Calibration of the Space-borne Compton Polarimeter POLAR flight model with 100% polarized X-ray beams

TL;DR

This paper details the calibration process of the POLAR space-borne gamma-ray polarimeter using 100% polarized X-ray beams, demonstrating its effective polarimetric capabilities for gamma-ray burst observations.

Contribution

It introduces a calibration method for the POLAR detector using polarized X-ray beams and evaluates its performance, which was not previously documented.

Findings

POLAR FM has good polarimetric capabilities.

Calibration with polarized X-ray beams is effective.

The detector responds well to polarized gamma-ray signals.

Abstract

POLAR is space-borne detector designed for a precise measurement of gamma-ray polarization of the prompt emissions of Gamma-Ray Bursts in the energy range 50 keV - 500 keV. POLAR is a compact Compton polarimeter consisting of 40$\times$ 40 plastic scintillator bars read out by 25 multi-anode PMTs. In May 2015, we performed a series of tests of the POLAR flight model with 100\% polarized x-rays beams at the European Synchrotron Radiation Facility beam-line ID11 aming to study thresholds, crosstalk between channels and responses of POLAR flight model to polarized X-ray beams. In this paper we present the data analysis method and some analysis results. According the results, POLAR FM has good polarimetric capabilities.