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  • compton polarimeter as a focal plane detector for hard x-ray telescope: sensitivity estimation with geant4 simulations

    جزئیات بیشتر مقاله
    • تاریخ ارائه: 1392/07/24
    • تاریخ انتشار در تی پی بین: 1392/07/24
    • تعداد بازدید: 931
    • تعداد پرسش و پاسخ ها: 0
    • شماره تماس دبیرخانه رویداد: -
     x-ray polarimetry can be an important tool for investigating various physical processes as well as their geometries at the celestial x-ray sources. however, x-ray polarimetry has not progressed much compared to the spectroscopy, timing and imaging mainly due to the extremely photon-hungry nature of x-ray polarimetry leading to severely limited sensitivity of x-ray polarimeters. the great improvement in sensitivity in spectroscopy and imaging was possible due to focusing x-ray optics which is effective only at the soft x-ray energy range. similar improvement in sensitivity of polarisation measurement at soft x-ray range is expected in near future with the advent of gem based photoelectric polarimeters. however, at energies >10 kev, even spectroscopic and imaging sensitivities of x-ray detector are limited due to lack of focusing optics. thus hard x-ray polarimetry so far has been largely unexplored area. on the other hand, typically the polarisation degree is expected to increase at higher energies as the radiation from non-thermal processes is dominant fraction. so polarisation measurement in hard x-ray can yield significant insights into such processes. with the recent availability of hard x-ray optics (e.g. with upcoming nustar, astro-h missions) which can focus x-rays from 5 kev to 80 kev, sensitivity of x-ray detectors in hard x-ray range is expected to improve significantly. in this context we explore feasibility of a focal plane hard x-ray polarimeter based on compton scattering having a thin plastic scatterer surrounded by cylindrical array scintillator detectors. we have carried out detailed geant4 simulation to estimate the modulation factor for 100 % polarized beam as well as polarimetric efficiency of this configuration. we have also validated these results with a semi-analytical approach. here we present the initial results of polarisation sensitivities of such focal plane compton polarimeter coupled with the reflection efficiency of present era hard x-ray optics.

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