Noise Modeling and Calibration of a Two-Stage Cryogenic Charge Amplifier for the SPLENDOR Experiment

arXiv:2510.01463v1 Announce Type: new
Abstract: The SPLENDOR Collaboration studies novel narrow-gap semiconductors and engineered a substrate agnostic detector platform to achieve $mathcal{O}$(meV) energy sensitivity designed for low mass dark matter searches. This was achieved using low-capacitance and low-noise commercial CryoHEMTs in a split-stage topology integrated throughout a dilution refrigerator. Designed with a source-follower HEMT at the base temperature stage and a voltage amplifier at 4,K, this amplifier has input-limited voltage noise of 10 $text{nV}/sqrt{text{Hz}}$ and current noise of 100 $text{aA}/sqrt{text{Hz}}$ at 1kHz. In agreement with this noise level and a photon calibration, this amplifier has a $text{19} pm text{4} $ electron resolution.