value is a predetermined threshold. The distance (length of time) between the two points where the two tangents intersect the horizontal axis (a straight line representing the signal reference) is defined as the pulse wave's time width. The pulse wave's time width corresponds to the duration of the pulse wave. The time width varies depending on the pulse wave and characterizes it. The signal processing device 2 may also use the distance between the two points where the signal value is a predetermined threshold as the pulse wave's time width. The signal processing device 2 may also use the pulse wave's time width obtained by other methods.

[0144] Figure 23 is a schematic characteristic diagram showing an example of a pulse wave when the interval between events is short. In the figure, the horizontal axis represents time, and the vertical axis represents the signal value. In the example shown in Figure 23, the interval between events is shorter than in the example shown in Figure 22. Multiple pulse waves are spaced short apart, and a pulse wave group is generated consisting of multiple overlapping pulse waves. A pulse wave group corresponds to a response wave group. A pulse wave group is defined as a set of multiple pulse waves contained between one point where the signal value reaches a predetermined threshold and the next point where the signal value reaches a predetermined threshold. For example, a pulse wave group is generated when the interval between two events is less than or equal to the time width of a single pulse wave, that is, when the interval between adjacent pulse waves is less than or equal to the time width of a single pulse wave.

[0145] As shown in Figure 23, the height from the signal reference to the peak of the pulse wave group is defined as the pulse height of the pulse wave group. The pulse height of the pulse wave group does not correspond to the energy of the detected radiation. Also, as shown in Figure 23, tangents to the pulse wave group are generated at two points where the signal value of the pulse wave group is a predetermined threshold, and the distance (length of time) between the two points where the two tangents intersect the horizontal axis is defined as the time width of the pulse wave group. The time width of the pulse wave group is the length of time from the beginning of the first pulse wave included in the pulse wave group to the end of the last pulse wave, and corresponds to the duration of the pulse wave group. There are pulse wave groups that have a time width equivalent to that of a single pulse wave, and these pulse wave groups cannot be distinguished from a single pulse wave based on their time width. For this reason, signals that appear to consist of a single pulse wave may actually consist of signals that consist of pulse wave groups.

[0146] As shown in Figure 21, the signal processing device 2 includes an A / D conversion unit 21, a wave height measurement unit 222, a feature quantity measurement unit 232, a processing unit 24, a first counting unit 251, a second counting unit 252, a third counting unit 253, and a fourth counting unit 254. The wave height measurement unit 222 and the feature quantity measurement unit 232 are connected to the A / D conversion unit 21. Between the A / D conversion unit 21 and the wave height measurement unit 222 and the feature quantity measurement unit 232, a conversion unit that converts the signal to cancel out waveform distortion due to signal delay and a noise reduction unit that removes noise from the signal may also be connected.

[0147] The A / D conversion unit 21 receives a signal containing pulse waves from the radiation detector 1 and performs A / D conversion on the signal containing pulse waves. The pulse height measurement unit 222 receives a signal from the A / D conversion unit 21, measures the pulse height of the pulse waves or pulse wave group contained in the signal, and inputs the pulse height to the processing unit 24. The feature quantity measurement unit 232 receives a signal from the A / D conversion unit 21 and measures the time width of the pulse waves or pulse wave group as a feature quantity of the pulse waves or pulse wave group contained in the signal. The feature quantity measurement unit 232 inputs the time width to the processing unit 24.

[0148] The processing unit 24 has pre-stored information for identifying a first range and multiple second ranges. If the time width measured by the feature measurement unit 232 is included in the first range, the processing unit 24 inputs an instruction to the first counting unit 251 to add +1 to the wave height measured by the wave height measurement unit 222. If the time width is included in the second range relating to a double pulse wave group, the processing unit 24 inputs an instruction to the second counting unit 252 to add +1 to the wave height measured by the wave height measurement unit 222. If the time width is included in the second range relating to a triple pulse wave group, the processing unit 24 inputs an instruction to the third counting unit 253 to add +1 to the wave height measured by the wave height measurement unit 222. If the time width is included in the second range relating to a quadruple pulse wave group, the processing unit 24 inputs an instruction to the fourth counting unit 254 to add +1 to the wave height measured by the wave height measurement unit 222. The first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254 perform counting according to the input instructions.

[0149] The signal processing device 2 executes the processes from S41 to S47. In S41, the signal processing device 2 receives a signal including pulse waves from the radiation detector 1. In S43, the pulse height measurement unit 222 measures the pulse height of the pulse wave or pulse wave group, and the feature measurement unit 232 measures the time width (feature) of the pulse wave or pulse wave group. The signal processing device 2 repeatedly executes the processes from S41 to S47. The signal processing device 2 outputs data showing the relationship between the pulse height of the pulse wave or pulse wave group and the counts counted by the first count unit 251, the second count unit 252, the third count unit 253, and the fourth count unit 254. The analysis device 3 receives the data output by the signal processing device 2 and stores the data in the storage unit 34.

[0150] The analyzer 3 performs the processes from S31 to S34. In S32, the calculation unit 31, similar to Embodiment 3, uses equation (2) to calculate the corrected count number I C The calculation is performed. The values ​​of the correction coefficients k2, k3, and k4 are stored in the storage unit 34 beforehand. The calculation unit 31 uses the correction coefficients stored in the storage unit 34 to calculate the correction count I. CBy calculating the corrected count I1 in the first count unit 251, the count I1 is corrected. In S33, the calculation unit 31 calculates the corrected count I C A second spectrum is generated based on this. Through the processing in S31 to S34, the analyzer 3 generates the first and second spectra as shown in Figure 13 and displays them on the display unit 44.

[0151] In Embodiment 6, the radiation detection device 10 generates a second spectrum in which the influence of a group of pulse waves having a time width equivalent to that of a single pulse wave is reduced. Correction count I C This is the number obtained by subtracting the number of pulse wave groups whose time width is within the first range from the number of pulse waves or pulse wave groups whose time width is within the first range, which is statistically estimated based on the number of pulse wave groups whose time width is within one of several second ranges. As a result, the pulse wave count corresponding to the detection of radiation can be brought closer to the true value, and the occurrence of a thump peak caused by a pulse wave group having a time width equivalent to that of a single pulse wave is suppressed. The radiation detection device 10 can generate a second spectrum as the radiation spectrum in which the thump peak has been sufficiently removed. In Embodiment 6, as well, it is possible to compare the first spectrum including the thump peak with the second spectrum from which the thump peak has been removed. It is also possible to use a composite spectrum obtained by combining the first spectrum for a certain energy range with the second spectrum for another energy range.

[0152] Furthermore, similar to Embodiment 4, the radiation detection device 10 may not have the first counting unit 251, the second counting unit 252, the third counting unit 253, and the fourth counting unit 254 in the signal processing device 2, and the radiation count may be performed by the analysis device 3. The radiation detection device 10 may also be configured to correct the time width, which is a feature quantity, according to the pulse height. Alternatively, similar to Embodiment 5, the radiation detection device 10 may be configured to use the duration of a pulse wave or a pulse wave group as a feature quantity, with a group of pulse waves consisting of multiple pulse waves whose intervals between adjacent pulse waves are less than or equal to an upper limit L.

[0153] <Embodiment 7> Embodiment 7 shows a configuration in which the time width, which is a feature of a step wave or a group of step waves, is measured in a different way from Embodiments 1 to 5. Figure 24 is a block diagram showing the functional configuration of the radiation detector 1 and the signal processing device 2 according to Embodiment 7. The configuration of the radiation detector 1 and the analyzer 3 is the same as in Embodiment 3. The signal processing device 2 according to Embodiment 7 does not have a differential unit 231 and an integral unit 233 compared to the signal processing device 2 according to Embodiment 3. The feature measurement unit 232 is connected to the trapezoidal shaping unit 221. The other configurations of the signal processing device 2 are the same as in Embodiment 3.

[0154] The trapezoidal shaping unit 221 converts the step wave or group of step waves contained in the signal into a trapezoidal wave by shaping the waveform of the signal input from the A / D conversion unit 21 using multiple trapezoidal shaping filters with different time constants. The trapezoidal shaping unit 221 inputs the signal shaped using a trapezoidal shaping filter with a long time constant to the wave height measurement unit 222, and inputs the signal shaped using a trapezoidal shaping filter with a short time constant to the feature quantity measurement unit 232. That is, the wave height measurement unit 222 receives a trapezoidal wave generated using a trapezoidal shaping filter with a long time constant from the trapezoidal shaping unit 221. The feature quantity measurement unit 232 also receives a trapezoidal wave generated using a trapezoidal shaping filter with a short time constant from the trapezoidal shaping unit 221.

[0155] The wave height measurement unit 222 receives a signal from the trapezoidal shaping unit 221 and measures the wave height of the trapezoidal wave generated using a trapezoidal shaping filter with a long time constant. The feature quantity measurement unit 232 receives a signal from the trapezoidal shaping unit 221 that includes a trapezoidal wave generated using a trapezoidal shaping filter with a short time constant, differentiates the input signal, and measures its time width.

[0156] Figure 25 is a schematic graph showing examples of step wave groups, trapezoidal waves, and waveforms obtained by differentiating a trapezoidal wave. The first graph from the top shows a double step wave group, the second shows a signal containing a double step wave group shaped using a trapezoidal filter with a long time constant, and the third shows a signal containing a double step wave group shaped using a trapezoidal filter with a short time constant. The fourth graph from the top shows the differentiated signal obtained by differentiating the signal containing a double step wave group shaped using a trapezoidal filter with a short time constant. In the graph, the horizontal axis represents time, the vertical axis of the first, second, and third graphs from the top represents the signal value, and the vertical axis of the fourth graph from the top represents the derivative value.

[0157] The wave height measurement unit 222 receives a signal containing a trapezoidal wave generated using a trapezoidal shaping filter with a long time constant, as shown in the second graph from the top, and measures the wave height of the trapezoidal wave. The feature quantity measurement unit 232 receives a signal containing a trapezoidal wave generated using a trapezoidal shaping filter with a short time constant, as shown in the third graph from the top. If the step wave group is a double step wave group, two trapezoidal waves are included in the signal. Similarly, if the step wave group is a triple or more step wave group, three or more trapezoidal waves are included in the signal. If the signal input from the A / D conversion unit 21 to the trapezoidal shaping unit 221 contains a single step wave, the signal input to the feature quantity measurement unit 232 contains a single trapezoidal wave.

[0158] The feature measurement unit 232 differentiates the input signal to generate a differentiated signal with local maxima and local minimum. If the step wave group is a double step wave group, a differentiated signal with two local maxima and local minimum is generated, as shown in the fourth graph from the top. Similarly, if the step wave group is a triple or more step wave group, a differentiated signal with three or more local maxima and local minimum is generated. If the signal input from the A / D conversion unit 21 to the trapezoidal shaping unit 221 contains a single step wave, a differentiated signal with a single local maxima and local minimum is generated.

[0159] The feature measurement unit 232 defines the time width, which is a feature of the step wave or step wave group, as the length of time from the first maximum value to the last minimum value included in the differential signal. That is, the feature measurement unit 232 measures the time width by measuring the length of time from the first maximum value to the last minimum value. For example, the feature measurement unit 232 generates a second-order differential signal by further differentiating the differential signal, and measures the time width by measuring the length of time from the point where the value of the second-order differential signal first becomes zero to the point where the value of the second-order differential signal last becomes zero.

[0160] In Embodiments 1 to 5, the time width or duration is measured by generating tangents to the differential waveform at two points where the differential value of the step wave or step wave group is a predetermined threshold, and calculating the length of time between the two points where the two tangents intersect the horizontal axis. The time width or duration measured by the method described in Embodiments 1 to 5 is prone to fluctuation depending on the wave height of the step wave or step wave group. That is, the time width or duration measured by the method described in Embodiments 1 to 5 is affected by the energy of the radiation. The time width measured in Embodiment 7 is less prone to fluctuation depending on the wave height of the step wave or step wave group and is less affected by the energy of the radiation. Therefore, in Embodiment 7, the signal processing device 2 can accurately determine the time width without being affected by the energy of the radiation.

[0161] Similar to Embodiment 3, the signal processing device 2 executes the processes in S41 to S47. In S43, the feature measurement unit 232, as described above, differentiates the signal containing the trapezoidal wave generated using a trapezoidal shaping filter with a short time constant, and measures the time length from the first maximum value to the last minimum value included in the differentiated signal to measure the time width. In S47, the second counting unit 252, the third counting unit 253, or the fourth counting unit 254 counts +1 for the wave height measured by the wave height measurement unit 222. Similar to Embodiment 3, the analysis device 3 executes the processes in S31 to S34. In this way, the radiation detection device 10 generates a second spectrum with the thumb peak removed. The radiation detection device 10 according to Embodiment 7 is capable of accurately identifying the time width and accurately generating a second spectrum with the thumb peak removed.

[0162] The time width measurement method described in Embodiment 7 may also be applied to Embodiments 1, 2, 4, and 5. In the configuration in which the time width measurement method described in Embodiment 7 is applied to Embodiments 1, 2, and 4, similarly, the feature measurement unit 232 is connected to the trapezoidal shaping unit 221, and receives a signal shaped using a trapezoidal shaping filter with a short time constant from the trapezoidal shaping unit 221 to measure the time width. In the configuration in which the time width measurement method described in Embodiment 7 is applied to Embodiment 5, similarly, the feature measurement unit 232 is connected to the trapezoidal shaping unit 221, and receives a signal shaped using a trapezoidal shaping filter with a short time constant from the trapezoidal shaping unit 221. The feature measurement unit 232 measures the duration of a step wave or step wave group by measuring the length of time from the first maximum value to the last minimum value included in the differential signal.

[0163] In Embodiment 7, the signal processing device 2 further performs dead time correction processing. Detecting radiation takes a certain amount of time, and during this time, other radiation cannot be detected. For this reason, each time an event occurs in which the radiation detection element 11 detects radiation, the processing unit 24 stops the radiation detection process for a predetermined time. The length of time that the processing unit 24 stops the radiation detection process for each event is called the dead time. The radiation count rate is calculated from the number of times the radiation detection process has been stopped and the dead time. Since correcting the first count number reduces the radiation count, the count rate corresponding to the corrected count number is less than the count rate calculated from the dead time. Therefore, the processing unit 24 performs dead time correction processing to increase the dead time related to the step wave group whose time width is included in the second range in accordance with the decrease in the count number.

[0164] If a step wave group included in the second range relating to a double step wave group occurs once, statistically, the double step wave group whose time width is included in the first range has occurred (-k2) times. Therefore, by multiplying the dead time by (1-k2), the dead time can be corrected to increase by the amount of the double step wave group whose time width is included in the first range. That is, in the dead time correction process, the processing unit 24 takes the value obtained by multiplying the dead time relating to the step wave group by (1-k2) as the corrected dead time when the time width is included in the second range relating to the double step wave group.

[0165] Similarly, in the dead time correction process, if the second range relating to a triple step wave group includes a time width, the processing unit 24 uses the value obtained by multiplying the dead time relating to the step wave group by (1-k3) as the corrected dead time. If the second range relating to a quadruple step wave group includes a time width, the processing unit 24 uses the value obtained by multiplying the dead time relating to the step wave group by (1-k4) as the corrected dead time. Dead time correction can also be performed in the same way when considering a step wave group in which five or more step waves overlap.

[0166] The processing unit 24 performs a process to stop the radiation detection process for the duration of the corrected dead time each time an event occurs in which the radiation detection element 11 detects radiation. By performing dead time correction, the radiation detection device 10 can set the dead time more accurately and measure the radiation count rate more accurately.

[0167] The dead time correction process described in Embodiment 7 may also be performed in Embodiments 1 to 6. In Embodiments 1 to 4, the processing unit 24 performs similar dead time correction according to the second range which includes the time width of the step wave group. In Embodiment 5, the processing unit 24 performs similar dead time correction according to the duration of the step wave group. In Embodiment 6, the processing unit 24 performs similar dead time correction according to the time width or duration of the pulse wave group.

[0168] <Embodiment 8> In embodiments 1 to 7, removing the sum peak tends to reduce the intensity of the peaks included in the spectrum. Embodiment 8 shows a method of restoring the intensity of the peaks included in the radiation spectrum by increasing the count of multiple step waves that caused the step wave group, in accordance with the intensity of the step wave group.

[0169] The configuration of the radiation detection device 10 according to Embodiment 8 is the same as that of any of Embodiments 2 to 4. The radiation detection device 10 performs the same processing as that of any of Embodiments 2 to 4. The analyzer 3 calculates for each wave height a first count, a second count, and a corrected count I obtained by correcting the first count. C The data is stored in the memory unit 34. The first count is the count counted by the first count unit 251, and the second count is, for example, the count counts counted by the second count unit 252, the third count unit 253, and the fourth count unit 254, respectively.

[0170] Figure 26 is a schematic characteristic diagram showing examples of spectra representing the relationship between the first spectrum, the second spectrum, and the second count number and wave height. From top to bottom, the first spectrum is shown first, the second spectrum is shown as a solid line second, and the spectrum representing the relationship between the second count number and wave height is shown as a solid line third. The horizontal axis in the figure represents the wave height of the step wave. The vertical axis in the first figure from the top represents the count number from the first count unit 251, and the vertical axis in the second figure represents the corrected count number I C The third figure shows the second count, with the vertical axis representing the second count. The second count is, for example, the count counted by the second counting unit 252.

[0171] The first spectrum shown in Figure 26 includes peaks with wave heights of 2, 4, and 6. Here, the peak with wave height 6 is assumed to be a thumb peak resulting from a group of step waves containing a step wave with wave height 2 and a step wave with wave height 4, with a time width within the first range. When a step wave with wave height 2 and a step wave with wave height 4 occur, in reality, a thumb peak with wave height 4 resulting from a group of step waves formed by the superposition of two step waves with wave height 2, and a thumb peak with wave height 8 resulting from a group of step waves formed by the superposition of two step waves with wave height 4, can also occur. Furthermore, a thumb peak resulting from a group of step waves with three or more superpositions can also occur. However, in the example shown in Figure 26, for the sake of simplicity, we will only consider the thumb peak with wave height 6 resulting from a double group of step waves formed by the superposition of a step wave with wave height 2 and a step wave with wave height 4. The second spectrum does not include the peak with wave height 6, which is a thumb peak. The spectrum showing the relationship between the second count and wave height has a peak at wave height 6.

[0172] The analyzer 3 further performs a process to recover the radiation count. Figure 27 is a flowchart showing an example of the procedure for the process to recover the radiation count performed by the analyzer 3 according to Embodiment 8. The analyzer 3 calculates the corrected count from the first count to the first count. C The subtracted value is calculated by subtracting the value (S61). The subtracted value is an estimated value of the number of step wave groups whose time width is included in the first range, and corresponds to the intensity of the thumb peaks removed by the processing in S31 to S34. If only double step wave groups are considered, the subtracted value is (-k2I2) according to equation (1). If up to quadruple step wave groups are considered, the subtracted value is (-k2I2-k3I3-k4I4) according to equation (2). In S61, the calculation unit 31 calculates the subtracted value by calculating (-k2I2-k3I3-k4I4) using, for example, the counts counted by the second count unit 252, the third count unit 253 and the fourth count unit 254 and the correction coefficients k2, k3 and k4.

[0173] In the third figure from the top in Figure 26, the thumb peaks caused by the step wave group whose time width falls within the first range are shown by dashed lines. The intensity of these thumb peaks is the subtracted value. The subtracted value can be calculated from the second count and the correction coefficient. In S61, the calculation unit 31 calculates the subtracted value for each wave height. In S61, the calculation unit 31 calculates the correction count I from the count counted by the first count unit 251. C The subtracted value can also be calculated by subtracting from the original value.

[0174] The analyzer 3 then divides the subtraction value at each wave height and generates divided values ​​assigned to each of the lower wave heights (S62). A thumb peak occurs when multiple step waves with wave heights lower than the thumb peak overlap. In the second spectrum after removing the thumb peak caused by the step wave group whose time width is included in the first range, the intensity of the peaks corresponding to the multiple step waves included in this step wave group is reduced. By dividing the number of step wave groups whose time width is included in the first range and adding them to each of the wave heights lower than the wave height of the step wave group, the count of each step wave included in the step wave group increases, and the reduced peak intensity is restored. In S62, the calculation unit 31 divides the subtraction value at one wave height into multiple divided values. The sum of the multiple divided values ​​becomes the subtraction value. The calculation unit 31 assigns multiple divided values ​​to multiple wave heights lower than the one wave height. The calculation unit 31 calculates the correction count I at the assigned wave height. C Each division value is determined in proportion to the value. The calculation unit 31 calculates the division value for each subtraction value at each wave height.

[0175] The analyzer 3 then corrects the division value to count I C By adding to this, the corrected count I C Further correction is performed (S63). In S63, the calculation unit 31 calculates all of the multiple division values ​​assigned to each wave height by the correction count I for each wave height. C This is added to the count of the step wave that was included in the step wave group whose time width falls within the first range. In S62 and S63, the calculation unit 31 calculates the division value according to the subtraction value at each wave height and corrects the count I CThe correction is performed sequentially for each wave height, starting from the lower wave height side (lower energy side). When performing a calculation for the next wave height after a calculation for a certain wave height, the number of correction counts I that have been corrected so far is used. C The respective division values ​​may be calculated in proportion to this.

[0176] The analyzer 3 uses the corrected corrected count I C This generates a third spectrum that shows the relationship between the wave height and the wavelength. S64 ). S64 So, the corrected number of corrected counts I C A third spectrum is generated by associating the wave height (energy of the radiation) with each other and storing them in the memory unit 34. In the second figure from the top in Figure 26, the third spectrum is shown as a dashed line. The intensity of the peak with a wave height of 6, which is a thumb peak, is distributed to the peak with a wave height of 2 and the peak with a wave height of 4, and the intensities of the peaks with wave heights of 2 and 4 increase. Since the intensity of the peak with a wave height of 4 is greater than the intensity of the peak with a wave height of 2, the increase in the intensity of the peak with a wave height of 4 is greater than the increase in the intensity of the peak with a wave height of 2.

[0177] The analyzer 3 displays the third spectrum. S65 ). S65 The calculation unit 31 then displays the third spectrum on the display unit 44. The calculation unit 31 may also display the third spectrum along with the first and second spectra. The calculation unit 31 may also perform a process to switch between displaying the first or second spectrum and displaying the third spectrum. S65 After this is completed, the analyzer 3 terminates the process for restoring the radiation count.

[0178] As described in detail above, in Embodiment 8, the radiation detection device 10 divides the subtraction value at each wave height corresponding to the number of step wave groups whose time width is included in the first range, and then corrects the number of counts I at multiple lower wave heights. C Add to this. The division value is the number of correction counts at multiple wave heights I CThis is proportional to the number of step wave groups whose time widths fall within the first range, thereby increasing the count of the multiple step waves contained within that group. The peak intensity in the spectrum of the radiation from which the thumb peak has been removed is recovered by the amount of the thumb peak intensity caused by the step wave groups whose time widths fall within the first range. A third spectrum is obtained in which the peak intensity is increased compared to the second spectrum.

[0179] In Embodiment 8, the dead time correction process described in Embodiment 7 does not need to be performed. In Embodiment 8, the radiation count decreases by the number of counts of the step wave group whose time width is included in the first range, but the counts of the multiple step waves included in the step wave group increase. Therefore, the counting rate corresponding to the radiation count corresponds to the counting rate calculated from the dead time.

[0180] The process for restoring the radiation count described in Embodiment 8 may also be performed in Embodiment 5 or 6. In Embodiment 5, the analyzer 3 restores the intensity of the peaks included in the radiation spectrum by increasing the count of multiple step waves included in a step wave group according to the number of step wave groups whose durations fall within a first range. In Embodiment 6, the analyzer 3 restores the intensity of the peaks included in the radiation spectrum by increasing the count of multiple pulse waves included in a pulse wave group according to the number of pulse wave groups whose time width or durations fall within a first range.

[0181] In embodiments 2 to 8, the radiation detection device 10 may be configured to smooth the second count in the direction of the change in pulse height. For example, the analyzer 3 smooths the second count using a smoothing filter. Since statistical errors are superimposed on the second count, a correction count closer to the true value can be calculated by performing a correction process using the smoothed second count.

[0182] Embodiments 1 to 8 show a configuration in which a step wave is used as the response wave, and Embodiment 6 shows a configuration in which a pulse wave is used as the response wave. However, the signal processing device 2 may use other response waves. For example, the signal processing device 2 may use a response wave that has a shape similar to a step wave, in which the signal value increases when radiation is detected and then decays with a specific time constant. In this configuration, the preamplifier 12 outputs a response wave having the aforementioned shape. The signal processing device 2 includes a filter between the A / D conversion unit 21 and the trapezoidal shaping unit 221 or the differential unit 231 that shapes the response wave having the aforementioned shape into a step wave. The signal processing device 2 uses the shaped step wave to perform the same processing as in Embodiments 1 to 5, 7 and 8.

[0183] In embodiments 1 to 8, the functions of the signal processing device 2 are shown to be implemented in hardware, but the signal processing device 2 may also be configured to implement some or all of its functions in software. In embodiments 1 to 8, the functions of the signal processing device 2 are shown to be implemented by irradiating the sample 6 with radiation and detecting the radiation generated from the sample 6, but the radiation detection device 10 may also be configured to detect radiation that has been transmitted through the sample 6 or reflected by the sample 6. The radiation detection device 10 may also be configured to scan the sample 6 with radiation by changing the direction of the radiation. The radiation detection device 10 may also be configured to irradiate a moving sample with radiation. The radiation detection device 10 may also be configured not to include an irradiation unit 42, a sample stage 5, or a display unit 44.

[0184] The matters described in each embodiment can be combined with each other. Furthermore, the independent and dependent claims described in the claims can be combined with each other in any combination, regardless of the form of reference. In addition, the claims use a form in which claims referencing two or more other claims (multi-claim form), but are not limited to this. A form in which multi-claims referencing at least one multi-claim (multi-multi-claim) may also be used.

[0185] The present invention is not limited to the embodiments described above, and various modifications are possible within the scope of the claims. That is, embodiments obtained by combining technical means that have been appropriately modified within the scope of the claims are also included in the technical scope of the present invention. [Explanation of Symbols]

[0186] 1. Radiation detector 10. Radiation detection device 11. Radiation detection element 2 Signal Processing Device 232 Feature Measurement Unit 24 Processing Unit 25 Count Section 251 First Count Section 252 Second Count Section 253 Third Count Section 254 4th Count Section 3 Analyzer 30 Recording media 341 Computer Programs

Claims

1. In a method for processing a signal that includes a response wave generated in response to the detection of radiation, Measure the feature quantities corresponding to the duration of the response wave, or a group of response waves consisting of multiple response waves. The number of response waves or response wave groups containing the measured feature quantities within a predetermined first range that includes the feature quantities of a single response wave is counted by wave height. Depending on the response wave or group of response waves in which the feature quantity is not included in the first range, a correction process is performed to subtract a specific value from the counted number. A signal processing method characterized by the following:

2. The aforementioned specific value is the number of response wave groups that contain the feature in the first range, in a predetermined ratio to the number of response wave groups that do not contain the feature in the first range. The signal processing method according to feature 1.

3. Determine whether the measured feature is included in the first range. If the measured feature quantity falls within the first range, the response wave or group of response waves is counted by wave height. If the measured feature quantity does not fall within the first range, the response wave or response wave group is not counted, and the correction process is performed. The signal processing method according to claim 1 or 2.

4. A first count is generated by counting response waves or response wave groups that contain the feature quantity within the first range, separately for each wave height, and not counting response waves or response wave groups that do not contain the feature quantity within the first range. A second count is generated by counting response waves or response wave groups whose feature quantities are included in a second range corresponding to a predetermined time range that exceeds the time range corresponding to the first range, by wave height. In the correction process, the first count is corrected by adding a value obtained by multiplying the second count by a predetermined correction coefficient to the first count. The correction coefficient is determined based on the ratio of the probability that the feature quantities of the response wave group fall within the second range to the probability that the feature quantities of the response wave group fall within the first range. The signal processing method according to claim 1 or 2.

5. Multiple second ranges and correction coefficients corresponding to each of the second ranges are defined. In the correction process, the correction coefficient corresponding to the second range that includes the measured feature quantities is used. The signal processing method according to feature 4.

6. A first spectrum is generated that shows the relationship between the first count and the wave height. A second spectrum is generated that shows the relationship between the corrected value of the first count and the wave height. The signal processing method according to feature 4.

7. For each wave height, calculate a subtracted value by subtracting the corrected value of the first count from the first count. Multiple division values ​​obtained by dividing the subtraction value at one wave height are assigned to multiple wave heights lower than the one wave height, and the division values ​​are values ​​proportional to the value obtained by correcting the first count at the assigned wave height. For each wave height, the above subtraction value is used to generate the above-mentioned multiple division values. The division value is added to the value obtained by correcting the first count at the assigned wave height, thereby further correcting the first count. The signal processing method according to feature 4.

8. The aforementioned feature quantity is the time width of the response wave or the response wave group. The signal processing method according to claim 1 or 2.

9. The aforementioned feature quantity is the length of time from the beginning of the first response wave included in the response wave group to the end of the last response wave included in the response wave group. The signal processing method according to claim 1 or 2.

10. The response wave is a step wave or a pulse wave. The signal processing method according to claim 1 or 2.

11. A feature quantity measurement unit that measures feature quantities corresponding to the duration of a response wave generated in response to the detection of radiation, or a group of response waves consisting of multiple response waves, A determination unit that determines whether the measured feature quantity is included in a predetermined first range that includes the feature quantity of a single response wave, A correction unit counts the number of response waves or response wave groups in which the feature quantity is included in the first range, according to the wave height, and subtracts a specific value from the counted number depending on the response waves or response wave groups in which the feature quantity is not included in the first range. A signal processing device characterized by comprising:

12. A radiation detector that generates a response wave in response to incident radiation, When the radiation detector generates a response wave, or a group of response waves consisting of multiple response waves, a feature quantity measurement unit measures a feature quantity corresponding to the duration of the generated response wave or group of response waves. A determination unit that determines whether the measured feature quantity is included in a predetermined first range that includes the feature quantity of a single response wave, A correction unit counts the number of response waves or response wave groups in which the feature quantity is included in the first range, according to the wave height, and subtracts a specific value from the counted number depending on the response waves or response wave groups in which the feature quantity is not included in the first range. A radiation detection device characterized by comprising the following features.

13. A first spectrum generation unit generates a first spectrum that represents the relationship between the wave height and the number of response waves or response wave groups in which the feature quantity is included in the first range, counted by wave height, and the wave height. A second spectrum generation unit generates a second spectrum that represents the relationship between the value obtained by correcting the first count number by the correction unit and the wave height. The radiation detection device according to claim 12, further comprising the following:

14. When the feature quantity corresponding to the duration of a response wave or a group of response waves generated in response to the detection of radiation falls within a predetermined first range that includes the feature quantity of a single response wave, a first count number is obtained, which is generated by counting the response waves or group of response waves by wave height. A second count is obtained by counting response waves or response wave groups, separated by wave height, in a second range corresponding to a predetermined time range that exceeds the time range corresponding to the first range, in which the feature quantity is included. From the first count, subtract the number of response wave groups in which the feature quantities are included in the first range, according to the second count. A computer program characterized by causing a computer to perform a process.

Images