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 ±0.10. The system performed well in Spider during its successful 16 day flight.
Original language | English (US) |
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Article number | 014501 |
Journal | Review of Scientific Instruments |
Volume | 87 |
Issue number | 1 |
DOIs | |
State | Published - Jan 1 2016 |
All Science Journal Classification (ASJC) codes
- Instrumentation