Pulse Height Analyzer and Radioactivity Measuring Device

Abstract

To provide a pulse wave height analyzer and a radioactivity measuring device that can make it possible to perform digital pulse signal processing in real-time while preventing the increase of differential non-linearity errors in digital calculations.SOLUTION: A pulse wave height analyzer 14 generates wave height distribution data having a count that can be mapped to each of a plurality of channels by digital operations on digital signals of signal pulses output from a radiation detector 11. A processing unit 24 of the pulse wave height analyzer 14 maps at least one pre-conversion channel to at least one post-conversion channel and also distribute the counts that are mapped to the at least one pre-conversion channel to the at least one post-conversion channel according to digital amplification when converting channels by predetermined digital amplification for a digital signal.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a pulse height analyzer and a radioactivity measuring device.

Background Art

[0002] Conventionally, for example, in order to suppress an increase in the error of differential non-linearity due to digital operations between pulse height spectra, etc., a method of correcting the channel width using a real-number histogram is known (see, for example, Non-Patent Document 1).

Prior Art Documents

Non-Patent Documents

[0003]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Non-Patent Document 1 is an example applied to the pulse height distribution data after measurement. However, in digital pulse signal processing by, for example, a digital MCA (Multi Channel Analyzer), it corresponds to digital gain processing, and it is desired to be processed in real time for each event (one count) of radiation.

[0005] An object of the present invention is to provide a pulse height analyzer and a radioactivity measuring device capable of performing digital pulse signal processing in real time while suppressing an increase in the error of differential non-linearity in digital operations.

Means for Solving the Problems

[0006] In order to solve the above problems and achieve the above object, the present invention adopts the following aspects. (1) A pulse height analyzer according to one aspect of the present invention is a pulse height analyzer that generates pulse height distribution data having counts associated with each of a plurality of channels by digital operations on digital signals of signal pulses output from a radiation detector. When converting the channels by a predetermined digital amplification of the digital signals, at least one channel before conversion is associated with at least one channel after conversion, and the count associated with the at least one channel before conversion is distributed to the at least one channel after conversion according to the digital amplification. The processing unit is provided, and the processing unit adds 1 to the integer count value of the channel where the fractional part of the real integrated count value is carried over.

[0007] (2) A pulse height analyzer according to one aspect of the present invention is a pulse height analyzer that generates pulse height distribution data having counts associated with each of a plurality of channels by digital operations on digital signals of signal pulses output from a radiation detector. When converting the channels by a predetermined digital amplification of the digital signals, at least one channel before conversion is associated with at least one channel after conversion, and the count associated with the at least one channel before conversion is distributed to the at least one channel after conversion according to the digital amplification. The processing unit is provided, and when the processing unit associates one channel before conversion with one or more channels after conversion by the digital amplification and performs channel conversion for each input of one event of the digital signal, after the input of the one event, the integrated value obtained by distributing the one count associated with the one channel before conversion to the one or more channels after conversion as a real count value and the integrated value of the integer count values of the same channels before the input of the one event are obtained. The difference may be obtained, and the one count may be distributed only to the channel having the largest difference and assigned to the integer count value.

[0008] (3) In the pulse height analysis device according to (1) above, the processing unit uses the predetermined digital amplification as logarithmic amplification (logarithmic conversion), and when the digital amplification associates one of the channels before conversion with one or more channels after conversion and sequentially performs conversion from the minimum channel to the maximum channel of the pulse height distribution data, the count associated with the one channel before conversion is associated with the one or more channels after conversion and the integrated value distributed as a real-valued count value is divided into an integer part and a fractional part (fractional part), and the fractional part may be associated with 1 count to the channel where the integrated value is rounded up to an integer and distributed as an integer-valued count value.

[0009] (4) The radiation measurement device according to one aspect of the present invention includes the pulse height analysis device according to at least any one of (1) to (3) above, a radiation detector that outputs the signal pulse, and a converter that converts the signal pulse or an amplified pulse obtained by amplifying the signal pulse into the digital signal at a predetermined sampling frequency.

Advantages of the Invention

[0010] According to (1) above, by providing a processing unit that distributes the count of one channel before conversion to a plurality of channels after conversion according to digital amplification or arranges the counts of a plurality of channels before conversion to one channel after conversion, appropriate digital pulse signal processing can be executed while suppressing an increase in the differential non-linearity error. For example, even when the number of bits of the ADC is small or the shaping time (time constant) of the digital filter is short, an increase in the differential non-linearity error can be suppressed.

[0011] In the case of the above (2), by providing a processing unit that adds 1 to the integer count value of the channel where the difference between the real-valued integrated count value after the input of one event and the integer-valued integrated count value before the input of one event is maximized, it is possible to generate integer-valued wave height distribution data that is accurately approximated to the real number type while suppressing an increase in rounding error. By adding 1 count to the integer count value of an appropriate one channel after conversion for each event, it is possible to execute digital pulse signal processing suitable for real-time measurement and the like.

[0012] In the case of the above (3), by providing a processing unit that adds 1 to the integer count value of the channel where the fractional part (decimal part) of the real-valued integrated count value is carried over when conversion is sequentially performed from the minimum channel to the maximum channel, it is possible to generate integer-valued wave height distribution data that is accurately approximated to the real number type while suppressing an increase in rounding error. By sequentially batch-converting the counts of all channels, it is useful in cases such as when the display scale is logarithmically converted.

[0013] According to the above (4), by providing a pulse height analyzer that executes appropriate digital pulse signal processing while suppressing an increase in the error of differential non-linearity in digital operations, it is possible to improve the accuracy and convenience of radioactivity measurement.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0015] Hereinafter, a radioactivity measuring device including a pulse height analyzer according to an embodiment of the present invention will be described with reference to the accompanying drawings.

[0016] FIG. 1 is a diagram showing a schematic configuration of a radioactivity measuring device 10 equipped with a pulse height analyzer 14 according to an embodiment. The radioactivity measuring device 10 of the embodiment includes a radiation detector 11, a preamplifier 12, a high-speed ADC 13, and a pulse height analyzer 14.

[0017] The radiation detector 11 is a semiconductor detector made of, for example, germanium, etc. The radiation detector 11 detects radiation (for example, gamma rays, X-rays, and beta rays) emitted from a sample, etc. The radiation detector 11 outputs a signal pulse having a peak value according to the energy of the radiation to be detected. The preamplifier 12 amplifies the analog signal pulse output from the radiation detector 11 . A high-speed ADC (Analog to Digital Converter) 13 converts the analog signal pulses output from the preamplifier 12 into digital signal pulses at a predetermined sampling frequency.

[0018] The pulse height analyzer 14 is, for example, a digital MCA (Multi Channel Analyzer) that performs real-time digital signal processing. The pulse height analyzer 14 includes, for example, a digital filter 21, an input unit 22, an output unit 23, and a processing unit 24. The digital filter 21 performs digital signal processing for pulse detection such as waveform shaping (e.g., triangular wave shaping or trapezoidal wave shaping), pole-zero adjustment, pulse height discrimination, amplification by digital gain, and timing detection on the digital signal pulses input from the preamplifier 12. The digital filter 21 is realized by, for example, an FPGA (Field Programmable Gate Array).

[0019] The input unit 22 includes, for example, a touch panel that outputs a signal according to an operator's input operation, various switches, or a keyboard. The input unit 22 transmits a signal according to the operator's input operation to the digital filter 21 and the processing unit 24. The output unit 23 includes a display device such as a touch panel and displays various data and information received from the processing unit 24.

[0020] The processing unit 24 is a software functional unit that functions when a predetermined program is executed by a processor such as a CPU (Central Processing Unit). The software functional unit is an ECU (Electronic Control Unit) that includes a processor such as a CPU, a ROM (Read Only Memory) that stores the program, a RAM (Random Access Memory) that temporarily stores data, and electronic circuits such as a timer. At least a part of the processing unit 24 may be an integrated circuit such as an LSI (Large Scale Integration). In the embodiment shown in FIG. 1, the digital filter 21 and the processing unit 24 are separate components, but it is not limited thereto. They may be components having functions that are mutually compatible, or, for example, an FPGA that processes histogram creation including digital gain processing may be provided.

[0021] The processing unit 24 performs digital signal processing such as peak amplitude value detection and histogram creation of the peak amplitude value on the pulse signal output from the digital filter 21 according to the signal etc. input from the input unit 22. The histogram of the peak amplitude value is wave height distribution data showing the correspondence between the channel indicating the peak amplitude value and the count for each channel. The histogram of the peak amplitude value is, for example, an energy spectrum when the radiation detector 11 outputs a signal pulse having a wave height value corresponding to the energy of radiation.

[0022] (Gain amplification) The processing unit 24 performs gain amplification processing for digitally amplifying the pulse signal by a predetermined gain r. The processing unit 24 performs digital amplification, for example, by distributing the count of one channel before conversion of the wave height distribution data to a plurality of channels after conversion or arranging the counts of a plurality of channels before conversion to one channel after conversion.

[0023] An example in the case where the predetermined gain r is an appropriate value from 0.5 to 1.5 will be described below. When the processing unit 24 performs gain amplification with a predetermined gain r (0.5 ≤ r ≤ 1.5) that is an appropriate value from 0.5 to 1.5, for example, the count c of channel n before conversion (that is, before amplification) is distributed to the counts in the channel range after conversion (that is, after amplification). The channel range after conversion is the range from channel (INT(n×r)) to channel (INT(n×r)+2) by the INT function indicating integerization by rounding down. That is, the count c of channel n before conversion is distributed from a minimum of one channel to a maximum of three channels according to the gain r. The range of the real channel after conversion obtained by the channel n before conversion and the gain r is the range from the first real channel d1 (=n×r) to the second real channel d2 (=d1+r=(n+1)×r). The range of the integer channel after conversion corresponding to the range of the real channel after conversion is the range from the first integer channel n1 (=INT(d1)) to the second integer channel n2 (=INT(d2)).

[0024] The counts c0 of the converted integer channel n1, the count c1 of the converted integer channel (n1 + 1), and the count c2 of the converted integer channel (n1 + 2) are described as shown in any of the following formulas (1), (2), and (3) according to the first integer channel n1 and the second integer channel n2. When the difference between the first integer channel n1 and the second integer channel n2 is zero (that is, when n2 - n1 = 0), each count c0, c1, c2 is described as shown in the following formula (1). That is, the count c of the channel n before conversion is arranged only in the converted integer channel n1.

[0025]

Number

[0026] When the difference between the first integer channel n1 and the second integer channel n2 is 1 (that is, when n2 - n1 = 1), each count c0, c1, c2 is described as shown in the following formula (2). That is, the count c of the channel n before conversion is distributed to the two converted integer channels n1, (n1 + 1).

[0027]

Number

[0028] When the difference between the first integer channel n1 and the second integer channel n2 is 2 (that is, when n2 - n1 = 2), each count c0, c1, c2 is described as shown in the following formula (3). That is, the count c of the channel n before conversion is distributed to the three converted integer channels n1, (n1 + 1), (n1 + 2).

[0029]

Number

[0030] FIG. 2 is a diagram showing an example of digital gain amplification (×1.1) in the pulse height analyzer 14 of the embodiment. FIG. 3 is a diagram showing an example of the count before distribution and the count after distribution in the pulse height analyzer 14 of the embodiment. As shown in FIGS. 2 and 3, for example, when the gain r is 1.1 (r = 1.1), as shown in the above formula (2) or formula (3), the count c of channel n before conversion is distributed to two integer channels n1, (n1 + 1) or three integer channels n1, (n1 + 1), (n1 + 2) after conversion.

[0031] For example, as shown in FIG. 2, the count N0 of channel 0 before conversion (before channel amplification) is distributed to the count (N0 / 1.1) of channel 0 after conversion (after channel amplification) and the count (N0×0.1 / 1.1) of channel 1. The count N1 of channel 1 before conversion is distributed to the count (N1×0.9 / 1.1) of channel 1 after conversion and the count (N1×0.2 / 1.1) of channel 2 after conversion. Thus, the count of channel 1 after conversion is the count obtained by adding the count (N0×0.1 / 1.1) and the count (N1×0.9 / 1.1).

[0032] For example, as shown in FIG. 3, for the count N0 (= 11), count N1 (= 22), count N2 (= 33), and count N3 (= 11) of channels 0, 1, 2, and 3 before conversion, the count of channel 0 after conversion is N0 / 1.1 = 10. The count of channel 1 after conversion is (N0×0.1 / 1.1 + N1×0.9 / 1.1 = 19), the count of channel 2 after conversion is (N1×0.2 / 1.1 + N2×0.8 / 1.1 = 28), and the count of channel 3 after conversion is (N2×0.3 / 1.1 + N3×0.7 / 1.1 = 16).

[0033] FIG. 4 is a diagram showing examples of the spectra before and after amplification of the example and the comparative example in the pulse height analyzer 14 of the embodiment. The example shown in Fig. 4 (after count distribution) is an example in which channels are converted by a gain r (= 1.1) and counts are distributed to the converted channels. In the example, the wave height distribution data by the channels before conversion (before channel amplification) and the wave height distribution data (after channel amplification) obtained by multiplying the channels before conversion by a predetermined gain r (= 1.1) and distributing the counts to the converted channels are shown. The comparative example shown in Fig. 4 (without count distribution) is an example in which channels are simply converted by a gain r (= 1.1). In the comparative example, the wave height distribution data by the channels before conversion (before channel amplification) and the wave height distribution data (after channel amplification) obtained by multiplying the channels before conversion by a predetermined gain r (= 1.1) are shown.

[0034] In the comparative example, as the channels after conversion are rounded down (truncated) without count distribution, channels where the increase or decrease in counts is specifically increased occur, such as channels where the count becomes zero. On the other hand, in the example, as the channels after conversion are rounded down and counts are distributed, channels where the increase or decrease in specific counts is increased do not occur. Also, in the example, the peak shape changes correctly (analogously) according to the gain r.

[0035] Fig. 5 is a diagram showing an example of digital gain amplification (×0.9) in the pulse wave height analyzer 14 of the embodiment. As shown in Fig. 5, for example, when the gain r is 0.9 (r = 0.9), as shown in the above formula (1) or the above formula (2), the count c of the channel n before conversion is distributed to one integer channel n1 after conversion or two integer channels n1, (n1 + 1) after conversion. For example, as shown in FIG. 5, the count N0 of channel 0 before conversion (before channel amplification) is arranged in channel 0 after conversion (after channel amplification). The count N1 of channel 1 before conversion is distributed to the count of channel 0 after conversion (N1×0.1 / 0.9) and the count of channel 1 (N1×0.8 / 0.9). Thus, the count of channel 0 after conversion becomes the count obtained by adding count N0 and count (N1×0.1 / 0.9). The count N2 of channel 2 before conversion is distributed to the count of channel 1 after conversion (N2×0.2 / 0.9) and the count of channel 2 after conversion (N2×0.7 / 0.9). Thus, the count of channel 1 after conversion becomes the count obtained by adding count (N1×0.8 / 0.9) and count (N2×0.2 / 0.9).

[0036] Table 1 below shows, for each of the gains r being 1.1, 0.8, and 1.21, the channel n before conversion, the count c of channel n, the destination real channel indicating the range of the real channel after conversion (first real channel d1(=n×r)~second real channel d2(=d1+r=(n + 1)×r)), the destination integer channel indicating the range of the integer channel after conversion (first integer channel n1(=INT(d1))~second integer channel n2(=INT(d2))), the first destination count C(INT(n×r)) indicating the count c0 of the integer channel n1 after conversion, the second destination count C(INT(n×r)+1) indicating the count c1 of the integer channel (n1 + 1) after conversion, and the third destination count C(INT(n×r)+2) indicating the count c2 of the integer channel (n1 + 2) after conversion.

[0037]

Table 1

[0038] (Logarithmic conversion) The processing unit 24 performs a logarithmic conversion process of converting the channels of the wave height distribution data from a linear scale to a logarithmic scale by digitally logarithmically amplifying the pulse signal. For example, the processing unit 24 performs logarithmic conversion by distributing the count of one channel before conversion to a plurality of channels after conversion or arranging the counts of a plurality of channels before conversion to one channel after conversion.

[0039] An example in the case where the number of channels is 10 bits on a logarithmic scale with base 10 will be described below. FIG. 6 is a diagram showing an example of digital logarithmic conversion in the pulse wave height analyzer 14 of the embodiment. Table 2 below shows the channel n before conversion, the count c of channel n, the Log channel after conversion, the Log channel (scaled) when normalized to Log(1024)=1023, the destination channel for the count c described by an integer corresponding to the Log channel (scaled), and an example of the count for each destination channel.

[0040]

Table 2

[0041] As shown in Table 2 above, when the adjacent channel interval of the Log channel (scaled) after conversion is 1 or more, the processing unit 24 distributes the count c of one channel n before conversion to a plurality of destination channels. On the other hand, when the adjacent channel interval of the Log channel (scaled) after conversion is less than 1, the processing unit 24 arranges the counts c of a plurality of channels n before conversion to one destination channel. The destination channel is an integer-type channel corresponding to the Log channel (scaled) after conversion. For example, in the case of the channel n (= 1) before conversion shown in FIG. 6 and Table 2 above, the Log channel (scaled) is 102.300, and the destination channel is an integer channel from 1 to 103. From 1 to 102 of the destination channels, the count c (= N1) of the channel n (= 1) before conversion is evenly distributed, and at the end (boundary) channel 103, the count c (= N1) of the channel n (= 1) before conversion and the count c2 (= N2) of the channel n + 1 (= 2) before conversion are combined according to the ratio of the channel widths of the Log channel (scaled) and the destination channel.

[0042] When the processing unit 24 arranges the counts c of a plurality of channels n before conversion in one destination channel because the adjacent channel interval of the Log channel (scaled) after conversion is less than 1, at the end (boundary) of the Log channel after conversion, the count c is distributed according to the ratio of the channel widths of the Log channel (scaled) and the destination channel. The ends (boundaries) of the Log channel after conversion are, for example, between Log1010 and Log1011 and between Log1017 and Log1018 shown in Table 2 above. For example, in the case of the channel n (= 1017) before conversion, the count c (= N1017) is distributed to the two destination channels 1022 and 1023 according to the ratio of the channel widths of each of Log1017 and Log1018 of the Log channel (scaled) and 1022 of the destination channel.

[0043] FIG. 7 is a diagram showing examples of the pre-conversion spectrum (Linear) and the post-conversion spectrum (Log) of the example and the comparative example in the pulse height analyzer 14 of the embodiment. The example shown in FIG. 7 is an example of converting the channel from a linear scale to a logarithmic scale and distributing the count to the channel after conversion. In the example, the wave height distribution data (Linear) in which the count c of each channel n before conversion is 100 and the wave height distribution data (Log) obtained by distributing the count c to the destination channel according to the Log channel (scaled) after conversion are shown. The comparative example shown in Fig. 7 is simply an example of converting channels from a linear scale to a logarithmic scale. In the comparative example, wave height distribution data (Linear) where the count c of each channel n before conversion is 100 and wave height distribution data (Log) obtained by the Log channel (scaled) after conversion without count distribution are shown.

[0044] In the comparative example, after scale conversion, the intervals between adjacent Log channels are unequal intervals (i.e., logarithmic intervals), and the count values obtained by dividing the count c by the intervals between adjacent Log channels without count distribution are arranged in association with the Log channel (scaled). As a result, as the Log channel increases, the interval between Log channels becomes less than 1 and narrows, and the count value per channel associated with the Log channel (scaled) increases excessively. Along with this, for example, there arises a problem that the integrated value of the count values associated with all Log channels (scaled) becomes larger than the integrated value of the counts c of all channels n before conversion. In contrast, in the embodiment, after scale conversion, by performing count distribution, the intervals between adjacent destination channels are equal intervals (i.e., 1), and the integrated value of the counts of all destination channels is the same as the integrated value of the counts c of all channels n before conversion.

[0045] (Integerization) If the processing unit 24 regards channel conversion such as the gain amplification and logarithmic conversion described above as a function in display, it may generate wave height distribution data based on the real - type count values obtained by count distribution. However, as a general function of the pulse wave height analyzer 14, integer - type wave height distribution data may be generated such that 1 is added to the count of one channel for each event. For example, when the processing unit 24 performs channel conversion on the digital signal pulses for each event input to the pulse height analyzer 14, it obtains the difference between the real-valued count value (i.e., the integrated value since the start of measurement) after the input of one event and the integer-valued count value (i.e., the integrated value since the start of measurement) before the input of one event within the channel range of the distribution destination for one count, and generates an integer-valued count value by adding 1 to the count of the channel with the largest difference.

[0046] For example, for each event sequentially input to the pulse height analyzer 14, when a predetermined channel n (= n0) before conversion corresponds to three channels after conversion (destination integer channels), namely channel n1, channel (n1 + 1), and channel (n1 + 2), the one count associated with the channel n (= n0) before conversion is distributed to the three channels n1, (n1 + 1), and (n1 + 2) after conversion. In the following example, the counts (real-valued count values) distributed to each of the three channels n1, (n1 + 1), and (n1 + 2) after conversion are, for example, 0.2, 0.3, and 0.5 in sequence. It is assumed that the same event is continuously input (counted up for the same channel).

[0047] First, when the real and integer integrated counts (count values integrated from the start of measurement) of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) before the input of 1 event are zero, the real integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) after the input of 1 event are approximately 0.2, 0.3, and 0.5 in sequence. Thereby, 1 count associated with the channel n (= n0) before conversion is associated only with the channel (n1 + 2) among the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) where the difference between the real integrated count after the input of 1 event and the integer integrated count before the input of 1 event is the largest (= 0.5), and is allocated to the integer count value of the channel (n1 + 2). The integer integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) after the input of 1 event are 0, 0, and 1 in sequence.

[0048] Next, the real integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) before the input of a new 1 event are 0.2, 0.3, and 0.5 in sequence, and the integer integrated counts are 0, 0, and 1 in sequence. When allocating 1 count associated with the channel n (= n0) before conversion to the three converted channels n1, channel (n1 + 1), and channel (n1 + 2), the real integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) are 0.4, 0.6, and 1.0 in sequence. Thereby, 1 count associated with the channel n (= n0) before conversion is associated only with the channel (n1 + 1) among the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) where the difference between the real integrated count after the input of the new 1 event and the integer integrated count before the input of the new 1 event is the largest (= 0.6), and is allocated to the integer count value of the channel (n1 + 1). The integer integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) after the input of the new 1 event are 0, 1, and 1 in sequence.

[0049] Next, the real-valued integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) before the input of a new 1 event are sequentially 0.4, 0.6, and 1.0, and the integer-valued integrated counts are sequentially 0, 1, and 1. When distributing 1 count associated with the channel n (= n0) before conversion to the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) after the input of a new 1 event, the real-valued integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) are sequentially 0.6, 0.9, and 1.5. As a result, 1 count associated with the channel n (= n0) before conversion is only associated with the channel n1 where the difference between the real-valued integrated count after the input of the new 1 event and the integer-valued integrated count before the input of the new 1 event is the largest (= 0.6) among the three converted channels n1, channel (n1 + 1), and channel (n1 + 2), and is allocated to the integer-valued count value of the channel n1. The integer-valued integrated counts of each of the three converted channels n1, channel (n1 + 1), and channel (n1 + 2) after the input of the new 1 event are sequentially 1, 1, and 1.

[0050] As described above, the pulse height analyzer 14 of the embodiment distributes the count of one channel before conversion to a plurality of channels after conversion or arranges the counts of a plurality of channels before conversion to one channel after conversion according to digital amplification such as gain amplification and logarithmic conversion. Thereby, appropriate digital pulse signal processing can be executed while suppressing an increase in the differential non-linearity error. For example, even when the number of bits of the ADC is small or the shaping time (time constant) of the digital filter is short, an increase in the differential non-linearity error can be suppressed. For example, in the case of gain amplification, it is possible to suppress the occurrence of a channel in which a specific increase or decrease in count increases. For example, in the case of logarithmic conversion, the intervals between adjacent destination channels are equal intervals (i.e., 1), and the accuracy can be improved by detecting the maximum energy of the beta-ray spectrum or the like. Also, the integrated value of the counts of all the destination channels is the same as the integrated value of the counts c of all the channels n before conversion, and appropriate conversion can be performed.

[0051] By providing a processing unit 24 that adds 1 to the integer count value of the channel where the difference between the real-valued integrated count value after the input of one event and the integer-valued integrated count value before the input of one event is maximized, it is possible to generate integer-valued pulse height distribution data that is accurately approximated to the real-valued type while suppressing an increase in rounding error. By adding 1 count to the integer count value of an appropriate one channel after conversion for each event, digital pulse signal processing suitable for real-time measurement or the like can be executed.

[0052] The radioactivity measurement device 10 of the embodiment includes a pulse height analyzer 14 that executes appropriate digital pulse signal processing while suppressing an increase in the error of differential non-linearity in digital calculation, thereby improving the accuracy and convenience of radioactivity measurement.

[0053] (Modification example) Hereinafter, a modification example of the embodiment will be described. Note that the same parts as those in the above-described embodiment are denoted by the same reference numerals, and the description thereof is omitted or simplified.

[0054] In the above-described embodiment, the processing unit 24 generates an integer count value by adding 1 to the count of the channel where the difference between the real-valued count value after the input of one event and the integer-valued count value before the input of one event is the largest for each event process, but the present invention is not limited to this. For example, instead of performing the above-described logarithmic conversion for each event, the processing unit 24 may sequentially perform the conversion from one channel, accumulate the counts separately for the integer part and the fractional part (mantissa part), and generate an integer-type count value by adding 1 to the count of the channel where the accumulated value of the fractional part is rounded up to an integer.

[0055] In the above-described embodiment, the processing unit 24 of the pulse height analyzer 14 is assumed to operate in response to various command signals input from the input unit 22, but it is not limited thereto. For example, it may operate in response to various command signals input from an external device such as a personal computer.

[0056] The embodiments of the present invention are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, as well as in the invention described in the claims and its equivalent scope.

Explanation of Reference Numerals

[0057] 10... Radioactivity measurement device, 11... Radiation detector, 12... Preamplifier, 13... High-speed ADC (converter), 14... Pulse height analyzer, 21... Digital filter, 22... Input unit, 23... Output unit, 24... Processing unit.

Claims

1. A pulse height analysis device that generates pulse height distribution data having counts associated with each of a plurality of channels by digital operation on a digital signal of a signal pulse output from a radiation detector, when converting the channel by a predetermined digital amplification of the digital signal, at least one channel before conversion is associated with at least one channel after conversion, and the count associated with the at least one channel before conversion is associated with the at least one channel after conversion according to the digital amplification and arranged, comprising a processing unit, the processing unit adds 1 to the integer count value of the channel where the fractional part of the real-valued integrated count value overflows, A pulse height analysis device characterized by this.

2. The processing unit, the predetermined digital amplification is logarithmic amplification, when associating one channel before conversion with one or a plurality of channels after conversion by the digital amplification and performing conversion sequentially from the smallest channel to the largest channel of the pulse height distribution data, the integrated value obtained by dividing the count associated with the one channel before conversion into an integer part and a fractional part and associating the fractional part with 1 count for the channel where the integrated value overflows and arranging it as an integer count value, The pulse height analysis device according to Claim 1, characterized by this.

3. The pulse height analysis device according to Claim 1 or Claim 2, a radiation detector that outputs the signal pulse, a converter that converts the signal pulse or an amplified pulse obtained by amplification of the signal pulse into the digital signal at a predetermined sampling frequency, Comprising A radioactivity measurement device characterized by this.

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