A HEMT-based cryogenic charge amplifier with sub-100 eVee ionization resolution for massive semiconductor dark matter detectors

Abstract

We present the design and noise performance of a fully cryogenic (T=4 K) HEMT-based charge amplifier for readout of massive semiconductor dark matter detectors operating at sub-Kelvin temperatures. The amplifier has been developed to allow direct detection experiments such as CDMS and EDELWEISS to probe WIMP masses below 10 GeV/c 2 while retaining electromagnetic background discrimination. The amplifier dissipates only 1 mW of power and has a measured noise performance three times better than traditional JFET-based charge amplifiers. The predicted ionization energy resolution using the measured intrinsic amplifier noises and typical detector characteristics is σ E ≈ 100 eV ee (33 electrons). We have measured a calibrated baseline energy resolution of σ E = 91 eV ee when coupled to a live CDMS-II detector. To our knowledge, this is the best resolution achieved on such massive (≈150 pF capacitance) radiation detectors.

Low-Noise HEMTs for Coherent Elastic Neutrino Scattering and Low-Mass Dark Matter Cryogenic Semiconductor Detectors

“…Proper design of the cold amplifier is required to ultimately be limited by only the input HEMT noise. Previous work by some of the authors [27] has demonstrated 91 eV ee baseline RMS ionization resolution with a HEMT-based cryogenic charge amplifier with a 240g CDMS-II cryogenic germanium detector, nearly matching the model predictions. However, the complexity required to implement a HEMT-based fully cryogenic charge amplifier for the hundreds of ionization channels present in a reasonably-sized experiment requires us to explore amplifier topologies where the use of cryogenic HEMTs is limited to only the input transistor.…”

“…The current noise dominates the resolution for the 100 pF HEMT while is negligible for the 5 pF HEMT. Our model predicts an remarkable 19 eV ee rms ionization baseline resolution for the 5 pF HEMT which is one order of magnitude better than the best resolution achieved on ionisation with cryogenic detectors [1,27].…”

Diamond detectors for direct detection of sub-GeV dark matter

“…In principle, the readout time can be arbitrarily long by taking R b → ∞, but in practice the readout time is always limited by either pileup events or by rising noise at low frequency (often called 1/f noise), presumably caused by stochastic transitions in two-level systems. Recent work using High Electron-Mobility Transistors (HEMTs) by the SuperCDMS and EDELWEISS collaborations demonstrated a charge readout with a noise corner of around 4 kHz (τ ≈ 40 µsec) and a white noise floor of N v ∼ 0.2 nV/ √ Hz, resulting in a charge resolution of ∼ 35 electron-hole pairs for C det ≈ 150 pF and C in ≈ 100 pF [48]. These amplifiers can be produced with variable C in down to <10 pF, and it has been shown that the 1/f noise scales as C −1/2 in while the white noise is invariant to gate capacitance [49].…”

Prospects for exploring New Physics in Coherent Elastic Neutrino-Nucleus Scattering

“…• Ge and Si: are semiconductor materials that can perform electronic/nuclear recoil discrimination down to the energy threshold providing the ionization baseline resolution is good enough [37].…”