A High Stability Pulser and Charge Injection Capacitor for Servostabilization of High Resolution Gamma Ray Spectrometers

This paper discusses the design of a reference pulser and air-dielectric capacitor for use in stabilization of high-resolution gamma-ray spectrometers. Additionally, the adverse effects of coaxial cable series resistance and detector coupling capacitor instability are considered. The reference pulser circuitry is completely transistorized and features a highly-stable dual-transistor pulse generation network. The temperature stability of the pulser output is ¿ ±5 PPM/°C from 10°C to 50°C. The long-term stability is approximately ±. 02 channels per day. The air-dielectric capacitor is a three-terminal device constructed of Kovar-steel and glass. The rigid glass-metal seal insures long-term stability. The capacitance temperature coefficient from liquid nitrogen to room temperature is approximately + 10 ppM/° C. Data are presented which shows that the series resistance of a coaxial cable will cause significant pulse drift when terminated and essentially no drift if left unterminated. An analysis also indicates that drift in a detector coupling capacitor can produce uncorrectable spectral drift.