Moncelsi, L., Ade, Peter A. R. ![]() ![]() |
Abstract
A cryogenic achromatic half-wave plate (HWP) for submillimetre astronomical polarimetry has been designed, manufactured, tested and deployed in the Balloon-borne Large-Aperture Submillimeter Telescope for Polarimetry (BLASTPol). The design is based on the five-slab Pancharatnam recipe and it works in the wavelength range 200–600 μm, making it the broadest-band HWP built to date at (sub)millimetre wavelengths. The frequency behaviour of the HWP has been fully characterized at room and cryogenic temperatures with incoherent radiation from a polarizing Fourier transform spectrometer. We develop a novel empirical model, complementary to the physical and analytical ones available in the literature, that allows us to recover the HWP Mueller matrix and phase shift as a function of frequency and extrapolated to 4 K. We show that most of the HWP non-idealities can be modelled by quantifying one wavelength-dependent parameter, the position of the HWP equivalent axes, which is then readily implemented in a map-making algorithm. We derive this parameter for a range of spectral signatures of input astronomical sources relevant to BLASTPol, and provide a benchmark example of how our method can yield improved accuracy on measurements of the polarization angle on the sky at submillimetre wavelengths.
Item Type: | Article |
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Date Type: | Publication |
Status: | Published |
Schools: | Physics and Astronomy |
Subjects: | Q Science > QB Astronomy |
Uncontrolled Keywords: | magnetic fields; polarization; balloons; instrumentation: polarimeters; techniques: polarimetric; submillimetre: ISM |
Publisher: | Oxford University Press |
ISSN: | 0035-8711 |
Funders: | Leverhulme |
Date of Acceptance: | 24 October 2013 |
Last Modified: | 25 Oct 2022 09:34 |
URI: | https://orca.cardiff.ac.uk/id/eprint/59178 |
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