Design and performance of a 50 mK rapid turnaround detector characterization system

Upcoming major NASA missions such as the Einstein Inflation Probe and the Single Aperture Far-Infrared Observatory will require arrays of detectors with thousands of background-limited elements sensitive to wavelengths from ∼ 50 μ m to ∼ 3 mm . Because of the low power levels present in space with cryogenic telescopes, these detectors will likely operate at temperatures below 100 mK. In order to make rapid progress on detector development, the cryogenic testing cycle must be made convenient and quick. We have developed a cryogenic detector characterization system capable of testing superconducting detector arrays in formats up to 8 × 32 , read out by SQUID multiplexers. The system relies on the cooling of a two-stage adiabatic demagnetization refrigerator immersed in a liquid helium bath. This approach permits a detector to be cooled from 300 K to 50 mK in under 6 h, so that a test cycle begun in the morning will be over by the end of the day. The system is modular, with two identical immersible units, so that while one unit is cooling, the second can be reconfigured for the next battery of tests.