Dependence of line widths of scintillation counters with NaI(Tl)-crystals on integration time constant

Abstract

The output pulses of the multiplier are integrated with a fixed large time constant ϑ 1 and simultaneously with an adjustable time constant ϑ 2 ≦ ϑ 1; the pulse amplitude can thus be alternatively defined by two distinct procedures: by measurement of the total or of a partial charge of the pulses. In a coincidence experiment with two single channel spectrometers I and II, spectrometer II records the amplitude distribution of such pulses integrated with time constant ϑ 2, as are coincident with pulses of fixed total charge, selected by spectrometer I. The coincidence line shows the small effect of incomplete integration upon the total line width, the large “intrinsic” contribution of the crystal to the line width being suppressed by the coincidence arrangement.