Dc superconducting quantum interference device amplifier for gravitational wave detectors with a true noise temperature of 16 μK

Abstract

We report on the noise characterization of a two-stage dc superconducting quantum interference device (SQUID) amplifier developed for resonant gravitational wave detectors. The back action noise is estimated by coupling the SQUID to an electrical resonator at 1.6 kHz with Q=1.1 × 106. From measurements of back action and additive SQUID noise, performed in the temperature range 1.5-4.2 K, an upper limit is set on the noise temperature Tn, of the device at the resonator frequency. The best value obtained at 1.5 K is Tn ≤16 μK and corresponds to 200 resonator quanta. The thermal component of the noise temperature is found in reasonable agreement with the predicted value. © 2001 American Institute of Physics.