Characteristics of high-rate energy spectroscopy systems using HPGe coaxial detectors and time-variant filters

A high-rate, high-resolution gamma spectrometer system is described. The system consists of a reverse electrode HPGe coaxial detector, a transistor reset preamplifier, an active, semi-Gaussian prefilter, a gated integrator, and a unique data acquisition system consisting of a 10 μs, 13 bit ADC, fast FIFO memory, 8k by 23 bit data memory, and computer interface circuitry under the control of a Z-80A μP. The effects of the various components on the throughput are described and throughput data is presented. The resolution and peak shift for various shaping times are presented for count rates up to 1 Mcps input rate using a mixed 22Na and 60Co source. The low rate resolutions of 57Co and 60Co for various shaping times using either the semi-Gaussian or gated integrator output are discussed as well as the low energy resolution and peak shifts in the presence of high energy events