QUBIC V: Cryogenic system design and performance

Abstract

Current experiments aimed at measuring the polarization of the Cosmic Microwave Background (CMB) use cryogenic detector arrays and cold optical systems to boost the mapping speed of the sky survey. For these reasons, large volume cryogenic systems, with large optical windows, working continuously for years, are needed. Here we report on the cryogenic system of the QUBIC (Q and U Bolometric Interferometer for Cosmology) experiment: we describe its design, fabrication, experimental optimization and validation in the Technological Demonstrator configuration. The QUBIC cryogenic system is based on a large volume cryostat, using two pulse-tube refrigerators to cool at ~3K a large (~1 m^3) volume, heavy (~165kg) instrument, including the cryogenic polarization modulator, the corrugated feedhorns array, and the lower temperature stages; a 4He evaporator cooling at ~1K the interferometer beam combiner; a 3He evaporator cooling at ~0.3K the focal-plane detector arrays. The cryogenic system has been tested and validated for more than 6 months of continuous operation. The detector arrays have reached a stable operating temperature of 0.33K, while the polarization modulator has been operated from a ~10K base temperature. The system has been tilted to cover the boresight elevation range 20 deg -90 deg without significant temperature variations. The instrument is now ready for deployment to the high Argentinean Andes.

arXiv commentThis is one of a series of papers on the QUBIC experiment status - This version of the paper matches the one accepted for publication on Journal of Cosmology and Astroparticle Physics

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Cited by in corpus (7)

• QUBIC I: Overview and ScienceProgram
• QUBIC VIII: Optical design and performance
• QUBIC II: Spectro-Polarimetry with Bolometric Interferometry
• QUBIC III: Laboratory Characterization
• QUBIC VI: cryogenic half wave plate rotator, design and performances
• Broadband anti-reflection coating for sub-terahertz optics using dielectric multilayers
• QUBIC VII: The feedhorn-switch system of the technological demonstrator