Design and Characterization of a DC-SQUID Amplifier for TES Detectors

The DC Superconducting Quantum Interference Device (dc-SQUID) has been widely recognized as the preferred readout technology for high-sensitivity superconducting Transition Edge Sensors. In this study, we present the design, fabrication, and characterization of a novel first-order gradiometric dc-SQUID amplifier incorporating intra-coil resistors, specifically tailored for TES detector applications. The measured results demonstrate that the proposed intra-coil resistors design significantly enhances the flux-voltage transfer coefficient VΦ. Through a systematic comparative analysis of various intra-coil resistor configurations, we observe a positive correlation between VΦ and the intra-coil resistor conductance. This enhancement in VΦ effectively reduces the noise contribution from the backend readout circuit, thereby improving the overall system sensitivity. The developed amplifier has been successfully implemented into the readout system of an X-ray TES microcalorimeter, demonstrating its practical applicability in high-performance detector systems.