http://arxiv.org/abs/2105.08734
The Primordial Inflation Polarization Explorer (PIPER) is a stratospheric balloon payload to measure polarization of the cosmic microwave background. Twin telescopes mounted within an open-aperture bucket dewar couple the sky to bolometric detector arrays. We reduce detector loading and photon noise by cooling the entire optical chain to 1.7 K or colder. A set of fountain-effect pumps sprays superfluid liquid helium onto each optical surface, producing helium flows of 50–100 cm^3 / s at heights up to 200 cm above the liquid level. We describe the fountain-effect pumps and the cryogenic performance of the PIPER payload during two flights in 2017 and 2019.
A. Kogut, T. Essinger-Hileman, D. Fixsen, et. al.
Thu, 20 May 21
30/56
Comments: 23 pages including 14 figures, accepted for publication in Review of Scientific Instruments
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