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Rev Sci Instrum. 2016 Jan;87(1):014501. doi: 10.1063/1.4939435.

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

Author information

1
School of Earth and Space Exploration, Arizona State University, Tempe, Arizona 85287, USA.
2
School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom.
3
Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada.
4
Department of Physics, Princeton University, Princeton, New Jersey 08544, USA.
5
Department of Physics and CERCA, Case Western Reserve University, Cleveland, Ohio 44106, USA.
6
Division of Physics, Mathematics and Astronomy, California Institute of Technology, Pasadena, California 91125, USA.
7
Canadian Institute for Theoretical Astrophysics, University of Toronto, Toronto, Ontario M5S 3H8, Canada.
8
School of Mathematics, Statistics and Computer Science, University of KwaZulu-Natal, Durban, South Africa.
9
Theoretical Physics, Blackett Laboratory, Imperial College, London, United Kingdom.
10
Department of Physics, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
11
Department of Physics, University of Toronto, Toronto, Ontario M5S 1A7, Canada.
12
National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
13
Jet Propulsion Laboratory, Pasadena, California 91109, USA.
14
Department of Physics, Stanford University, Stanford, California 94305, USA.
15
Kavli Institute for Cosmology, University of Cambridge, Cambridge, United Kingdom.
16
Department of Astronomy and Astrophysics, University of Toronto, Toronto, Ontario M5S 3H4, Canada.
17
Institut d'Astrophysique Spatiale, Orsay, France.

Abstract

We describe the cryogenic half-wave plate rotation mechanisms built for and used in Spider, a polarization-sensitive balloon-borne telescope array that observed the cosmic microwave background at 95 GHz and 150 GHz during a stratospheric balloon flight from Antarctica in January 2015. The mechanisms operate at liquid helium temperature in flight. A three-point contact design keeps the mechanical bearings relatively small but allows for a large (305 mm) diameter clear aperture. A worm gear driven by a cryogenic stepper motor allows for precise positioning and prevents undesired rotation when the motors are depowered. A custom-built optical encoder system monitors the bearing angle to an absolute accuracy of ±0.1(∘). The system performed well in Spider during its successful 16 day flight.

PMID:
26827333
DOI:
10.1063/1.4939435
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