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Abstract

The development of a high-resolution gamma ray spectrometer incorporating a germanium lithium-drift radiation detector is described. Sources of electrical noise in detectors and low-noise field-effect transistor preamplifiers are discussed. Modifications were made to available preamplifier circuits with a slight improvement in noise characteristics. A very-low-noise preamplifier using a 2N3823 field-effect transistor was tested, and an unconventional design inductive-load field-effect transistor preamplifier was built and tested. Refinements on germanium detector preparation techniques previously in use are described with particular reference to the starting material used. The design of a stainless steel cryostat to house germanium detectors is discussed. Performance characteristics of a 5 cc. detector are given. Preliminary measurements with it of the Doppler broadening of the annihilation peak in Ni and Zn are presented. A spectrum of annihilations of ortho-positronium formed in Freon 12 is given. The detector system is evaluated with reference to suitability in positron physics.