Electronics for high resolution spectroscopy with compound semiconductors

A wide variety of applications require high resolution, high sensitivity, gamma ray spectrometers which are portable, compact, and rugged enough for field operations. We are developing a laboratory prototype of a semiconductor detector system meeting these requirements. This spectrometer uses multiple CdTe radiation detectors for high counting efficiency, digital nonlinear pulse risetime compensation circuitry for high energy resolution and high sensitivity, and a low power thermoelectric cooler for low electronic noise. The use of digital compensation allows arbitrary, very accurate compensation with no rejection. These three techniques were integrated in the prototype, which achieved an energy resolution of 5 keV (0.75%) FWHM at 662 keV, without rejecting any 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 other compound semiconductors which also have performance limited by poor charge collection, such as CdxZn1-xTe. A low power, compact, very portable, rugged implementation has been designed. (orig.)