2016
2015
Abstract
We describe the Spider ight cryostat, which is designed to cool six millimeter-wavelength telescopes during an Antarctic
long-duration balloon ight. The cryostat, one of the largest to have own on a stratospheric payload, uses liquid 4He
to deliver cooling power to stages at 4.2 and 1.6 K. Stainless steel capillaries facilitate a high ow impedance connection
between the main liquid helium tank and a smaller superuid 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 3He 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 ight in the
2014{2015 Antarctic summer. The cryostat had a total hold time of 16.8 days, with 15.9 days occurring during ight.