GEMS x-ray polarimeter performance simulations

Wayne H. Baumgartner; Tod Strohmayer; Tim Kallman; J. Kevin Black; Joanne E. Hill; Jean H. Swank; Keith M. Jahoda

doi:10.1117/12.927270

17 September 2012 GEMS x-ray polarimeter performance simulations

Wayne H. Baumgartner, Tod Strohmayer, Tim Kallman, J. Kevin Black, Joanne E. Hill, Jean H. Swank, Keith M. Jahoda

Proceedings Volume 8443, Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray; 84434K (2012) https://doi.org/10.1117/12.927270
Event: SPIE Astronomical Telescopes + Instrumentation, 2012, Amsterdam, Netherlands

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.

Citation Download Citation

Wayne H. Baumgartner, Tod Strohmayer, Tim Kallman, J. Kevin Black, Joanne E. Hill, Jean H. Swank, and Keith M. Jahoda "GEMS x-ray polarimeter performance simulations", Proc. SPIE 8443, Space Telescopes and Instrumentation 2012: Ultraviolet to Gamma Ray, 84434K (17 September 2012); https://doi.org/10.1117/12.927270

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