ELECTRONICS FOR HIGH-RESOLUTION SPECTROSCOPY WITH COMPOUND SEMICONDUCTORS

A wide variety of applications require high resolution, high sensitivi ty, gamma ray spectrometers which are portable, compact, and rugged en ough for field operations. We are developing a laboratory prototype of a semiconductor detector system meeting these requirements. This spec trometer uses multiple CdTe radiation detectors for high counting effi ciency, digital nonlinear pulse risetime compensation circuitry for hi gh energy resolution and high sensitivity, and a low power thermoelect ric cooler for low electronic noise. The use of digital compensation a llows arbitrary, very accurate compensation with no rejection. These t hree techniques were integrated in the prototype, which achieved an en ergy resolution of 5 keV (0.75%) FWHM at 662 keV, without rejecting an y counts, using a detector volume of 4 x 4 x 2 mm CdTe. With a 1.6 cm diam x 2 mm CdTe detector, a resolution of 15 keV (2%) FWHM at 662 keV was measured. The same technology has been successfully applied to ot her compound semiconductors which also have performance limited by poo r charge collection, such as CdxZn1-xTe. A low power, compact, very po rtable, rugged implementation has been designed.