Cryogenic magnetic shielding for SCUBA-2

摘要

SCUBA-2 is a new wide-field submillimeter continuum instrument being commissioned on the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. SCUBA-2 uses large-scale arrays of superconducting bolometers with SQUID- (superconducting quantum interference device) based multiplexing and amplification. The sensitivity of the devices that compose the detector arrays to magnetic fields is such that magnetic shielding, consisting of superconducting and high-permeability materials, was fitted to the detector enclosure at 1 K to reduce the magnetic field strength at the focal plane. This paper describes the design and construction of the cryogenic shielding, and presents verification measurements. The shielding performance was found to meet the instrument requirements, and compared well to the modelled results.