MEASURING CMB POLARIZATION WITH QUIET: THE Q/U IMAGING EXPERIMENT

Abstract

Phase I of the Q/U Imaging ExperimenT (QUIET) measures the Cosmic Microwave Background polarization anisotropy spectrum at angular scales 25 . l . 1000. QUIET has deployed two independent receiver arrays. The 40-GHz array took data between Oc- tober 2008 and June 2009. The 90-GHz array was deployed in June 2009 and observations are ongoing. Described in this proceeding are the instrument, analysis procedures, and expected science reach for the QUIET Phase I arrays. We also briefly discuss the science forecasts for QUIET Phase II in which arrays roughly an order-of-magnitude larger will be deployed. 1. Science Motivation Anisotropies present in the polarized Cosmic Microwave Background (CMB) can be used to constrain models describing the physics in the very early Universe. Maps of the polarized CMB can be decomposed into E-mode (curl-free) and B-mode (divergence-free) components. Measurements of the E-mode anisotropy spectrum will break degeneracies between cosmological parameters when used in conjunction with the CMB temperature anisotropy spectrum. Many inflation models predict that gravity waves generated during inflation will leave a unique signature in the B-mode polarization spectrum near angular scales of l ≃ 100. In those models, measurement of the ratio, r , of the amplitude of the B- to E-mode spectrum will yield the energy-scale of inflation. Placing upper limits of r <0.01 can rule out large classes of inflationary models. 2. QUIET Instrument and Observations 2.1. QUIET Instrument The QUIET instrument consists of two independent receivers. Each receiver com- prises a hexagonal array of High Electron Mobility Transistor (HEMT)-based po- larimeters: one array operates at 40 GHz (Q band) with 19 polarimeters and the other at 90 GHz (W band) with 90 polarimeters. The Q-band receiver dedicates one pair of polarimeters (hereafter: TT channels) to the observation of the CMB temperature anisotropy spectrum. The W-band receiver has three pairs of TT chan- nels. The external optics are a 1.4-m Cross-Dragone reflector design with FWHM beamwidth of 27 arcmin at Q-band and 12 arcmin at W-band. Salient characteristics of QUIET Phase I are shown in Table 1. As shown in a cut-away view of the W-band cryostat (Fig. 1), light enters the