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Proceedings Paper

Sensitivity of a photoelectric x-ray polarimeter for astronomy: the impact of gas mixture and pressure
Author(s): Luigi Pacciani; Enrico Costa; Giuseppe Di Persio; Marco Feroci; Paolo Soffitta; Luca Baldini; Ronaldo Bellazzini; Alessandro Brez; Nicolas Lumb; Gloria Spandre
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Paper 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.

Paper Details

Date Published: 14 February 2003
PDF: 12 pages
Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003); doi: 10.1117/12.459275
Show Author Affiliations
Luigi Pacciani, Istituto di Astrofisica Spaziale-CNR (Italy)
Enrico Costa, Istituto di Astrofisica Spaziale-CNR (Italy)
Giuseppe Di Persio, Istituto di Astrofisica Spaziale-CNR (Italy)
Marco Feroci, Istituto di Astrofisica Spaziale-CNR (Italy)
Paolo Soffitta, Istituto di Astrofisica Spaziale-CNR (Italy)
Luca Baldini, INFN/Pisa (Italy)
Ronaldo Bellazzini, INFN/Pisa (Italy)
Alessandro Brez, INFN/Pisa (Italy)
Nicolas Lumb, INFN/Pisa (Italy)
Gloria Spandre, INFN/Pisa (Italy)

Published in SPIE Proceedings Vol. 4843:
Polarimetry in Astronomy
Silvano Fineschi, Editor(s)

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