Design and Performance of the X-ray polarimeter X-Calibur

TL;DR

X-Calibur is a newly designed X-ray polarimeter that effectively measures polarization in the 20-80keV range, promising advancements in high-energy astrophysics observations.

Contribution

The paper presents the design, construction, calibration, and testing of the X-Calibur polarimeter, demonstrating its high efficiency and potential for space-based applications.

Findings

Achieved ~80% detection efficiency.

Successfully calibrated and tested with polarized X-ray beams.

Demonstrated potential for broader energy range operation.

Abstract

X-ray polarimetry promises to give qualitatively new information about high-energy astrophysical sources, such as binary black hole systems, micro-quasars, active galactic nuclei, neutron stars, and gamma-ray bursts. We designed, built and tested a X-ray polarimeter, X-Calibur, to be used in the focal plane of the balloon-borne InFOCuS grazing incidence X-ray telescope. X-Calibur combines a low-Z scatterer with a CZT detector assembly to measure the polarization of 20-80keV X-rays making use of the fact that polarized photons scatter preferentially perpendicular to the electric field orientation. X-Calibur achieves a high detection efficiency of ~80%. The X-Calibur detector assembly is completed, tested, and fully calibrated. The response to a polarized X-ray beam was measured successfully at the Cornell High Energy Synchrotron Source. This paper describes the design, calibration and performance of the X-Calibur polarimeter. In principle, a similar space-borne scattering polarimeter could operate over the broader 2-100keV energy band.