19 October 2012 An examination of the sensitivity and systematic error of the NASA GEMS Bragg Reflection Polarimeter using Monte-Carlo simulations
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Abstract
The Bragg Reflection Polarimeter (BRP) on the NASA Gravity and Extreme Magnetism Small Explorer Mission is designed to measure the linear polarization of astrophysical sources in a narrow band centered at about 500 eV. X-rays are focused by Wolter I mirrors through a 4.5 m focal length to a time projection chamber (TPC) polarimeter, sensitive between 2{10 keV. In this optical path lies the BRP multilayer reflector at a nominal 45 degree incidence angle. The reflector reflects soft X-rays to the BRP detector and transmits hard X-rays to the TPC. As the spacecraft rotates about the optical axis, the reflected count rate will vary depending on the polarization of the incident beam. However, false polarization signals may be produced due to misalignments and spacecraft pointing wobble. Monte-Carlo simulations have been carried out, showing that the false modulation is below the statistical uncertainties for the expected focal plane offsets of <~ 2 mm.
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Ryan Allured, Takashi Okajima, Regina Soufli, Mónica Fernández-Perea, Ryan O. Daly, Hannah Marlowe, Scott T. Griffiths, Michael J. Pivovaroff, Philip Kaaret, "An examination of the sensitivity and systematic error of the NASA GEMS Bragg Reflection Polarimeter using Monte-Carlo simulations", Proc. SPIE 8487, Novel Optical Systems Design and Optimization XV, 848703 (19 October 2012); doi: 10.1117/12.930065; https://doi.org/10.1117/12.930065
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