A low noise preamplifier for HPGe detectors with auxiliary output for over range signal spectroscopy

We present a low-noise Charge-Sensitive Preamplifier for HPGe detectors able to swiftly recover from saturation, featuring an auxiliary output signal used for high-resolution pulse-height spectroscopy of the over-range signals. Using the auxiliary output for analyzing the signals larger than ~15 MeV (mostly charged particles and heavy ions) and the principal preamplifier output for analyzing all other signals (ionizing radiations and charged particles) a wide overall spectroscopic energy range of 5keV to 180MeV is obtained. A single Pole-Zero adjustment serves both the principal preamplifier channel as well as the auxiliary output channel. The energy resolution of the auxiliary channel is better than 0.1% typically. The Equivalent Noise Charge of the preamplifier is 115 electrons r.m.s., i.e. ~0.8 keV fwhm, using a BF862 as input transistor operated at room temperature while simulating the detector with a capacitance of 22 pF.