Systematic effects from an ambient-temperature, continuously rotating half-wave plate

T. Essinger-Hileman, A. Kusaka, J. W. Appel, S. K. Choi, K. Crowley, S. P. Ho, N. Jarosik, L. A. Page, L. P. Parker, S. Raghunathan, S. M. Simon, S. T. Staggs, K. Visnjic

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Abstract

We present an evaluation of systematic effects associated with a continuously rotating, ambient-temperature half-wave plate (HWP) based on two seasons of data from the Atacama B-Mode Search (ABS) experiment located in the Atacama Desert of Chile. The ABS experiment is a microwave telescope sensitive at 145 GHz. Here we present our in-field evaluation of celestial (Cosmic Microwave Background (CMB) plus galactic foreground) temperature-to-polarization leakage. We decompose the leakage into scalar, dipole, and quadrupole leakage terms. We report a scalar leakage of ∼0.01%, consistent with model expectations and an order of magnitude smaller than other CMB experiments have been reported. No significant dipole or quadrupole terms are detected; we constrain each to be <0.07% (95% confidence), limited by statistical uncertainty in our measurement. Dipole and quadrupole leakage at this level lead to systematic error on r ≲ 0.01 before any mitigation due to scan cross-linking or boresight rotation. The measured scalar leakage and the theoretical level of dipole and quadrupole leakage produce systematic error of r < 0.001 for the ABS survey and focal-plane layout before any data correction such as so-called deprojection. This demonstrates that ABS achieves significant beam systematic error mitigation from its HWP and shows the promise of continuously rotating HWPs for future experiments.

Original languageEnglish (US)
Article number094503
JournalReview of Scientific Instruments
Volume87
Issue number9
DOIs
StatePublished - Sep 1 2016

All Science Journal Classification (ASJC) codes

  • Instrumentation

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    Essinger-Hileman, T., Kusaka, A., Appel, J. W., Choi, S. K., Crowley, K., Ho, S. P., Jarosik, N., Page, L. A., Parker, L. P., Raghunathan, S., Simon, S. M., Staggs, S. T., & Visnjic, K. (2016). Systematic effects from an ambient-temperature, continuously rotating half-wave plate. Review of Scientific Instruments, 87(9), [094503]. https://doi.org/10.1063/1.4962023