JPS5814062A - Pulse height analyser - Google Patents

Abstract

PURPOSE:To provide a high-precision pulse height analysis by storing the output of a radiation ray detector in a memory, giving an address of a predetermined width to the upper and lower ones across the address of the maximum data in the memory taken as a standard, thereby enabling correct setting of a window width. CONSTITUTION:Detecting at 2 radiation ray from a radiation soruce only the detected value larger than a predetermined value 14 is passed through 13 to eliminate noise and is fed to the sample hold circuit 15 and the control circuit 15. The circuit 16 detects a peak value of input pulse which is fed to the circuit 15 as a sample hold signal to pick up sample of the input pulses. The hold value at circuit 15 is written into a memory 18 after A/D conversion at 17. The lower bit of address at the memory 18 corresponds to the energy level L and the upper bit to the energy level U. The number of detected-value occurrences is then sequentially stored in the address region of the window width which is determined by each address corresponding to the level L and U, providing data distribution of the window width. The data is memory 18 are used for pulse height analysis.

Description

[Detailed description of the invention] The present invention relates to a pulse height analyzer.

In radiation measurement, a window is set for the detected energy, and the distribution of the number of energy detections within this window (generally called the count value) is taken to obtain data for wave height analysis. The window settings are set around the peak value of the number of detections.

The relationship between this count value, detected energy, and window is shown in FIG. In the figure, the horizontal axis shows energy (KeV), and the vertical axis shows the count value (the number of detections in the measurement time period). Characteristic C indicates the number of detections for each level of energy.

The shaded area indicates the window, L is the lower one energy value, and U is the upper energy value.
The energy level between and the count value (number of detections) at each level are the data to be analyzed for wave height. For example, the figure shows that at energy level E, P detections were obtained in the measurement time period. The detected value of these P times, that is, the counted value becomes the peak value.

A conventional circuit for obtaining the characteristics of such a whistle as shown in Fig. 1 is shown in Fig. g2. Radiation ll1l from the radiation source 1 is detected by the detector 2. Detection value of detector 2, preamplifier 3
The signal is taken in, amplified by additional teeth, and guided to an upper limit value comparator 4 and a lower limit value comparator 5. The upper limit comparator 4 selects the upper limit value U shown in FIG.
The magnitude relationship is compared with the lower limit value of the lower limit value comparator 5L in FIG. If the detected value corresponding value, which is the output of the preamplifier 3, is between U and L, the AND gate 6 opens and outputs an output indicating that the energy level is within the range that can be selected between U and L within the setting window. occurs. This output is taken in by the counter 7 and used for counting.

Although this conventional example can generate data as shown in FIG. 1, it has one major drawback. This is the point where the peak value P varies left and right. It would be good if the inside of the window could be changed according to the variation, but since the cause of the fluctuation is due to drift etc., it has been difficult to make a corresponding change in the inside of the window. The causes of the drift include, firstly, fluctuations in the high voltage applied to the photomultiplier tube constituting the detector 2, and secondly, the drift of the preamplifier 3. As a result, highly accurate peak counting measurement was not possible. Furthermore, it made highly accurate wave height analysis impossible.

An object of the present invention is to provide a pulse height analyzer that enables highly accurate pulse height analysis.

The gist of the present invention is to stop setting the window in advance, and first store all the outputs of the detector except for the noise level digitally in the memory as data, and then search the memory after storing. By determining the address that has the largest amount of data, and using the determined address as a reference address, giving addresses of a predetermined width before and after it, it is possible to make correct settings during the window.

The details will be explained below.

FIG. 3 is an embodiment of the present invention, and FIG. 4 is a time chart. Detector 2 detects radiation 11 from radiation source 1 . In Figure 4, people B, C', and D.

The pulses E and F are equivalent (-). Noise removal circuit 12
is a setting device 14 having a preset setting value vth, a setting value Vtb of this setting device 14, and a detected value 2 of the detector 2.
a, and outputs only the detected value larger than the set value vth. In FIG. 4, pulse C is removed as noise, and pulses A and B are removed.

The low levels of D, Fl, and F have been removed. Of course,
Similarly to FIG. 2, the preamplifier 3 may be inserted on the output side of the detector 2. The output of the comparator 15 is a signal from which signals with amplitudes smaller than the set value are removed.

The output 13 of the comparator 15 is the sample hold circuit 15.
and input to the control circuit 16. The control circuit 16 receives the output 1311 of the comparator 15, has a starting point synchronized with the rising edge of the output 1311, and controls the output of the comparator 13 in a time period T (indicated by M in FIG. 4) during a certain period of time. Perform peak detection.

The time required to detect the peak from the output 13m differs depending on each waveform. In FIG. 4, Δt1. Δt7.
This time is indicated by Δtsr*. The peak detection result is sent to the sample-and-hold circuit 15 as a sample-and-hold signal 16a, which samples the comparator output at that point as a peak, and thereafter holds that peak for a certain period of time until the end of T0. This result is shown by signal 15m in FIG. In addition to performing fIiJ and peak detection within the control circuit 16, the sample and hold circuit 15 may also have this function. In any case, peak detection requires a certain amount of processing time, and therefore, in order to detect the peak of the output of the comparator 16, the output itself to be sampled and held must be processed for the processing time. delay is required. Similarly, in addition to peak detection, it is also possible to integrate and obtain an average value and output the cough average value instead of the peak.

The output 15m of the sample and hold circuit 15 is sent to the human converter 17. 17 AD converters The hold output of the sample hold circuit 15 is taken in and AD converted.

The start point of this AD conversion is determined by the AD conversion start command signal 16b of the control circuit 16. Conversion is started by the command signal 16b of the AD converter 17, and an AD conversion end signal 17m is generated upon completion of the AD conversion. On the other hand, control circuit 1
When 6 receives this AD conversion end signal 17m from the AD converter 17, it immediately writes it into the memory 18. 1 Command signal 16c
occurs. This causes the memory 18 to write data. ! In the diagram s4, the signal 16b is generated with a delay of Δ with respect to the signal 15a, the signal 17a is generated with a delay of Δτ1 with respect to 16b, and the signal 16c is generated with a delay of ΔrJ with respect to 17a. Both are due to hardware delays.

The data write operation in memory 1B will be described. memory 18
is addressed by a detection value which is digitized data of the AD converter 17. memory 18
Among the addresses, the lower (start) address corresponds to energy level L, and the upper (final) address corresponds to energy level U. Therefore, 18 addresses are accessed in accordance with the detected value. On the other hand, the data to be written is "1" for one detected value (the detected value after removing noise). For the same detection value, sequentially ``''1
" is added by the number of times of detection, and the added value is stored as data. Therefore, in the address area of the window width defined by the address corresponding to energy level L and the address corresponding to energy level U, each The number of occurrences of detected values for each energy level is stored sequentially, and a data distribution with a window width determined by U and L in FIG. 1 is obtained.

Similarly, when the memory is formed by kakunta formation,
The data is simply counted and stored without being read out.

In the case of register format, read and add "1",
The operation of writing again is required. It is arbitrary whether the memory configuration is magnetic or circuit-based.

The data stored in memory 18 is used for wave height analysis. At the time of this wave height analysis, according to the digital storage format of this embodiment, it is necessary to determine which energy level indicates a peak, that is, to determine the peak value P on the distribution by searching the data in the L memory 18. This is easily possible. By specifying a predetermined range of addresses in the plus and minus directions around the address (address) indicating this peak value, it is possible to specify a window according to the peak value.

Thereby, wave height analysis data with the peak value as the center of gravity can be easily obtained. A computer is used for actual wave height analysis. In the figure, 20 is calculated by computer, total x root 20
reads the data in the memory 18 and performs wave height analysis processing. Similarly, the capacity of the memory 18 may be large enough to store data for wave height analysis in one cycle, or may be large enough to store data for wave height analysis in multiple cycles.

According to the present invention described above, a two-dimensional distribution of measured values for energy measured over a certain period can be stored in the memory, and therefore a highly accurate pulse height analyzer can be provided.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of wave height analysis, FIG. 2 is a diagram of a conventional example, FIG. 3 is a diagram of an embodiment of the present invention, and FIG. 4 is a time chart. DESCRIPTION OF SYMBOLS 1... Radiation source, 2... Detector, 12... Noise removal circuit, 15... Sample hold circuit, 16...
Control circuit, 17... AD converter, 18... Memory. Figure 1 Figure 2

Claims (1)

[Claims] 1. A detector that detects radiation that occurs in time series from a radiation source, and when the detected value of the generated radiation is larger than a preset value for noise removal. A comparison means for outputting the detection value of the large level, a holding means for taking in the output of the comparison means, detecting and holding an output corresponding value for each occurrence, and A for taking in the mosquito hold value and converting it into AD.
A D converter and a memory that is addressed in accordance with the amplitude level of the output of the human converter are accessed by an address corresponding to the output of the AD converter, and each time an output occurs, a memory within the appropriate address is accessed. A memory means is formed by multiplying the data by 1' and storing the data, and the data having the maximum value among the data in the address corresponding to the output of the AD converter stored in the memory means is determined, and the data having the maximum value is determined. means for setting a predetermined address before and after the address as a reference address as a reference address, and reading data corresponding to the middle address of the window for wave height analysis;
A wave height analyzer consisting of: 2. The wave height analyzer according to claim 1, wherein the output corresponding value is a peak value for each generated output.