Accurate determination of Ge(Li) spectrometer efficiency and practical correction for dead time and pulse pile-up

The accurate adjustment is described of the semiconductor Ge(Li) spectrometer efficiency by means of 137Cs and 141Ce activity standards of the EFF type produced by UVVVR Prague. A comparison is made of three methods for determining analyzer dead time correction and the correction for count rate losses due to pulse pile-up. The spectrum acquisition proceeded in real time mode while the analyzer dead time and the pile-up effect corrections were made using a CI 104 R pulse generator. The 137Cs peak area determination was performed as a summation over the (-3 FWHM, +2 FWHM) region from which the linear background was subtracted obtained by fitting to adjacent regions of 1 FWHM in length. In testing the methods, the corrected 137Cs peak area was studied in dependence on the total count rate. This was altered within 600 and 50,000 s-1 by placing a 141Ce source to different distances from the detector. The 137Cs source was in a constant position. (B.S.)