Performance of the PRAXyS X-ray Polarimeter

TL;DR

This paper evaluates the performance of the PRAXyS X-ray polarimeter, demonstrating its sensitivity and accuracy in measuring X-ray polarization across 2.5 to 8 keV energies, crucial for astrophysical observations.

Contribution

The study provides the first comprehensive performance assessment of the PRAXyS X-ray polarimeter using polarized and unpolarized sources at multiple energies.

Findings

Measured modulation factors of 27%, 43%, and 59% at 2.7, 4.5, and 8.0 keV.

Polarization angles measured were consistent with expected values.

False polarization limit of less than 1% with unpolarized X-ray source.

Abstract

The performance of the Time Projection Chamber (TPC) polarimeter for the Polarimeter for Relativistic Astrophysical X-ray Sources (PRAXyS) Small Explorer was evaluated using polarized and unpolarized X-ray sources. The PRAXyS mission will enable exploration of the universe through X-ray polarimetry in the 2-10 keV energy band. We carried out performance tests of the polarimeter at the Brookhaven National Laboratory, National Synchrotron Light Source (BNL-NSLS) and at NASA's Goddard Space Flight Center. The polarimeter was tested with linearly polarized, monochromatic X-rays at 11 different energies between 2.5 and 8.0 keV. At maximum sensitivity, the measured modulation factors at 2.7, 4.5 and 8.0 keV are 27%, 43% and 59%, respectively and the measured angle of polarization is consistent with the expected value at all energies. Measurements with a broadband, unpolarized X-ray source placed a limit of less than 1% on false polarization in the PRAXyS polarimeter.