JP2001242257A - Radiation measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiation detector capable of accurately detecting radiation in a wide range while simplifying signal processing. SOLUTION: The amount of charge proportional to radiation energy detected by a cold semiconductor detector 1 is amplified by an amplifier 2, converted into a digital signal by an analog-to-digital converter part 3 and inputted to a charge generation depth determining part 5 of a signal processing part 4. The charge generation depth determining part 5 specifies charge generation depth on the basis of an electron signal and a hole signal of the digital signal, and a hole signal correcting part 6 corrects the wave height loss of the hole signal according to the charge generation depth. A total signal correcting part 7 obtains radiation energy by obtaining the wave height value of real charge from the hole signal corrected by the hole signal correcting part 6, and the electron signal detected by the cold semiconductor detector 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation measuring apparatus for detecting an electric charge proportional to the energy of radiation with a semiconductor detector at normal temperature and performing digital signal processing to measure the radiation.

[0002]

2. Description of the Related Art As a radiation detecting apparatus, there is an apparatus which detects radiation by using a normal temperature semiconductor detector. A room-temperature semiconductor detector generates an electric charge in proportion to the energy of radiation incident on the crystal, and an electric field is applied to the electron pair (electrons and holes) of the electric charge generated by the room-temperature semiconductor detector. Is applied to collect the amount of charge to measure the energy of the incident radiation.

In general, a room-temperature semiconductor detector has a small mobility of holes in a crystal, so that the total charge itself is lost due to capture or recombination of holes into a crystal defect or the like, and the room-temperature semiconductor detector has a problem. The signal is not proportional to the incident radiation energy. That is, since the signal wave height is lost by the charge amount of the holes that have been captured and annihilated, there is a disadvantage that the energy resolution and the peak Compton ratio are low.

Therefore, a radiation detecting apparatus has been proposed which detects radiation by processing a detection signal of a room-temperature semiconductor detector. In other words, a method is proposed in which the detection signal from a room-temperature semiconductor detector is digitally processed and the signal wave height is corrected and energy resolution is improved by pattern recognition using a neural network and adaptation to the model waveform using the least squares method. ("Atomic Energy Society of Japan 1997 Spring Annual Conference Proceedings, B16 Sakai, et al." And "Atomic Energy Society of Japan 1995
Autumn meeting proceedings, C16 Fukuda and others ”).

FIG. 9 is a block diagram of a conventional radiation detecting apparatus using such a normal temperature semiconductor detector. The signal of the ordinary temperature semiconductor detector 1 is amplified by a charge-sensitive preamplifier 2, the signal from the preamplifier 2 is digitized by an A / D converter 3, and the signal digitized by the A / D converter 3 is subjected to signal processing. Processing such as neural network and model fitting is performed by the unit 4. Thus, the loss of the signal wave height corresponding to the charge amount of the holes that have been captured and annihilated is corrected, and the radiation is detected.

[0006]

However, in the digital signal processing of the radiation detection apparatus as described above, there is a problem that a process of fitting with a model prepared in advance occurs, so that the amount of calculation is large and the processing takes time. . Further, when the analog input voltage level is fixed at the time of A / D conversion in which the detection signal of the room temperature semiconductor detector 1 is digitally processed, accuracy cannot be ensured in an environment having a wide analog input voltage level input. is there.

In general, a normal temperature semiconductor detector uses a crystal having a small thickness in order to reduce the loss of holes. However, a thin crystal has a drawback that its sensitivity to high-energy radiation is low. . Furthermore, when the radiation intensity of the measurement object is weak and the sensitivity is insufficient, a crystal having a large area is required, and there is a problem that it is difficult to increase the area with a thin crystal.

An object of the present invention is to provide a radiation detecting apparatus capable of simplifying signal processing and detecting radiation over a wide measuring range with high accuracy.

[0009]

According to the present invention, there is provided a radiation measuring apparatus, comprising: a room-temperature semiconductor detector for detecting an amount of charge of electrons and holes generated in proportion to irradiation radiation; A radiation measuring apparatus comprising: an A / D conversion unit that converts a charge amount detected by a detector into a digital signal; and a signal processing unit that calculates radiation energy based on the digital signal from the A / D conversion unit. The signal processing unit includes a charge generation depth determination unit that specifies a charge generation depth based on the electronic signal and the hole signal converted to digital signals by the A / D conversion unit, and the charge generation depth determination unit A hole signal correction unit that corrects the peak height loss of the hole signal in accordance with the charge generation depth specified in the above, the hole signal corrected by the hole signal correction unit, and the hole signal corrected by the room temperature semiconductor detector. From electronic signals Characterized in that a total signal correcting unit for obtaining a radiation energy seeking the peak value of the charge.

In the radiation measuring apparatus according to the first aspect of the present invention, the charge amount proportional to the radiation energy detected by the room temperature semiconductor detector is amplified by an amplifier, converted into a digital signal by an A / D converter, and processed. Input to the charge generation depth determining unit. The charge generation depth determination unit specifies the charge generation depth based on the electronic signal and the hole signal of the digital signal, and the hole signal correction unit corrects the peak loss of the hole signal according to the charge generation depth. . Then, the all-signal correcting unit obtains the peak value of the true charge from the hole signal corrected by the hole signal correcting unit and the electronic signal detected by the room-temperature semiconductor detector to obtain radiation energy.

According to a second aspect of the present invention, in the radiation measuring apparatus according to the first aspect of the present invention, the charge generation depth determining unit determines a discontinuous point of a signal gradient from a rising edge of the digital signal. A determination unit; and a charge generation depth calculation unit that separates an electron signal and a hole signal based on the discontinuity point from the discontinuity point determination unit and specifies a charge generation depth. .

[0012] In the radiation measuring apparatus according to the second aspect of the present invention, in addition to the operation of the first aspect, the signal gradient discontinuity determining unit of the charge generation depth determining unit determines the discontinuity of the signal gradient from the rising edge of the digital signal. A point is obtained, and the charge generation depth is specified by separating the electron signal and the hole signal based on the discontinuous point from the discontinuous point determination unit in the charge generation depth calculation unit.

According to a third aspect of the present invention, in the radiation measuring apparatus according to the second aspect, the signal slope discontinuity determination unit determines a signal slope from a minimum value of a second derivative of a signal waveform of the digital signal. A discontinuous point is obtained, or a discontinuous point of a signal gradient is obtained by comparing a first-order differential value of the signal waveform of the digital signal with a predetermined threshold value.

According to a third aspect of the present invention, in addition to the function of the second aspect of the present invention, the signal waveform of the digital signal is secondarily differentiated, and the signal gradient is determined when the second derivative value is the minimum value. As a discontinuous point of. Further, the signal waveform of the digital signal is first-order differentiated, the first-order differential value is compared with a predetermined threshold value, and when the threshold value is reached, the signal gradient is determined as a discontinuous point.

According to a fourth aspect of the present invention, in the radiation measuring apparatus according to the second aspect of the present invention, the charge generation depth calculator calculates a ratio between a peak value of the electron signal and a peak value of the hole signal, The charge generation depth is specified by the rise time or the rise time of the hole signal.

In the radiation measuring apparatus according to a fourth aspect of the present invention, in addition to the function of the second aspect of the present invention, the charge generation depth is specified by the ratio between the peak value of the electron signal and the peak value of the hole signal. Further, the charge generation depth is specified by the rise time of the electron signal or the rise time of the hole signal.

According to a fifth aspect of the present invention, in the radiation measuring apparatus according to the first aspect, the hole signal correction unit includes:
The hole height to obtain the theoretical value of the signal peak value due to holes based on the measured value distribution of the signal peak value due to electrons and the signal peak value due to holes at the charge generation depth specified by the charge generation depth determination unit. A theoretical value calculating unit, and a hole decay unit that corrects the attenuation of the signal peak value due to holes based on the charge generation depth based on the theoretical value of the signal peak value due to holes obtained by the hole peak theoretical value calculating unit. And a correction operation unit.

In the radiation measuring apparatus according to the fifth aspect of the present invention, in addition to the operation of the first aspect of the present invention, the charge generation depth determining unit specifies the charge generation depth determining unit by the theoretical hole height calculating unit of the hole signal correcting unit. The theoretical value of the signal peak value due to holes is obtained based on the measured value distribution of the signal peak value due to electrons at the charge generation depth and the signal peak value due to holes. The attenuation of the signal peak value due to holes is corrected according to the charge generation depth based on the theoretical value of the signal peak value due to holes obtained by the calculation unit.

In the radiation measuring apparatus according to a sixth aspect of the present invention, in the fifth aspect of the present invention, the theoretical hole crest value calculating section obtains an ideal curve from a signal distribution region in which the signal crest value of electrons is dominant. It is characterized in that the theoretical value of the signal peak value due to the hole is obtained.

In the radiation measuring apparatus according to the sixth aspect of the present invention, in addition to the operation of the fifth aspect, an ideal curve is obtained from a signal distribution region in which the signal peak value due to electrons is dominant, and the theoretical value of the signal peak value due to holes is obtained. Find the value.

According to a seventh aspect of the present invention, in the radiation measuring apparatus according to any one of the first to sixth aspects, a plurality of A / D converters are provided according to a plurality of analog input ranges. It is characterized by.

In the radiation measuring apparatus according to the seventh aspect of the present invention, in addition to the function of any one of the first to sixth aspects of the present invention, a plurality of A / D converters can be used to control an A / D signal in each analog input range. D-convert. This ensures accuracy over a wide analog input range.

According to an eighth aspect of the present invention, in the radiation measuring apparatus according to any one of the first to sixth aspects, the A / D conversion section has a plurality of analog input ranges and is provided at regular intervals. The analog input range is switched.

[0024] In the radiation measuring apparatus according to the invention of claim 8, in addition to the operation of any one of the inventions of claims 1 to 6, a plurality of analog input ranges can be switched at predetermined time intervals. A / D conversion is performed. This ensures accuracy over a wide analog input range.

According to a ninth aspect of the present invention, in the radiation measuring apparatus according to any one of the first to eighth aspects, the all-signal correcting section includes a hole corrected by the hole signal correcting section. The charge generation depth is designated based on the signal peak value obtained by the above method, and the depth of the detection position in the room-temperature semiconductor detector is extracted from the charge generation depth.

In the radiation measuring apparatus according to the ninth aspect of the present invention, in addition to the function of any one of the first to eighth aspects, the signal peak value due to the holes corrected by the hole signal correcting section is obtained. The charge generation depth is specified based on this. Then, the depth of the detection position in the room temperature semiconductor detector is extracted from the charge generation depth. This simulates a detector having an arbitrary thickness smaller than the physical thickness of the room-temperature semiconductor detector, and measures radiation in a wide energy range.

[0027]

Embodiments of the present invention will be described below. FIG. 1 is a configuration diagram of the radiation detection apparatus according to the first embodiment of the present invention.

The room-temperature semiconductor detector 1 is made of CdTe, CZT or the like, and its detection signal is amplified by a charge-sensitive preamplifier 2 and digitized by an A / D converter 3. A / D
The digital signal digitally converted by the conversion unit 3 is input to the charge generation depth determination unit 5 of the signal processing unit 4, and the charge generation depth is obtained from the digital signal.

The charge generation depth determined by the charge generation depth determination unit 5 is input to a hole signal correction unit 6, where the hole signal is corrected according to the charge generation depth. Then, the true signal peak value is calculated from the corrected hole signal and electronic signal in the all-signal correcting unit 7.

FIG. 2 is a configuration diagram of the charge generation depth determining unit 5. The charge generation depth determination unit 5 inputs the digital signal digitally converted by the A / D conversion unit 3 to the signal gradient discontinuity point determination unit 8 and obtains the discontinuity of the signal gradient from the rising edge of the digital signal. Can be Then, the charge generation depth calculator 9 calculates the charge generation depth from the discontinuous point of the slope of the signal to determine the charge generation depth.

FIG. 3 is an explanatory diagram of signal processing in the signal gradient discontinuous point determination section 8. FIG. 3A shows the A / D converter 3
FIG. 4 is a characteristic diagram of a signal level of a digital signal digitally converted in FIG.

In many cases, the mobility of electrons is larger than the mobility of holes. Therefore, in the digitized digital signal, a fast rising component X due to the movement of electrons is first observed as shown in FIG. Then, a slow component Y due to the movement of holes appears. The signal height in FIG. 3A is proportional to the charge collected on the electrode, and when all charges generated by the incidence of radiation have been collected, the signal height is proportional to the energy of the incident radiation.

As shown in FIG. 3B, the discontinuous point Z of the signal gradient is a point at which the digital signal is secondarily differentiated and has a minimum value R after the signal rises, as shown in FIG. 3B. Let it be a continuous point Z. Alternatively, as shown in FIG. 3C, the discontinuous point Z is obtained by comparing the first derivative of the digital signal with a previously calculated threshold value S of the slope. By calculating the discontinuous point Z of the signal gradient, the rising of the signal can be separated into the signal component X due to the movement of electrons and the signal component Y due to the movement of holes.

Next, signal processing in the charge generation depth calculator 9 will be described. FIG. 4 is an explanatory diagram of signal processing in the charge generation depth calculation unit 9. 4A is a characteristic diagram of a digital signal obtained by converting a detection signal from the room temperature semiconductor detector 1 by the A / D converter 3, FIG. 4B is a schematic diagram of a crystal of the room temperature semiconductor detector 1, and FIG. FIG. 4C is a characteristic diagram of the signal of the electron pair generated at the positions A and B in FIG.

The signal rise is separated into a signal component caused by the movement of electrons and a signal component caused by the movement of holes, and the signal peak value SX due to electrons, the signal peak value SY due to holes, and the electronic signal X in FIG. Attention is paid to the rise time TX and the rise time TY of the hole signal.

Assuming that there is no loss of the hole signal Y, FIG.
When electric charges are generated at the positions A and B as shown in (b), electrons move to the anode and holes move to the cathode, and a signal is generated by movement of the electrons and holes.

The electron pair signal SA generated at the position A in FIG. 4C indicates that the electron reaches the anode at the point a and the hole reaches the cathode at the point d. On the other hand, the electron pair signal SB generated at the position B indicates that the electrons reach the anode at the point b in FIG.
The point c indicates that the holes have reached the cathode.

The signal peak values SXA and SXB due to electrons and the signal peak values SYA and SYB due to holes are proportional to the moving distance of electrons and holes. Therefore, the signal peak values SXA, SXB due to electrons and the signal peak values SYA, due to holes,
Since the ratio to SYB corresponds to the charge generation depth, the charge generation depth can be specified from the ratio between the signal peak value of electrons and the signal peak value of holes. For example, when the signal peak value due to electrons is equal to the signal peak value due to holes, an electric charge is generated at the midpoint between the two electrodes. In this case, electric charges are generated near the cathode.

In FIG. 4C, the case where the radiation having the same energy is incident at the positions A and B is described. However, even if the energy of the incident radiation is different, the signal peak value SX of the electron and If the ratio to the signal peak value SY due to holes is taken, the present invention can be applied to radiation of arbitrary energy.
However, since the charge generated near the anode can not ignore the capture of holes, the hole signal is lost and the actual charge generation depth is not calculated, but does not affect the correction of the hole crest loss. The actual charge generation depth can be obtained after correcting the peak loss of the holes.

Next, attention is paid to the rise time TX of the electronic signal X and the rise time TY of the hole signal in FIG. As shown in FIG. 4C, the electron signal rise time TX and the hole signal rise time TY are, as shown in FIG. 4C, a time TX0 (moving distance) in which electrons move between the electrodes and a time TY0 (moving distance) in which holes move between the electrodes. Distance).

Therefore, the time T during which the electrons move between the electrodes is T
If X0 and the time TY0 during which the holes move between the electrodes are obtained in advance, (rise time of the electron signal) / (time when the electrons move between the electrodes), (rise time of the hole signal) /
Since (the time when holes move between the electrodes) corresponds to the charge generation depth, the charge generation depth can be specified from the rise time of the electron or hole signal. Signal rise time
Since (time required for electrons or holes to move in a semiconductor at room temperature) is not related to loss, a correct charge generation depth can be obtained without correction.

FIG. 5 is a block diagram of the hole signal correction section 6. The charge generation depth specified by the charge generation depth determination unit 5 is input to the theoretical hole wave height calculation unit 10 of the hole signal correction unit 6, and the charge generation depth is calculated by the theoretical hole wave height calculation unit 10. The theoretical value of the signal peak value due to holes is obtained based on the measured value distribution of the signal peak value due to electrons and the signal peak value due to holes at the charge generation depth specified by the determination unit 5. And
The hole attenuation correction operation unit 11 corrects the attenuation of the signal peak value due to the holes in accordance with the charge generation depth based on the theoretical value of the signal peak value due to the holes obtained by the theoretical hole peak value operation unit 10. .

FIG. 6 is an explanatory diagram of the signal processing of the hole signal correction unit 6. FIG. 6A illustrates a theoretical theoretical value of the hole crest value.
FIG. 4 is an explanatory diagram in a case where a theoretical value of a signal peak value due to holes is obtained by using FIG. In FIG. 6A, the signal peak value of electrons is plotted on the horizontal axis, the signal peak value of holes is plotted on the vertical axis, and the measured values of the signal peak value of electrons and the signal peak value of holes are plotted. is there.

The measured value distributions of the signal peak value due to electrons and the signal peak value due to holes are a distribution M1 due to the photoelectric effect when all the energy of the incident radiation is absorbed, and a part of the energy of the incident radiation is absorbed. And the distribution M2 due to Compton scattering in the case where the distribution is performed.

Attention is now focused on the distribution M1 due to the photoelectric effect. Since the electronic signal is more dominant in the distribution on the right side in the graph of FIG. 6A, the distribution region is where the electronic signal is dominant. From the distribution region where the electronic signal is dominant, an ideal curve f2 of the distribution due to the photoelectric effect is obtained. Further, a correction function using the charge generation depth x as a function is obtained from the approximate curve f1 and the ideal curve f2 of the actual distribution. Then, the crest loss is corrected from these.

Specifically, the charge generation depth is x, the approximate curve is f1 (x), the ideal curve is f2 (x), the hole signal peak value is S, and the corrected hole signal peak value is S '
The hole signal can be corrected by the equation S ′ = S × f2 (x) / f1 (x).

This is effective only for radiation having the photopeak shown in FIG. To apply this to radiation of any energy, the horizontal axis in FIG. 6A needs to be (electron signal peak value) / (total signal peak value). With respect to the distribution of the photoelectric peaks in FIG. 6A, the horizontal axis represents (electron signal peak value) / (total signal peak value), and the vertical axis represents the signal peak value due to holes before correction and FIG. 6A. When the peak value of the signal due to the corrected holes is plotted, a distribution as shown in FIG. 6B is obtained.

The two distributions are approximated by a curve to correct the signal peak value of holes, and the signal peak value of holes obtained by the correction and the signal peak value of electrons are added.
A peak value proportional to the energy of the incident radiation is obtained. Specifically, (electron signal peak value) / (total signal peak value)
Is x, the approximate curve of the hole distribution before correction is g1 (x), the approximate curve of the hole distribution after correction is g2 (x), the signal peak value of the hole before correction is S, and the value after correction is S. The signal peak value of the hole is S '
Then, the signal of the hole can be corrected by the equation S ′ = S × g2 (x) / g1 (x).

Next, a second embodiment of the present invention will be described. FIG. 7 is a configuration diagram of a radiation measuring apparatus according to the second embodiment of the present invention. FIG. 7A shows a configuration in which a plurality of A / D converters 3 having different input ranges are provided, and FIG. The parentheses indicate an A / D converter 3 having a plurality of input ranges and switching.

As shown in FIG. 7A, the signal of the normal temperature semiconductor detector 1 is amplified by the preamplifier 2 and input to a plurality of A / D converters 3 having different analog input voltage levels. Thereby, bit accuracy can be ensured for a wide analog input voltage level. FIG.
A / D having a plurality of input ranges as shown in FIG.
By switching the input range of the conversion unit 3 at regular intervals, bit accuracy is similarly secured for a wide analog input voltage level.

Next, in order to simulate a detector having an arbitrary thickness smaller than the physical thickness of the normal temperature semiconductor detector 1, the entire signal correction unit 7 of the signal processing unit 4 uses the hole signal correction unit 6. The charge generation depth is designated based on the corrected signal peak value of the holes. Then, the depth of the detection position in the room temperature semiconductor detector 1 is extracted from the charge generation depth, and a detector having an arbitrary thickness smaller than the physical thickness of the room temperature semiconductor detector 1 is simulated.

FIG. 8 is an explanatory diagram for extracting a signal at an arbitrary depth from the ordinary temperature semiconductor detector 1. When the signal peak value of electrons is plotted on the horizontal axis and the signal peak value of holes corrected by the hole signal correction unit 6 is plotted on the vertical axis, the distribution is as shown in FIG.

From FIG. 8, the charge generation depth is specified as follows. For example, in FIG. 8, the straight line y = x has a depth that is half the thickness of the entire normal temperature semiconductor crystal. The area below this straight line is the cathode-side half, and the area above this line is the anode-side half. Therefore, in order to extract only the signal generated from the cathode at a portion having a thickness of の of the entire thickness of the normal-temperature semiconductor crystal, a signal below the straight line y = x may be extracted.

Now, assuming that the thickness of the crystal is t and the depth of charge generation from the cathode is d (0 <d <t), a signal generated from the cathode to the depth d is extracted by a straight line. y = ｛d
The signal below / (t−d)｝ x may be extracted.
For example, in order to extract only a signal generated from the cathode at a portion having a thickness of 1/5 of the thickness of the entire normal temperature semiconductor crystal, d
= T / 5, the straight line y = {d / (t−d)} x = x /
Signals below 4 need only be extracted. By this method, a crystal having an arbitrary thickness smaller than the actual crystal thickness can be simulated.

[0055]

As described above, according to the present invention,
Simple digital processing can improve the energy resolution and peak / Compton ratio of a semiconductor detector at room temperature.
It is extremely effective practically. Further, by providing a plurality of analog input ranges, it is possible to expand the measurement energy range of the room temperature semiconductor detector, which is extremely effective practically. In addition, radiation can be detected using a large-area thick detector with the same accuracy as a thin detector.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a radiation detection apparatus according to a first embodiment of the present invention.

FIG. 2 is a configuration diagram of a charge generation depth determining unit according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram of signal processing in a signal gradient discontinuous point determination unit according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram of signal processing in a charge generation depth calculation unit according to the first embodiment of the present invention.

FIG. 5 is a configuration diagram of a hole signal correction unit according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram of signal processing of a hole signal correction unit according to the first embodiment of the present invention.

FIG. 7 is a configuration diagram of a radiation measuring apparatus according to a second embodiment of the present invention.

FIG. 8 is an explanatory diagram of a process of extracting a signal at an arbitrary depth of the room-temperature semiconductor detector.

FIG. 9 is a configuration diagram of a conventional example.

[Explanation of symbols]

1: normal temperature semiconductor detector, 2: charge-sensitive preamplifier, 3
... A / D converter, 4 ... signal processor, 5 ... charge generation depth determiner, 6 ... hole signal corrector, 7 ... all signal corrector, 8 ... signal gradient discontinuous point determiner, 9 ... charge Generation depth calculation unit, 10
... Hole peak height calculation unit, 11 ... Hole attenuation correction calculation unit

Claims (9)

[Claims] A room-temperature semiconductor detector for detecting the amount of charge of electrons and holes generated in proportion to the applied radiation;
Radiation measurement comprising: an A / D converter for converting an amount of electric charge detected by the room temperature semiconductor detector into a digital signal; and a signal processor for obtaining radiation energy based on the digital signal from the A / D converter. In the apparatus, the signal processing unit includes a charge generation depth determination unit that specifies a charge generation depth based on the electronic signal and the hole signal converted into digital signals by the A / D conversion unit, and the charge generation depth. A hole signal correction unit that corrects the peak height loss of the hole signal according to the charge generation depth specified by the determination unit; and a hole signal corrected by the hole signal correction unit and the room-temperature semiconductor detector. A radiation measuring apparatus comprising: a full signal correction unit that obtains a peak value of a true charge from a detected electronic signal and obtains radiation energy. 2. The charge generation depth determination unit according to claim 1, wherein the signal gradient discontinuity determining unit determines a signal gradient discontinuity from a rise of the digital signal, and a discontinuous point from the discontinuity determination unit. The radiation measurement apparatus according to claim 1, further comprising: a charge generation depth calculation unit configured to separate an electron signal and a hole signal to specify a charge generation depth. 3. The signal gradient discontinuous point determination unit determines a discontinuous point of a signal gradient from a minimum value of a second derivative of a signal waveform of the digital signal, or a first derivative of a signal waveform of the digital signal. 3. The radiation measuring apparatus according to claim 2, wherein a discontinuous point of the signal inclination is obtained from a comparison between the value and a predetermined threshold value. 4. The charge generation depth calculation unit specifies a charge generation depth based on a ratio between a peak value of an electronic signal and a peak value of a hole signal, a rise time of an electron signal or a rise time of a hole signal. The radiation measuring apparatus according to claim 2, wherein: 5. The hole signal correction unit according to claim 5, wherein the hole signal correction unit determines a positive value based on a measured value distribution of a signal peak value of electrons and a signal peak value of holes at the charge generation depth specified by the charge generation depth determining unit. A theoretical hole height calculating unit for calculating a theoretical value of the signal peak value due to the holes, and a positive value corresponding to the charge generation depth based on the theoretical value of the signal peak value of the holes determined by the theoretical hole height calculating unit. The radiation measurement apparatus according to claim 1, further comprising a hole attenuation correction calculation unit that corrects the attenuation of the signal peak value due to the holes. 6. The theoretical hole peak value calculating section calculates an ideal curve from a signal distribution region in which a signal peak value of electrons is dominant and obtains a theoretical value of a signal peak value of holes. 6. The radiation measuring device according to 5. 7. The radiation measuring apparatus according to claim 1, wherein a plurality of A / D converters are provided according to a plurality of analog input ranges. 8. The A / D converter according to claim 1, wherein the A / D converter has a plurality of analog input ranges, and switches the analog input range at regular time intervals. Radiation measurement device. 9. The all-signal correction unit specifies a charge generation depth based on a signal peak value of a hole corrected by the hole signal correction unit, and determines the charge generation depth from the charge generation depth. The radiation measurement apparatus according to claim 1, wherein a depth of the detection position is extracted.