The thermal design, characterization, and performance of the S pider long-duration balloon cryostat

Abstract

We describe the Spider flight cryostat, which is designed to cool six millimeter-wavelength telescopes during an Antarctic long-duration balloon flight. The cryostat, one of the largest to have flown on a stratospheric payload, uses liquid 4 He to deliver cooling power to stages at 4.2 and 1.6 K. Stainless steel capillaries facilitate a high flow impedance connection between the main liquid helium tank and a smaller superfluid tank, allowing the latter to operate at 1.6 K as long as there is liquid in the 4.2 K main tank. Each telescope houses a closed cycle 3 He adsorption refrigerator that further cools the focal planes down to 300 mK. Liquid helium vapor from the main tank is routed through heat exchangers that cool radiation shields, providing negative thermal feedback. The system performed successfully during a 17 day flight in the 2014-2015 Antarctic summer. The cryostat had a total hold time of 16.8 days, with 15.9 days occurring during flight.

A New Limit on CMB Circular Polarization from SPIDER

“…The SPIDER payload features six monochromatic receivers housed in a shared cryostat (Gudmundsson et al 2015). Each receiver includes a stepped HWP polarization modulator to reduce the potential impact of systematic errors due to beam asymmetries and instrument polarization (Bryan 2014;Bryan et al 2016).…”

280 GHz Focal Plane Unit Design and Characterization for the Spider-2 Suborbital Polarimeter

“…Over 2300 transition-edge sensors (TES) are cooled to their 300 mK operating temperature by a closedcycle, helium-3 adsorption refrigerator at the base of each telescope, and read out by timedivision multiplexing (TDM) superconducting quantum interference devices (SQUID). [4][5][6][7][8] The first SPIDER instrument was launched in January 2015 from McMurdo Station in Antarctica and contained six 95 and 150 GHz slot-antenna-coupled TES arrays fabricated at JPL. 10,11 During the 16 day flight, SPIDER-1 observed 10% of the sky from an altitude of 36 km and collected 2 TB of raw data, currently under analysis.…”

A cryogenic rotation stage with a large clear aperture for the half-wave plates in the Spider instrument

“…The rotation mechanisms must, on average, generate only a small amount of heat to conserve liquid helium during flight. Boiling off ∼ 75 L of liquid helium would have shortened the flight by an entire day [6], so we required that the mechanisms dissipate far less than that amount.…”