Gamma Scintillation Spectrometer Research Articles

Ṡtabilization of a gamma scintillation spectrometer against zero and gain drifts

In this paper is described the theory, design, and performance of a device which corrects zero and gain drifts of any origin in a gamma-ray scintillation spectrometer consisting of NaI(Tl) crystal and multichannel pulse-height analyzer. This correction is automatic and continuous througout operation of the spectrometer. Stability of peak channel numbers to 0.1 percent or better seems attainable over indefinite periods of time without important penalties. Reference gamma rays, having low and high energies, respectively, and accompanied always by coincident beta rays which uniquely distinguish them from all other gamma rays, are emitted from a special source close to the detector. The spectrometer determines the channel number of these reference gamma rays as for other gamma rays, but does not store the counts in its memory. The stabilization device adjusts zero and gain, by means of feedback voltages applied to analyzer window threshold and photomultiplier dynode voltage, respectively, so as to hold the two reference peaks always in the preassigned channels. Thus the same reference spectrum is used for all experimental spectra (without, however, contributing appreciably to background), and the stabilization feedback loop encompasses the entire analogue portion of the spectrometer.

Nuclear spectroscopy of 173Tm

The 173Tm nucleide was produced by the (γ, p) reaction by using an intense bremsstrahlung from a linear electron accelerator. A 174Yb target enriched to 99% was used. The radiations from 173Tm were measured by means of a beta and gamma scintillation spectrometer. Two beta-ray groups with end-point energies of 1.26 and 0.86 MeV were found, and K X-ray, 395 and 460 keV gamma rays were observed. The excited states at 395 and 460 keV in 173Yb were identified as 1 2 + [651] and 1 2 − [521] intrinsic states, respectively. It was found that the 395 keV state is an isometric level with a half life of 2.9 μsec. The assignments were made with the aid of electron - K X-ray and electron - beta coincidence methods.

Experimental determination of the absorption coefficients of gamma rays through different barriers

The absorption coefficients of gamma rays from 0·14 to 2·76 MeV, for six materials of different atomic number ranging from 6 to 82 have been determined. The experiments were performed using a gamma scintillation spectrometer. The areas under the photoelectric peaks as well as their heights have been used for calculating the absorption coefficients. A detailed comparison between experimental and theoretical results was discussed.

WHOLE-BODY COUNTING TECHNIQUE FOR LABELED GLOBULIN

The metabolic behavior of radioactively labeled proteins, the biological half-life or degradation rate, may be determined from serum concentration curves. The quantities of retained isotope are inferred from the analyses of excreta obtained from complete 24-hour samples collected for a number of successive days. Lippincott and co-workers¹determined the turnover of I¹³¹-labeled beta and gamma globulins, prepared by chemical fractionation, by the use of the conventional method of blood and urine sampling, and also by a new technique utilizing the whole-body gamma spectrometer. The latter procedure provides an excellent method for measuring retention of labeled globulins over long periods of time following administration of small amounts of isotopes. A whole-body gamma scintillation spectrometer was utilized in this study for the in vivo detection of gamma radiation. The data from the spectrometer are in the form of pulse-height spectra obtained by analysis of the amplified output of the

Coincidence summing and non-linearity studies with a two-crystal scintillation gamma spectrometer

Abstract A two-crystal 4 π NaI(Tl) scintillation gamma spectrometer has been used for studying coincidence summing effects with special reference to the energy calibration in the region 0.5 to 4 MeV of coincidence sum peaks of cascade gammas. From observed deviations of the sum peak positions from those expected according to calibrations with single photopeaks, the nonlinear response of NaI(Tl) has been investigated. The pulse height per unit energy as a function of energy appears to approach a constant value with increasing energy up to 4 MeV. A slight shift in single photopeak position when ollimation is introduced was observed at most gamma energies with a single crystal spectrometer. Possible reasons for the apparent non-linearity are discussed.

Activation analysis of cadmium in small biopsy samples

Biopsy samples of human kidney, comprising only 2–15 mg, were successfully analysed for cadmium by activation analysis. The procedure adopted was, after reactor irradiation and dissolution, a sulphide precipitation which is treated by alkali. For accurate work a final phosphate precipitation is used but in many cases the first precipitate is studied directly by means of a gamma-scintillation spectrometer and multichannel analyser.

Analyses of small samples of monazites with a gamma scintillation spectrometer

AbstractThe possibility of applying gamma ray analysis to approximately 50 mg samples of monazite has been investigated. Three ranges of low energy gamma radiation, under 0.3 MeV, were counted with a Gamma Scintillation Spectrometer.This extremely simple method led to very good results with samples containing only one radioactive component. With monazites containing uranium as well as thorium, the latter component being in excess, results were also good. For uranium contents that were only a few tenths of a per cent, the results did not attain the precision of chemical analysis.In a leached mineral where the simultaneous contents of uranium, radium in excess and thorium had to be determined, the method failed, due to the smallness of the contribution of UX in the emitted radiation with respect to that of the radium family. In this case we were able to calculate an approximate value for the thorium content and make a rough estimate of the total radium content of the mineral.With this spectrometer the use of longer counting times gives only a slight improvement in the precision of the counts. The use of somewhat larger samples will however diminish the important background fraction in the low activity countings and hence it will give a corresponding increase in the reliability of the results.

The Determination of Zirconium-95 Plus Niobium-95 By Anion-Exchange Separation From Other Fission Products

A rapid and simple anion-exchange method is described for the separation of Zr 95 plus Nb 95 from other fission products. The zirconium and niobium are adsorbed onto a 7 mm diameter column 100 mm in length of Dowex-l-X4, 100–200 mesh resin from a hydrofluoric acid solution of the fission products. The resin is counted directly, using a 3-in. NaI(T1) well-type crystal and a gamma scintillation spectrometer. Yields of greater than 99.5 per cent are obtained. The activity levels of the major fission products (Ru 106 , Cs 137 and Ce 144 ) are reduced by more than 95 per cent. Distribution coefficients were established for the adsorption of zirconium and niobium from HF solutions ranging from 0.1 to 6 M in concentration. Elution characteristics are described for tracer amounts of Ru 106 , Ce 144 and Cs 137 in HF solutions alone and in the presence of macro amounts of U, Fe and Al. The maximum amount of U which can be tolerated and an estimation of the error in counting caused by the displacement of Zr and Nb by U are given.

Antiparticles in Space

Hoyle obtained a steady-state model for an expanding universe by introducing continuous creation of matter into the field equations of general relativity. Morrison has speculated that the creation of matter throughout the universe may take place by formation of particle--antiparticle pairs which subsequently are segregated by a repulsive force between matter and anti-matter. Burbidge and Hall have estimated that the ratio of antimatter to matter in our galaxy can not exceed -- 10/sup -7/ This investigation points out that a slightly more stringent limit for this ratio is sugge sted by cosmic ray measurements. More precise information concerning the density of antiparticles in the galaxy can be obtained by carrying a simple scintillation gamma spectrometer some distance from the earth in a satelite or space probe. (A.C.)

Gamma lines in the decay of 202T1

The gamma-radiation of 202 T1 was reinvestigated by means of a gamma-scintillation spectrometer. Two new gamma-lines were found viz. of 523 and 965 keV. An estimation was made for the transition-energy to the ground state of 202 Hg and a level scheme of 202 Hg was set up. The ratio of the energies of the second and first excited states was compared with the values of neighbouring nuclei.

The internal Compton effect: A determination of cross section and angular correlation

The internal Compton effect, a nuclear transition in which there is a simultaneous ejection of a bound electron and emission of a gamma ray, has been unambigously demonstrated. The experiment concerned the 662 keV transition in Ba 137m and was carried out with a gamma scintillation spectrometer and a beta-ray spectrometer in coincidence. The presence of other effects was carefully considered. The experimental cross section was found to be 1.86 × 10 −5 photons in the energy region 97 keV – 120 keV per conversion electron at 90° between the electron and photon directions. Angular correlation experiments were carried out. Comparison with various theories shows that the theory by Spruch and Goertzel does fit the experimental results excellently both regarding absolute cross section and angular correlation.

Radio-Caesium in Dried Milk

A gamma scintillation spectrometer method for measuring the radio-caesium and potassium content of dried milk is described.The changes with time of the 137Cs activity in dried milk from Frome, Somerset are presented. Levels of 137Cs activity in full cream dried milk collected in October-December 1956 from five different areas have been measured.

The decay of the UX-complex

The radiations of the UX-complex and of pure UZ were reinvestigated by means of a double-focusing beta-ray spectrometer and a gamma-scintillation spectrometer. A rapid method was worked out to obtain relative pure UX 2 samples. The gamma-rays were measured with a photographical method. Sixteen gamma-transitions were found in UZ and twelve in UX 2 ; five of these transitions seemed to occur in both decays. From these data and a β—e − coincidence measurement in UX 1 a tentative level scheme of the UX-complex was set up. The UZ-level proved to be the ground state of 234 Pa, 60 ± 15 keV below the UX 2 level.

Influence of the distance between source and crystal on the detection-efficiency of a gamma-scintillation spectrometer

Synopsis The influence of the distance between source and crystal on the counting efficiency of a scintillation spectrometer has been studied. For gamma-rays of energy larger than 400 keV the efficiency may vary by a factor of two depending on the distance from source to crystal. The experimentally observed dependence may be fully explained by simple geometrical arguments.