Radiant energy – Automatic/serial detection of similar sources
Patent
1985-10-18
1988-08-02
Fields, Carolyn E.
Radiant energy
Automatic/serial detection of similar sources
250364, 250362, G01T 1204
Patent
active
047615559
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention concerns an automatic radioactivity measurement method and its apparatus in an efficiency tracing method of a liquid scintillation measurement.
2. Description of the Prior Art
The liquid scintillation counter presently in use has been developed for measuring the radioactivity of only .sup.3 H and .sup.14 C, and the radioactivity measurement method for these radionuclides is already accomplished. Besides, we have an efficiency tracing method which is effected to find the radioactivities for many kinds of radionuclides by using the liquid scintillation counter. (reference book: "Liquid Scintillation Measurement Method" by H. Ishikawa p. 159, Nanzando (1981); reference paper: M. Takiue and H. Ishikawa, "Nuclear Instrument and Method" 148, 157 (1978)).
With the efficiency tracing method it is possible to obtain the radioactivities of almost all pure beta- and beta-gamma emitters. However, the conventional efficiency tracing method has the following drawbacks, because it is manually performed. Therefore, it is currently of no practical use.
(1) Constant attention has to be paid to change manually the measurement conditions several times, while samples are measured.
(2) The selection of the best measurement region is not easy.
(3) In carrying out the efficiency tracing method, the relation between several counting efficiencies of the standard sample and the several counting rates of the subject sample is manually plotted on a graphic paper, as shown in FIG. 1, to find an extrapolated value (i.e. radioactivity of the subject sample) through drawing an efficiency tracing curve. Therefore, it is very time-consuming to perform this procedure.
(4) An accurate graph can't always be obtained, because of manual drawing.
(5) Since the error calculation for the efficiency tracing method is much more complicated than that in any other methods, the error of radioactivity is not actually determined. Thus the conventional efficiency tracing method by manual operation seems to be uncompleted as a measurement method of radioactivity.
The purpose of this invention is to provide an automatic efficiency tracing method which eliminates the drawbacks of the conventional method, and its apparatus.
SUMMARY OF THE INVENTION
The following explains a radioactivity measurement method by using the liquid scintillation counter which has an automated efficiency tracing method.
(A) Pulses having various pulse heights, which are produced in the liquid scintillation counter, are measured in the regions between a lower and an upper levels of a pulse height analyzer. The regions have several widths, and the same regions are respectively used for the measurement of a standard sample and a subject sample whose radioactivity is being determined.
(B) In order to set up and fix the appropriate regions, an ADC (analog-to-digital converter) and a memory circuit of a multi-channel pulse height analyzer, which are installed in the liquid scintillation counter, work as follows;
A pulse height is converted to the number of clock pulses, and then the channel number of the memory circuit, which is equal to the number of the clock pulses, is selected. Then various pulses are accumulated in each corresponding channel number. In this invention, a computer has the programs to set up fixedly the several lower and upper levels of the channel number and to count simultaneously the number of pulses existing at each region between the fixed lower and upper levels. In this method, each value measured in the several regions can be simultaneously obtained by only one measurement. The computer which has the programs capable of performing these procedures is installed in the liquid scintillation counter to execute the automatic efficiency tracing method.
(C) In the case where this measurement is performed under each region of R.sub.1, R.sub.2, - - - R.sub.m, let the counting efficiencies (%) of the standard sample be X.sub.1, X.sub.2, - - - X.sub.m respectively and the counting rate (cpm) of the subje
REFERENCES:
patent: 3725657 (1973-04-01), Laney
Ishikawa et al, "Radioassay by an Efficiency Tracing Technique Using a Liquid Scintillation Counter", Int. J. Appl. Radiat. Isot., 35(6), pp. 463-466, 6-84.
Ishikawa Kiroaki; "Ekitai Scintillation Sokuteiho", 20 Apr. 1981 (20.4.81), Nanzando, pp. 159-162.
Ishikawa Hiroaki, "Kiso Katei Text 9-3 Ekitai Scintillation Sokutei", Jun. 1983 (06.83), Genken Radioisotope, Genshiro Kenkyusho, pp. 21-22.
Makoto Takiue and Hiroaki Ishikawa; Thermal Neutron Reaction Cross Section Measurements for Fourteen Nuclides with a Liquid Scintillation Spectrometer; 1978; pp. 157-161.
Fields Carolyn E.
Ishikawa Industry Co., Ltd.
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