Cryogenic performance of a low-noise JFET-CMOS preamplifier for HPGe detectors

Cryogenic low-noise charge sensitive preamplifiers have been developed and realized for the GERmanium Detector Array (GERDA). An integrated JFET-CMOS preamplifier, which is fully functional at cryogenic temperatures, has been tested in conjunction with an unsegmented p-type HPGe detector. Both the crystal and the preamplifier were operated inside a liquid nitrogen dewar at 77 K. The detector capacitance was similar to 60 pF. An optimum resolution of 1.6 keV FWHM has been obtained for the pulser line at 6 mu s shaping time. A resolution of 2.1 keV FWHM has been achieved for the 1.332 MeV line from a Co-60 source. A wide bandwidth (rise time of similar to 16 ns) permits use of pulse-shape analysis techniques to localize the position of the photon interactions inside the crystal. A low power consumption (23 mW) makes the preamplifier suitable for a multi-channel array of germanium detectors.