Radiation detector, radiation measurement device, and setting method of radiation detector

Abstract

To provide a radiation detector, a radiation measurement device, and a setting method of the radiation detector that can suppress double counting that detects a single pulse in a duplicate manner by multiple counters in the time of switching counters and acquire high-accuracy data.SOLUTION: A radiation detector 100 which can detect the radiation with continuous exposure includes: a sensor 110 which generates a pulse when a particle of radiation is detected; multiple counters 140a, 140b which are provided so as to be able to count the pulses; a setting retention circuit 150 which retains setting of the off-time that turns off both the multiple counters 140a, 140b; and a control circuit 160 which switches the counter that counts the pulse after the set off-time for a trigger signal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a radiation detector capable of detecting radiation by continuous exposure, a radiation measuring device, and a method for setting a radiation detector. [Background technology]

[0002] Conventionally, radiation detectors that enable continuous exposure by switching between multiple counters are known (see, for example, Patent Document 1). The radiation detector described in Patent Document 1 switches counters when a trigger signal is received, thereby eliminating the dead time that occurs when reading detection data and achieving continuous exposure.

[0003] However, when measurements are taken with continuous exposure in zero-deadband mode, the time (time constant) for a single pulse to exceed the threshold has a certain width, and if the counter switches during that time, one photon that entered the radiation detector is counted as two (for example, see Non-Patent Document 1). This double-counting phenomenon causes the number of counted X-ray photons to be greater than the actual number, resulting in an error.

[0004] Non-Patent Document 1 reports a phenomenon in which the number of photons detected during continuous exposure deviates from an ideal curve showing the number of detected photons relative to the number of incident photons, and errors due to double counting become particularly noticeable when the exposure time is shortened. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-096841 A [Non-patent literature]

[0006] [Non-Patent Document 1] Johannes Moller, Mario Reiser et al., “Implications of disturbed photon-counting statistics of Eiger detectors for X-ray speckle visibility experiments”, Journal of synchrotron radiation, Accepted 4 May 2019 Summary of the Invention [Problem to be solved by the invention]

[0007] As mentioned above, in the zero-dead mode, double counting occurs when the counter of the digital circuit is switched. Figure 10 is a timing chart showing an example of double counting. Figure 10 shows the wave height of the pulse input to the counter circuit, the on / off of each counter that counts the pulse, and the count by the counter.

[0008] 10, in a conventional radiation detector, when a pulse P01 reaches only counter C01, counter C01 counts 1. However, when a pulse P02 reaches both counters C01 and C02 at the timing of counter switching, each of counters C01 and C02 counts 1, resulting in a total count of 2.

[0009] The present invention has been made in consideration of the above circumstances, and has an object to provide a radiation detector, a radiation measuring device, and a method for setting a radiation detector that can suppress double counting, in which a single pulse is detected redundantly by multiple counters when switching counters, and obtain highly accurate data. [Means for solving the problem]

[0010] (1) In order to achieve the above object, the radiation detector of the present invention is a radiation detector capable of detecting radiation by continuous exposure, and is characterized by comprising: a sensor that generates a pulse when a particle of radiation is detected; a plurality of counters arranged to be able to count the pulses; a setting retention circuit that retains settings of an off time for turning off all of the plurality of counters; and a control circuit that switches the counter that counts pulses after the set off time in response to a trigger signal.

[0011] (2) In the radiation detector described above in (1), the off time is a time constant.

[0012] (3) Furthermore, the radiation detector of the present invention is a radiation detector capable of detecting radiation by continuous exposure, and comprises a sensor which generates a pulse when a particle of radiation is detected, a plurality of counters arranged to be able to count the pulses, and a control circuit which switches the counter which counts the pulses in response to a trigger signal, and is characterized in that the number of detected photons relative to the number of incident photons falls on a theoretical curve specified based on the radiation source.

[0013] (4) The radiation detector according to any one of (1) to (3) above is characterized in that it is a one-dimensional or two-dimensional detector.

[0014] (5) Furthermore, a radiation measuring device of the present invention is a radiation measuring device capable of measuring radiation by continuous exposure, and is characterized by comprising a radiation source that continuously irradiates radiation, a sample holding unit that holds a sample, and a radiation detector described in any one of (1) to (3) above.

[0015] (6) Furthermore, a method for setting a radiation detector of the present invention is a method for setting a radiation detector that detects radiation by continuous exposure, and is characterized by including a step of receiving an input for setting an off time for turning off all of a plurality of counters possessed by the radiation detector, and a step of causing the radiation detector to retain the input setting. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1 is a schematic diagram illustrating a configuration of a radiation detector. [Diagram 2] 4 is a flowchart showing the operation of the radiation detector. [Diagram 3] 11 is a timing chart showing an example of suppressing double counting. [Figure 4] 11 is a timing chart showing an example of suppressing counting losses. [Diagram 5] FIG. 1 is a schematic diagram showing a configuration of a radiation measuring device. [Figure 6] FIG. 2 is a schematic diagram showing imaging of multiple frames. [Figure 7] FIG. 1 is a plan view showing an example of a radiation measuring device. [Figure 8] FIG. 1 is a side view showing an example of a radiation measuring device. [Figure 9] FIG. 2 is a schematic diagram showing a configuration of a radiation detector when set up. [Figure 10] 11 is a timing chart showing an example of an occurrence of double counting. [Figure 11] Graphs (a) and (b) show the results of XPCS measurements of comparative examples (using burst mode and zero dead mode, respectively). [Figure 12] Graphs (a) and (b) show the results of XPCS measurements in the example (using burst mode and zero dead mode, respectively). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] Next, an embodiment of the present invention will be described with reference to the drawings. In order to facilitate understanding of the description, the same reference numerals are used to refer to the same components in each drawing, and duplicated description will be omitted.

[0018] [Radiation detector configuration] 1 is a schematic diagram showing the configuration of a radiation detector 100. The radiation detector 100 is a detector that can detect radiation by continuous exposure by switching a counter in synchronization with a trigger signal. The radiation detector 100 is a semiconductor detector having a zero- to two-dimensional data buffer function, but is preferably a one- or two-dimensional detector. The radiation to be detected is likely to function well when it is X-rays, but is not limited thereto and may be α-rays, β-rays, γ-rays, neutron rays, etc.

[0019] The radiation detector 100 includes a sensor 110 , a gate 115 , a detection circuit 120 , a switching circuit 130 , a first counter 140 a , a second counter 140 b , a setting and holding circuit 150 , a control circuit 160 and a readout circuit 170 .

[0020] The sensor 110 generates a pulse when a particle of radiation is detected. The sensor 110 generates a pulse when a particle of radiation is detected. The sensor 110 can detect the intensity of the X-ray flux incident on the light receiving surface as surface information.

[0021] Gate 115 is opened and closed by an electronic shutter in response to the transmission of the pulse. In the zero dead mode, gate 115 is always open, and the exposure time is continuous. Since a recovery time is required until the analog circuit is stable when it is cut off, opening and closing of gate 115 is not used. Note that the analog circuit is located before gate 115, and the digital circuit is located after it.

[0022] The detection circuit 120 judges whether the pulse is higher than a reference value, and if so, sends it as a voltage signal to one of the multiple counters 140a, 140b that is currently counting. The switching circuit 130 switches the counter that counts the voltage signal when it receives a counter switching signal from the control circuit 160.

[0023] Counter 140a (first counter) and counter 140b (second counter) have the same functions and are provided to be able to count pulses. In the example shown in Fig. 1, two counters are provided, but three or more counters may be provided. By switching the counters, exposure can be maintained without dead time.

[0024] The setting retention circuit 150 retains the setting of the off time when all of the multiple counters are turned off. The off time is the time when all of the multiple counters in the radiation detector 100 are turned off. The off time is preferably a time constant. This prevents overlapping of the times when the pulses exceed the thresholds in the multiple counters, thereby preventing double counting and counting errors. In this way, high-speed and highly accurate data can be obtained. The threshold is preset by the provider of the radiation detector 100.

[0025] The time constant is the time it takes for the pulse height to exceed a threshold. Strictly speaking, the time constant is determined for each pixel. The time constant here includes not only the time constant for each pixel, but also the global time constant (a statistical value such as the average value across the entire detection surface). It is preferable that the time constant is not a numerical value for a single point determined by the above definition, but has a width centered on the statistical value such that the standard deviation or double counting error for all pixels falls within the statistical error.

[0026] The control circuit 160 switches the counter that counts pulses among the multiple counters after a set off-time in synchronization with a signal received from an external device or an internally generated trigger signal. Specifically, in response to the trigger signal, it ends the counting of one of the counters that is currently counting, and starts the off-time whose setting is held by the setting holding circuit 150. Then, after the off-time ends, it starts the counting of the other counter.

[0027] This allows radiation to be detected without dead time by maintaining an exposure state in which radiation is continuously incident. It also makes it possible to suppress double counting, in which a single pulse is detected by multiple counters at the time of counter switching. Examples of signals received from external devices include signals that specify the time or position when the position of the arm or the position of the sample is changed. Note that the term "sample" refers to the object of analysis, and includes products.

[0028] The read circuit 170 reads the count value from the counter that has just finished counting between the timings of occurrence of the trigger signal. It is preferable to read the count value from the counter when the counter finishes counting and enters the off-time. While one counter is in the off-time and running, the count value is read from the other counter, so that the other counter can prepare to start counting for the next switchover. By finishing reading the count value from the counter early, the counter can be returned to a counting-enabled state at an early stage.

[0029] The radiation detector 100 is preferably a one-dimensional or two-dimensional detector. In a zero-dimensional detector, there are no adjacent pixels and charge sharing does not occur. In such a case, an option to increase the threshold and reduce the time constant as a method of suppressing double counting is also possible. In contrast, if the threshold is increased in a one-dimensional or two-dimensional detector, the charge sharing amount cannot be counted and a dead area is created. In the present invention, by providing an off time when switching the counter, even in a one-dimensional or two-dimensional detector, double counting can be suppressed without creating a dead area.

[0030] [Radiation detector operation] The operation of the radiation detector 100 configured as described above will now be described. Fig. 2 is a flow chart showing the operation of the radiation detector. First, radiation is irradiated onto a sample in a zero dead mode (step S1). When a particle of radiation that has entered the detection surface is detected by the sensor 110, a pulse is generated. First, one of the counters starts measuring radiation (step S2). The pulses are counted by one of the counters.

[0031] Then, when an external or internal trigger signal is received, the control circuit 160 causes one of the counters to end counting the pulses, and the read circuit 170 starts reading out the count data from the counter that has finished counting (step S3). At the same time, an off time starts (step S4). During the off time, neither counter counts.

[0032] After the off-time ends, the other counter starts counting pulses (step S5). While the other counter is continuing to count, the reading of the count data from the one counter that finished counting earlier is completed (step S6).

[0033] Thereafter, the radiation measuring device using the radiation detector 100 judges whether the measurement has been completed (step S7), and if the measurement has not been completed, returns to step S3, waits for a trigger signal, and switches the counter. In this manner, steps S3 to S7 are repeated until the measurement is completed. On the other hand, if it is judged in step 7 that the measurement has been completed, the counting is stopped and the measurement is completed.

[0034] By such an operation of the radiation detector 100, double counting is suppressed, and the count number I1 when a single exposure is performed with a single counter and the count number I when a continuous exposure is performed by switching between multiple counters are N This significantly reduces errors in continuous exposures with short exposure times.

[0035] Considering the case where radiation is incident at random timing and counting losses due to overlapping pulses can be ignored, the number of counts I1 when one frame is exposed by a single counter can be expressed as formula (1) using the exposure time T1 (s) and the average incident intensity I0 (cps).

number

[0036] Next, consider the case where multiple counters are switched for exposure. expis the exposure time for one frame, the number of counts when N images are taken is I N can be expressed by equation (2).

number

[0037] where T1 and T exp If the following relationship is set, the total exposure time is the same for both, so I1 and I N should match.

number

[0038] However, double counting occurs when the counter is switched, so in reality, N is expressed as equation (4).

number

[0039] τ is the time constant of the detector. Also, from equations (1), (3) and (4), I1 and I N The ratio is calculated.

number

[0040] From this formula, the increase in intensity due to double counting is τ / T exp I understand that. exp If is sufficiently long compared to τ, double counting is rare and the error is small, but if T exp If the off time is set to a short time, the probability of double counting increases, resulting in a large error. To solve this problem, the off time T off If we set, equation (4) can be rewritten as follows:

number

[0041] T off If the off time is set so that = τ, then equation (6) becomes equation (7).

number

[0042] Equation (8) is derived from equations (1), (3), and (7), and I N and I1 were shown to be consistent.

number

[0043] In this way, double counting is suppressed by inserting an off time, and measurements with fewer errors can be expected even with continuous short-time exposures. The number of detected photons relative to the number of incident photons falls on a theoretical curve that is specified based on the radiation source. This makes it possible to significantly suppress errors in measurements with short exposures when using a high-intensity radiation source.

[0044] The theoretical curve is expressed as the distribution of the probability of double counting versus the probability of counting incident photons per pixel (X-ray intensity). In the rightmost diagram of Figure 3 in Non-Patent Document 1, the theoretical curve is expressed by a solid line as a Poisson-Gamma (PG) distribution. In conventional radiation detectors, when a high-intensity radiation source is used, the probability of double counting can be higher than the value given by the theoretical curve during short-term exposure, but the present invention can reduce such occurrences. In particular, when the number of detected photons per pixel is 1×10 -4 More than 1×10 -2 In this range, double counting is prevented and the number of detected photons relative to the number of incident photons falls on a theoretical curve that is specified based on the radiation source.

[0045] For example, assuming that the pulse time constant τ is 100 ns, the exposure time Texp for one frame is 50 μs, and that the X-rays are incident at random times, the probability of double counting can be calculated as follows:

number

[0046] Assuming that the average intensity I of the incident X-rays is 2 Mcps and the number of images N is 10,000, the true count number can be calculated as follows.

number

[0047] On the other hand, if this method is not applied, the estimated count number can be calculated as follows.

number

[0048] Under these conditions, the error due to double counting (+2000 counts) is greater than the statistical error (±1000 counts) calculated using the square root of the true count number. The present invention is effective when such an error due to double counting is large.

[0049] [Preventing double counting] Fig. 3 is a timing chart showing an example of double count suppression. Fig. 3 shows the wave height of the pulse input to the counter circuit, the on / off of each counter that counts the pulse, and the count by the counter (similar to Fig. 4).

[0050] 3, in the radiation detector 100, the counter that counts is switched between counter 140a and counter 140b, so that the exposure time (Exp time) of each frame continues without interruption. The time constant of the pulse signal of the incident photon is about 100 ns, and the effect of suppressing double counting is particularly high when the exposure time Exp time per frame is set to 100 μs or less for measurement.

[0051] After one of the counters 140a and 140b finishes counting, it waits for an off time Ta, and then the other counter starts a counting time Tb. During the counting time Tb, the counter turns on and counts. The sum of the off time Ta and the counting time Tb corresponds to the conventional counting time. By providing the off time Ta, it is possible to prevent the counter from having sensitivity for that time due to the pulse width of the incident photon.

[0052] In the radiation detector 100 that operates in this way, if pulses P11 and P12 reach the counters as in the example of Fig. 10, pulse P12 enters counter 140a just before it turns off, and is counted only by counter 140a. At the timing when counter 140b turns on, pulse P12 is below the threshold, so pulse P12 is not counted by counter 140b.

[0053] In other words, the time when the pulse P12 exceeds the threshold overlaps with the count time Tb of the counter 140a, so the counter 140a counts the pulse P12. However, due to the existence of the off time Ta, the time when the pulse P12 exceeds the threshold does not overlap with the count time Tb of the counter 140b, so the counter 140b does not count the pulse P12. Therefore, in this case, double counting does not occur.

[0054] [Preventing counting errors] Fig. 4 is a timing chart showing an example of suppressing count losses. As shown in Fig. 4, in counters 140a and 140b, after one of the counters finishes counting, the other counter waits for an off-time Ta, and then starts a counting time Tb. The off-time Ta corresponds to the time constant of the pulse. The time constant of the pulse is, for example, about 100 ns.

[0055] In the radiation detector 100 that operates in this way, if the pulse P22 reaches the counter circuit, the pulse P22 enters the counter circuit after the counter 140a turns off and before the counter 140b turns on. In this case, when the counter 140b turns on after a waiting time of the time constant, the wave height of the pulse P22 still exceeds the threshold value, so it is counted by the counter 140b.

[0056] In other words, the time when the pulse P22 exceeds the threshold does not overlap with the counting time Tb of the counter 140a, so the counter 140a does not count the pulse P22. However, since the off-time Ta is set by the time constant of the pulse, the time when the pulse P22 exceeds the threshold overlaps with the counting time Tb of the counter 140b, so the counter 140b counts the pulse P22. Therefore, in this case, no counting loss occurs. In this way, even though there is a gap in the counting time, by setting the gap equal to the time constant of the pulse, measurement without counting loss is realized.

[0057] [Application example] The radiation detector 100 is particularly suitable for XPCS measurements and ultra-fine slice single crystal structure analysis, which require a short exposure time. If high-speed measurements are not performed, the error due to double counting is buried in statistical errors. However, if high-speed measurements are possible in zero-deadband mode, this error becomes non-negligible. In particular, if the exposure time is shortened in zero-deadband mode, the error due to double counting becomes significant, so suppressing double counting becomes important.

[0058] The radiation detector 100 can be used for radiation measurement in continuous exposure by being mounted on a radiation measurement device. Fig. 5 is a schematic diagram showing the configuration of a radiation measurement device 200. The radiation measurement device 200 includes a radiation source 210, a sample holder 220, and the radiation detector 100.

[0059] The radiation source 210 continuously irradiates radiation. The sample holder 220 holds the sample S. The radiation detector 100 enables measurements that suppress double counting and counting errors caused by switching the counter. This makes it possible to obtain highly accurate data in single crystal structure analysis, XPCS, and the like.

[0060] FIG. 6 is a schematic diagram showing the imaging of multiple frames. In single crystal structure analysis, multiple images are taken while moving the goniometer, and the images are added together to perform the analysis. When analyzing with only one frame of image, double counting does not occur, but when these images are added together to calculate the intensity, an error occurs in the conventional method due to the effect of double counting caused by counter switching. Intensity is extremely important in single crystal structure analysis, and if the error becomes large, the accuracy of the structure analysis deteriorates. In the present invention, the piled-up radiation intensity is equal to the intensity of one frame multiplied by N, so that measurements can be made with any settings without worrying about errors according to the exposure time or the number of piled-up images.

[0061] In XPCS (X-ray Photon Correlation Spectroscopy) measurements, coherent X-rays are irradiated onto a moving particle and the time change (fluctuation) of the scattering intensity is measured. In order to observe the fast movement of particles, the exposure time must be shorter than the particle fluctuation time, so the scattering intensity of each frame is inevitably small. Furthermore, because coherent X-rays are used, the scattering intensity becomes even smaller. Therefore, in XPCS measurements, the scattering intensity per frame is very small.

[0062] For this reason, XPCS measurements require small errors even under conditions of short exposure and low intensity. When double counting occurs and the scattering intensity of one frame becomes high, the contrast between the images before and after it becomes large (or small). As a result, errors become prominent in the short time domain, making it impossible to accurately measure the fast movement of particles. In such cases, the present invention, which suppresses double counting and counting errors, is particularly effective.

[0063] (Single crystal analysis equipment) As a specific example, an example in which the radiation detector 100 is incorporated into an X-ray analysis device will be described. Fig. 7 is a plan view showing an X-ray analysis device 300 as an example of a radiation measurement device. The X-ray analysis device 300 is a single crystal structure analysis device for taking an X-ray diffraction image, and includes an X-ray source 310, a sample stage 320, an arm 330, a control unit, and the radiation detector 100. The X-ray source 310 continuously irradiates the sample S0 with X-rays.

[0064] The radiation detector 100 can control the amount to be measured by the signal from the goniometer while in the exposure state, and output the measurement data in synchronization with the goniometer signal. Continuous exposure improves the throughput of the measurement time and suppresses double counting and counting errors.

[0065] The sample stage 320 and the arm 330 are linked and can be rotated around the sample S0 at a constant speed under the control of the control unit. The radiation detector 100 is provided at the end of the arm 330, and its movement around the sample S0 together with the arm 330 is controlled.

[0066] The X-ray analysis apparatus 300 has the radiation detector 100 as described above, and thus can count X-rays with continuous exposure without dead time by switching the counter using, for example, an arm movement control signal from the control unit as a trigger signal.

[0067] (Production line) 8 is a side view showing an X-ray analysis device 400 as an example of a radiation measurement device. The X-ray analysis device 400 is a production line capable of inspection by X-rays, and includes an X-ray source 410, a roller 420, a belt 425, a control unit 440, and a radiation detector 100. The X-ray source 410 continuously irradiates X-rays onto a product S1.

[0068] The belt 425 moves due to the rotation of the roller 420, and moves the product S1 in the direction of the arrow in the figure. The belt 425 moves at a constant speed under the control of the control unit 440. The radiation detector 100 is provided on the opposite side of the X-ray source 410 with the belt 425 and the product S1 in between, and controls the movement of the product S1 together with the belt 425.

[0069] The X-ray analysis device 400, having the above-mentioned radiation detector 100, can count X-rays with continuous exposure without dead time by switching the counter using, for example, a belt control signal from the control unit 440 as a trigger signal. In this case, double counting and counting errors can be suppressed.

[0070] [Radiation detector settings] In order for the radiation detector 100 to function, not only is it necessary to have a counter switching mechanism, but it is also necessary to set the off time, which must be set by an operator with specialized knowledge.

[0071] 9 is a schematic diagram showing the configuration of the radiation detector 100 during setup. When the radiation detector 100 is used by a user without setting the off time, an operator on the provider's side sets the off time. To set the off time, it is necessary to connect a computer 500 to the radiation detector 100. The operator operates the computer 500 to set the internal circuitry of the radiation detector 100.

[0072] First, the computer 500 displays a setting screen for the radiation detector 100 and receives input from an operator to set the off time. The computer 500 then stores the input setting in the radiation detector. This allows an update to be performed to set the off time in the radiation detector capable of continuous exposure by switching the counter, and makes it possible to obtain highly accurate data by suppressing double counting.

[0073] [Example] XPCS measurements were performed on a specific sample using a conventional radiation detector and the radiation detector 100 of the present invention. Measurement results were obtained as a comparative example and an example. Figures 11(a) and (b) are both graphs showing the XPCS measurement results of the comparative example (using burst mode and zero dead zone mode, respectively). Figures 12(a) and (b) are both graphs showing the XPCS measurement results of the example (using burst mode and zero dead zone mode, respectively).

[0074] The horizontal axis represents time, and the vertical axis represents the correlation function calculated from the time change of X-ray intensity. In the measurement results shown in Figures 11(a) and (b), it can be seen that the leftmost point (circled point) is significantly off. The phenomenon in which the value at the leftmost point (minimum time) is off occurs when one incident photon is double-counted, resulting in counting pulses across two adjacent frames.

[0075] In XPCS measurement, it is extremely important to accurately measure the time change of X-ray intensity. When double counting occurs at the time of counter switching, pulses are always counted across two adjacent frames. As a result, the minimum time point (≒Exp time) calculated from the intensity change of adjacent frames is significantly different from the true value.

[0076] On the other hand, when the present invention is applied, double counting does not occur even if X-rays are incident when the counter is switched, so the temporal change in X-ray intensity can be accurately captured. Therefore, as shown in Figures 12(a) and (b), the value does not deviate even at the point of minimum time, and an accurate correlation function can be obtained. In other words, the correlation function plot becomes continuous. In this way, it has been demonstrated that the present invention is extremely effective in accurately measuring the change in X-ray intensity over an extremely short time. [Explanation of symbols]

[0077] 100 Radiation detector 110 Sensors Gate 115 120 Detection circuit 130 Switching Circuit 140a First Counter 140b Second Counter 150 Setting retention circuit 160 Control circuit 170 Readout circuit 200 Radiation measuring device 210 Radiation Source 220 Sample holder 300 X-ray analyzer 310 X-ray source 320 Sample stage 330 Arm 400 X-ray analyzer 410 X-ray source 420 Lola 425 Belt 440 Control Unit 500 Computers S, S0 sample S1 Products P01, P02, P11, P12, P21, P22 Pulse Ta Off time Tb Counting time

Claims

1. A radiation detector capable of detecting radiation with continuous exposure, comprising: a sensor that generates a pulse when a particle of radiation is detected; A plurality of counters each capable of counting pulses; a setting retention circuit for retaining a setting of an off time for turning off any of the plurality of counters; a control circuit for switching a counter that counts pulses after a set off time in response to a trigger signal.

2. 2. The radiation detector according to claim 1, wherein the off time is a time constant.

3. 2. The radiation detector according to claim 1, wherein the number of detected photons relative to the number of incident photons falls on a theoretical curve specified based on the radiation source.

4. 3. The radiation detector according to claim 1, which is a one-dimensional or two-dimensional detector.

5. A radiation measurement device capable of measuring radiation by continuous exposure, comprising: A radiation source that continuously emits radiation; A sample holder for holding a sample; A radiation measuring device comprising: the radiation detector according to claim 1 or 2.

6. A method for setting a radiation detector for detecting radiation by continuous exposure, comprising the steps of: receiving an input for setting an off time for turning off all of a plurality of counters included in the radiation detector; and causing the radiation detector to retain the input settings.

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