QUBIC V: Cryogenic system design and performance

MASI, S.; SCÓCCOLA, CLAUDIA G.; AND THE QUBIC COLLABORATION

JOURNAL OF COSMOLOGY AND ASTROPARTICLE PHYSICS

IOP PUBLISHING LTD

Lugar: Londres; Año: 2021

1475-7516

Current experiments aimed at measuring the polarization of the CosmicMicrowave Background (CMB) use cryogenic detector arrays and cold opticalsystems to boost the mapping speed of the sky survey. For these reasons, largevolume cryogenic systems, with large optical windows, working continuously foryears, are needed. Here we report on the cryogenic system of the QUBIC (Q and UBolometric Interferometer for Cosmology) experiment: we describe its design,fabrication, experimental optimization and validation in the TechnologicalDemonstrator configuration. The QUBIC cryogenic system is based on a largevolume cryostat, using two pulse-tube refrigerators to cool at ~3K a large (~1m^3) volume, heavy (~165kg) instrument, including the cryogenic polarizationmodulator, the corrugated feedhorns array, and the lower temperature stages; a4He evaporator cooling at ~1K the interferometer beam combiner; a 3Heevaporator cooling at ~0.3K the focal-plane detector arrays. The cryogenicsystem has been tested and validated for more than 6 months of continuousoperation. The detector arrays have reached a stable operating temperature of0.33K, while the polarization modulator has been operated from a ~10K basetemperature. The system has been tilted to cover the boresight elevation range20 deg -90 deg without significant temperature variations. The instrument isnow ready for deployment to the high Argentinean Andes.