JP2004347368A - Radiation monitor - Google Patents

Radiation monitor Download PDF

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Publication number
JP2004347368A
JP2004347368A JP2003142353A JP2003142353A JP2004347368A JP 2004347368 A JP2004347368 A JP 2004347368A JP 2003142353 A JP2003142353 A JP 2003142353A JP 2003142353 A JP2003142353 A JP 2003142353A JP 2004347368 A JP2004347368 A JP 2004347368A
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Prior art keywords
preamplifier
radiation
voltage pulse
pulse
temperature coefficient
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JP2004347368A5 (en
JP4540301B2 (en
Inventor
Kenichi Mogi
健一 茂木
Shoichi Nakanishi
正一 中西
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Mitsubishi Electric Corp
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Mitsubishi Electric Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a radiation monitor capable of inexpensively and effectively compensating the temperature of a radiation detector. <P>SOLUTION: The radiation monitor is provided with the radiation detector 1 for detecting the radiation of an object to be measured and converting it into a current pulse corresponding to a detected quantity; a preamplifier 2 for converting a current pulse of the radiation detector 1 into a voltage pulse; and a main amplifier 3 for amplifying a voltage pulse of the preamplifier 2, cutting a high-frequency noise component by a filter, and inputting it to a rate meter. The preamplifier 2 is provided with a negative feedback resistor 24 having a positive temperature coefficient, and a negative temperature coefficient which appears in a peak value of an output voltage pulse of the main amplifier 3 is compensated on the basis of the temperature characteristics of the radiation detector 1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【０００１】
【発明の属する技術分野】
この発明は、原子力発電所、病院、研究所等で使用される放射線モニタ、特に放射線検出器に温度補償を施した放射線モニタに関するものである。
【０００２】
【従来の技術】
放射線を検出する放射線検出器は、その種類により固有の温度特性を有している。従って、放射線を安定した精度で測定するためには、放射線検出器の温度特性に対して温度補償を施す必要があり、種々の方法が考えられ実用化されている。
そのうちの１つとして、放射線検出器の出力電流パルスを電圧パルスに変換するために使用される前置増幅器に温度補償機能を持たせた方法が安価で効果が大きいことから広く用いられている。その具体的手段としては、前置増幅器の負帰還容量に負の温度特性を持たせて放射線検出器の温度特性を補償するようにしていた。（例えば特許文献１参照）。
【０００３】
【特許文献１】
特公平４−１２０４８号公報（ｐ１左欄８行−右欄１６行、第１図）
【０００４】
【発明が解決しようとする課題】
従来の放射線モニタは以上のように構成され、放射線検出器の温度特性により前置増幅器の出力電圧パルスの波高値に現れる負の温度係数を前置増幅器に設けた負の温度係数の負帰還容量で補償するものであるため、前置増幅器の出力電圧パルスの波高値は補償することができるが、その結果としてパルス幅に負の温度係数が現れ、前置増幅器の出力電圧パルスを増幅するために設けられる主増幅器のゲイン−周波数特性により補償が目減りするという問題点があった。
この発明は、上記のような問題点を解決するためになされたものであり、安価で効果的に放射線検出器の温度補償を行なうことができる放射線モニタを提供することを目的とする。
【０００５】
【課題を解決するための手段】
この発明に係る放射線モニタは、測定対象の放射線を検出し、検出量に対応した電流パルスに変換する放射線検出器、上記放射線検出器の電流パルスを電圧パルスに変換する前置増幅器及び上記前置増幅器の電圧パルスを増幅すると共に、高周波ノイズ成分をフィルタカットしてレートメータに入力する主増幅器を備えた放射線モニタにおいて、上記前置増幅器に正の温度係数の負帰還抵抗を設け、上記放射線検出器の温度特性にもとづいて上記主増幅器の出力電圧パルスの波高値に現れる負の温度係数を補償するようにしたものである。
【０００６】
【発明の実施の形態】
実施の形態１．
以下、この発明の実施の形態１を図にもとづいて説明する。図１は、実施の形態１による放射線モニタの構成を示すブロック図である。この図に示すように、この実施の形態の放射線モニタは、測定対象の放射線を検出し、検出量に対応した電流パルスに変換する放射線検出器１と、放射線検出器１の出力電流パルスを電圧パルスに変換する前置増幅器２と、前置増幅器２の出力電圧パルスを増幅すると共に、高周波ノイズ成分をフィルタカットする主増幅器３と、主増幅器３の出力である増幅された電圧パルスの波高を弁別し、所定レベル未満のパルスをノイズとして除去すると共に、所定レベル以上のパルスを放射線による信号としてデジタルパルスを出力する波高弁別器４と、波高弁別器４の出力デジタルパルスにもとづいて放射線を測定するレートメータ５とから構成されている。
【０００７】
また、前置増幅器２は更に、入力端子２１と、アンプ２２と、負帰還容量２３と、負帰還抵抗２４と、出力端子２５とから構成されている。
アンプ２２は入力抵抗が大きいため、入力端子２１から入力された放射線検出器１の出力電流パルスが負帰還容量２３で電荷積分され、電圧に変換されて波高値を形成する。負帰還容量２３の容量値をＣとし、負帰還抵抗２４の抵抗値をＲとすると、上記波高値が時定数ＣＲで減衰する電圧パルスとして出力端子２５から出力される。
【０００８】
図２は、実施の形態１の前置増幅器２における負帰還抵抗２４の抵抗値Ｒの温度係数を示す図である。図中にａで示すように、抵抗値Ｒは正の温度係数を持つようにされている。また、図３は、実施の形態１の主増幅器３のゲイン−周波数特性を示す図である。この特性は、増幅された電圧パルスに重畳されている高周波ノイズを除去する高周波阻止特性のため、高周波領域ではｂで示すように、ゲインが低下する特性を持っている。即ち、入力パルスのパルス幅が広くなって周波数が低下するとゲインが大きくなり、バルス幅が狭くなって周波数が高くなるとゲインが小さくなるように動作する。
【０００９】
図４は、放射線検出器１の温度特性に対する補償動作を示す図であり、（Ａ）は前置増幅器２の出力電圧パルスを示し、（Ｂ）は主増幅器３の出力電圧パルスを示す。この図において、ｄは基準温度時における前置増幅器２の出力電圧パルスの波高値であり、ｔｓは基準温度時における前置増幅器２の出力電圧パルスのパルス幅である。また、ｅは同じく低温時における波高値、ｔＬは低温時におけるパルス幅、ｆは同じく高温時における波高値、ｔＨは高温時におけるパルス幅であり、Ｌは上述した波高値弁別用の所定レベルである。また、ｇは上記各波高値ｄ〜ｆを主増幅器３に入力した時の主増幅器３の出力である増幅された電圧パルスである。放射線検出器１の出力電流パルスの電荷量、即ち前置増幅器２の入力電荷量Ｑと容量値Ｃと前置増幅器２のゲインＧとの関係は、
Ｇ＝Ｑ／Ｃ
となる。
【００１０】
放射線検出器１の出力電流パルスの電荷量Ｑは負の温度係数を有するため、結果として前置増幅器２の出力電圧パルスの波高値は負の温度特性を持っている。一方、前置増幅器２の負帰還抵抗の抵抗値Ｒは上述のように、正の温度特性を有しているため、パルス幅は正の温度特性となり、主増幅器３のゲイン−周波数特性と組み合わせた総合特性は放射線検出器１の温度係数を補償するように動作するものである。なお、上述した実施の形態１のように、負の温度係数を持つ放射線検出器としては、プラスチックシンチレーション検出器やＰＩＮ型Ｓｉ半導体検出器等がある。
【００１１】
実施の形態２．
次に、この発明の実施の形態２を図にもとづいて説明する。図５は、実施の形態２における前置増幅器２の負帰還容量２３の容量値Ｃの温度係数を示す図である。図中にｈで示すように、容量値Ｃは負の温度係数を持つようにされている。図６は、実施の形態２における前置増幅器２の出力電圧パルスの波高値及び前置増幅器２のゲインを示す図である。この図において、ｉは負帰還容量２３の容量値Ｃの温度係数がゼロの時の波高値、ｊは容量値Ｃの温度係数が負の時の前置増幅器２のゲイン、ｋは負帰還容量２３の容量値Ｃの温度係数が負の時の波高値をそれぞれ示している。前置増幅器２の入力の電荷Ｑと容量値Ｃと前置増幅器２のゲインＧの関係は、上述のように、Ｇ＝Ｑ／Ｃであるから、前置増幅器２は放射線検出器１の負の温度係数でＱが低下した分を容量値Ｃの負の温度特性で補償するように動作し、その結果、前置増幅器２の出力電圧パルスの波高値はｋで示すように安定化されることになる。
【００１２】
図７は、実施の形態２における放射線検出器１の温度特性に対する補償動作を示す図であり、（Ａ）は前置増幅器２の出力電圧パルスを示し、（Ｂ）は主増幅器３の出力電圧パルスを示す。この図において、ｍは基準温度時における前置増幅器２の出力電圧パルスの波高値であり、ｔｓは基準温度時における前置増幅器２の出力電圧パルスのパルス幅である。また、ｎは同じく低温時における波高値、ｔＬは低温時におけるパルス幅、ｐは同じく高温時における波高値、ｔＨは高温時におけるパルス幅であり、Ｌは上述した波高値弁別用の所定レベルである。
また、ｑは上記各波高値ｍ〜ｐを主増幅器３に入力した時の主増幅器３の出力である増幅された電圧パルスである。
【００１３】
これから分かるように、前置増幅器２の出力の波高値を安定化するために容量値Ｃを負の温度係数とすると時定数ＣＲが負の温度係数となりパルス幅が負の温度係数を持つようになるため、主増幅器３の出力である増幅された電圧パルスの波高値は負の温度係数になってしまう。容量値Ｃの温度係数に対して負帰還抵抗２４の抵抗値Ｒの温度係数について、絶対値が等しくかつ極性が逆になるように、即ち、抵抗値Ｒを正の温度係数とすることにより、主増幅器３の出力である増幅された電圧パルスの波高値とパルス幅の両方を安定化することができる。
【００１４】
実施の形態３．
次に、この発明の実施の形態３を図にもとづいて説明する。図８は、実施の形態３における前置増幅器２の負帰還容量２３の温度特性を示す図である。
図８のｒで示すような凸型の容量のものとしては、セラミックコンデンサが知られている。図９は、上述のような特性の負帰還容量を使用した場合の前置増幅器による温度補償動作を示す図である。
放射線検出器の中でもＮａｌ（Ｔｌ） シンチレーション検出器やＣｓｌ（Ｅｕ） シンチレーション検出器等を使用した場合には、上記前置増幅器の出力電圧パルスの波高値が所定の温度で極大値となり、特性曲線が図９においてｓで示すように、凸型となる温度特性を示すことが知られている。また、ｓは負帰還抵抗２４の抵抗値Ｒの温度係数がゼロの時の前置増幅器２の出力電圧パルスの波高値、ｕは前置増幅器２の電流−電圧変換ゲイン、ｖは主増幅器３の出力電圧パルスの波高値をそれぞれ示している。
このように、前置増幅器２の負帰還容量２３の容量値Ｃが所定の温度で極大値となり、特性曲線が図８に示すように、凸型となる温度係数を持たせることにより、前置増幅器２の出力電圧パルスに現れる負の温度係数を補償することができる。
【００１５】
【発明の効果】
この発明に係る放射線モニタは、測定対象の放射線を検出し、検出量に対応した電流パルスに変換する放射線検出器、上記放射線検出器の電流パルスを電圧パルスに変換する前置増幅器及び上記前置増幅器の電圧パルスを増幅すると共に、高周波ノイズ成分をフィルタカットしてレートメータに入力する主増幅器を備えた放射線モニタにおいて、上記前置増幅器に正の温度係数の負帰還抵抗を設け、上記放射線検出器の温度特性にもとづいて上記主増幅器の出力電圧パルスの波高値に現れる負の温度係数を補償するようにしたものであるため、安価で高精度な放射線モニタを得ることができる。
また、主増幅器の周波数特性に影響されることなく機器を組み合わせることができる。更に、所定の温度で前置増幅器の出力電圧パルスの波高値が極大値となるような温度係数を有する放射線検出器に対して前置増幅器の負帰還容量が所定の温度で極大値となる温度係数を有するようにしたことにより、低温度領域に亘って高精度を維持することができる。
【図面の簡単な説明】
【図１】この発明の実施の形態１による放射線モニタの構成を示すブロック図である。
【図２】実施の形態１の前置増幅器における負帰還抵抗の抵抗値Ｒの温度係数を示す図である。
【図３】実施の形態１の主増幅器のゲイン−周波数特性を示す図である。
【図４】実施の形態１における放射線検出器の温度特性に対する補償動作を示す図である。
【図５】この発明の実施の形態２における前置増幅器の負帰還容量の容量値Ｃの温度係数を示す図である。
【図６】実施の形態２における前置増幅器の出力電圧パルスの波高値及び前置増幅器のゲインを示す図である。
【図７】実施の形態２における放射線検出器の温度特性に対する補償動作を示す図である。
【図８】この発明の実施の形態３における負帰還容量の温度特性を示す図である。
【図９】実施の形態３における放射線検出器の温度特性に対する補償動作を示す図である。
【符号の説明】
１ 放射線検出器、 ２ 前置増幅器、 ３ 主増幅器、
４ 波高弁別器、 ５ レートメータ、 ２１ 入力端子、
２２ アンプ、 ２３ 負帰還容量、 ２４ 負帰還抵抗、
２５ 出力端子。[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation monitor used in a nuclear power plant, a hospital, a research laboratory, and the like, and more particularly to a radiation monitor in which a radiation detector is subjected to temperature compensation.
[0002]
[Prior art]
A radiation detector that detects radiation has a unique temperature characteristic depending on the type. Therefore, in order to measure radiation with stable accuracy, it is necessary to perform temperature compensation on the temperature characteristics of the radiation detector, and various methods have been considered and put to practical use.
As one of them, a method in which a preamplifier used for converting an output current pulse of a radiation detector into a voltage pulse is provided with a temperature compensation function is widely used because it is inexpensive and effective. As a specific means, the negative feedback capacitance of the preamplifier has a negative temperature characteristic to compensate for the temperature characteristic of the radiation detector. (See, for example, Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Publication No. 4-12048 (p1 left column 8 lines-right column 16 lines, FIG. 1)
[0004]
[Problems to be solved by the invention]
The conventional radiation monitor is configured as described above, and the negative feedback coefficient of the negative temperature coefficient provided in the preamplifier has a negative temperature coefficient appearing in the peak value of the output voltage pulse of the preamplifier due to the temperature characteristics of the radiation detector. Therefore, the peak value of the output voltage pulse of the preamplifier can be compensated, but as a result, a negative temperature coefficient appears in the pulse width, and the output voltage pulse of the preamplifier is amplified. However, there is a problem that the compensation is reduced due to the gain-frequency characteristic of the main amplifier provided in the above.
The present invention has been made to solve the above problems, and has as its object to provide a radiation monitor capable of inexpensively and effectively performing temperature compensation of a radiation detector.
[0005]
[Means for Solving the Problems]
A radiation monitor according to the present invention includes a radiation detector that detects radiation to be measured and converts the radiation into a current pulse corresponding to a detected amount, a preamplifier that converts a current pulse of the radiation detector into a voltage pulse, and the preamplifier. In a radiation monitor including a main amplifier for amplifying a voltage pulse of an amplifier and filtering a high-frequency noise component to input to a rate meter, a negative feedback resistor having a positive temperature coefficient is provided in the preamplifier, and the radiation detection is performed. A negative temperature coefficient appearing in the peak value of the output voltage pulse of the main amplifier is compensated based on the temperature characteristic of the device.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
Hereinafter, a first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of the radiation monitor according to the first embodiment. As shown in this figure, a radiation monitor of this embodiment detects a radiation to be measured, converts the radiation into a current pulse corresponding to the detected amount, and outputs an output current pulse of the radiation detector 1 as a voltage. A preamplifier 2 for converting the output voltage into a pulse, a main amplifier 3 for amplifying an output voltage pulse of the preamplifier 2 and filtering out a high-frequency noise component, and a wave height of the amplified voltage pulse output from the main amplifier 3 A pulse height discriminator 4 that discriminates and removes a pulse lower than a predetermined level as noise and outputs a digital pulse as a signal of radiation of a pulse higher than a predetermined level, and measures the radiation based on a digital pulse output from the pulse height discriminator 4. And a rate meter 5.
[0007]
The preamplifier 2 further includes an input terminal 21, an amplifier 22, a negative feedback capacitor 23, a negative feedback resistor 24, and an output terminal 25.
Since the amplifier 22 has a large input resistance, the output current pulse of the radiation detector 1 input from the input terminal 21 is charge-integrated by the negative feedback capacitor 23 and converted into a voltage to form a peak value. Assuming that the capacitance value of the negative feedback capacitor 23 is C and the resistance value of the negative feedback resistor 24 is R, the peak value is output from the output terminal 25 as a voltage pulse attenuated by the time constant CR.
[0008]
FIG. 2 is a diagram illustrating a temperature coefficient of the resistance value R of the negative feedback resistor 24 in the preamplifier 2 according to the first embodiment. As shown by a in the figure, the resistance value R has a positive temperature coefficient. FIG. 3 is a diagram illustrating gain-frequency characteristics of the main amplifier 3 according to the first embodiment. This characteristic is a high-frequency rejection characteristic for removing high-frequency noise superimposed on the amplified voltage pulse, and thus has a characteristic that the gain decreases in the high-frequency region as shown by b. That is, the gain is increased when the pulse width of the input pulse is widened and the frequency is lowered, and the gain is reduced when the pulse width is narrowed and the frequency is high.
[0009]
4A and 4B are diagrams showing a compensation operation for the temperature characteristic of the radiation detector 1, wherein FIG. 4A shows an output voltage pulse of the preamplifier 2, and FIG. 4B shows an output voltage pulse of the main amplifier 3. In this figure, d is the peak value of the output voltage pulse of the preamplifier 2 at the reference temperature, and ts is the pulse width of the output voltage pulse of the preamplifier 2 at the reference temperature. Moreover, e is also a peak value at a low temperature, t L is the pulse width at a low temperature, f is also a peak value at high temperatures, the t H is the pulse width at high temperature, L is predetermined for a peak value discriminator described above Level. Further, g is an amplified voltage pulse which is an output of the main amplifier 3 when each of the peak values d to f is input to the main amplifier 3. The charge amount of the output current pulse of the radiation detector 1, that is, the relationship between the input charge amount Q and the capacitance value C of the preamplifier 2 and the gain G of the preamplifier 2 is as follows.
G = Q / C
It becomes.
[0010]
Since the charge amount Q of the output current pulse of the radiation detector 1 has a negative temperature coefficient, as a result, the peak value of the output voltage pulse of the preamplifier 2 has a negative temperature characteristic. On the other hand, since the resistance value R of the negative feedback resistor of the preamplifier 2 has a positive temperature characteristic as described above, the pulse width becomes a positive temperature characteristic and is combined with the gain-frequency characteristic of the main amplifier 3. The overall characteristics operate so as to compensate for the temperature coefficient of the radiation detector 1. Note that, as in the first embodiment, examples of the radiation detector having a negative temperature coefficient include a plastic scintillation detector and a PIN-type Si semiconductor detector.
[0011]
Embodiment 2 FIG.
Next, a second embodiment of the present invention will be described with reference to the drawings. FIG. 5 is a diagram illustrating a temperature coefficient of the capacitance value C of the negative feedback capacitor 23 of the preamplifier 2 according to the second embodiment. As shown by h in the figure, the capacitance value C has a negative temperature coefficient. FIG. 6 is a diagram illustrating the peak value of the output voltage pulse of the preamplifier 2 and the gain of the preamplifier 2 according to the second embodiment. In this figure, i is the peak value when the temperature coefficient of the capacitance value C of the negative feedback capacitor 23 is zero, j is the gain of the preamplifier 2 when the temperature coefficient of the capacitance value C is negative, and k is the negative feedback capacitance. 23 shows the peak value when the temperature coefficient of the capacitance value C of 23 is negative. As described above, the relationship between the charge Q at the input of the preamplifier 2, the capacitance value C, and the gain G of the preamplifier 2 is G = Q / C. Is operated so as to compensate for the decrease in Q by the temperature coefficient of the above with the negative temperature characteristic of the capacitance value C. As a result, the peak value of the output voltage pulse of the preamplifier 2 is stabilized as indicated by k. Will be.
[0012]
7A and 7B are diagrams showing a compensation operation for the temperature characteristic of the radiation detector 1 according to the second embodiment, wherein FIG. 7A shows an output voltage pulse of the preamplifier 2 and FIG. Indicates a pulse. In this figure, m is the peak value of the output voltage pulse of the preamplifier 2 at the reference temperature, and ts is the pulse width of the output voltage pulse of the preamplifier 2 at the reference temperature. Also, n is the peak value at low temperature, t L is the pulse width at low temperature, p is the peak value at high temperature, t H is the pulse width at high temperature, and L is the predetermined value for discriminating the peak value described above. Level.
In addition, q is an amplified voltage pulse which is an output of the main amplifier 3 when each of the peak values m to p is input to the main amplifier 3.
[0013]
As can be seen, if the capacitance value C is set to a negative temperature coefficient in order to stabilize the peak value of the output of the preamplifier 2, the time constant CR becomes a negative temperature coefficient and the pulse width has a negative temperature coefficient. Therefore, the peak value of the amplified voltage pulse output from the main amplifier 3 has a negative temperature coefficient. With respect to the temperature coefficient of the resistance value R of the negative feedback resistor 24 with respect to the temperature coefficient of the capacitance value C, the absolute value is equal and the polarity is reversed, that is, by making the resistance value R a positive temperature coefficient, Both the peak value and the pulse width of the amplified voltage pulse output from the main amplifier 3 can be stabilized.
[0014]
Embodiment 3 FIG.
Next, a third embodiment of the present invention will be described with reference to the drawings. FIG. 8 is a diagram illustrating temperature characteristics of the negative feedback capacitor 23 of the preamplifier 2 according to the third embodiment.
As a capacitor having a convex capacity as shown by r in FIG. 8, a ceramic capacitor is known. FIG. 9 is a diagram showing a temperature compensation operation by a preamplifier when a negative feedback capacitor having the above-described characteristics is used.
When a Nal (Tl) scintillation detector or a Csl (Eu) scintillation detector is used among the radiation detectors, the peak value of the output voltage pulse of the preamplifier reaches a maximum value at a predetermined temperature, and the characteristic curve Is known to exhibit a convex temperature characteristic as shown by s in FIG. Further, s is the peak value of the output voltage pulse of the preamplifier 2 when the temperature coefficient of the resistance value R of the negative feedback resistor 24 is zero, u is the current-voltage conversion gain of the preamplifier 2, and v is the main amplifier 3 Respectively show the peak values of the output voltage pulses.
In this way, the capacitance value C of the negative feedback capacitor 23 of the preamplifier 2 becomes a maximum value at a predetermined temperature, and the characteristic curve has a convex temperature coefficient as shown in FIG. The negative temperature coefficient appearing in the output voltage pulse of the amplifier 2 can be compensated.
[0015]
【The invention's effect】
A radiation monitor according to the present invention includes a radiation detector that detects radiation to be measured and converts the radiation into a current pulse corresponding to a detected amount, a preamplifier that converts a current pulse of the radiation detector into a voltage pulse, and the preamplifier. In a radiation monitor including a main amplifier for amplifying a voltage pulse of an amplifier and filtering a high-frequency noise component to input to a rate meter, a negative feedback resistor having a positive temperature coefficient is provided in the preamplifier, and the radiation detection is performed. Since the negative temperature coefficient appearing in the peak value of the output voltage pulse of the main amplifier is compensated based on the temperature characteristic of the detector, an inexpensive and highly accurate radiation monitor can be obtained.
Further, devices can be combined without being affected by the frequency characteristics of the main amplifier. Furthermore, for a radiation detector having a temperature coefficient such that the peak value of the output voltage pulse of the preamplifier becomes a maximum value at a predetermined temperature, the temperature at which the negative feedback capacity of the preamplifier reaches a maximum value at a predetermined temperature is obtained. By having the coefficient, high accuracy can be maintained over the low temperature region.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a radiation monitor according to Embodiment 1 of the present invention.
FIG. 2 is a diagram illustrating a temperature coefficient of a resistance value R of a negative feedback resistor in the preamplifier according to the first embodiment;
FIG. 3 is a diagram illustrating gain-frequency characteristics of the main amplifier according to the first embodiment;
FIG. 4 is a diagram showing a compensation operation for temperature characteristics of the radiation detector according to the first embodiment.
FIG. 5 is a diagram showing a temperature coefficient of a capacitance value C of a negative feedback capacitance of a preamplifier according to a second embodiment of the present invention.
FIG. 6 is a diagram illustrating a peak value of an output voltage pulse of a preamplifier and a gain of the preamplifier according to the second embodiment.
FIG. 7 is a diagram showing a compensation operation for temperature characteristics of the radiation detector according to the second embodiment.
FIG. 8 is a diagram showing temperature characteristics of a negative feedback capacitance according to the third embodiment of the present invention.
FIG. 9 is a diagram showing a compensation operation for temperature characteristics of the radiation detector according to the third embodiment.
[Explanation of symbols]
1 radiation detector, 2 preamplifier, 3 main amplifier,
4 wave height discriminator, 5 rate meter, 21 input terminals,
22 amplifier, 23 negative feedback capacitance, 24 negative feedback resistance,
25 Output terminal.

Claims (3)

測定対象の放射線を検出し、検出量に対応した電流パルスに変換する放射線検出器、上記放射線検出器の電流パルスを電圧パルスに変換する前置増幅器及び上記前置増幅器の電圧パルスを増幅すると共に、高周波ノイズ成分をフィルタカットしてレートメータに入力する主増幅器を備えた放射線モニタにおいて、上記前置増幅器に正の温度係数の負帰還抵抗を設け、上記放射線検出器の温度特性にもとづいて上記主増幅器の出力電圧パルスの波高値に現れる負の温度係数を補償するようにしたことを特徴とする放射線モニタ。A radiation detector that detects radiation to be measured and converts it into a current pulse corresponding to the detected amount, a preamplifier that converts the current pulse of the radiation detector into a voltage pulse, and amplifies the voltage pulse of the preamplifier. In a radiation monitor including a main amplifier that filters out high-frequency noise components and inputs the same to a rate meter, a negative feedback resistor having a positive temperature coefficient is provided in the preamplifier, and A radiation monitor wherein a negative temperature coefficient appearing in a peak value of an output voltage pulse of a main amplifier is compensated. 測定対象の放射線を検出し、検出量に対応した電流パルスに変換する放射線検出器、上記放射線検出器の電流パルスを電圧パルスに変換する前置増幅器及び上記前置増幅器の電圧パルスを増幅すると共に、高周波ノイズ成分をフィルタカットしてレートメータに入力する主増幅器を備えた放射線モニタにおいて、上記前置増幅器に正の温度係数の負帰還抵抗と、負の温度係数の負帰還容量とを設け、上記放射線検出器の温度特性にもとづいて上記前置増幅器の出力電圧パルスの波高値に現れる負の温度係数を補償すると共に、波高値の補償の結果発生するパルス幅の負の温度特性も補償するようにし、上記主増幅器の出力電圧パルスの波高値とパルス幅の両方を安定化したことを特徴とする放射線モニタ。A radiation detector that detects radiation to be measured and converts it into a current pulse corresponding to the detected amount, a preamplifier that converts the current pulse of the radiation detector into a voltage pulse, and amplifies the voltage pulse of the preamplifier. In a radiation monitor including a main amplifier that filters a high-frequency noise component and inputs the filtered signal to a rate meter, the preamplifier is provided with a negative feedback resistor having a positive temperature coefficient and a negative feedback capacitance having a negative temperature coefficient, A negative temperature coefficient appearing in the peak value of the output voltage pulse of the preamplifier is compensated based on a temperature characteristic of the radiation detector, and a negative temperature characteristic of a pulse width generated as a result of the peak value compensation is also compensated. A radiation monitor characterized in that both the peak value and the pulse width of the output voltage pulse of the main amplifier are stabilized. 測定対象の放射線を検出し、検出量に対応した電流パルスに変換する放射線検出器、上記放射線検出器の電流パルスを電圧パルスに変換する前置増幅器及び上記前置増幅器の電圧パルスを増幅すると共に、高周波ノイズ成分をフィルタカットしてレートメータに入力する主増幅器を備え、上記放射線検出器は、所定の温度で上記前置増幅器の電圧パルスの波高値が極大値となるような温度係数を有する放射線モニタにおいて、上記前置増幅器の負帰還容量が所定の温度で極大値となる温度係数を有するようにすることにより、上記前置増幅器の出力電圧パルスに現れる温度係数を補償するようにしたことを特徴とする放射線モニタ。A radiation detector that detects radiation to be measured and converts it into a current pulse corresponding to the detected amount, a preamplifier that converts the current pulse of the radiation detector into a voltage pulse, and amplifies the voltage pulse of the preamplifier. The radiation detector has a temperature coefficient such that the peak value of the voltage pulse of the preamplifier becomes a maximum value at a predetermined temperature at a predetermined temperature. In the radiation monitor, the temperature coefficient appearing in the output voltage pulse of the preamplifier is compensated for by making the negative feedback capacity of the preamplifier have a temperature coefficient that becomes a maximum value at a predetermined temperature. A radiation monitor characterized by the following.
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