JP3198763B2 - Wave height stabilization circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplification gain using a reference signal in a radiation measuring device or the like which amplifies a pulse signal having a significant peak value and performs measurement in accordance with the division of the peak value. And a wave height stabilizer for controlling the wave height stably.

[0002]

2. Description of the Related Art A radiation detector such as a semiconductor radiation detector or a NaI scintillation detector outputs a pulse-like detection signal having a peak value proportional to the energy of the incident radiation every time the radiation enters the detector. I do. In a radiation measurement device that measures the amount of radiation related to both the frequency of radiation generation and its energy using a semiconductor radiation detector or NaI scintillation detector, etc., the amplification gain is kept stable for a long time. Therefore, a peak height stabilizing circuit is added to the measuring device.

A crest stabilizing circuit gives a signal which serves as a reference for the gain with respect to radiation energy, for example, a signal obtained by irradiating a reference source or irradiating light to the detector, and the degree of deviation of the output. Is obtained as an output signal, and this is used to control the gain of the entire system to stabilize the gain. FIG. 5 shows a block diagram of an example of a radiation measuring apparatus using a wave height stabilizing circuit according to the related art for measuring the frequency of occurrence of radiation in a specific energy range.

In FIG. 5, reference numeral 1 denotes a reference gamma ray source;
Is a radiation detector such as a NaI scintillation detector to which energy information is given by an output signal peak value;
32 and 39 are single channel pulse height analyzers, 4 is a differential count rate meter, 5 is an integrating circuit, 6 is a detector bias power supply, 7
Is a counting rate meter. In the radiation measuring apparatus having the configuration shown in FIG. 5, if the reference gamma ray source 1 is, for example, ¹³⁷ Cs, the energy spectrum of the signal output from the detector 2 is shown in FIG.
And a photo peak p of ¹³⁷ Cs is obtained.

[0005] Single channel wave height analyzers 31, 32 and
39 uses the output signal of the detector as an input signal, selectively extracts only a signal in a predetermined specific height range, that is, a radiation component in a specific energy range, and shapes the signal by the radiation into a waveform of a fixed height and width. The signal is output as a signal, and a symbol such as B or C indicating the set specific energy range is added to the end and is represented as SCAB or the like.

The specific energy range set in the single-channel pulse height analyzers 31 and 32 is such that, as shown in FIG. 6, the SCAB 31 is in the region indicated by b in the left half of the reference photo peak p in accordance with the reference photo peak. , And SCAC32
Is set to measure radiation that gives a pulse signal of a peak value corresponding to the area indicated by c in the right half of the reference photo peak p.

The differential counting rate meter 4 comprises SCAB31 and SCA
An output signal of C32 is input, and if there is a difference in the frequency of occurrence of both pulse signals, an electric signal proportional to the positive or negative difference is output depending on which is more. Therefore, if the numbers of the two inputs per unit time are equal, the output signal becomes zero. The integrating circuit 5 integrates the output signal of the differential counting rate meter 4 and, when the output of the differential counting rate meter 4 becomes 0, maintains the integration result up to that time and outputs it to the bias power supply 6 as a control signal. I do.

The detector bias power supply 6 is a power supply for supplying a voltage applied to the NaI scintillation detector 2. When this voltage is increased, the peak value of the output signal of the detector with respect to radiation having the same energy is increased, and the amplification gain of the system is increased. Rises,
Conversely, when it is lowered, the amplification gain of the system decreases. The output voltage of the detector bias power supply 6 is controlled by the output signal of the integration circuit 5.

On the other hand, the SCAM 39 selectively extracts a signal in the energy range to be measured and outputs the signal to the counting rate meter 7. The selected energy range can be set arbitrarily. In the case of the example shown in FIG. The photo peak of the gamma ray source is set in a region outside the photo peak. In such a situation,
When the amplification gain of the measurement system increases due to a change in the photomultiplier of the scintillation detector 2 or the output voltage of the detector bias power supply 6 for some reason, as shown in the spectrum model diagram of FIG. The peak value of p is shifted to a slightly higher value (higher energy value), so that the number of output signals of SCAC32 increases and the number of output signals of SCAB31 decreases. Then, a signal in the direction of decreasing the output voltage of the bias power supply 6 is output from the differential counting rate meter 4 according to the situation, and the integration circuit 5
The output is supplied to the bias power supply 6 to lower the bias voltage, the peak value of the signal corresponding to the photo peak also becomes lower, and moves to the lower energy. Then, when the signal wave numbers in the measurement energy range of the SCA31 and SCA32 become equal and the number of output signals of the SCA31 and SCA32 become equal, the operation is stabilized. In this way, the peak of the photo peak can be kept constant.

As a result, the measurement energy range of the SCAM 39 is also kept constant, and accurate measurement results can be obtained in the counter 7.

[0011]

According to the prior art crest stabilizing circuit having the configuration illustrated in FIG. 5, the radiation range of other nuclides is not mixed in the energy range of the reference photo peak, and the reference photo peak is not increased. When observed independently, the peak height stabilization circuit functions normally. However, radiation of various energies from a plurality of nuclides is mixed, and the bottom of the photopeak due to radiation from other nuclides overlaps the energy range of the reference photopeak as a background, as shown by the thick solid line in FIG. In such a case, even when the SCAB 31 and the SCAC 32 divide the original energy range of the reference photopeak equally, the pulse signal input to the differential counting rate meter 4 causes Since a pulse signal is included, the output of the differential counting rate meter 4 does not become stable in this state because it becomes 0, and the pulse wave amplification gain is set so as to be stabilized at a photo peak different from the reference. Changes.

In addition, when the background increases and the ratio of the reference signal decreases, it becomes difficult to detect the photopeak stably, and the accuracy of stabilization of the wave height is reduced. Occurs. In view of the above points, an object of the present invention is to provide a peak height stabilization method capable of operating even under worse measurement conditions where other signals are mixed in the energy range of the reference photo peak.

[0013]

In order to achieve the above object,
In a peak height stabilizing circuit according to the present invention, first and second peak height analyzers for selectively extracting a signal in a peak value range that equally divides a peak value range of a reference signal and outputting the extracted signal as a shaped pulse signal; First and second count rate meters for measuring the frequency of the output pulse signal of each of the first and second pulse height analyzers, and adjacent to the measured peak value range of the first and second pulse height analyzers. A third peak value analyzer that outputs a pulse signal obtained by selectively extracting a background signal and outputting a shaped pulse signal, and a third peak signal analyzer and a third peak signal analyzer. Third and fourth count rate meters for measuring the frequency of the output pulse signal, the count rate by the background signal component in the energy range selected by the first to fourth pulse height analyzers, and the energy value as an independent variable. And two undecided The values of the two undetermined constants are obtained by calculation based on the values of the count rates output by the third and fourth count rate meters, and the values of the undetermined constants are determined by the approximation function. A count rate based on a background signal component in an energy range defined by the first and second count rate meters is calculated, subtracted from a count rate output of the first and second count rate meters, and calculated based on a contribution component of a reference signal. An arithmetic circuit for outputting the count rate is provided.

In order to match the variation range of the independent variable of the function approximating the background to the peak value range selected by the first to fourth peak analyzers, the peak value as a variable is converted by a linear linear equation. . When the background signal component changes corresponding to the peak value in the peak value range near the reference signal, a linear quadratic equation is applied as a function approximating the background signal component. on the other hand,
If the rate of change of the background signal component can be considered to be equal, a linear linear equation is applied as a function approximating the background signal component.

[0015]

As described above, when the background signal component near the peak value region of the reference signal is approximated by a function determined by two undetermined constants, the peak range of the background signal component outside the reference signal peak region is selectively extracted. The count rate output values of the third and fourth count rate meters connected to the third and fourth pulse height analyzers are independent 2 values including the two undetermined constants, respectively.
In an arithmetic circuit which is represented by an equation and provided with the outputs of the third and fourth count rate meters as inputs, the two equations are solved for the undetermined constant, and the value of the undetermined constant is determined.

Further, the arithmetic circuit uses the constant value of the background approximation function determined as described above to perform the first
And the second pulse height analyzer and the reference signal output by the first and second first and second count rate meters connected to the pulse height analyzer. The contribution of the background signal component is calculated and obtained, and this value is subtracted from the output values of the first and second count rate meters to calculate the value of the difference between the count rates due to only the reference signal component, thereby amplifying the gain of the pulse height. As a control signal.

When the peak value as a variable is converted by a linear linear equation, the range of change of the independent variable of the approximation function matches the peak value range selected by the first to fourth pulse height analyzers. When a linear quadratic equation is applied as a function, the background signal component is adapted to a measurement environment that changes according to the peak value,
When the linear function is used as the approximation function, it is suitable for a measurement environment where the rate of change of the background signal component is uniform.

[0018]

1 is a block diagram showing an embodiment of a counting rate meter provided with a peak height stabilizing circuit according to the present invention, and FIG.
FIG. 2 is an enlarged spectrum diagram for explaining the operation of the peak height stabilizing circuit having the block configuration described above, and the present invention will be described below with reference to these diagrams. In FIG. 1, reference numeral 1 denotes a reference gamma ray source, and 2 denotes a radiation detector of a type to which energy information is given by a peak value of an output signal such as a NaI scintillation detector, which is output by a power supply voltage supplied from a detector bias power supply 6. The gain with respect to the signal peak value fluctuates. 31 to 34 are single-channel wave height analyzers constituting a wave height stabilizing circuit; 401 to 404.
Is a count rate meter which also constitutes a wave height stabilizing circuit, and 81 generates an output voltage control signal of a detector bias power supply 6 for generating a bias voltage to be applied to the detector 1 by using an output of the count rate meter as an input. The output of the arithmetic circuit 81 is smoothed and stabilized by the integrating circuit 5 and input as a control signal to the detector bias power supply 6.

On the other hand, reference numeral 39 denotes a pulse height analyzer (SCAM) for selecting a peak value range to be observed from among the stabilized detector output pulse signals, and a pulse having a peak value range selected by the SCAM. The signal is counted by the counting rate meter 7 as a measured value. Next, the operation of the main wave height stabilizing circuit will be described with reference to the spectrum enlarged view of FIG.

In FIG. 2, since radiations of various energies from a plurality of nuclides are mixed, the tail of the photopeak due to radiation from other nuclides falls in the background (hereinafter referred to as BG) in the energy range of the reference photopeak. (Abbreviation). Therefore, as shown in FIG. 2, the reference photo peak region and the region adjacent to the peak region are defined by the energy Ep corresponding to the peak of the reference photo peak as a boundary and the width of the energy region where the reference photo peak exists. Channels B and C having a channel width W of ２, and channels A and D having predetermined widths Wa and Wd adjacent to the reference photopeak region are divided into A and D.
The energy selection range of the single-channel peak-height analyzers 31 to 34 constituting the above-mentioned peak-height stabilizing circuit is assigned to each of the channels D to D, the peak-height analyzer assigned to each channel, and the counting rate connected to the peak-height analyzer. Are represented by channel symbols such as SCAA and RMA, respectively.

When the energy selection range of each single-channel pulse height analyzer is set as described above, the output of the count rate meter RMA or RMD connected to the SCAA or the SCAD is output from other nuclides not including the reference photopeak component. While the count rate values a ′ and d ′ due to radiation (BG) are output from the count rate meters RMB and RMC connected to SCAB and SCAC, the count rate values b and c of the reference photopeak component are added to the BG values. The count rate values Nb and Nc represented by the following equations (1) and (2) are obtained by adding the count rate values b 'and c' for the component contribution.

[0022]

Nb = b + b '(1)

[0023]

Nc = c + c '(2) By the way, if it can be considered that BG due to radiation from other nuclides in the reference photopeak region is changing depending on energy, this BG count rate is set to energy x. A function f (x) having two undetermined constants can be selected as a function to be approximated as a variable.

Therefore, wave height analyzers SCAA to SCAD
Are allocated as described above, the counting rates a ′, b ′, c ′ and d ′ caused by BG in each channel are obtained.
Expresses the integral function of the approximation function f (x) of the BG as F (x)
Are represented by the following equations (3) to (6).

[0025]

A ′ = F (Ep−W) −F {Ep− (W + Wa)} (3)

[0026]

B ′ = F (Ep) −F (Ep−W) (4)

[0027]

C ′ = F (Ep + W) −F (Ep) (5)

[0028]

D ′ = F ｛Ep + (W + Wb)｝ − F (Ep + W) (6) Equations (3) to (6) are integral functions of a function f (x) having two undetermined constants. Since this is an independent expression obtained by substituting different known values for the variable of F (x), it includes two undetermined constants. The value of the undetermined constant is measured as a measurement value not including the reference photopeak contribution, and is used as a peak value analyzer SCAA.
Can be obtained by calculation from the equations (3) and (6) representing the signals a ′ and d ′ output by the count rate meters RMA and RMD connected to SAD and SCAD.

When the undetermined constant is determined, this value is substituted into the equations (4) and (5) to obtain the peak height analyzers SCAB and SCAA.
The output signals Nb and Nc output from the count rate meters RMB and RMC whose energy ranges of the reference photopeaks are set in the measurement range by C determine the count rate values b 'and c' for the BG component contribution. Therefore, the values a and b of the net count rate based on the reference photopeak can be derived from Expressions (1) and (2).

The value a of the net count rate based on the reference photo peak a
And b are obtained, and if an output signal corresponding to the value of the difference is obtained, the amplification gain of the pulse signal amplification circuit system can be kept constant by the same technique as that described in the section of the prior art. The arithmetic circuit 81 is a circuit that calculates the difference between the net count rate values a and b by executing the above-described arithmetic operation, and calculates and outputs a control signal for the output voltage of the detector bias power supply based on the difference value.

As the BG approximation function, a range of variables most suitable for the BG situation in an arbitrary function determined by two undetermined constants can be selected based on the second aspect of the present invention. For example, the energy width of the channels A to D centered on the reference photo peak Ep is assumed to be W, and the BG state during this period is changed to (Et, B) outside the channel A.
When trying to approximate in a variable range corresponding to π to 3π / 2 of a cosine function having a vertex as an apex, first, the energy x as a variable is set between π and 3π / 2 by a linear equation (7) based on claim 2. To the variable θ defined by The coefficients β and α of this conversion equation can be determined by equations (8) and (9) obtained by adapting the above-mentioned conditions of the variable range.

[0032]

Θ = β (x−α) (7)

[0033]

Π = β (Et−α) (8)

[0034]

## EQU9 ## 3π / 2 = β (Ep + 2W-α) (9) Cosine function cos using θ obtained by the above conversion as a variable
By θ, a linear equation (1
0) is defined as a BG approximation function, the equation (10) becomes
With (Et, B) as the apex, the value at the outer boundary of the channel D is A + B, and the expected function is obtained in which the change during the change corresponds to a change between π and 3π / 2 of the cosine function.

[0035]

F (x) = A (1 + cos θ) + B (10) In a BG environment in which a strong photopeak of another nuclide exists very close to the reference photopeak, the BG component depends on the energy as a variable. If a quadratic equation in which the rate of change increases as a function of the BG approximation depending on the independent variable is selected as a BG approximation function, the BG
Is more appropriately approximated.

In many cases, the radionuclide in the measurement environment is fixed to a certain type. Therefore, when a BG of a nuclide whose tail overlaps with the reference photopeak is approximated by a quadratic equation, the BG at the top of the quadratic equation is independent. The energy value Et corresponding to the value of the variable can be estimated and determined in advance. Therefore, the variable x is converted into a linear expression (x-Et) based on the invention of claim 2, and the vertex represented by the expression (11) defined by the two undetermined coefficients A and B is (Et, B) If the quadratic equation is an approximation function of BG, the situation of BG can be appropriately approximated even when a nuclide whose tail overlaps the reference photo peak exists in the measurement environment.

[0037]

F (x) = A (x−Et) ² + B (11) The quadratic equation of the above equation (11) is selected as a BG approximation function, and the width of the SCAA measurement area where the count rate becomes a low value is selected. When only the energy selection width W with respect to the reference photo peak is set to twice and the energy selection width of the other channels is set to the same W, the counting rate in each channel is determined by the value of the energy selection width of the channel and the formula 11) and Equation (3)
Or (8), and the following equation (12) to (15) obtained by substituting ε = Ep−Et.

[0038]

Equation 12] a '= A (Ep -W- Et) 3/3 + B (Ep -W) - {A (Ep -3W-Et) 3/3 + B (Ep -3W)} = A (3ε 2 W-24εW ² + 26W ³ ) + 2BW (12)

[0039]

Equation 13] b '= A (Ep -Et) 3/3 + BEp - {A (Ep -W-Et) 3/3 + B (Ep -W)} = A (3ε 2 W-3εW 2 + W 3) + BW (13 )

[0040]

Equation 14] c '= A (Ep + W -Et) 3/3 + B (Ep + W) - {A (Ep -Et) 3/3 + BEp} = A (3ε 2 W + 3εW 2 + W 3) + BW (14)

[0041]

Equation 15] d '= A (Ep + 2W -Et) 3/3 + B (Ep + 2W) - {A (Ep + W-Et) 3/3 + B (Ep + W)} = A (3ε 2 W + 9εW 2 + 7W 3) + BW ( 15) Since ε and W are known values set in advance, Equation (12)
The values A and B of the undetermined constants are obtained by the counting rate meter R
It can be obtained from the value a'd 'of the BG count rate in the area adjacent to the reference photo peak measured by MA and RMD.

When the values of the undetermined constants A and B are determined,
This value is substituted into Expressions (13) and (14), and the output signals Nb output from the count rate meters RMB and RMC whose energy range of the reference photopeak is set in the measurement range by the pulse height analyzers SCAB and SCAC. And Nc, BG
Since the count rate values b ′ and c ′ of the component contribution are obtained, the net count rate values b and c based on the reference photopeak can be derived from Equations (1) and (2).

When a quadratic equation is selected as the BG approximation function, it is assumed that the arithmetic circuit 7 of FIG. 1 has a calculation program assembled so that the above calculation is executed. On the other hand, G in a wide energy range near the reference photo peak
When the G component changes uniformly, a linear function can be selected as a function approximating BG. Therefore, claim 4
According to the invention of the above, a linear function of a variable x represented by the equation (7) is selected by two undetermined constants K and M as a function f (x) approximating BG, and energy selection of channel A and channel D is performed. FIG. 3 shows a block configuration of an embodiment in which the widths Wa and Wd are set to twice the energy selection width W with respect to the reference photopeak as shown in the spectrum enlarged view of FIG. explain.

[0044]

F (x) = KX + M (16) The setting of the energy selection width of channels A and D to twice the energy selection width W with respect to the reference photopeak is based on the input measured in channels A and D. The count rate of the pulse signal is set to a high value such that the effect of the statistical fluctuation of the number of input pulses is sufficiently low to obtain a stable and accurate undetermined constant of the approximate function.

In FIG. 3, components denoted by the same reference numerals as those in FIG. 1 for explaining the first invention function in the same manner as in FIG. 1, and the description thereof will be omitted. Reference numeral 41 in FIG. 3 denotes a difference between the input of the shaped pulse signals output by the SCAA and the SCAD corresponding to the pulse signal in the peak range selected by the SCAA and the SCAD, and the input frequency difference between the two pulse signals as the output signal. Dynamic counting rate meter,
Reference numeral 42 designates an input of a shaped pulse signal corresponding to a pulse signal in a peak range selected by SCAB and SCAC in which an energy region obtained by dividing a reference photopeak into two is set as a counting range, and an input of both pulse signals. This is a differential counting rate meter that uses a frequency difference as an output signal. And 82
BG approximation function f based on the outputs of differential count rate meters 41 and 42
Using (x), the count rates a and b based on the reference photopeak component in the energy region selected by SCAB and SCAC are obtained separately from the BG count rate component.
This is an arithmetic circuit that generates a control signal of a detector bias power supply 6 that generates a bias voltage to be applied to the detector 1 so that the difference between the values of the two and c becomes zero.

When equation (16) is selected as the approximate function f (x) of BG, the integral function F (x) is calculated by the following equation (17).
Becomes

[0047]

F (x) = 1 / 2Kx ² + Mx + D (17) By the way, the width Wa and Wd of the measurement area adjacent to the reference photo peak set in SCAA and SCAD are set to the measurement area of the reference photo peak as described above. Since twice the width W is set, these values and Expression (17) are substituted into Expressions (3) to (8) to obtain the reference photo peak and each measurement adjacent to the reference photo peak. Count rate values a'b'c 'of channels A, B, C and D due to only BG components
And d ′ are determined by the following equations (18) to (21).

[0048]

Equation 18] a '= K (Ep -W) 2/2 + M (Ep -W) - {K (Ep -3W) 2/2 + M (Ep -3W)} = 2 (KEp + M) W-4KW 2 = 2n -8m (18)

[0049]

Equation 19] ^{b '= KEp 2/2 +} MEp 2 - {K (Ep -W) 2/2 + M (Ep -W)} = (KEp + M) W-KW 2/2 = n-m (19)

[0050]

Equation 20] c '= K (Ep + W ) 2/2 + M (Ep + W) - {KEp 2/2 + MEp 2} = (KEp + M) W + KW 2/2 = n + m (20)

[0051]

Equation 21] d '= K (Ep + 3W ) 2/2 + M (Ep + 3W) - {K (Ep + W) 2/2 + M (Ep + W)} = 2 (KEp + M) W + 4KW 2 = 2n + 8m (21) In addition, the formula In (9) to (12), the undefined constants of the following equations (22) and (23) are defined to simplify the expressions of the equations.

[0052]

N = (KEp + M) W (22)

[0053]

Equation 23] m = KW ^2/2 (23) Equation (18), when determining the value of the undetermined constants n and m from (21), equation (24) and (25) is obtained.

[0054]

N = (d ′ + a ′) / 4 (24)

[0055]

M = (d′−a ′) / 16 (25) By substituting the values of n and m obtained as described above into equations (19) and (20), the values of b ′ and c ′ are obtained. Expressions (26) and (27), which are expressions determined by the values of a ′ and d ′, are obtained.

[0056]

B ′ = nm− (3d ′ + 5a ′) / 16 (26)

[0057]

C ′ = n + m = (5d ′ + 5a ′) / 16 (27) The values of b ′ and c ′ thus obtained are substituted into equations (1) and (2) to determine the difference between them. And the following equation (28) is obtained.

[0058]

Nc−Nb = (c + c ′) − (b + b ′) = (c−b) + (c′−b ′) = (c−b) + (d′ ─a ′) / 8 (28) Equation (28) is used to calculate the count rates in A and D measured by the differential count rate meter 42 from the value of the count rate difference Nc─Nb between the channels C and B measured by the differential count rate meter 41. Subtracting 1/8 of the difference value, that is, (d′ ─a ′) / 8, indicates that the difference (c−b) in the count rate due to the reference photo peak in channels C and B can be obtained.

The arithmetic circuit 82 shown in FIG. 3 receives a signal corresponding to the value of Nc-Nb output from the differential counting rate meter 42 as one input and d'-a 'input from the other input terminal. １ ／ of the output signal of the differential counting rate meter 42 corresponding to the value of, and subtracting the value of the counting rate from the reference photo peak (c−b).
Is output. And arithmetic circuit
The output of 82 is smoothed and stabilized by the integration function of the integration circuit 5 and is input to the bias power supply 6 as a control signal, but this integration circuit 5 is not always necessary.

[0060]

As described above, in the peak height stabilizing circuit applied to the pulse signal measuring apparatus in which the peak value of the signal according to the present invention is significant, the contribution of the counting rate caused by the background is determined. Approximate by a function determined by two undetermined constants having the energy value as an independent variable, and using the count rate value obtained by two sets of measurement systems having a measurement peak range outside the peak value range of the reference signal, The values of the two undetermined constants are obtained by calculation, and the background contribution of the count rate in the peak value range of the reference signal is estimated by the background approximation function of the determined constant. Even if other signals due to the background are mixed in, the counting rate based only on the reference signal component is correctly captured, and the effect that the wave height stabilizing circuit operates stably and accurately is obtained. It is.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is an enlarged spectrum diagram for explaining the operation of the embodiment of FIG. 1;

FIG. 3 is a block diagram showing a configuration of another embodiment of the present invention.

FIG. 4 is an enlarged spectrum diagram for explaining the operation of the embodiment of FIG. 2;

FIG. 5 is a block diagram showing a configuration of a radiation measuring apparatus having a peak height stabilizing circuit according to a conventional technique.

FIG. 6 is a spectrum chart for explaining the operation of the peak height stabilizing circuit;

FIG. 7 is a spectrum diagram illustrating the operation of the peak height stabilizing circuit when the gain changes.

FIG. 8 is a spectrum diagram illustrating a state where a reference photo peak and a background are superimposed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Reference radiation source 2 Detector 31-34,39 Single channel wave height analyzer 401-404 Count rate meter 5 Integrating circuit 6 Detector bias power supply 7 Count rate meter 81,82 Operation circuit

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-5-87933 (JP, A) JP-A-4-166792 (JP, A) JP-A-2-2577084 (JP, A) JP-A-58-1983 200186 (JP, A) Actually open 1987-84778 (JP, U) Actually open 1983-42741 (JP, U) Actually open, 55-44219 (JP, U) Actually open, 51-131273 (JP, U) European Patent Application Publication 566191 (EP, A2) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01T 1/36 G01T 1/17 G01T 1/20 H03G 3/30

Claims (4)

(57) [Claims] 1. A crest value range of a reference signal is equally divided with respect to a signal source to which a pulse signal of a known crest value applied to a pulse signal measuring apparatus having a meaningful crest value of a signal is provided. In the peak stabilization circuit that controls the amplification gain of the pulse height based on the pulse count rate measurement value measured in the above step, a signal in the peak value range that equally divides the peak value range of the reference signal is selected and extracted as a shaped pulse signal. The first to output
And a second pulse height analyzer; first and second count rate meters for measuring the frequency of output pulse signals of the first and second pulse height analyzers; and the first and second pulse height analyzers A third and a fourth peak-height analyzer, in which a peak value region adjacent to the measured peak value range is set as a measured peak value range, and a background signal is selectively extracted and shaped as a shaped pulse signal; A third and a fourth count rate meter for measuring the frequency of the output pulse signal of each of the four pulse height analyzers; and a count rate by a background signal component in an energy range selected by the first to fourth pulse height analyzers. Is approximated by a function determined by two undetermined constants using the energy value as an independent variable, and the values of the two undetermined constants are calculated by the count rate values output by the third and fourth count rate meters. Determined by, undecided The count rate based on the background signal component in the energy range determined by the first and second count rate meters is calculated by the approximation function in which the value of the constant is determined, and the count rate of the first and second count rate meters is calculated. And a calculation circuit for subtracting the count rate output from the count rate output to output a count rate based on the contribution component of the reference signal. 2. The peak height stabilizing circuit according to claim 1, wherein the independent variable of the function that approximates the background is a variable obtained by converting a peak value as a variable by a linear linear equation. 3. The function for approximating a background is a linear function.
3. The peak height stabilizing circuit according to claim 1, wherein the following equation is obtained. 4. The function for approximating the background is a linear one.
The wave height stabilizing circuit according to claim 1, wherein the following equation is obtained.