Reduction of the low energy background of a phoswich detector

Modifications to a phoswich detector and its attendant electronics to suppress contributions from dark current which can effect a worthwhile reduction to the background contribution in the 12 to 40 keV range are reported. The comparative background spectra of a 20 cm diameter phoswich with (a) a single 18 cm diameter photomultiplier and (b) three 7.5 cm diameter photomultipliers and multichannel analyser triggered by the coincident output from two tubes, are shown graphically. Reasons for the improved performance with the second arrangement are considered. (U.K.)