JP6964877B2 - Positron annihilation life measuring device, adjustment method of radiation measuring instrument, radiation measuring instrument - Google Patents

Description

The present invention relates to a positron annihilation lifetime measuring device for analyzing various structures of a substance by measuring the lifetime of positrons in the substance. Further, the present invention relates to a method for adjusting a radiation measuring instrument when measuring radiation using a plurality of radiation detectors at the same time. It also relates to a radiation measuring instrument in which a plurality of radiation detectors are used at the same time.

By measuring the lifetime of positrons in a substance, information on pores and various point defects in crystals of metals, semiconductors, etc. can be obtained. In addition, information on nanoscale voids can be obtained from sub-nano in insulators such as polymers. For this reason, a positron annihilation lifetime measurement method is used in which a substance is irradiated with positrons and its lifetime in the substance is measured. The positron annihilation lifetime measurement method is known to be particularly effective for sub-nano to nano-scale structural evaluation of atomic vacancies and the like.

In the positron annihilation lifetime measurement method, the timing at which a positron disappears is recognized by measuring a γ-ray having an energy of about 511 keV when the positron reacts with an electron in a substance and disappears by pair annihilation. On the other hand, the start timing for measuring this lifetime is the time when the positron enters the substance. In the usual positron annihilation lifetime measurement method, ²² Na is used as the positron source, and the positron generated when the nucleus of ^{22 Na decays by β +} is used for the measurement. Since the positron source is provided in contact with the sample substance, the timing at which the positron enters the substance can be regarded as the timing at which the atomic nucleus is ^{generated by β + decay in 22 Na.} At the ^{time of this β +} decay, γ-rays having an energy of 1.27 MeV are generated at the same time as the positrons, so the timing at which the γ-rays are measured is set as the start timing of the life measurement. Therefore, 1.27 MeV γ-rays are used as start signal γ-rays (start γ-rays), and about 511 keV γ-rays are used as stop signal γ-rays (stop γ-rays). The lifetime of positrons in the sample can be measured by measuring.

A general configuration of a positron annihilation lifetime measuring device is described in, for example, Non-Patent Document 1. FIG. 16 is a simplified diagram showing an outline of the positron annihilation lifetime measuring device 900. Here, it is assumed that the positron source as described above is installed in the small sample S. Therefore, the above two types of γ-rays are emitted from the small sample S. A γ-ray detector (start detector 91) for detecting the γ-ray γ1 for the start signal and a γ-ray detector (stop detector 92) for detecting the γ-ray γ2 for the stop signal are used. In both γ-ray detectors, a combination of a scintillator and a photomultiplier tube is used. In this case, the photomultiplier tube detects an optical pulse generated by the incident of γ-rays on the scintillator, so that a pulse output is obtained each time one γ-ray photon is incident. Further, since the energy of γ-rays can be recognized by the pulse height of this pulse output, it is possible to distinguish between the two types of γ-rays as described above. It is possible to set so that only the γ-ray γ1 for the stop signal is detected and the detector 92 for the stop detects only the γ-ray γ2 for the stop signal.

Therefore, as shown in FIG. 16, the pulse output P1 in the stop detector 92 is detected immediately after the pulse output P0 in the start detector 91. Here, the delay time of the pulse output P1 from the pulse output P0 corresponds to the lifetime of the positron, but this time difference is actually very small, and when viewed on a longer time scale, the pulse output P1 and the pulse output. It can be recognized that P0 is almost simultaneous. Therefore, in the configuration of FIG. 16, when these simultaneities are recognized by the match detection circuit 93, it is presumed that the pulse output P0 and the pulse output P1 correspond to a single positron generation / extinction event. NS. Therefore, the match detection circuit 93 emits a trigger signal to the digital oscilloscope 94 when these simultaneities are recognized, and the digital oscilloscope 94 receives the trigger signal, so that the pulse outputs P0 and P1 are sent to the digital oscilloscope 94. It is captured. Here, instead of the digital oscilloscope, a measuring device such as a digitizer that can similarly realize the functions described below can be used. At this time, in order to facilitate this measurement, a certain delay time is given to the pulse output P1 by the delay circuit 95, and in the digital oscilloscope 94, as shown in FIG. 16, the actual pulse outputs P0 and P1 are actually used. The time difference Δt of the detection time of is measured. This measurement is performed every time the pulse outputs P0 and P1 whose simultaneity is recognized by the match detection circuit 93 are obtained. The delay time of the pulse output P1 from the pulse output P0 corresponds to the lifetime of the positron, but due to statistical fluctuations, this delay time actually varies from measurement to measurement.

Actually, in the start detector 91 and the stop detector 92, many radiation components (background components, etc.) and noise components different from those of the start signal γ-ray γ1 and the stop signal γ-ray γ2 are detected. Among them, only the pulse outputs P0 and P1 whose simultaneity is recognized as described above are effective components. Further, of the γ-rays γ1 for the start signal and the γ-rays γ2 for the stop signal actually generated in the positron source or the sample S, the ones actually detected by the start detector 91 and the stop detector 92 are actually detected. The components that are a part of it and are not detected as a pair by these two detectors do not contribute to the above-mentioned positron annihilation lifetime measurement at all. For these reasons, among the pulse outputs detected by the start detector 91 and the stop detector 92, the components that contribute to the measurement of the positron annihilation lifetime are actually very small.

Therefore, the PC (personal computer) 96 connected to the digital oscilloscope 94 by measuring Δt each time the pulse outputs P0 and P1 whose simultaneity is recognized as described above is obtained is as shown in FIG. , The measured Δt histogram is generated, and from this histogram, the average value of the positron annihilation lifetime and its variation can be recognized by a well-known statistical method. In this case, since it is necessary to increase the number of events in this histogram in order to reduce the statistical error and improve the measurement accuracy of the positron annihilation lifetime, the start detector 91 and the stop detector 92 are used. It is effective to increase the number of counts (number of samples), and for this purpose, it is necessary to take a sufficiently long measurement time. The measurement time actually required for this is as long as 4 hours or more, for example. That is, in the positron annihilation lifetime measurement, a long measurement time was required to obtain a sufficient number of samples in order to secure sufficient measurement accuracy.

Therefore, it is not easy to measure the positron annihilation lifetime with high accuracy in the configuration of FIG. A technique for improving such a point is described in, for example, Patent Document 1. In the configuration described here, the pulse waveforms of the outputs of the start detector 91 and the stop detector 92 are digitally processed in order to improve the measurement accuracy of Δt.

Further, in order to efficiently detect γ-rays effective for measuring the positron annihilation lifetime and secure a sufficient number of samples, Patent Document 1 includes a large number (three or more) γ-ray detectors around the sample. It is also described to be placed. With this configuration, the detection efficiency of γ-rays emitted when positrons are generated / extinguished can be increased, and the number of recognized positron generation / extinction events can be increased. The configuration of the positron annihilation life measuring device 910 using two start detectors is shown in FIG. 17 in correspondence with FIG. In this case, start detectors 91A and 91B having the same specifications are used, and these pulse outputs P0A and P0B are both input to the match detection circuit 93 and the digital oscilloscope 94. In this case, the simultaneity of the pulse output P0A and the pulse output P1 and the simultaneity of the pulse output P0B and the pulse output P1 are recognized, and the pulse output P1 and the pulse output P0A or P0B recognizing the simultaneity thereof are recognized. Is taken into the digital oscilloscope 94, Δt is calculated in the same manner as described above, and the life is calculated by the PC 96 using the histogram. In the example of FIG. 17, two start detectors are used, but by using three or more, the detection efficiency of γ-rays at the time of positron generation can be further improved. Alternatively, by using a plurality of stop detectors instead of a plurality of start detectors, the detection efficiency of γ-rays at the time of positron extinction can be improved, and the number of recognized positron generation / extinction events can be similarly increased. You can also. Further, the start detector and the stop detector can be enlarged to widen the detectable spatial range of each, and the detection efficiency can be similarly improved. That is, it is expected that such a configuration can measure the positron annihilation lifetime with high accuracy in a short measurement time.

Further, since the spread (Doppler spread) around about 511 keV in the energy spectrum of the stop signal γ-ray γ2 emitted by pair annihilation reflects the momentum of the pair annihilated electron in reaction with the positron, this spread is measured. As a result, information about the electrons in the substance that became the sample S can be obtained. Therefore, in the above measurement, AMOC (positron annihilation lifetime / momentum correlation) measurement, which measures the energy spectrum of the stop signal γ-ray γ2 in detail, is also performed. In AMOC measurement, along with the start detector and stop detector (both scintillator + photomultiplier tube) used only for timing detection as described above, the time resolution is inferior but high energy resolution. A detector for spectrum measurement (semiconductor detector) capable of measuring the energy spectrum of γ-rays with high accuracy is used. Therefore, in AMOC measurement, γ-rays are detected in three systems. Generally, when a pair of positrons annihilates, two photons are emitted in almost opposite directions, so this semiconductor detector is installed at a position opposite to that of the stop detector with respect to the sample.

In order to measure the simple positron annihilation lifetime as shown in FIGS. 16 and 17, simultaneous detection in the two systems of the start detector 91 and the stop detector 92 was required, but in the case of AMOC measurement, the simultaneity of detection was required. In addition to the above, the simultaneity of detection in three systems with the addition of a detector for spectrum measurement is required. For this reason, in AMOC measurement, the detection efficiency is particularly low, a longer measurement time is required, and in reality, one measurement may take one week or more. Therefore, if the detection efficiency can be improved by using a plurality of detectors for the same purpose (for start and stop) as in the configuration of FIG. 17, it is particularly effective in AMOC measurement.

Haruo Saito, "Positron Life Measurement Method", Positron Science, No. 2, p. 21, February 2014

Japanese Unexamined Patent Publication No. 2003-215251

If the number of γ-ray detectors is increased as shown in FIG. 17, the detection efficiency of γ-rays emitted when positrons are generated and extinguished can be increased, but the measurement accuracy of the positron annihilation lifetime is improved. That was actually difficult. The reason for this will be explained.

To be precise, the time difference Δt measured in the configuration of FIG. 17 is roughly classified into the time difference ΔtA between the output pulse P1 and the output pulse P0A and the time difference ΔtB between the output pulse P1 and the output pulse P0B. The finally obtained histogram is a mixture of ΔtA and ΔtB as Δt. This situation is schematically shown in FIG. In FIG. 18, as shown in (i), ΔtA was tentatively measured individually by the output pulse P0A, and ΔtB was tentatively measured by the output pulse P0B, and histograms relating to ΔtA and ΔtB were obtained as shown in (ii). And. Since ΔtA and ΔtB are measured values for the same positron generation / extinction phenomenon, ideally (ii) when γ-ray detectors having the same specifications are used as the start detectors 91A and 91B. ), The histograms of ΔtA and ΔtB are the same within the range of statistical error. In this case, the finally obtained histogram (iii) for Δt is the sum of the two histograms that should be the same in (ii), so that the number of samples is increased with the same shape as in (ii). It becomes a thing. Therefore, even if the statistical error is reduced and the measurement time is short, the positron annihilation lifetime and its variation can be calculated with high accuracy from the histogram of (iii). Here, when the output pulses P0A and P0B are input to the same measurement channel, the digital oscilloscope 94 cannot actually distinguish between the output pulse P0A and the output pulse P0B. What is finally obtained here is the histogram of (iii).

However, when the separate start detectors 91A and 91B are used, even if they have the same specifications, the pulse output recognized by the digital oscilloscope 94 may be due to the difference in the wiring length used. The timing of is not constant. For example, a deviation of 3 mm in the position of the γ-ray detector and the wiring length corresponds to a time difference of 10 ps, and this time difference is a value that cannot be ignored compared with the time resolution required for measuring the positron annihilation lifetime. .. Therefore, as shown in FIG. 19, in the histograms of ΔtA and ΔtB, which should be the same in (ii), a non-negligible deviation occurs in the horizontal axis direction, and these are overlapped (iii). ) Is different from the histogram of Δt that should be originally obtained ((iii) in FIG. 18), and it is difficult to accurately calculate the positron annihilation lifetime and the like from this histogram. If all the detectors used are adjusted so that there is no such time difference, or if this is configured to be corrected at the time of processing, these problems can be solved, but it requires a great deal of effort. bottom.

In the configuration of FIG. 17, two start detectors are used, but such a situation becomes more remarkable when three or more start detectors are used. The same applies when a plurality of stop detectors are provided.

Further, as described above, the detection efficiency can be improved by increasing or increasing the density of the scintillators of the start detector and the stop detector and widening the detection target range by these. However, in general, when the scintillator is increased in density or size in this way, the time resolution thereof deteriorates, so that the measurement accuracy such as the positron annihilation lifetime deteriorates. Furthermore, the cost of using such a detector having a single high-density or large scintillator is higher than that of using a detector having a plurality of smaller scintillators.

Therefore, even if a plurality of γ-ray detectors are used, it is actually difficult to measure the lifetime of positrons with high accuracy. Alternatively, more generally, for the above reasons, when a plurality of radiation detectors are used in parallel, it is difficult to perform high-precision measurement by using each radiation detector at the same time.

The present invention has been made in view of such problems, and an object of the present invention is to provide an invention for solving the above problems.

The present invention has the following configurations in order to solve the above problems.
The positron annihilation lifetime measuring device of the present invention has a start detector that detects γ-rays generated by the generation of positrons and outputs a pulse, and a start detector that detects γ-rays generated by the annihilation of positrons and outputs a pulse. A stop detector is provided, and the delay time of the pulse output timing of the stop detector from the pulse output timing of the start detector is set for a plurality of events of generation / disappearance of positrons. A positron extinction life measuring device that measures and recognizes the life of a positron from the measured histogram of the delay time, wherein a plurality of γ-ray detectors are used as the start detector or the stop detector. The outputs of the γ-ray detector are connected and used to generate a single input signal that is mixed while maintaining the relationship between the pulse outputs on the time axis in each, and the said in the input signal. A common counting unit that recognizes the pulse output and recognizes the delay time corresponding to the pulse output, a histogram generation unit that generates a histogram of the delay time, and a life calculation unit that calculates the life from the delay time histogram. , And other than at least one of the plurality of γ-ray detectors before generating the input signal so that the histogram of the delay time can be obtained for each γ-ray detector in the histogram generator. Further, the histogram generating unit includes at least one individual histogram which is a histogram of the delay time obtained for each γ-ray detector. After performing an operation that is uniformly shifted with respect to the delay time, an overall histogram superimposed on the other individual histograms is generated, and the lifetime calculation unit calculates the lifetime from the overall histogram. It is characterized by.
The positron annihilation lifetime measuring apparatus of the present invention is characterized in that, in order to impart the distinctiveness, the pulse shape of the pulse output is defined for each γ-ray detector in the discriminant generator. do.
In the positron annihilation lifetime measuring device of the present invention, the discriminant generation unit assigns a shift time having a constant time difference determined for each γ-ray detector to the pulse output, and the histogram generation unit provides the histogram generation unit. It is characterized in that it is obtained by separating the individual histogram from the histogram obtained by using the input signal according to the time series of the delay time.
The positron extinction lifetime measuring device of the present invention detects a γ-ray generated by the generation of a positivity and outputs a pulse, and detects a γ-ray generated by the extinction of a positron and outputs a pulse. A stop detector is provided, and the delay time of the pulse output timing of the stop detector from the pulse output timing of the start detector is set for a plurality of events of generation / disappearance of positrons. It is a positron extinction life measuring device that measures and recognizes the life of positrons from the measured histogram of the delay time, and a plurality of γ-ray detectors are used as the start detector or the stop detector. The outputs of the γ-ray detector are connected and used to generate a single input signal that is mixed while maintaining the relationship between the pulse outputs on the time axis in each, and the said in the input signal. A common counting unit that recognizes the pulse output and recognizes the delay time corresponding to the pulse output, a histogram generation unit that generates a histogram of the delay time, and a life calculation unit that calculates the life from the delay time histogram. The common counting unit recognizes the delay time for each of the γ-ray detectors by discriminating the pulse output in the input signal for each of the plurality of γ-ray detectors according to the waveform. The histogram generation unit generates an individual histogram which is a histogram of the delay time obtained for each γ-ray detector, and performs an operation in which at least one of the individual histograms is uniformly shifted with respect to the delay time. After that, an overall histogram superimposed on the other individual histograms is generated, and the lifetime calculation unit calculates the lifetime from the overall histogram.
The adjustment method of the radiation measuring instrument of the present invention is an adjustment method of a radiation measuring instrument that detects radiation by simultaneously using a plurality of radiation detectors, each of which detects radiation and outputs a pulse. Using a radiation source that emits the first radiation to be detected at substantially constant time intervals from the reference timing, the outputs of the plurality of radiation detectors are output in a plurality of events in which each of the radiation detectors detects the first radiation. When generating a single input signal mixed while maintaining the relationship between the pulse outputs on the time axis in each, and recognizing the time difference corresponding to the pulse output and the pulse output in the input signal. In addition, for outputs other than at least one of the plurality of radiation detectors so that the histogram corresponding to each output of the plurality of radiation detectors can be identified in the recognized histogram of the time difference. The input signal was generated by imparting distinctiveness, and at least one of the individual histograms, which was the histogram obtained for each radiation detector, was uniformly shifted with respect to the delay time. The present feature is that the total shift time, which is the shift amount when superimposed on the other individual histograms, is calculated, and the detection timing of each radiation detector is corrected by using the total shift time.
In the adjusting method of the radiation measuring instrument of the present invention, the radiation source emits a second radiation different from the first radiation at a substantially fixed time interval from the first radiation, and the second radiation is separate from the radiation detector. (2) A reference radiation detector for detecting radiation is used, and the timing at which the reference radiation detector detects the second radiation is set as the reference timing.
The method for adjusting a radiation measuring instrument of the present invention is characterized in that, in order to impart the distinctiveness, the pulse shape of the pulse output is set to a mode determined for each radiation ray detector.
In the adjustment method of the radiation measuring instrument of the present invention, when the input signal is generated, a shift time having a constant time difference determined for each radiation detector is given to the pulse output to generate the individual histogram. It is characterized in that it is obtained by separating the individual histogram from the histogram of the time difference obtained by using the input signal according to the time series of the time difference.
The radiation measuring instrument of the present invention is a radiation measuring instrument that detects radiation by simultaneously using a plurality of radiation detectors, each of which detects radiation and outputs a pulse, and the plurality of said radiation detectors have time in each. A measuring unit that is connected and used to generate a single mixed input signal while maintaining the relationship between the pulse outputs on the axis, and obtains a measurement result regarding the pulse output from the input signal. Identification that generates the distinctiveness corresponding to each of the plurality of radiation detectors to the pulse output before generating the input signal so that the measurement result can be obtained for each of the plurality of radiation detectors in the measuring unit. It is characterized in that it includes a sex generating unit, and the measuring unit separates and recognizes the measurement result into each of the plurality of radiation detectors based on the discriminative property.
In the radiation measuring instrument of the present invention, the discriminative generator is characterized in that the pulse shape of the pulse output has a mode defined for each radiation detector.
In the radiation measuring instrument of the present invention, the discriminative generation unit is characterized in that a constant shift time determined for each radiation detector is given to the pulse output.
In the radiation measuring instrument of the present invention, when the pulse output from each of the plurality of radiation detectors is input, the discriminative generator transmits the identification signal set for each of the plurality of radiation detectors to the pulse. The determination signal generated by outputting in synchronization with the output is output, and the measuring unit recognizes the pulse output for each of the plurality of radiation detectors from the input signal with reference to the determination signal. It is a feature.
In the radiation measuring instrument of the present invention, a plurality of the radiation detectors are arranged and installed, and the measuring unit outputs position information in the arrangement of the radiation detectors that output the pulse together with the pulse output in the input signal. It is characterized by recognizing.
The radiation measuring instrument of the present invention is characterized in that a plurality of the radiation detectors are arranged in a ring shape surrounding a measurement target.

Since the present invention is configured as described above, when a plurality of radiation detectors are used in parallel, it is possible to perform high-precision measurement by using each radiation detector at the same time.

It is a figure which shows the structure of the positron annihilation life measuring apparatus which concerns on embodiment of this invention. The state of the pulse output from each detector in the positron annihilation lifetime measuring apparatus according to the embodiment of the present invention ((i) (i)') and the histogram (iii) of Δt measured thereby are schematically shown. It is a figure. It is a figure which shows typically the procedure of processing with respect to the histogram of Δt obtained in the positron annihilation lifetime measuring apparatus which concerns on embodiment of this invention. Examples of pulse outputs (i) and (ii) of each detector, an input signal (iii) generated by using the pulse outputs (i) and (ii) in a modified example of the positron annihilation lifetime measuring device according to the embodiment of the present invention, and an individual histogram (iv). Is. It is a figure which shows the state of each histogram in the case where a noise component exists in the positron annihilation lifetime measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the state of each histogram in the case where a noise component exists in the modification of the positron annihilation lifetime measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the structure of the discriminative generation part in the modification of the positron annihilation life measuring apparatus which concerns on embodiment of this invention. It is a figure which shows the example of other configurations of the start detector and the stop detector in the positron annihilation life measuring apparatus which concerns on embodiment of this invention. It is a histogram of Δt actually measured when the shift time is given in the positron annihilation lifetime measuring apparatus which is the Example of this invention. This is the result of comparing the histogram obtained by the positron annihilation lifetime measuring device according to the embodiment of the present invention with the histogram obtained by the conventional positron annihilation lifetime measuring device at the same count rate. This is a result of comparing the overall histograms of the positron annihilation lifetime measuring device according to the embodiment of the present invention when a shift time is applied and when discrimination is performed based on the pulse output waveform. It is a figure which shows the apparatus configuration for carrying out the adjustment method of the radiation measuring instrument which concerns on embodiment of this invention. It is a figure which shows an example of the structure of the radiation measuring instrument which concerns on embodiment of this invention. It is a figure which shows another example of the structure of the radiation measuring instrument which concerns on embodiment of this invention. It is a figure which shows an example of another structure of the distinctiveness generating part used in the radiation measuring instrument which concerns on embodiment of this invention. It is a figure which shows the structure of the conventional positron annihilation life measuring apparatus (the 1). It is a figure which shows the structure of the conventional positron annihilation life measuring apparatus (the 2). This is an example of an ideal Δt histogram obtained in a conventional positron annihilation lifetime measuring device (No. 2). This is an example of an actual Δt histogram obtained in the conventional positron annihilation lifetime measuring device (No. 2).

In the positron annihilation lifetime measuring apparatus of the present invention, by using a plurality of γ-ray detectors at the same time, it is possible to improve the γ-ray detection efficiency when positrons are generated and extinguished. On the other hand, by correcting the deviation of the detection timing of each γ-ray detector, the γ-ray detection timing can be accurately recognized. Therefore, the positron annihilation life measuring device can measure the positron life and the like with high accuracy. Further, the method of correcting such a timing deviation in a plurality of γ-ray detectors in this positron annihilation life measuring device is not limited to the positron annihilation life measuring device, and when a plurality of radiation detectors are used at the same time, each detector is used. It is generally applicable when identifying the measurement result and correcting the detection timing. Furthermore, the configuration applied in this positron annihilation lifetime measuring device can also be applied when a plurality of radiation detectors are used at the same time (including the case of an array type radiation detector), whereby a single measurement can be performed. It is possible to perform high-precision measurement using a unit (channel).

In the positron annihilation life measuring device 100, two start detectors 11A and 11B having the same specifications are used as in the positron annihilation life measuring device 910 shown in FIG. When detecting the start signal γ-ray γ1, a pulse output P0A is emitted from the start detector 11A, and a pulse output P0B is emitted from the start detector 11B. Further, the stop detector 12 is also used in the same manner, and when detecting the stop signal γ-ray γ2, a pulse output P1 is emitted from the stop detector 12, and the pulse output P1 is a digital oscilloscope ( Input to the common counting unit) 14. The match detection circuit 13 issues a trigger for capturing the input signal to the digital oscilloscope 14 when the simultaneity between the pulse output P0A or P0B and the pulse output P1 is recognized. The digital oscilloscope 14 measures the time difference Δt between the pulse output P0A from the start detector 11A, the pulse output P0B from the start detector 11B, and the pulse output P1 from the stop detector 12, and the PC ( Similarly, the personal computer) 16 generates a Δt histogram. That is, the PC 16 functions as a histogram generation unit that generates a histogram of Δt.

However, the input signal input to the digital oscilloscope 14 here is different from the case of the configuration of FIG. In the configuration of FIG. 1, the pulse output P0A and the pulse output P0B are input to the digital oscilloscope 14 as input signals by the same path. At that time, the pulse output P0A receives the delay circuit 21A and the pulse output P0B receives the delay circuit 21B. After passing through, the delay circuit 21A and the delay circuit 21B are given different delay times. That is, in the configuration of FIG. 1, the pulse outputs P0A and P0B merge after passing through the discriminant generator 20 including the delay circuits 21A and 21B to generate a single input signal, and this input signal is used as a digital oscilloscope. 14 is used as an object for measuring the time difference Δt with the pulse output P1. The digital oscilloscope 14 similarly recognizes the pulse outputs P0A and P0B in this input signal, and measures the time difference Δt between these and the pulse output P1.

FIG. 2 is a diagram schematically showing the state of Δt measured in this case, corresponding to FIG. Here, in (i), the time difference ΔtA between the pulse outputs P0A and P1 and the time difference ΔtB between the pulse outputs P0B and P1 correspond to the common positron annihilation lifetime, as described above. Here, the delay times of the delay circuits 21A and 21B are the cases where the time interval between the pulse output P1 and the pulse output P0B is based on the pulse output P0A as shown in (i)'in the digital oscilloscope 14. In addition to the original time interval of ΔtB, the shift time T is set to be uniformly extended. The shift time T is set sufficiently longer than the assumed positron annihilation lifetime. The pulse output P0B whose timing is uniformly set to precede by T and the pulse output P0A are merged to generate a single input signal.

In FIG. 2, (iii) schematically shows a histogram obtained by measuring Δt using this input signal. This histogram can be created by the PC 16 connected to the digital oscilloscope 14. In FIG. 18 (iii), the distribution of a single peak in the original distribution based on the positron annihilation lifetime is seen, and in FIG. 19 (iii), the original distribution based on the positron annihilation lifetime is in the horizontal axis direction. A distribution was obtained in which the two peaks were mixed due to the addition of the deviated ones, and the two distributions were difficult to separate. On the other hand, in (iii) of FIG. 2, which is a histogram of the measured Δt, since T was uniformly added to ΔtB, the two were clearly separated on the horizontal axis (time axis). The distribution of peaks is seen, the distribution of peaks on the left corresponds to the histogram of ΔtA, and the distribution of peaks on the right corresponds to the histogram of ΔtB. That is, in this case, using a single input signal, histograms (individual histograms) for each of the start detectors 11A and 11B (ΔtA, ΔtB) can be obtained separately on the horizontal axis. As described above, since the histogram of ΔtA and the histogram of ΔtB are essentially based on γ-ray detectors having the same measurement target and the same specifications, if there is no deviation on the horizontal axis, a statistical error will occur. It should match within the range. By uniformly assigning the shift time T to the pulse output P0B, in (iii) of FIG. 2, the histograms (individual histograms) of ΔtA and ΔtB that could not be separated in (iii) of FIG. It can be obtained separately using one digital oscilloscope 14.

When measuring Δt to obtain the histogram of FIG. 16 or FIG. 18 (iii), the digital oscilloscope 94 of FIGS. 15 and 16 sets the measurement time range T0. This T0 is the range (maximum value) on the horizontal axis in the histogram of (iii) in FIGS. 16 and 18. In order to accurately calculate the positron annihilation lifetime, T0 is preferably set long so as to sufficiently include the histogram of (iii) in FIG. On the other hand, if T0 is taken too long, the time resolution in the histogram is lowered. Therefore, T0 is set sufficiently longer than the assumed positron annihilation lifetime within the range in which the time resolution in the histogram can be sufficiently secured. NS.

The range T1 when obtaining the histogram of (iii) in FIG. 2 is set longer than the shift time T. Further, the shift time T is preferably set long so that the histogram of ΔtA and the histogram of ΔtB can be sufficiently separated in the time axis direction. On the other hand, as in the case of T0, when T1 is lengthened, the time resolution of the histogram is lowered. Therefore, the shift time T is preferably the same as the above T0. In this case, the range T1 is preferably about twice the range T0 described above.

The histogram of ΔtB (distribution on the right side) obtained in FIG. 2 (iii) matches the histogram of ΔtA (distribution on the left side) within a statistical error range except for the deviation in the horizontal axis (time axis) direction. It should be. Therefore, if this ΔtB histogram is shifted in the horizontal axis direction, it can be duplicated with the ΔtA histogram, and if the counts of each histogram are added in this state, the number of samples is large and the statistical accuracy is higher. A high histogram (overall histogram) can be obtained, and the PC 16 can use this to more accurately calculate the positron annihilation lifetime and the like. As a method for calculating this, as a well-known method, for example, a method similar to that described in Non-Patent Document 1 can be used. In this configuration, the PC 16 functions as a histogram generator that generates the above-mentioned Δt histogram, extracts individual histograms from the histogram, and obtains an integrated histogram, and calculates the positron annihilation lifetime from the overall histogram. Functions as a life calculation unit.

The amount of deviation in the horizontal axis direction in the histogram of ΔtB is generated by the above-mentioned shift time T and the above-mentioned timing deviation in the start detectors 11A and 11B. The shift time T is a set value set by the delay circuits 15, 21, etc., but the timing deviation in the start detectors 11A, 11B is not a set value, and is generally used when the measurement for this purpose is not performed separately. The target is unknown.

Here, since there is a precondition that the histograms of ΔtA and ΔtB match within the range of statistical error except for the shift amount in the time axis direction, the shift amount (total shift time) is calculated (corrected) conversely. can do. FIG. 3 schematically shows a process for this purpose. First, as shown in FIG. 3A, the histogram of ΔtB can be shifted to the left by Ts to match the histogram of ΔtA. In this case, due to the existence of statistical variability, the two do not exactly match, but they can be duplicated by various methods. To do this, for example, make sure that specific points in each distribution (for example, peaks or points that have a constant ratio to the peak) match, that the centroids match, and that the difference between the two is minimized by the least squares method. It is possible to consider a method such as making it so that. After that, if the shifted ΔtB histogram is added to the ΔtA histogram, this histogram becomes a histogram consisting of a sufficient number of samples, like the histogram of FIG. 18 (iii). It can be calculated more accurately. The shift amount at this time is the total shift time Ts in which the above shift time T and the shift due to the timing difference between the two detectors are added.

In this method, a single measuring instrument (digital oscilloscope 14) is used to obtain a histogram of ΔtA and a histogram of ΔtB by selectively assigning a shift time T to the pulse output P0B of the start detector 11B. Can be obtained separately using. Further, these histograms can be added to obtain a histogram with a large number of samples and a small statistical error. Using this histogram, the positron annihilation lifetime and the like can be calculated with high accuracy.

The process shown in FIG. 3 can be easily performed using the PC 16 connected to the digital oscilloscope 14. Further, in the positron annihilation life measuring device 100 (FIG. 1), the delay circuits 21A and 21B (identification) are different from the positron annihilation life measuring device 910 (FIG. 17) which also uses two start detectors. Only the point where the sex generator 20) is provided, and a single measuring instrument (digital oscilloscope 14) can be similarly used for the measurement of ΔtA and ΔtB (Δt). Therefore, the positron annihilation life measuring device 100 can be realized at low cost. In the above configuration, the PC 16 also serves as a histogram generation unit that generates histograms of Δt, ΔtA, and ΔtB, and a lifetime calculation unit that calculates the positron annihilation lifetime from the entire histogram. May be good.

In the above configuration, two start detectors are used, but even when one start detector is used and two stop detectors are used, the output of one of the stop detectors is also used. By giving a shift time to, the individual histogram on the stop detector side can be separated and recognized, and the same processing as described above can be performed. Further, by providing three or more start detectors and stop detectors and assigning different shift times to outputs other than one of them, an individual histogram corresponding to each detector can be similarly obtained. It can be separated and recognized, and the same processing can be performed.

In the configuration of FIG. 1, in order to accurately calculate the positron annihilation lifetime, the timing of the pulse output from the start detectors 11A and 11B and the stop detector 12 adjusted so that the outputs are comparable is set to the positron. It is required to recognize with a time resolution sufficiently smaller than the time width of the spectrum of the extinction lifetime. At this time, as described above, it is necessary to precisely adjust the timing when the digital oscilloscope 14 recognizes this pulse output. In the configuration of FIG. 1, this adjustment only needs to be performed on the start detector 11A and the stop detector 12, and does not need to be performed on the start detector 11B. Therefore, the positron annihilation lifetime measuring device 100 can be easily adjusted. Further, even when a large number of detectors are provided as described above, if adjustments are made only to some of the detectors, adjustments to other detectors become unnecessary.

In the configuration of FIG. 1, for example, a spectrum measurement detector (semiconductor detector) is installed on the upper side of the sample S, and simultaneous measurement with the spectrum measurement detector, the start detectors 11A and 11B, and the stop detector 12 is performed. AMOC measurement can also be performed as a configuration for performing the above. Also in this case, since two start detectors can be used at the same time and a histogram obtained by these can be obtained with high accuracy, the AMOC measurement can be performed with higher accuracy or in a shorter time.

In the configuration of FIG. 1, by uniformly assigning the shift time T to the output of the start detector 11B, the ΔtB histogram and the ΔtA histogram can be recognized separately on the horizontal axis (time axis). Therefore, the digital oscilloscope 14 measures only the time difference Δt between the pulse output and the pulse output P1 recognized in the input signal without recognizing whether the pulse output in the input signal is P0A or P0B. In this case, in the histogram (FIG. 2 (iii)) obtained from the measurement result of Δt, the histograms of ΔtA and ΔtB are separated and recognized. If the final measurement result required is a histogram of Δt, the digital oscilloscope 14 does not need to recognize whether the pulse output in the input signal is P0A or P0B, and ΔtA, ΔtB in the histogram. It is sufficient if the distribution of can be identified, and for this purpose, the shift time T needs to be given to only one pulse output as described above. In performing such processing, an analog circuit can be used instead of the digital oscilloscope 14 described above.

On the other hand, when a digital oscilloscope 14 capable of performing various digital processes is used, the pulse output of the input signal can be discriminated by the waveform. In the start detectors 11A and 11B, for example, even if the scintillator and the photomultiplier tube used have the same specifications, the waveforms of the pulse outputs can be set to be different as described later. In such a case, the digital oscilloscope 14 can identify the pulse outputs P0A and P0B and then obtain an individual histogram (FIG. 18 (ii)), which can be used to perform the same processing as in FIG. can.

Therefore, as a modification of the positron annihilation lifetime measuring device 100, the pulse shapes of the pulse outputs P0A and P0B are replaced with the discriminant generator 20 that imparts the shift time T to the pulse output P0B as described above. A distinctiveness generating unit that imparts distinctiveness can be used. The signal condition in this case and the outline of the measurement are schematically shown in FIG. In FIG. 4, (i) is the output signal of the start detector 11A, (ii) is the output signal of the start detector 11B, and (iii) is the output signal of the stop detector 12. The pulse output P0A in the output signal (i) of the start detector 11A, the pulse output P0B in the output signal (ii) of the start detector 11B, and the pulse output P1 in the output signal (iii) of the stop detector 12. Are issued in chronological order. Here, the input signal generated from the signals of (i), (ii), and (iii) is shown in (iv), and the pulse output shown by the dotted line here is the pulse output P1 of the stop detector 12. It is a pulse output P0A or P0B whose simultaneity with is not recognized, and although it is output from the start detector 11A and the start detector 11B, the trigger signal is not emitted from the match detection circuit 13, so the digital oscilloscope It is a pulse output that is not captured in 14.

Here, the shift time T is not added to the output of the start detector 11B, and the output signal of (i) and the output signal of (ii), which are found to be simultaneous with the pulse output P1, merge. Therefore, the input signal input to the digital oscilloscope 14 is (iv). Here, the pulse output P0A and the pulse output P0B are mixed, but if the digital oscilloscope 14 can distinguish between the pulse output P0A and the pulse output P0B, the pulse output P0A recognizes the pulse output P0A as shown in FIG. 4 (v). If this is done, the time difference between this and the pulse output P1 can be recognized as ΔtA, and if the pulse output P0B is recognized, the time difference between this and the pulse output P1 can be recognized as ΔtB. From this result, the PC 16 can generate a histogram (individual histogram) of ΔtA and ΔtB.

In the example of FIG. 2, the histogram of ΔtB is given a shift time T from the histogram of ΔtA, whereas in this case, the shift time T is not given. However, as described above, in the start detector 11A and the start detector 11B, there is a timing deviation for each detector, and the histogram of ΔtB shifts by this amount of deviation from the histogram of ΔtA in the horizontal axis direction. ing. Therefore, by performing the same processing as in FIG. 3, this deviation amount is calculated as the total shift time Ts, the histogram of ΔtB and the histogram of ΔtA are overlapped and integrated, and the histogram with less statistical error ( The whole histogram) can be obtained. Using this histogram, the positron annihilation lifetime can be calculated with high accuracy as well.

In the case where the pulse output P0A and the pulse output P0B are discriminated from each other according to the waveform and counted, the measurement can be performed with higher accuracy than when the shift time T is set as described above. This point will be described below.

Even when effective pulse outputs P0A and P0B are selected by performing simultaneous counting, it is actually difficult to completely remove a random noise component irrelevant to the generation and disappearance of positrons, and this noise component is , Has an adverse effect on the calculation of positron annihilation lifetime. The situation of each histogram in the presence of such a noise component is schematically shown in FIG. FIG. 5A is a histogram of Δt when a single start detector is used in the presence of such a noise component, and if the noise is random, the noise component is vertical in this. It becomes N, which is an offset component of the axis, and the peak value of the portion that becomes the original signal is S0. In order to reduce the influence of noise and calculate the positron annihilation lifetime from this histogram with high accuracy, it is preferable that these ratios S0 / N are large.

In this case, the histogram obtained when the process of imparting the shift time T as shown in FIG. 2 is performed is shown in FIG. 5 (b) in correspondence with (iii) of FIG. Here, since the shift time T is uniformly assigned to the pulse output P0B and the outputs of the start detector 11A and the start detector 11B are superimposed, the peak value S0 corresponding to the pulse output P0A is A portion and a portion having a peak value S0 corresponding to the pulse output P0B are obtained separately on the horizontal axis. Here, the noise component is 2 × N because the outputs of the two detectors are superimposed. Therefore, in the histogram of FIG. 5 (b), the ratio of the peak value and the noise of the portion that becomes the original signal is S0 / (2 × N), which is half that of the case of FIG. 5 (a).

In this case, FIG. 5 (c) shows a situation in which the histogram of ΔtB is separated and superimposed on the histogram of ΔtA as shown in FIG. In this case, the peak of the portion that becomes the original signal due to superposition is 2 × S0, while the noise component is 2 × 2 × N. Therefore, in this case, the ratio of the peak value of the portion that becomes the original signal to the noise is (2 × S0) / (4 × N) = S0 / (2 × N). That is, this ratio in this case is half that in the case of using a single start detector (FIG. 5A). In this example, since there were two start detectors, the denominator of this ratio was 2 × N, but when there are n start detectors, the denominator is n × N. This ratio is further reduced. That is, when an individual histogram for each detector is obtained by giving a shift time as in the configuration of FIG. 1, the influence of the noise component increases as the number of detectors increases.

On the other hand, as shown in FIG. 4, the situation in the case where the pulse output P0A and the pulse output P0B are discriminated and counted is similarly shown in FIG. Here, FIG. 6A is a histogram when counting is performed without discrimination, which is the same as FIG. 19 (iii). Here, if the histograms to be obtained by the individual detectors are as shown in FIG. 5A, the noise components overlap in the histogram similar to that in FIG. 19 (iii), so that in FIG. 6A. The noise component is 2 × N as in FIG. 5 (b). Further, in this distribution, the portion that becomes the original signal has a shape different from the original distribution because the distributions in which the peak positions are deviated are superimposed as described above. When the pulse output P0A and the pulse output P0B are discriminated, the histogram of FIG. 6A is obtained separately for each of the pulse outputs P0A and P0B. Here, the number of counts due to the original pulse output is divided into two, one for the pulse output P0A and one for the pulse output P0B. On the other hand, regarding the waveform of the pulse that is the noise component, since it does not correspond to either, it is not impossible in principle to remove the noise at the time of this counting, but in reality, the noise is completely eliminated by this discrimination. It is difficult to remove. Here, it is assumed that the noise is divided into two, one recognized as the pulse output P0A and the other recognized as the pulse output P0B. This corresponds to the case where the influence of noise is the largest in this method.

The histogram of ΔtA obtained in this case is shown in FIG. 6 (b), and the histogram of ΔtB (individual histogram) is shown in FIG. 6 (c). The noise levels in each are N1 and N2, both of which are half (= N) of the noise level (= 2 × N) in FIG. 6 (a), while the peak value of the portion that becomes the original signal is shown in FIG. 5 (a). Since the result is S0 as in a), each histogram is the same as in FIG. 5 (a) after all. After that, the histogram (overall histogram) when the processing shown in FIG. 3 is performed is shown in FIG. 6 (d). In this case, the peak value of the portion that becomes the original signal is 2 × S0, and the noise level is 2 × N. Therefore, the ratio of the peak value of the portion that becomes the original signal to the noise is (2 × S0) / (2 × N) = S0 / N, which is equal to FIG. 5 (a) and in the case of FIG. 5 (c). It will be twice as much as. That is, in this case, the proportion of the noise component in the entire histogram is smaller than in the case of FIG. 5C, and this processing can relatively reduce the noise component. Therefore, when discriminating by waveform, the contribution of the noise component can be relatively reduced as compared with the case where the shift time T is given, and the positron annihilation lifetime and the like can be measured with higher accuracy. This ratio does not change even when the number of start detectors is increased.

Therefore, such an effect becomes particularly remarkable when the number of detectors (the number of individual histograms obtained by discriminating each waveform) increases. Further, as described above, the result of FIG. 6 shows that the noise is recognized as either the pulse output P0A or P0B, but at least a part of the noise is either the pulse output P0A or P0B depending on the pulse shape. It can be excluded at the time of measurement as it does not correspond to.

As described above, when γ-ray detectors with the same specifications are used as start detectors 11A and 11B, a method of molding the pulse outputs P0A and P0B so that they are different in order to discriminate them according to the waveforms. An example of is described. FIG. 7 is a diagram showing a configuration and a signal waveform of an example of the distinctiveness generation unit 30 when this method is used. If the start detector 11A and the start detector 11B have the same specifications, the pulse outputs P0A and P0B have the same shape as a single peak immediately after they are output, and it is difficult to distinguish them by waveform. It has become. Here, the output of the start detector 11A passes through the molding section 31A, and the output of the start detector 11B passes through the molding section 31B. The molding portions 31A and 31B are provided with a branch portion 32 that divides the signal voltage and branches one of them, and delay circuits 33A and 33B that impart a delay time to a part of the signal divided by the branch portion 32, respectively. .. The signal after passing through the delay circuits 33A and 33B merges with the other signal after passing through the branch portion 31. Therefore, the shapes of the pulse outputs P0A and P0B after passing through the molding portions 31A and 31B, respectively, have a shape in which a sub-peak is added after the main peak corresponding to the other signal.

In the example of FIG. 7, the delay time given by the delay circuit 33B is set longer than the delay time given by the delay circuit 33A. As a result, the intervals between the main peak and the sub peak at the pulse outputs P0A and P0B are different. In the digital oscilloscope 14, the output pulse composed of the main peak and the sub peak can be recognized as a single output pulse, and the pulse outputs P0A and P0B can be identified by the interval between the main peak and the sub peak. If Δt is calculated based on the main peak, Δt can be appropriately measured as described above even if such a pulse shape is used.

The configuration of FIG. 7 is a method for imparting distinctiveness to the waveforms of the pulse outputs P0A and P0B emitted by the start detectors 11A and 11B having the same specifications, and the pulse outputs P0A and P0B. As long as the detection time can be properly recognized and counted, other configurations can be used to shape the pulse output waveform into other shapes. For example, in the example of FIG. 7, each output is branched to give a delay time to form a sub-peak, but a sub-peak can also be generated by using reflection or the like. Alternatively, it is also possible to incorporate a circuit that generates a square wave or the like when a signal is generated, and to recognize the pulse output for each detector by combining the square waves. Alternatively, the pulse outputs P0A and P0B of the start detectors 11A and 11B are both output via the preamplifier, but if the pulse waveform itself output at this time has distinctiveness that can be recognized by the digital oscilloscope. , It is not necessary to newly impart the above-mentioned distinctiveness. Further, the shift time may be given as described above, and the waveform may be set in this way for each detector.

With the above configuration, the positron annihilation lifetime can be precisely measured using a plurality of γ-ray detectors. In the configuration of FIG. 1, start detectors 11A and 11B are provided so as to face each other with the sample S in between, and stop detectors are provided at positions orthogonal to these. Other configurations can be used as long as γ1 and γ-ray γ2 for stop signals can be detected.

FIG. 8 is a view showing an example of another configuration of the start detector and the stop detector ((a) and (b) are top views, and (c) is a perspective view). In FIG. 8A, start detectors 11A and 11B and stop detectors 12 are installed around the sample S at 120 ° intervals on the same plane. In this case, the above configuration is applied to the start detectors 11A and 11B, the time difference between the pulse output of the start detector 11A and the pulse output of the stop detector 12, and the pulse output of the start detector 11B. After obtaining each histogram of the time difference between the pulse output of the stop detector 12 and the pulse output of the stop detector 12, the above process of superimposing these can be performed.

On the contrary, in FIG. 8B, the start detector 11 and the stop detectors 12A and 12B are installed around the sample S at an interval of 120 °. In this case, the above configuration is applied to the stop detectors 12A and 12B, the time difference between the pulse output of the start detector 11 and the pulse output of the stop detector 12A, and the pulse output of the start detector 11. After obtaining each histogram of the time difference of the pulse output of the stop detector 12B, the above process of superimposing these can be performed.

In FIG. 8 (c), the start detectors 11A and 11B and the stop detector 12A are installed at intervals of 120 ° around the sample S on the same plane as in FIG. 8 (a). Further, the stop detector 12B is installed so as to be orthogonal to this plane. In this case, by applying the above configuration to each of the start detectors 11A and 11B and the stop detectors 12A and 12B, the pulse output of the start detector 11A and the pulse of the stop detector 12A are applied. Output time difference, pulse output of start detector 11B and pulse output of stop detector 12A, time difference between pulse output of start detector 11A and pulse output of stop detector 12B, start detector 11B After obtaining four histograms of the time difference between the pulse output and the pulse output of the stop detector 12B, these can be superposed.

In the case of FIGS. 8A and 8B, the number of histograms superimposed was two, whereas the histogram obtained in this case is an overlay of four histograms, so the number of counts in the histogram is further increased. And the statistical error can be reduced. In this case, when the shift time T is assigned as shown in FIG. 3, the shift time T assigned to each combination is set so that the above four combinations can be identified on the time axis. NS. On the other hand, when the shape of the pulse output is given distinctiveness as shown in FIG. 7, the pulse output of the start detector 11A, the pulse output of the start detector 11B, and the pulse output of the stop detector 12A are used. The pulse output of the stop detector 12B may be identifiable.

In FIG. 3, when performing the process of superimposing the histograms, the total shift time Ts was calculated in consideration of the shift time T and the amount of timing shift for each detector. It is considered that the total shift time Ts does not change after the device is set up and the sample S and each detector are fixed. Therefore, the work of moving the histogram of ΔtB so as to overlap with the histogram of ΔtA and calculating the total shift time Ts is as long as the change with time of the measurement timing of each detector and the change of the position of the sample S can be ignored. If only the first measurement is performed and the Ts is stored, the entire histogram can be generated without measuring the Ts after that. Thereby, the processing time can be further shortened. Regarding this point, even when the histogram of ΔtA and the histogram of ΔtB are separated by giving the shift time T (FIG. 3), the pulse output itself is discriminated without giving the shift time T, and the histogram of ΔtA and the histogram of ΔtB are discriminated. This is the same in both cases of obtaining the histograms of (FIG. 4) individually.

In the above example, since the start detectors 11A and 11B have the same specifications, it is assumed that the individual histograms based on these have the same specifications within the range of statistical error. However, as long as the individual histograms can be superposed in the same manner as described above and a histogram with less statistical variation can be obtained, they do not have to have the same specifications. The same applies when three or more start detectors are provided and when a plurality of stop detectors are provided.

A histogram of Δt was actually prepared for the same sample S using the positron annihilation lifetime measuring device 100 (Example device) having the configuration shown in FIG. ^{As the sample S, a combination of 22} Na as the positron generation source and polyethylene as the substance to be measured for the positron annihilation lifetime was used. Here, FIG. 9 is a histogram of Δt measured by the digital oscilloscope 14 after applying the shift time T to the pulse output P0B, and corresponds to FIG. 2 (iii). Here, two distributions having the same shape are clearly separated on the horizontal axis, and the distribution on the left side corresponds to the pulse output P0A and the distribution on the right side corresponds to the pulse output P0B. Then, the whole histogram finally obtained after performing the processing shown in FIG. 3 is shown in FIG. Here, this overall histogram is shown as an example device (white circle), and the histogram obtained by the positron annihilation lifetime measuring device 900 (conventional device) shown in FIG. 16 is also shown by a black circle, and is shown by a black circle. The counting rate is the same. Here, in the embodiment, a higher count number is obtained, so that a result with high statistical accuracy is obtained. Further, in general, the detection efficiency of the radiation detector and the time resolution are in a trade-off relationship, but since the detection efficiency can be increased in this embodiment, the detection efficiency of the radiation detector itself is lowered. Even if it was made, the one with high time resolution could be used. For this reason, in the examples, a radiation detector with higher time resolution using a dense scintillator is used, and as a result, the distribution itself is sharpened, and the positron annihilation lifetime and the spread of the distribution (in the sample material). Information related to the structure of) can be calculated with higher accuracy.

Further, for the same measurement target, the entire histogram finally obtained after giving the shift time T for identification of the pulse output and the shape of the pulse output are set for each detector as described above. FIG. 11 shows the result of comparing the overall histograms finally obtained after discriminating by waveform. As described above, the distribution corresponding to the original positron annihilation lifetime is similarly obtained, but the noise component shown in FIG. 5A and the like is relatively significantly reduced when the waveform is discriminated. It was confirmed that it would be done.

Further, in the above, the positron annihilation life measuring device 100 has been described. However, in a radiation measuring instrument using a plurality of detectors at the same time, as in the case of the above-mentioned start detectors 11A and 11B, when the deviation of the detection timing in each radiation detector becomes a problem, the same as above. By using the method of, such a deviation of the detection timing can be calculated accurately, and this deviation can be corrected in the subsequent processing. Further, it is clear that this method can be applied as long as a plurality of detectors that perform photon counting like the above-mentioned γ-ray detector (radiation detector) are used, and here, the detection is performed by photon counting. Strictly speaking, the photon (photon) may be different from radiation, such as visible light. Therefore, the term "radiation" as used herein includes a broad concept including an arbitrary particle beam and a photon of an arbitrary energy.

That is, a plurality of radiation detectors subject to such adjustment are used as start detectors 11A and 11B in FIG. 1, and separately, a reference radiation detector is used as a stop detector 12, and a plurality of radiation detectors are used. The radiation detector (corresponding to the start detectors 11A and 11B) detects the start signal radiation (first radiation), and the reference radiation detector (stop detector 12) provided separately from these detects the stop signal radiation. (Second radiation) can be detected, the same operation as described above can be performed, the total shift time Ts can be calculated, and the difference in detection timing between the radiation detectors can be calculated. When these radiation detectors are used later, processing in consideration of this deviation can be performed, that is, the radiation measuring instrument can be adjusted.

Here, as the radiation source for the start signal radiation and the stop signal radiation, the above-mentioned sample S that emits γ-rays can be similarly used. However, if the time difference between the radiation for the stop signal and the radiation for the start signal is substantially constant (including the case where the time difference is zero: simultaneous), an individual histogram and an overall histogram can be generated in the same manner as above. Since the same processing as that of the positron annihilation lifetime measuring device 100 can be performed, a radiation source that emits radiation having such characteristics can be used instead of the sample S. Further, the radiation detected by this radiation detector is not limited to γ-rays. For example, other radiations (photons, α rays, β rays, etc.) can be used as the radiation for the start signal and the radiation for the stop signal. Further, it is not necessary that the radiation detected by the radiation detector to be adjusted in the original use and the radiation for the start signal and the radiation for the stop signal are the same type of radiation. For example, even when the radiation detector to be adjusted is originally for detecting charged particle beams, as long as the radiation detector can detect the same, the radiation for the start signal and the radiation for the stop signal are used. Gamma rays can also be used as the radiation. Further, the radiation for the start signal and the radiation for the stop signal do not have to be the same type of radiation.

FIG. 12 is a diagram showing an apparatus configuration when this adjustment method is carried out. Here, the radiation measuring instrument 41 in which three radiation detectors 41A, 41B, and 41C are used in parallel is the target of this adjustment, and the deviation of the radiation detection timing between them is measured. And. It is assumed that both the first radiation X1 which is the radiation for the start signal and the second radiation X2 which is the radiation for the stop signal are emitted from the radiation source X. The radiation detectors 41A to 41C correspond to the start detectors 11A and 11B in FIG. 1, and two start detectors were used in FIG. 1, but here, the radiation detector to be adjusted is It is assumed that there are three. The radiation detectors 41A to 41C both detect the first radiation X1 and emit pulse outputs P0A, P0B, and P0C, respectively, in the same manner as described above.

On the other hand, the reference radiation detector 42 corresponds to the stop detector 12 in FIG. The reference radiation detector 42 emits a pulse output P1 by detecting a second radiation X2 that can be distinguished from the first radiation X1 because the energy is different from that of the first radiation X1. The first radiation X1 and the second radiation X2 correspond to the above-mentioned start signal γ-ray γ1 and stop signal γ-ray γ2, respectively. In this case, the identification signal generation unit 43, like the positron annihilation lifetime measuring device 100 described above, has a histogram of Δt obtained by the digital oscilloscope 45 from a single input signal for each pulse output P0A, P0B, P0C. Distinguish each output so that the histogram can be separated. The match detection circuit 44 issues a trigger to the digital oscilloscope 45 when the synchrony of the pulse outputs P0A, P0B, P0C and the pulse output P1 is recognized before the input signal is generated, and the synchronism is recognized. The time difference Δt between any of the pulse outputs P0A, P0B, and P0C and the pulse output P1 is measured.

When the method of FIG. 2 is applied, a delay circuit is provided in the discriminant generator 43 or on the output side of the reference detector 42 in order to give different shift times to the pulse outputs P0B and P0C. Provided as appropriate. Further, when the method of FIG. 4 is applied, three molding portions corresponding to the molding portions 31A and 31B of FIG. 7 are provided. The description of such a delay circuit and a molded portion is omitted in FIG.

The PC46 generates a histogram of Δt measured by the digital oscilloscope 45 when the method of FIG. 2 is applied, and among the histograms of ΔtA, ΔtB, and ΔtC measured for each of the radiation detectors 41A, 41B, and 41C. Recognize the part corresponding to the histogram. After that, as shown in FIG. 3A, the total shift time of the ΔtB histogram with respect to the ΔtA histogram and the total shift time of the ΔtC histogram with respect to the ΔtA histogram can be calculated. The difference between each of these total shift times and the shift time T corresponds to the deviation of the detection timing from the radiation detectors 41A of the radiation detectors 41B and 41C.

Alternatively, when the method of FIG. 4 is applied, the digital oscilloscope 45 itself recognizes the ΔtA, ΔtB, and ΔtC measured for each of the radiation detectors 41A, 41B, and 41C, and the PC46 creates these histograms, respectively. do. After that, the total shift time of the ΔtB histogram with respect to the ΔtA histogram and the total shift time of the ΔtC histogram with respect to the ΔtA histogram can be calculated in the same manner as described above. Each of these total shift times corresponds to a deviation in detection timing from the radiation detectors 41A of the radiation detectors 41B and 41C.

Therefore, in the data processing when the radiation detectors 41A, 41B, and 41C are used thereafter, the deviation of the detection timing can be corrected by using this total shift time.

In the configuration of FIG. 12, similarly to the above-mentioned positron annihilation life measuring device 100, the detection timing of the radiation detectors 41A to 41C (corresponding to the start detectors 11A and 11B) and the reference radiation detector 42 (corresponding to the start detectors 11A and 11B) The deviation of the detection timing as described above was calculated based on the time difference of the detection timing of the stop detector 12). That is, in this case, the detection timing of the second radiation X2 by the reference radiation detector 42 is used as a reference (reference timing), and the first radiation X1 detected by the radiation detectors 41A to 41C is substantially constant from this reference timing. It was supposed to be issued after the time of. However, for example, when the oscillation timing of the first radiation X1 can be controlled with high accuracy, for example, this oscillation timing on the radiation source X side is set as the above reference timing, and this reference timing and the radiation detectors 41A to 41C (start). The same processing can be performed by setting the time difference from the detection timing of the detectors 11A and 11B) as ΔtA, ΔtB, and ΔtC. That is, as long as the reference timing can be secured with sufficient accuracy, the second radiation X2 and the reference radiation detector 42 for detecting the second radiation X2 are unnecessary. Therefore, as the above-mentioned radiation source X, a radiation source X ^{other than the one using 22} Na, for example, a pulsed beam or the like can be used.

Such an adjustment method is particularly effective when information related to radiation detection timing is important in a radiation measuring instrument in which a plurality of radiation detectors are used at the same time. The positron annihilation lifetime measuring device 100 as described above is a typical example of this, but this adjusting method can also be applied to other radiation measuring devices.

Further, as described above, the pulse output output signals are given distinctiveness for each radiation detector and then merged to generate a single input signal, and then for each radiation detector in this input signal. The configuration for recognizing the measurement result can be applied not only when adjusting the radiation measuring instrument but also when using the radiation measuring instrument normally. FIG. 13 shows an example in which such a configuration is applied to a radiation measuring instrument 200 including an array type radiation detector.

From this point of view, the radiation measuring instrument 200 corresponds to a generalized version of the positron annihilation lifetime measuring device 100. Here, an array type radiation detection unit 50 which is an array type (position detection type) is used. The array type radiation detection unit 50 is composed of 4 × 4 pixels 51, and each pixel 51 corresponds to the radiation detector 31A or the like, and emits a pulse output each time radiation is detected. The output of each pixel 51 is input to the discrimination generation unit 60 to generate discrimination, and the pulse outputs of each pixel 51 after passing through the discrimination generation unit 60 merge to generate a single input signal. From this input signal, the measuring unit 70 recognizes the measurement result of the pulse output for each pixel 51 based on the given distinctiveness. The measuring unit 70 corresponds to the combination of the digital oscilloscope 14 and the PC 16 in the positron extinction life measuring device 100.

In this case, the items to be discriminative given by the discriminant generation unit 60 can be appropriately set according to what kind of physical quantity is measured for the pulse output for each pixel 51 in the measuring unit 70. When the time difference between the pulse output of each pixel 51 and the other pulse output is the object of measurement in the measuring unit 70 as in the positron annihilation lifetime measuring device 100, the discriminant generation unit is described as described above. At 60, a different shift time can be assigned to each pixel 51. In this case, the measuring unit 70 cannot discriminate the pulse output for each pixel 51 in the input signal, but the required measurement result (in the case of the positron annihilation life measuring device 100 described above, for each start). A Δt histogram for each detector) can be obtained for each pixel 51.

On the other hand, when the discriminant generation unit 60 forms the pulse shape of the pulse output of each pixel 51 into a shape defined for each pixel 51 as shown in FIG. 7, the measurement unit 60 is described as described above. The 70 can recognize which pixel 51 the recognized pulse output is from. Therefore, even when a single input signal is used, the measuring unit 70 can recognize the pulse output for each pixel 51 and perform processing. This process includes, for example, counting for each pixel 51 per unit time, measuring the radiation energy spectrum by pulse height analysis, and the like, and the signal for each pixel can be accurately analyzed for time, energy, and the like. Alternatively, this makes it possible to correct the deviation of energy or the like that occurs between each pixel 51 in the same manner as the above-mentioned time (detection timing) deviation.

In the configuration of FIG. 13, when the measuring unit 70 recognizes the pulse output in the input signal, it can recognize the pixel 51 that emitted the pulse output, so that the photon that is the source of the pulse output is used. The position of the incident can be recognized. Therefore, such a configuration is particularly effective in a position detection type radiation measuring instrument. In the configuration of FIG. 13, the position in the two-dimensional array is recognized, and as another specific example of the radiation measuring instrument in which the information on the position where the photon is incident is particularly effective, PET (positron emission tomography) is used. There is a radiation measuring instrument in the law).

FIG. 14 is a diagram showing a configuration of a radiation measuring instrument 210 used in PET. Here, radiation detectors 52, 53, 54 (four each) corresponding to the above-mentioned pixel 51 are arranged in a ring shape surrounding the measurement target (subject). The positrons emitted from the positron source in the subject's body annihilate in the immediate vicinity and emit two 511 keV γ-ray photons in opposite directions in the same manner as described above. The direction in which this pair of γ-ray photons is emitted is indefinite, but the two pairs of radiation detectors 52, 53 and the pair of radiation detectors 52, 54 connected by the one-point chain line in FIG. Since a pair of γ-ray photons emitted from is detected by simultaneous measurement, if there are multiple pairs of radiation detectors that simultaneously detect γ-ray photons, the position of the source X is determined by the line connecting these pairs (Fig. It can be recognized as the intersection of the one-point chain line at 14. In this configuration, it is necessary to operate all the radiation detectors at the same time. At this time, the distinctiveness generator 61, for each set of the radiation detectors 52, 53, 54 as described above, Three that used 62 and 63, respectively, and merged the output of each radiation detector 52, the output of each radiation detector 53, and the output of each radiation detector 54 after passing through the discrimination generators 61, 62, 63, respectively. A measuring unit 70 that analyzes an input signal in a channel corresponding to each can be used. In this case, although the measuring unit 70 uses a large number of radiation detectors, it is used for the entire simultaneous measurement by simultaneous measurement by a measurement channel in which various signals from a plurality of radiation detectors are combined. be able to. In this way, instead of using a single distinctiveness generator that is common to all radiation detectors, the radiation detectors may be divided into multiple groups, and the distinctiveness generator and input signal may be provided for each group. good. In such a case, since it is sufficient to identify each radiation detector in the same group in the measurement using each input signal, a total of 12 radiation detectors are used in the configuration of FIG. 14, but only four types are used. The distinctiveness can be set so that the discriminant can be identified. Therefore, when setting the pulse output waveform as described above, there can be four types of these waveforms. Further, in this case, the distinctiveness generating units 61, 62, 63 may have completely the same configuration.

Further, in the TOF (Time Of Flight) type PET, the time difference of the detection timing of the pixel 51 that detects the pair of γ-rays substantially at the same time is also measured in the same manner as the above-mentioned positron annihilation life measuring device 100. The position information of the radiation source X can be obtained with higher accuracy. In this case, it is required to strictly adjust the detection timing of each pixel 51. In this case, a small source X in FIG. 12 can be placed at the center O in FIG. 14 and the adjustment method performed in the configuration of FIG. 12 can be similarly applied, thereby making the measurement of the time difference more. It can be done with high accuracy.

In the above-mentioned positron annihilation life measuring device 100 (FIG. 1), the adjustment method of the radiation measuring instrument (configuration of FIG. 12), and the radiation measuring instruments 200 and 210 (FIGS. 13 and 14), they are generated from the outputs of a plurality of detectors. In a single input signal, the output pulse of each detector was given distinctiveness. Here, as a specific method for imparting this distinctiveness, the result for each detector in the finally acquired measurement result (histogram of time difference in the positron annihilation lifetime measuring device 100) is identified and obtained. Anything that can be done is sufficient. As this method, in the positron annihilation lifetime measuring device 100, it was used to give a shift time.

Generally, in a pulse output generated by a radiation detector detecting radiation, it is possible to measure various information about this pulse output. This information is the timing and the number of counts of the pulse output in the positron annihilation lifetime measuring device 100. Since the information regarding the timing required here is only the time difference from the pulse output P0, the technique of imparting the shift time as described above has become effective. However, in the technique of imparting the shift time in this way, since the measurement unit does not identify the pulse output itself in the input signal, it is not always effective in other measurements, that is, each detection is performed by this technique. In many cases, the measurement results for each device cannot be obtained separately.

On the other hand, the method shown in FIGS. 4 and 7 can be applied in more cases in order for the measuring unit (digital oscilloscope 14) to identify the pulse output itself in the input signal. However, in the method of FIG. 7, since the shape of the falling portion of the pulse outputs P0A and P0B is set by the discriminant generation unit 30, for example, when the measuring unit performs measurement on the falling portion of the pulse output, the measurement unit is used. , The method of FIG. 7 is difficult to apply.

In such a case, the relationship on the time axis of the pulse output P0A and the relationship on the time axis of the pulse output P0B in the input signal are maintained, and the pulse waveforms of the pulse outputs P0A and P0B are not changed. Is preferable. For this purpose, instead of processing the waveform of the pulse output from each detector as in the discriminant generation unit 30 in FIG. 7, a judgment signal different from the input signal is generated and used as the input signal. It is also possible to output in synchronization and recognize the pulse output in the input signal for each detector by referring to this determination signal. FIG. 15 is a diagram showing the configuration of the distinctiveness generation unit 80 in correspondence with FIG. 7.

Again, since the waveforms of the pulse output P0A and the pulse output P0B are the same, it is difficult for the digital oscilloscope 14 (measurement unit) to simply identify them. Here, in the discriminant generation unit 80, an identification signal generation unit 81A is provided on the start detector 11A side, and an identification signal generation unit 81B is provided on the start detector 11B side. The identification signal generation unit 81B emits identification signals QA and QB, which are pulse signals, respectively. The identification signals QA and QB have different shapes, and it is possible to identify them with a digital oscilloscope.

A pulse output recognition unit 82 is connected to the start detector 11A and the start detector 11B, respectively, and the pulse output recognition unit 82 receives a trigger signal (identification signal generation trigger) when the pulse outputs P0A and P0B are input. ) Is emitted, and the waveforms of the input pulse outputs P0A and P0B are output as they are without any change. The identification signal generation units 81A and 81B receive the identification signal generation trigger and emit the identification signals QA and QB, respectively. Therefore, the identification signal QA is synchronized with the pulse output P0A, and the identification signal QB is generated in synchronization with the pulse output P0B. After that, the identification signals QA and QB merge to generate and output a determination signal.

On the other hand, the pulse outputs P0A and P0B merge in the state (shape) as they are output from the start detector 11A and the start detector 11B, respectively, and an input signal is generated as in FIG. 7. The determination signal and the input signal are input to the digital oscilloscope 14 (measurement unit) in synchronization. As described above, it is difficult for the digital oscilloscope 14 to determine whether the pulse output recognized in the input signal is the pulse output P0A or P0B when only the input signal is viewed. However, since it is possible to recognize whether the pulse signal in the determination signal to be input in synchronization with the input signal is either the identification signal QA or QB, the digital oscilloscope 14 inputs in synchronization with the input signal. By referring to the determination signal, the pulse outputs P0A and P0B in the input signal can be identified. Thereby, as in the case of using the configuration of FIG. 7, ΔtA and ΔtB can be measured, or various measurement results can be obtained for each of the start detectors 11A and 11B.

Unlike the configuration of FIG. 7, when the configuration of FIG. 15 is used, the pulse outputs P0A and P0B are present in the input signal in the form as output from the start detector 11A and the start detector 11B. Therefore, as compared with the case of using the configuration of FIG. 7, a wider range of measurement and processing can be performed by the digital oscilloscope 14 (measurement unit). For example, when the configuration of FIG. 15 is used, since the pulse shape is not processed in the input signal, it is possible to measure the waveforms of the pulse outputs P0A and P0B with the digital oscilloscope 14.

Further, for example, in order to measure ΔtA and ΔtB with a digital oscilloscope with high accuracy as described above, the timing of the pulse outputs P0A and P0B is immediately after being output from the start detector 11A and the start detector 11B. It needs to be maintained in the input signal as well as in the state. On the other hand, the accuracy of the timing of the identification signals QA and QB in the determination signal is determined by the pulse output (P0A or P0B) recognized in the input signal and the identification signal (QA or QB) recognized in the determination signal. Since it is sufficient if they are associated with each other, high accuracy as high as the timing of the pulse outputs P0A and P0B in the input signal is not required. Therefore, high time accuracy is not required for the identification signal generation unit 81A, the identification signal generation unit 81B, and the pulse output recognition unit 82 for generating the determination signal as described above. Alternatively, as the identification signals QA and QB, it is possible to adopt a shape that facilitates the identification of the two even if the accuracy of timing recognition is low. Therefore, as the identification signals QA and QB, for example, pulses having different pulse widths are used, or signals composed of a plurality of pulse trains such as the input signal in FIG. 7 are used. Can be adopted. The generation of such an identification signal is easy. Therefore, the distinctiveness generation unit 80 of FIG. 15 can be easily obtained. Further, in the configuration of FIG. 15, two detectors are used, but even when three or more detectors are used, one input signal and one determination signal can be used, and the number of detectors can be used. There is no need to add a measuring instrument (measurement channel) even if the number is three or more.

In the example of FIG. 15, in the discriminant generation unit 80, the pulse output recognition unit 82 issues an identification signal generation trigger without making any changes to the pulse outputs P0A and P0B. Similar to the configuration of FIG. 7, a branching portion may be used, and a pulse obtained by branching a part of the pulse outputs P0A and P0B without substantially changing the pulse shape may be used as an identification signal generation trigger. Even in such a case, the digital oscilloscope 14 can perform various processes in the same manner as described above using the input signal and the determination signal.

In addition, when imparting distinctiveness to the pulse output in the input signal, in addition to assigning the shift time as described above and setting the pulse waveform for each detector, the measurement unit can perform desired measurement. As long as it is possible, various kinds can be used. For example, the pulse wave height in the pulse output corresponds to the energy of the incident photon, and when the information on the photon energy is important, it is necessary to recognize the pulse wave height, but the measurement unit can measure the information on the photon energy. If it is not necessary, the discriminant generation unit may set the pulse wave height for each detector, and the measurement unit may set the pulse output to be discriminated by the pulse wave height. Further, a plurality of types of techniques for imparting distinctiveness in this way may be combined.

In addition to this, in the configurations of FIGS. 13 and 14, the configuration of the discriminant generation unit 60 can be appropriately set as long as the desired physical quantity is separated for each pixel 51 by the measurement unit 70. Further, as in the case of the above-mentioned positron annihilation lifetime measuring device, if the pulse output from each pixel 51 has a shape that can be directly identified by the measuring unit 70, it is not necessary for the discriminant generating unit 60 to specially impart distinctiveness. Therefore, the outputs from the respective pixels 51 can be merged as they are to be an input signal.

Similar to the above, when the array type radiation detection unit 50 is used to detect radiation, a measurement unit is provided for each pixel 51, or the same measurement is performed using a measurement unit having a measurement channel corresponding to each pixel 51. You can also get results. On the other hand, in the above configuration, since this measurement can be performed using a single measuring unit or a single measuring channel, the device configuration can be simplified and the cost can be reduced.

Further, for example, the array-type radiation detection unit 50 can be made of a semiconductor, that is, the array-type radiation detection unit 50 can be a semiconductor detector. In this case, the discriminative generator can be formed of a semiconductor circuit, and these can be configured in a common semiconductor chip.

As described above, in the above-mentioned positron annihilation life measuring device and the above-mentioned radiation measuring instrument, various high-precision measurements can be performed using a plurality of radiation measuring instruments, and the device configuration is simplified and the cost is reduced. can do.

11, 11A, 11B, 91, 91A, 91B Start detector (γ-ray detector, radiation detector)
12, 12A, 12B, 92 Stop detectors (γ-ray detector, radiation detector)
13, 44, 93 Match detection circuit 14, 45, 94 Digital oscilloscope (common measurement unit)
15, 21A, 21B, 33A, 33B, 95 Delay circuit 16 PC (personal computer, histogram generator, life calculation unit)
20, 30, 43, 60-63, 80 Distinguishing part 31A, 31B Molding part 32 Branching part 41, 200, 210 Radiation measuring instrument 41A, 41B, 41C, 52-54 Radiation detector 42 Reference radiation detector 46 , 96 PC (personal computer)
50 Array type radiation detector 51 pixels (radiation detector)
70 Measuring unit 81A, 81B Identification signal generation unit 82 Pulse output recognition unit 100, 900, 910 Positron annihilation life measuring device O Center S Sample X Astrophysical source X1 First radiation X2 Second radiation γ1 Start signal γ-ray γ2 Stop signal γ-ray

Claims (14)

It is equipped with a start detector that detects γ-rays generated with the generation of positrons and outputs a pulse, and a stop detector that detects γ-rays generated with the disappearance of positrons and outputs a pulse. The delay time of the pulse output timing of the stop detector from the pulse output timing of the start detector is measured for a plurality of events of positron generation / disappearance, and the measured delay time is A positron annihilation lifetime measuring device that recognizes the lifetime of positrons from a histogram.
As the start detector or the stop detector, a plurality of γ-ray detectors mix the outputs of the plurality of γ-ray detectors in a state where the relationship between the pulse outputs on the time axis is maintained. Connected and used to generate a single input signal
A common counting unit that recognizes the pulse output in the input signal and recognizes the delay time corresponding to the pulse output.
A histogram generator that generates a histogram of the delay time, and a histogram generator.
A life calculation unit that calculates the life from the delay time histogram,
Equipped with
Before generating the input signal, for the output other than at least one of the plurality of γ-ray detectors, so that the histogram of the delay time can be obtained for each γ-ray detector in the histogram generator. Further provided with a distinctiveness generating unit for imparting distinctiveness,
The histogram generation unit performs an operation in which at least one of the individual histograms, which is a histogram of the delay time obtained for each γ-ray detector, is uniformly shifted with respect to the delay time, and then the other. Generate an overall histogram superimposed on the individual histogram of
The positron annihilation life measuring device is characterized in that the life calculation unit calculates the life from the entire histogram. The positron annihilation lifetime according to claim 1, wherein the discriminant generation unit has a pulse shape of the pulse output in a mode determined for each γ-ray detector in order to impart the discriminative property. measuring device. In the discriminant generation unit, a shift time having a constant time difference determined for each γ-ray detector is given to the pulse output.
The first or second aspect of claim 1 or 2, wherein the histogram generation unit is obtained by separating the individual histogram from the histogram obtained by using the input signal according to the time series of the delay time. Positron annihilation lifetime measuring device. It is equipped with a start detector that detects γ-rays generated with the generation of positrons and outputs a pulse, and a stop detector that detects γ-rays generated with the disappearance of positrons and outputs a pulse. The delay time of the pulse output timing of the stop detector from the pulse output timing of the start detector is measured for a plurality of events of positron generation / disappearance, and the measured delay time is A positron annihilation lifetime measuring device that recognizes the lifetime of positrons from a histogram.
As the start detector or the stop detector, a plurality of γ-ray detectors mix the outputs of the plurality of γ-ray detectors in a state where the relationship between the pulse outputs on the time axis is maintained. Connected and used to generate a single input signal
A common counting unit that recognizes the pulse output in the input signal and recognizes the delay time corresponding to the pulse output.
A histogram generator that generates a histogram of the delay time, and a histogram generator.
A life calculation unit that calculates the life from the delay time histogram,
Equipped with
The common counting unit recognizes the delay time for each γ-ray detector by discriminating the pulse output in the input signal for each of the plurality of γ-ray detectors according to the waveform.
The histogram generation unit generates an individual histogram which is a histogram of the delay time obtained for each γ-ray detector, and at least one of the individual histograms is uniformly shifted with respect to the delay time. To generate an overall histogram superimposed on the other individual histograms.
The positron annihilation life measuring device is characterized in that the life calculation unit calculates the life from the entire histogram. It is a method of adjusting a radiation measuring instrument that detects radiation by using multiple radiation detectors, each of which detects radiation and outputs a pulse at the same time.
In a plurality of events in which each of the radiation detectors detects the first radiation using a radiation source that emits the first radiation detected by the radiation detector at substantially constant time intervals from the reference timing.
The outputs of the plurality of radiation detectors are mixed to generate a single input signal in which the relationship between the pulse outputs on the time axis is maintained, and the pulse outputs in the input signals and the pulse outputs are generated. When recognizing the time difference corresponding to the pulse output
Identification for outputs other than at least one of the plurality of radiation detectors so that the histogram corresponding to each output of the plurality of radiation detectors can be identified in the recognized histogram of the time difference. To generate the input signal by imparting sex,
Shift when at least one of the individual histograms, which is the histogram obtained for each radiation detector, is uniformly shifted with respect to the delay time, and then superimposed on the other individual histograms. Calculate the total shift time, which is the quantity,
A method for adjusting a radiation measuring instrument, which comprises correcting the detection timing of each radiation detector using the total shift time. The radiation source emits a second radiation different from the first radiation at a substantially fixed time interval from the first radiation.
A claim characterized in that a reference radiation detector that detects the second radiation separately from the radiation detector is used, and the timing at which the reference radiation detector detects the second radiation is set as the reference timing. Item 5. The method for adjusting the radiation measuring instrument according to Item 5. The method for adjusting a radiation measuring instrument according to claim 5 or 6, wherein the pulse shape of the pulse output has a mode determined for each radiation ray detector in order to impart the distinctiveness. When generating the input signal, a shift time having a constant time difference determined for each radiation detector is given to the pulse output.
Claim 5 according to claim 5, wherein when the individual histogram is generated, the individual histogram is obtained by separating the individual histogram from the histogram of the time difference obtained by using the input signal according to the time series of the time difference. Item 8. The method for adjusting a radiation measuring instrument according to any one of items up to item 7. Each is a radiation measuring instrument that detects radiation by using multiple radiation detectors that detect radiation and output pulses at the same time.
A plurality of the radiation detectors are connected and used to generate a single mixed input signal while maintaining the relationship between the pulse outputs on the time axis in each.
A measuring unit that obtains measurement results related to the pulse output from the input signal,
Identification that generates the distinctiveness corresponding to each of the plurality of radiation detectors to the pulse output before generating the input signal so that the measurement result can be obtained for each of the plurality of radiation detectors in the measuring unit. Sex generator and
Equipped with
A radiation measuring instrument characterized in that the measuring unit separates and recognizes the measurement result into each of the plurality of radiation detectors based on the distinctiveness. The radiation measuring instrument according to claim 9, wherein the discriminative generation unit has a pulse shape of the pulse output in a mode defined for each radiation detector. The radiation measuring instrument according to claim 10, wherein the discriminative generation unit imparts a constant shift time determined for each radiation detector to the pulse output. The distinctiveness generator
When the pulse output from each of the plurality of radiation detectors is input, the identification signal set for each of the plurality of radiation detectors is output in synchronization with the pulse output, and the generated determination signal is output. death,
According to any one of claims 9 to 11, the measuring unit recognizes the pulse output for each of the plurality of radiation detectors from the input signal with reference to the determination signal. The radiation measuring instrument described. A plurality of the radiation detectors are arranged and installed, and the measuring unit recognizes the position information in the arrangement of the radiation detectors that output the pulse together with the pulse output in the input signal. The radiation measuring instrument according to any one of items 9 to 12. The radiation measuring instrument according to claim 13, wherein the plurality of radiation detectors are arranged in a ring shape surrounding the measurement target.

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