JP3182037B2 - Live time measurement circuit for radiation measurement - Google Patents

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 elements contained in a sample by radiation measurement.

[0002]

2. Description of the Related Art In a radiation measurement, when quantitative measurement of elements contained in a sample is performed, measurement data of an unknown sample is compared with measurement data of a standard sample or a known sample as a reference and each element is included. Derived quantity. However, the data of the standard sample, the known sample, and the unknown sample cannot be simply compared because the irradiation current, voltage, inclination of the sample, and the like 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 becomes necessary to accurately measure the measured effective time. In other words,
In the measurement of radiation, due to the nature of the measurement system, a time must be measured as invalid time. One of them is pile-up.If multiple radiations occur at very short times, they will be combined as a single signal, resulting in an incorrect peak value. Must be timed. Another is a reset time in the optical pulse feedback preamplifier. During this period, no signal is output from the preamplifier even if radiation is generated, so that it is necessary to count the invalid time. The time obtained by subtracting these two invalid times from the total measurement time must be counted as the total valid 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. 5-6774 for measuring (measuring) live time. This circuit is a circuit in which the complexity of the circuit configuration in U.S. Pat. No. 3,814,937 is originally simplified by using the function of the ADC and the busy signal, and the outline thereof 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
Numeral 1 is for detecting a pile-up when a plurality of radiations are generated at a very short time. The pile-up signal f is supplied to the linear amplifier 2 so that the linear amplifier 12 detects the pile-up signal f while the pile-up signal f exists. The output is raised above the ULD level as shown 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 a busy signal (ADC BUSY) and reset by a detection signal of the delay logic 13. The busy signal (ADC BUSY)
This is a signal output from an 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.

[0005] The AD converter has a discrimination function based on the set ULD level. If the signal level from the linear amplifier 12 does not exceed the ULD level, the signal conversion area is set outside the signal conversion area. . Therefore, if it is desired to limit the spectrum measurement to only the necessary energy region, the upper limit of the energy is set to this ULD.
Set by level. In the AD converter, the condition that the signal level from the linear amplifier 12 does not exceed the ULD level, that is, the converter is in a convertible state is a condition for outputting the busy signal (ADC BUSY).

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

[0007]

However, in the above-described conventional live time measuring circuit, when the ULD level is changed, the live time also changes. That is, in some cases, it may be desired to limit the spectrum measurement to only the necessary energy region. In this case, the upper limit of the energy is 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, and the measurement of the live time is not restarted, so that the time is counted as an invalid time.

In the conventional live time measuring circuit, the reset time of the optical pulse feedback preamplifier is not counted as an invalid time. Therefore, when this kind of preamplifier is used, an error occurs in the live time. become.

An object of the present invention is to provide a live time measuring circuit for radiation measurement in which the live time does not change even when the ULD level is changed. Things. 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]

SUMMARY OF THE INVENTION To this end, the present invention provides a live time measuring circuit for measuring a live time for performing quantitative measurement of elements 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 a radiation generation timing from a radiation measurement input pulse and outputs a radiation detection signal, and detects a pile-up from the radiation detection signal Pile-up detection circuit, a clock circuit that measures the live time between the AD busy signal and the radiation detection signal, an ULD setting circuit that sets the upper limit level of the energy for AD conversion, and a peak of the shaped wave pulse signal The peak value of the AD is converted to AD and the output of the AD busy signal and the converted data generated by executing the AD conversion is ready. And an AD converter for generating a data ready signal for informing. When the pile-up is detected, the AD converter excludes the shaped wave pulse signal from the AD conversion target, and the shaped wave pulse signal is set by the ULD setting circuit. In the case of exceeding the upper limit level, only the AD busy signal is generated.

[0011]

In the live time measurement circuit for radiation measurement according to the present invention, a waveform shaping circuit for outputting a shaped wave pulse signal proportional to the peak value from the radiation measurement input pulse, and a radiation generation timing from the radiation measurement input pulse A signal detection circuit that detects a signal and outputs a radiation detection signal, a pile-up detection circuit that detects pile-up from the radiation detection signal, and a timing circuit that measures a live time between the AD busy signal and the radiation detection signal. The ULD setting circuit for setting the upper limit level of the energy at the time of AD conversion, the AD peak signal of the shaped wave pulse signal is AD converted, and the AD busy signal generated by executing the AD conversion and the output of the converted data are ready. And an AD converter that generates a data ready signal notifying that the pile-up is detected. Is configured to exclude the shaped wave pulse signal from the AD conversion target and generate only the AD busy signal when the shaped wave pulse signal exceeds the upper limit level set by the ULD setting circuit. Even when the input pulse exceeds the threshold, the AD conversion is executed to generate the AD busy signal, but the data memory can be prevented from taking in the data. Therefore, it is possible to prevent the live time from changing even when the ULD level is changed, and to provide an optical pulse feedback preamplifier by providing the timing circuit with a gate for the clock pulse that is closed by the reset pulse of the optical pulse feedback preamplifier. Reset time can be counted 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 for amplifying the radiation detection signal is a pulse having a peak value proportional to the energy of the radiation, but a low-level signal having extremely poor S / N. For this reason, it is necessary to amplify to a measurable extent. In FIG. 1, a waveform shaping circuit 1 is a filter circuit for amplifying a signal while removing noise, and is shaped into a Gaussian wave, a triangular wave, or the like proportional to the peak value of an 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 at the time of AD conversion. The ADC 4 is an analog-to-digital converter for AD converting the peak value of the peak of the shaped wave pulse signal. BSY signal and DATA Generate the RDY signal. However, when the shaped wave pulse signal exceeds the upper limit level set by the ULD setting circuit 3, the ADC 4
AD Generates only the BSY signal, No RDY signal is generated. Where AD The BSY signal is an AD busy signal generated by performing AD conversion,
DATA The RDY signal is a data ready signal for notifying the data memory 6 that the conversion data is ready to be output. The data memory 6 stores the DATA RDY
It is a memory for taking in converted data by generating a signal, and for storing AD converted peak value information.

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 each time a signal is detected. This signal b
Resets the live time flip-flop 7 and closes the live time gate 8. 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, the live time counter 9 uses the live time clock to set the live time counter. Time. The reset pulse c is a pulse generated when the optical pulse feedback preamplifier is reset. During this 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 a pile-up detection circuit 5 and used for detecting pile-up. The pile-up detection circuit 5 detects if a pile-up occurs,
A REJ signal is generated for C4 to instruct the C4 to exclude the shaped pulse signal from AD conversion. ADC4
Prohibits the execution of AD conversion upon receiving this REJ signal. For this reason AD BSY and DATA No RDY signal is generated. As a result, the piled up signal is not measured, and this time is measured as invalid time.

Conventional busy signal (ADC BUSY)
However, as shown in the conventional example of FIG. 2, if the output exceeds the ULD level, the output is out of the convertible area and is not output, and the measurement of the live time is not restarted. AD of the invention The BSY signal is shown in FIG.
As shown in the present invention, since the shaped wave pulse signal is generated regardless of whether or not 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
Irrespective of ULD level for valid signal
Execute AD conversion to AD To generate the BSY signal.
Live time even if you change the ULD level
Can be prevented from changing. Moreover,
DAT when the shape pulse signal exceeds the ULD level
A Since the RDY signal is not generated, the AD conversion
Prohibit the replacement data from being taken into the data memory,
Ensure that radiation above the ULD level is not measured.
Can be. In addition, during pile-up,
AD conversion is executed by the REJ signal from the loop detection circuit 5.
Prohibit AD BSY and DATA Generated RDY
This period was set as invalid time.
And the AD conversion data is stored in the data memory.
Prohibits capture and prevents radiation from being measured
Can be Optical pulse feedback preamplifier
Reset time is counted as invalid time
This means that even if this type of preamplifier is used,
The error can be prevented from occurring in the im.

[Brief description of the drawings]

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

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

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

[Explanation of symbols]

DESCRIPTION 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)

(57) [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 the circuit outputs a shaped wave pulse signal proportional to a peak value from an input pulse of radiation measurement. A waveform shaping circuit, a signal detection circuit for detecting a radiation generation timing from a radiation measurement input pulse and outputting a radiation detection signal, a pile-up detection circuit for detecting a pile-up from the radiation detection signal, and an AD busy signal A clock circuit that measures the live time between the signal and the radiation detection signal, a ULD setting circuit that sets the upper limit level of energy when performing AD conversion, and AD conversion that performs AD conversion on the peak crest value of the shaped wave pulse signal Generates an AD busy signal generated by execution and a data ready signal indicating that conversion data is ready to be output. An AD converter is provided. When the pile-up is detected, the AD converter excludes the shaped wave pulse signal from AD conversion targets, and the shaped wave pulse signal is
A live time measurement circuit for radiation measurement, wherein only an AD busy signal is generated when an upper limit level set by a setting circuit is exceeded. 2. The live time measuring circuit for radiation measurement according to claim 1, wherein the timing circuit includes a gate of a timing pulse which is closed by a reset pulse of the optical pulse feedback preamplifier.