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Proceedings Paper

GEMS x-ray polarimeter performance simulations
Author(s): Wayne H. Baumgartner; Tod Strohmayer; Tim Kallman; J. Kevin Black; Joanne E. Hill; Jean H. Swank; Keith M. Jahoda
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Paper Abstract

The Gravity and Extreme Magnetism Small explorer (GEMS) is an X-ray polarization telescope selected as a NASA small explorer satellite mission. The X-ray Polarimeter on GEMS uses a Time Projection Chamber gas proportional counter to measure the polarization of astrophysical X-rays in the 2-10 keV band by sensing the direction of the track of the primary photoelectron excited by the incident X-ray. We have simulated the expected sensitivity of the polarimeter to polarized X-rays. We use the simulation package Penelope to model the physics of the interaction of the initial photoelectron with the detector gas and to determine the distribution of charge deposited in the detector volume. We then model the charge diffusion in the detector, and produce simulated track images. Within the track reconstruction algorithm we apply cuts on the track shape and focus on the initial photoelectron direction in order to maximize the overall sensitivity of the instrument. Using this technique we have predicted instrument modulation factors μ100 for 100% polarized X-rays ranging from 10% to over 60% across the 2-10 keV X-ray band. We also discuss the simulation program used to develop and model some of the algorithms used for triggering, and energy measurement of events in the polarimeter.

Paper Details

Date Published: 17 September 2012
PDF: 14 pages
Proc. SPIE 8443, Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, 84434K (17 September 2012); doi: 10.1117/12.927270
Show Author Affiliations
Wayne H. Baumgartner, Univ. of Maryland, Baltimore County (United States)
NASA Goddard Space Flight Ctr. (United States)
Tod Strohmayer, NASA Goddard Space Flight Ctr. (United States)
Tim Kallman, NASA Goddard Space Flight Ctr. (United States)
J. Kevin Black, Rock Creek Scientific (United States)
NASA Goddard Space Flight Ctr. (United States)
Joanne E. Hill, NASA Goddard Space Flight Ctr. (United States)
Jean H. Swank, NASA Goddard Space Flight Ctr. (United States)
Keith M. Jahoda, NASA Goddard Space Flight Ctr. (United States)


Published in SPIE Proceedings Vol. 8443:
Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray
Tadayuki Takahashi; Stephen S. Murray; Jan-Willem A. den Herder, Editor(s)

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