Sensitivity of a photoelectric x-ray polarimeter for astronomy: the impact of gas mixture and pressure

Luigi Pacciani; Enrico Costa; Giuseppe Di Persio; Marco Feroci; Paolo Soffitta; Luca Baldini; Ronaldo Bellazzini; Alessandro Brez; Nicolas Lumb; Gloria Spandre

doi:10.1117/12.459275

14 February 2003 Sensitivity of a photoelectric x-ray polarimeter for astronomy: the impact of the gas mixture and pressure

Luigi Pacciani, Enrico Costa, Giuseppe Di Persio, Marco Feroci, Paolo Soffitta, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Nicolas Lumb, Gloria Spandre

Author Affiliations +

Proceedings Volume 4843, Polarimetry in Astronomy; (2003) https://doi.org/10.1117/12.459275
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

Abstract

A Micropattern detector in the focus of a grazing incidence telescope is nowadays the most powerful tool to perform a sensitive and reliable measurement of the linear polarization of celestial X-ray sources. The actual implementation of such a completely new device results from a trade-off of various factors and can provide a break-through increase of sensitivity with respect to traditional instrumental approaches. The sensitivity depends on the effective area of the optics and the modulation factor and efficiency of the detector. The latter strongly depends on the filling gas through various factors, including the absorption probability, the length of track versus the pixel size, the blurring introduced by the lateral diffusion during the drift. We discuss the impact of the choice of the filling gas on the sensitivity and on the operative band of the instrument, while the noble gases drive the efficiency, the organic quenching gases impact both in reducing the scattering and producing most straight tracks and on reducing diffusion. Some design solution are discussed both for a low energy oriented and high energy oriented polarimeters.

Citation Download Citation

Luigi Pacciani, Enrico Costa, Giuseppe Di Persio, Marco Feroci, Paolo Soffitta, Luca Baldini, Ronaldo Bellazzini, Alessandro Brez, Nicolas Lumb, and Gloria Spandre "Sensitivity of a photoelectric x-ray polarimeter for astronomy: the impact of the gas mixture and pressure", Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003); https://doi.org/10.1117/12.459275

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