Noise considerations for a very low threshold semiconductor detector system

The search for dark matter motivates development of a semiconductor detector system with a very low noise threshold. The CoGeNT and MAJORANA projects both make use of hyper-pure Ge detectors and are in principle sensitive to the ionization signals produced by dark matter particles scattering from Ge nuclei if sub-keV thresholds can be achieved.We describe progress toward mitigating noise on several fronts: the 1/f noise that is inherent in capacitors and may also be present in the depletion layer of pn junctions, and the aliasing noise that is endemic with FFTs taken digitally over a large frequency range. An operating front-end design with an ENC (equivalent noise charge) of 4.5 electrons RMS has been demonstrated.