Development of a Cryogenic Two-Stage HEMT Amplifier to Search for Dark Matter

Our understanding of dark dark matter is continuously refined by limit-setting experiments all around the world. Until very recently, most experiments have optimized their search towards a model of dark matter known as Weakly Interacting Massive Particles (WIMPs), which would occupy a mass regime on the order of GeV/c2 to TeV/c2. Today, this range has been mostly explored, and new experiments are fleshing out the extremities of these limits set by theory. The SPLENDOR (Search for Particles of Light Dark Matter with Narrow-Gap Semiconductors) collaboration is currently focused on dark matter candidates with masses on the MeV/c2 scale. In order to detect the charge signal produced by scattering events, SPLENDOR is designing a two-stage cryogenic HEMT-based amplifier with an estimated charge resolution approaching the single-electron level. To achieve this, charge amplification is decoupled from direct charge readout using a novel two-stage transistor configuration, and room-temperature passive filtering is applied to all bias lines before they enter the cryostat. In this talk, I will present initial results from the mostly-completed 2-stage cryogenic amplifier design, including non-optimized noise performance and estimated charge resolution based on our current experimental results.