Spider is a balloon-borne array of six telescopes that will observe the Cosmic Microwave Background. The 2624 antenna-coupled bolometers in the instrument will make a polarization map of the CMB with approximately one-half degree resolution at 145 GHz. Polarization modulation is achieved via a cryogenic sapphire half-wave plate (HWP) skyward of the primary optic. We have measured millimeter-wave transmission spectra of the sapphire at room and cryogenic temperatures. The spectra are consistent with our physical optics model, and the data gives excellent measurements of the indices of A-cut sapphire. We have also taken preliminary spectra of the integrated HWP, optical system, and detectors in the prototype Spider receiver. We calculate the variation in response of the HWP between observing the CMB and foreground spectra, and estimate that it should not limit the Spider constraints on inflation.
@article{arxiv.1006.3874,
title = {Modeling and characterization of the SPIDER half-wave plate},
author = {Sean A. Bryan and Peter A. R. Ade and Mandana Amiri and Steve Benton and Richard Bihary and James J. Bock and J. Richard Bond and Joseph A. Bonetti and H. Cynthia Chiang and Carlo R. Contaldi and Brendan P. Crill and Daniel O'Dea and Olivier Dore and Marzieh Farhang and Jeffrey P. Filippini and Laura Fissel and Natalie Gandilo and Sunil Golwala and Jon E. Gudmundsson and Matthew Hasselfield and Mark Halpern and Kyle R. Helson and Gene Hilton and Warren Holmes and Viktor V. Hristov and Kent D. Irwin and William C. Jones and Chao Lin Kuo and Carrie J. MacTavish and Peter Mason and Tracy Morford and Thomas E. Montroy and C. Barth Netterfield and Alexandra S. Rahlin and Carl D. Reintsema and Daniel Riley and John E. Ruhl and Marcus C. Runyan and Matthew A. Schenker and Jamil Shariff and Juan Diego Soler and Amy Trangsrud and Rebecca Tucker and Carole Tucker and Anthony Turner},
journal= {arXiv preprint arXiv:1006.3874},
year = {2015}
}