DOE-FAIR: Cryogenic Charge Amplifiers for Sub-GeV Dark Matter Detectors

A. Phipps, California State University East Bay (Principal Investigator)
N. Kurinsky, SLAC National Accelerator Laboratory (Co-Investigator)

Cryogenic charge amplifiers with resolution approaching single-electron sensitivity are a promising avenue towards direct detection of sub-GeV dark matter. This project continues development of a novel two-stage cryogenic charge amplifier based on commercial CryoHEMTs. The research is spearheaded by California State University East Bay (CSUEB), a minority-serving institution in the San Francisco Bay Area. Undergraduate students are actively involved in the research program, contributing significantly to various aspects of the project’s design and execution. Initial testing and development take place at the CSUEB cryogenics facility. Collaboration with SLAC enables access to sub-Kelvin temperature testing at the SLAC Millikelvin Facility.

During the first phase of the project, efforts are concentrated on enhancing the CSUEB cryogenic infrastructure, developing a preliminary warm electronics board, and refining the CryoHEMT noise model, particularly for low-capacitance HEMTs. This includes measuring current noise and noise variations with respect to bias power and temperature for CryoHEMTs suitable as amplifier inputs. The second phase will focus on developing an active amplifier reset mechanism, a refined cryogenic amplifier package, and an improved warm electronics package. Measurements of the standalone charge and energy resolution using a suitable semiconductor target material will also be performed.

The final product is a complete high-resolution charge amplifier system easily adaptable to any insulating cryogenic detector material which produces charge excitations with immediate applications to sub-GeV dark matter direct detection.