Intensity-coupled Polarization in Instruments with a Continuously Rotating Half-wave Plate

摘要

We discuss a systematic effect associated with measuring the polarization ofthe Cosmic Microwave Background (CMB) with a continuously rotating Half-WavePlate (HWP) using data from the E and B Experiment (EBEX). EBEX was aballoon-borne telescope designed to measure the polarization of the CMB as wellas that from Galactic dust. We show that EBEX measured excess polarizationcoupled to intensity, and provide a model for the origin of this polarizationinvolving detector non-linearity in the presence of a continuously rotatingHWP. We provide a map-based method to remove the excess polarization, showing81 (92) % of the excess polarization was removed on the CMB in the 150(250)~GHz datasets. Characterization and mitigation of this effect is importantfor future experiments aiming to measure the CMB B-modes on large angularscales using a HWP.