Commissioning of a common-user test facility to evaluate the effects of high-energy particles on next-generation cryogenic detectors

Cosmic rays affect the performance of any detector in space through the creation of spurious signal and/or slow build-up of radiation damage. To mitigate the effects of these high-energy particles on the observations of next-generation space missions, the interaction between state-of-the-art detectors will have to be understood through simulation and experimental verification. We present the first measurement results of a new cryogenic system designed to become a common-user test facility to evaluate the effects of high-energy particles on arrays of these high-sensitivity detectors. The system is based on pulse-tube precooled dilution refrigerator with a large experimental volume (ø = 29 cm, H = 30 cm). At 100 mK the system provides 650 µW of cooling power and an out-of-the box thermal stability of 76 µK rms. A first experiment with a semiconducting bolometer from the DIABOLO experiment shows a responsivity and noise level consistent with previous measurement in different cryogenic systems. However, the pulse-tube induced vibrations show as clear features in the noise. To irradiate the detectors a particle beam, such as the 25 MeV proton beam of the nearby ALTO facility, can be coupled to one of four ports. Simulations show that the aluminum-coated Mylar windows do not significantly affect the 25 MeV proton beam of TANDEM. First experiments at the ALTO facility for system verification are expected early 2019. Until that time, the thermal stability, vibration damping and EMI shielding will be improved and a flexible wiring will be developed, to accommodate multiple detector types.