JPH0519113B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a charge pulser for use in the calibration, testing or evaluation of a device that measures pulses output from a radiation detector.

[Technical background of the invention]

A gamma ray spectrometer exists as a device that analyzes the energy of gamma rays emitted from a radiation source.

FIG. 1 shows the detection section and preamplifier of this conventionally used device. The anode side of the germanium detector 11 is connected to the input terminal of a charge-sensitive operational amplifier 12, and a high voltage reverse bias is applied to the power supply terminal 13 on the cathode side.

In this device, when gamma rays enter the germanium detector 11, an electric charge proportional to the energy of the gamma rays is generated. The operational amplifier 12 integrates this to determine the total amount of charge, and outputs from the output terminal 14 a pulse with a peak value proportional to the energy of the γ-ray. After this pulse is amplified, it is applied to a pulse height analyzer and its energy is analyzed.

In this device, a test pulse input terminal 16 is arranged on the input terminal side of an operational amplifier 12 via a coupling capacitor 15. When testing the device parts after the preamplifier, a test pulse is input from the test pulse input terminal 16.

By the way, a stray capacitance 17 exists in the line on the input terminal side of the operational amplifier 12. Therefore, the charge generated from the germanium detector 11 during gamma ray measurement flows not only into the operational amplifier 12 but also into this stray capacitance 17, which causes the effective component of the signal to decrease and the S/N ratio to deteriorate. The value of the coupling capacitor 15 should also be set to 0.5 pF, for example, so as not to adversely affect the signal resolution.
It is selected to have a small value.

However, the presence of this coupling capacitor 15 causes a problem in that it distorts the shape of the input test pulse. FIG. 2a shows the signal waveform supplied from the germanium detector 11 to the operational amplifier 12. A test pulse having such a waveform is preferable. However, in reality, b1, c1, d1 in the same figure are generated using a pulse generator.
Even if various waveforms such as the above are applied to the test pulse input terminal 16, the signal waveforms supplied to the operational amplifier 12 become as shown in b2, c2, and d2 in the figure, and do not approximate that of the germanium detector 11. . For this reason, it has been impossible to test, calibrate, and evaluate device parts such as the above-mentioned pulse height analyzer with sufficient accuracy.

[Purpose of the invention]

In view of these circumstances, an object of the present invention is to provide a charge pulser that can generate a charge pattern similar to that generated by a charge collection type detector.

[Structure of the invention]

In the present invention, as shown in FIG.
The charge pulser is equipped with a gate circuit 24 that controls on/off the current output from the constant current circuit 21 to the output terminals 22 and 23, and a pulse generation circuit 25 that supplies gate pulses to the gate circuit. Then, a charge similar to that generated by the radiation detector is generated from the constant current circuit 21, and the output terminal 2
This charge appearing in 2 and 23 is used for device testing, etc.

〔Example〕

The present invention will be explained in detail with reference to Examples below.

FIG. 4 shows a state in which the charge pulser of this embodiment is connected to a preamplifier of a γ-ray spectrometer. The charge pulser includes a constant current circuit 27,
It is composed of an FET (field effect transistor) 28 and a pulse generation circuit 29. The preamplifier section 31 shown in the figure is a charge-sensitive preamplifier using an operational amplifier 32.

Now, the constant current circuit 27 of the charge pulser is shown in FIG.
As shown in FIG. 3, a waveform 33 similar to the charge pattern generated by a charge collection type radiation detector is generated as a constant current source. At the start of the rise of this waveform 33, a synchronizing signal 34 is output from the constant current circuit 27, and the pulse generating circuit 29 generates a gate pulse 35 (FIG. 5b) in synchronization with this signal. The gate pulse 35 is input to the gate of the FET 28 to turn it on. As a result, waveform 3 which is the same as waveform 33
6 (Figure 5c) is output from the FET source S,
It is applied to the input terminal A of the operational amplifier 32.

In this charge pulser, the wiring from the source S of the FET to the input terminal A of the operational amplifier 32 is made as short as possible to reduce the stray capacitance 37. Accordingly
The FET 28 provides charge to the operational amplifier 32 only when it is on, and does not have any adverse effects when it is off.

〔Effect of the invention〕

As explained above, according to the present invention, the amount and number of charges generated by a radiation detector can be arbitrarily simulated using a constant current circuit, making it easier to calibrate a device used in combination with a radiation detector. It can be done objectively.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram showing the main parts of a conventional gamma-ray spectrometer, and Figure 2 shows the waveform of the test pulse applied to this pulse input terminal and the signal waveform applied to the preamplifier, which are output from the radiation detector. 3 is a block diagram showing the principle configuration of the present invention; FIG. 4 is a circuit diagram showing a state in which a charge pulser is connected to a preamplifier in an embodiment of the present invention; FIG. 5 is a diagram of various waveforms for explaining the operation of this charge pulser. 11... germanium detector, 27... constant current circuit, 28... FET (field effect transistor),
29...Pulse generation circuit.

Claims (1)

[Claims] 1. A constant current source that generates a charge similar to that generated by a charge collection type radiation detector, a pulse generation circuit that generates a gate pulse in synchronization with this constant current source when it generates a charge, and this gate. A charge pulser comprising: a field effect transistor that is turned on by a pulse and supplies the charge to an output side.