Energy distributions of 1.12-MeV gamma rays Compton scattered byK-shell electrons of gold, lead, and thorium

Abstract

II. EXPERIMENTAL DETAILSIn the present experiment, a fast-slow coincidence system was used with resolving times of 30 nsec and 2 p, sec, respectively. Pulse-height analysis of anode pulses from the y detector was made with the help of a 20-channel analyzer gated by the output of the coincidence circuit. The linearity of pulse height was checked not only through the singles spectra of the y rays of different energies but also through the spectra obtained in the coincidence mode. Annihilation quanta from a Na source, and 1.17-and 1.33-MeV y rays from a~Co source were used for the spectral measurements in the coincidence mode. The photopeaks obtained in the coincidence mode agreed 'with the positions of the corresponding peaks in the singles spectra. Therefore, useful linearity and gain stability checks could be made more frequently in the singles mode than would have been possible in the coincidence mode. If a check showed a pulseheight shift of more than 2%, the corresponding data were discarded.Pulse-height distributions of the scattered y rays were studied at 60' and 100' scattering angles.In each case, the pulse-height distribution of false events was determined and subtracted from the measured distribution in order to obtain the "true" distribution. In all cases, the chance coineidenee rate was less than 1% of the total rate and was considered negligible. figure. With the help of the response function of the detector, it is necessary to deconvolute the pulse-height distribution in order to obtain the energy distr ibution. The deconvolution procedure is outlined in the Appendix.