STABLE 1-PF CHARGE INJECTION CAPACITOR FOR NUCLEAR PULSE PREAMPLIFIERS

Servostabilizers used with Ge(Li) γ-ray spectrometers are frequently referenced to pulser peaks obtained by injecting the output of a stable pulse generator into a charge sensitive preamplifier via a small capacitor. A 1 pF charge injection capacitor has been developed that meets the requirements of high resolution spectrometers. The three terminal air capacitor has a coaxial structure with electrodes made of Kovar. It has a temperature coefficient ranging from -1 to +6 ppm/°C and a long term stability of ±20 ppm, i.e., less than ±0.1 channel out of 4000. It adds only 1 pF of stray capacitance to ground at the preamplifier input and the noise added with 3 kV across it is negligible. © 1969 The American Institute of Physics.