title: Variable-delay polarization modulators for cryogenic millimeter-wave applications.
abstract: We describe the design, construction, and initial validation of the variable-delay polarization modulator (VPM) designed for the PIPER cosmic microwave background polarimeter. The VPM modulates between linear and circular polarization by introducing a variable phase delay between orthogonal linear polarizations. Each VPM has a diameter of 39 cm and is engineered to operate in a cryogenic environment (1.5 K). We describe the mechanical design and performance of the kinematic double-blade flexure and drive mechanism along with the construction of the high precision wire grid polarizers.
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: D T
authors.initials: DT
authors.lastname: Chuss
authors.affiliation: Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Eimer
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Fixsen
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: J
authors.initials: J
authors.lastname: Hinderks
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: A J
authors.initials: AJ
authors.lastname: Kogut
authors.affiliation: Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
authors.forename: J
authors.initials: J
authors.lastname: Lazear
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: P
authors.initials: P
authors.lastname: Mirel
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: E
authors.initials: E
authors.lastname: Switzer
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: G M
authors.initials: GM
authors.lastname: Voellmer
authors.affiliation: NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA.
authors.forename: E J
authors.initials: EJ
authors.lastname: Wollack