Design and Optimization of Low-Noise Wide-Bandwidth Charge Preamplifiers for High Purity Germanium Detectors

Design criteria for low-noise wide-bandwidth charge-sensitive preamplifiers for highly-segmented HPGe detectors are presented. The attention is focused on the optimization of the preamplifier noise, long-term gain stability, and bandwidth. The charge-sensitive preamplifiers of AGATA, i.e., the Advanced GAmma Tracking Array detector for next generation nuclear physics experiments, have been designed, realized and optimized using the proposed techniques. The circuit, in conjunction with the detector, provided an Equivalent Noise Charge of 101 electrons r.m.s., a rise time of ~ 8.3 ns, no appreciable line shift in long term acquisitions, a dynamic range of as much as 92 dB. An analytical study of the circuit is made. Computer simulations and experimental results are shown and critically discussed.