Calibration of the IXPE instrument

TL;DR

This paper details the comprehensive calibration procedures for the IXPE instrument, including ground-based and in-flight methods, to ensure accurate polarization measurements of X-ray sources.

Contribution

It presents the calibration setup and procedures for the IXPE instrument, highlighting the methods for polarization, gain, and energy calibration both on-ground and during the mission.

Findings

Calibration equipment can produce polarized and unpolarized radiation with precise control.

In-flight calibration uses radioactive sources for periodic detector calibration.

Calibration ensures accurate polarization and energy measurements throughout the mission.

Abstract

IXPE scientific payload comprises of three telescopes, each composed of a mirror and a photoelectric polarimeter based on the Gas Pixel Detector design. The three focal plane detectors, together with the unit which interfaces them to the spacecraft, are named IXPE Instrument and they will be built and calibrated in Italy; in this proceeding, we will present how IXPE Instrument will be calibrated, both on-ground and in-flight. The Instrument Calibration Equipment is being finalized at INAF-IAPS in Rome (Italy) to produce both polarized and unpolarized radiation, with a precise knowledge of direction, position, energy and polarization state of the incident beam. In flight, a set of four calibration sources based on radioactive material and mounted on a filter and calibration wheel will allow for the periodic calibration of all of the three IXPE focal plane detectors independently. A highly polarized source and an unpolarized one will be used to monitor the response to polarization; the remaining two will be used to calibrate the gain through the entire lifetime of the mission.