JPH07270343A - Live time-measuring circuit for instrumentation of radiation - Google Patents

Abstract

PURPOSE:To count the reset time of a preamplifier as the invalid time by providing a signal detection circuit outputting a radiation detection signal, a pileup detection circuit detecting a pileup, etc. CONSTITUTION:When a pileup is detected at 5, an AD converter 4 removes a shaped-wave pulse signal not to be AD-converted. When the shaped-wave pulse signal exceeds an upper limit level set by a ULD setting circuit 3, the converter 4 generates only an AD busy signal. Therefore, even an input pulse exceeding the ULD level is AD-converted to generate the AD busy signal, while a data memory 6 is prohibited from taking data. Even when the ULD level is changed, a live time is maintained unchanged. Since counting circuits 7-9 are provided with gates for counting pulses which are closed by a reset pulse from a preamplifier, a reset time can be counted as the invalid time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a live time measuring circuit for measuring a live time for quantitatively measuring an element contained in a sample by radiation measurement.

[0002]

2. Description of the Related Art In radiation measurement, when quantitatively measuring elements contained in a sample, the measured data of a standard sample or a known sample is used as a reference to compare with the measured data of an unknown sample, and each element is contained. The amount is derived. However, the data of the standard sample, the known sample, and the unknown sample cannot be simply compared because the irradiation current, the voltage, the inclination of the sample, etc. are different at the time of measurement and the radiation generation conditions (environment) are different. Therefore, it is necessary to correct the measurement conditions, and it is necessary to accurately measure the measured effective time. In other words,
In the measurement of radiation, due to the nature of the measurement system, time that must be counted as ineffective time occurs. One of them is pile-up, and if multiple radiations occur at very close times, they will be combined as one signal and produce an incorrect peak value. Must be timed. The other is the reset time in the optical pulse feedback preamplifier. During this period, since the signal is not output from the preamplifier even if radiation is generated, it is necessary to measure the invalid time as well. The time obtained by subtracting these two invalid times from the total measurement time must be counted as the total effective time, that is, the live time.

FIG. 3 is a diagram showing a conventional example of a live time measuring circuit for measuring radiation, which is a circuit proposed in Japanese Patent Publication No. 5-6674 for measuring (measuring) live time. This circuit originally has a simple circuit structure in US Pat. No. 3,814,937 by using the function of ADC and a busy signal, and its outline will be briefly described below.

In FIG. 3, a linear amplifier 12 shapes an input signal and sends an output signal e to an AD converter (not shown). Control logic 1
Reference numeral 1 is for detecting pile-up when a plurality of radiations are generated at extremely close times, and supplies the pile-up signal f to the linear amplifier 2 so that the linear amplifier 12 of the period in which the pile-up signal f exists. The output is raised above the ULD level as indicated by the dotted line e '. The delay logic 13 is a circuit that detects radiation from a signal input through the buffer 10. The flip-flop 14 is set by the busy signal (ADC BUSY) and reset by the detection signal of the delay logic 13. The busy signal (ADC BUSY) is
This is a signal output from the AD converter connected to the output of the linear amplifier 12. The counter timer 16 counts the live time clock 17 while the flip-flop 14 is set.

The AD converter has a discriminating function based on the set ULD level. If the signal level from the linear amplifier 12 does not exceed the ULD level, it is in the signal convertible area, and if it exceeds the ULD level, it is outside the signal convertible area. . Therefore, if you want to limit the spectrum measurement to only the required energy range, the upper limit of the energy is
Set by level. Then, in the AD converter, the condition that the signal level from the linear amplifier 12 does not exceed the ULD level, that is, the state in which conversion is possible is a condition for outputting the busy signal (ADC BUSY).

As described above, in the conventional live time measuring circuit in radiation measurement, the live time measurement is temporarily stopped by the radiation detection signal, and the live time is measured by the busy signal output in the signal convertible state of the AD converter. When the pile-up further occurs, the output of the linear amplifier 12 is set to AD.
The live time measurement is interrupted by raising the converter from the ULD level and setting it outside the signal convertible region where the busy signal (ADC BUSY) is not output.

[0007]

However, in the above-mentioned conventional live time measuring circuit, when the ULD level is changed, the live time also changes. That is, in some cases it may be desirable to limit the spectral measurements to only the energy range of interest. In this case, the upper limit of energy will be set at the ULD level. Therefore, even if it is a valid signal, if it exceeds the ULD level, it will be outside the convertible area and the busy signal (ADC B
USY) is not output, the live time measurement is not restarted, and the time is counted as an invalid time.

Further, in the above-mentioned conventional live time measuring circuit, since the reset time of the optical pulse feedback preamplifier is not measured as an invalid time, an error may occur in the live time when this type of preamplifier is used. become.

An object of the present invention is to solve the above problems and to provide a live time measuring circuit for radiation measurement in which the live time does not change even if the ULD level is changed. It is a thing. Still another object of the present invention is to enable the reset time of the optical pulse feedback preamplifier to be measured as an invalid time.

[0010]

To this end, the present invention is a live time measuring circuit for measuring a live time for quantitatively measuring an element contained in a sample by radiation measurement. A waveform shaping circuit that outputs a shaped wave pulse signal proportional to a high value, a signal detection circuit that detects the radiation generation timing from the input pulse of radiation measurement and outputs a radiation detection signal, and a pileup detection from the radiation detection signal A pile-up detection circuit, a timing circuit for measuring a live time between an AD busy signal and a radiation detection signal, a ULD setting circuit for setting an upper limit level of energy for AD conversion, and a peak of a shaped wave pulse signal. The output of the AD busy signal and conversion data generated by AD conversion of the peak value of AD and execution of AD conversion An AD converter that generates a data ready signal for notification is provided. The AD converter excludes the shaped wave pulse signal from the AD conversion target when pile-up is detected, and the shaped wave pulse signal is set by the ULD setting circuit. When the upper limit level is exceeded, only the AD busy signal is generated.

[0011]

In the live time measuring circuit for radiation measurement according to the present invention, a waveform shaping circuit for outputting a shaping wave pulse signal proportional to a peak value from an input pulse for radiation measurement, and a radiation generation timing for the input pulse for radiation measurement. And a radiation detection signal, a signal detection circuit for detecting radiation, a pileup detection circuit for detecting pileup from the radiation detection signal, and a timing circuit for measuring a live time between the AD busy signal and the radiation detection signal. , The ULD setting circuit for setting the upper limit level of energy for AD conversion, and the AD busy signal generated by AD conversion of the peak value of the peak of the shaped wave pulse signal and the AD conversion signal generated by executing the AD conversion are ready for output. And an AD converter which generates a data ready signal for notifying that the AD converter detects pile-up. Is configured to exclude the shaped wave pulse signal from the A / D conversion target and to generate only the AD busy signal when the shaped wave pulse signal exceeds the upper limit level set by the ULD setting circuit. It is possible to perform AD conversion and generate an AD busy signal even when the input pulse exceeds the limit, while preventing the data memory from taking in the data. Therefore, it is possible to prevent the live time from changing even if the ULD level is changed, and the optical pulse feedback preamplifier is provided by providing the clock circuit with a gate for the clock pulse that is closed by the reset pulse of the optical pulse feedback preamplifier. The reset time of can be measured as invalid time.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing an embodiment of a live time measuring circuit for radiation measurement according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the live time measuring circuit.

The output of the preamplifier that amplifies the radiation detection signal is a pulse having a peak value proportional to the energy of the radiation, but is a low level signal with extremely poor S / N. For this reason, it is necessary to amplify to a measurable degree. In FIG. 1, a waveform shaping circuit 1 is a filter circuit for the purpose of amplifying a signal while removing noise, and shaping by shaping into a Gaussian wave or a triangular wave proportional to the peak value of the input pulse of radiation measurement. It outputs a wave pulse signal. The ULD setting circuit 3 sets an upper limit level (Upper Level) of energy when AD conversion is performed. The ADC 4 is an analog-digital converter that AD-converts the peak value of the peak of this shaped wave pulse signal. BSY signal and DATA Generate the RDY signal. However, if the shaped wave pulse signal exceeds the upper limit level set by the ULD setting circuit 3, the ADC 4
AD Generates BSY signal only, DATA No RDY signal is generated. AD here The BSY signal is an AD busy signal generated by executing AD conversion, and
DATA The RDY signal is a data ready signal notifying the data memory 6 that the conversion data is ready to be output. The data memory 6 uses this DATA RDY
This is a memory for storing converted data when the converted data is taken in by generating a signal.

The signal detection circuit 2 detects the generation of a signal, that is, the generation timing of radiation, and generates a short pulse signal b for each detection of the signal. This signal b
Resets the live-time flip-flop 7 and closes the live-time gate 8. The live time counter 9 uses the live time clock while the live time gate 8 is open, that is, when the live time flip-flop 7 is set and the reset pulse c is not generated. Is to keep time. The reset pulse c is a pulse generated when the optical pulse feedback preamplifier is reset. During the reset period, the live time gate 8 is closed so that the reset time is not measured as the live time.

The signal b is also input to the pileup detection circuit 5 and used for pileup detection. The pile-up detection circuit 5 detects if the pile-up occurs, the AD
An REJ signal is generated for C4 to instruct the shaped wave pulse signal to be excluded from AD conversion. ADC4
Receives the REJ signal, it prohibits the execution of AD conversion. Therefore AD BSY and DATA No RDY signal is generated. As a result, the piled up signal is not measured, and this time is counted as an invalid time.

Conventional busy signal (ADC BUSY)
As shown in the conventional example of FIG. 2, when the level exceeds the ULD level, it is not output outside the convertible area, the live time measurement is not restarted, and it is measured as an invalid time. Invention AD The BSY signal is shown in FIG.
As described in the present invention, since the shaped wave pulse signal is generated regardless of whether it exceeds the ULD level, the live time does not change depending on the ULD level. Moreover, when the shaped wave pulse signal exceeds the ULD level, DATA Since the RDY signal is not generated, the converted data is not taken into the data memory 6.

[0017]

As is apparent from the above description, the present invention
According to the ULD level for valid signals
AD conversion to AD Generate a BSY signal
Since I decided to do so, even if I change the ULD level, the live time
Can be prevented from changing. Moreover,
DAT when the square wave pulse signal exceeds ULD level
A Since the RDY signal is not generated, the AD conversion
It is prohibited to take the replacement data into the data memory,
Do not measure radiation above the ULD level.
You can Furthermore, when pile-up,
AD conversion is executed by the REJ signal from the detection circuit 5.
Ban and AD BSY and DATA Generated RDY
Since this is not done, the period is counted as invalid time.
And the AD conversion data is stored in the data memory.
Prevents radiation from being measured because it is prohibited from being captured
Can be Also, optical pulse feedback preamplifier
I tried to count the reset time of as invalid time
Therefore, even if this kind of preamplifier is used,
Im not to make an error.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a live time measuring circuit for radiation measurement according to the present invention.

FIG. 2 is a waveform diagram for explaining the operation of the live time measurement circuit.

FIG. 3 is a diagram showing a conventional example of a live time measuring circuit for measuring radiation.

[Explanation of symbols]

1 ... Waveform shaping circuit, 2 ... Signal detection circuit, 3 ... ULD setting circuit, 4 ... ADC, 5 ... Pile-up detection circuit, 6 ... Data memory, 7 ... Live time flip-flop,
8 ... Live time gate, 9 ... Live time counter

Claims (2)

[Claims] 1. A live time measuring circuit for measuring a live time for quantitatively measuring an element contained in a sample by radiation measurement, wherein a shaping wave pulse signal proportional to a peak value is output from an input pulse of radiation measurement. Waveform shaping circuit, a signal detection circuit that detects a radiation generation timing from an input pulse of radiation measurement and outputs a radiation detection signal, a pileup detection circuit that detects pileup from the radiation detection signal, and an AD busy signal And a radiation detection signal for measuring a live time, a ULD setting circuit for setting an upper limit level of energy for AD conversion, and a peak value of a shaping wave pulse signal for AD conversion and AD conversion. Generates an AD busy signal generated by execution and a data ready signal indicating that the conversion data is ready to be output An AD converter includes an AD converter that excludes a shaped wave pulse signal from an AD conversion target when pile-up is detected, and the shaped wave pulse signal is ULD.
A live time measuring circuit for radiation measurement, which is configured to generate only an AD busy signal when the upper limit level set by the setting circuit is exceeded. 2. A live time measuring circuit for radiation measurement, wherein the time measuring circuit includes a gate of a time measuring pulse closed by a reset pulse of an optical pulse feedback preamplifier.