XL-CALIBUR Calibration

This page contains a summary of the XL-CALIBUR Calibration files which are currently in the Calibration Database (CALDB). The table links to the latest CALDB tar file and users can download it to install the XL-CALIBUR CALDB locally.

Instructions for installing the CALDB for XL-CALIBUR or other missions are available from the CALDB Installation page. The easiest way to access calibration data for XL-CALIBUR or other HEASARC-supported missions is via remote access, which allows direct access the current HEASARC XL-CALIBUR CALDB without having to install any calibration data locally.

Caldb access for XL-CALIBUR requires the latest version of the caldb.config file (updated 20220402 or later) which is available at https://heasarc.gsfc.nasa.gov/FTP/caldb/software/tools. Please replace your current $CALDBCONFIG file with this updated version.

Calibration Data Coming Soon

XL-CALIBUR Calibration
Latest CALDB (2025****)	Release Date 2025****	XL-CALIBUR caldb documents	Retrieve XL-CALIBUR caldb tar file

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Notes on ground Calibration

Prior to flight, the polarimeter was extensively characterized, with both unpolarized and polarized beams. For calibrating the pixel-by-pixel energy scale (1088 pixels in total, with 16 x 8 x 8 = 1024 pixels for the polarimeter walls and 8 x 8 = 64 pixels for the detector imaging the mirror focal point), the radioisotope Eu-152 was used. It provides emission lines around ~40 keV and ~120 keV, allowing the full polarimetric energy range to be calibrated. This calibration was done prior to the insertion of the beryllium scattering element (direct illumination), thus allowing the primary energy of the interactions to be reconstructed, without the influence of secondary events from the passive scatterer.

The polarimetric response was studied in detail in a pre-flight campaign during 2022. For this, the radioisotope Am-241 was used, yielding mainly photons with energy ~59.5 keV. The source was used both for direct illumination (unpolarized beam) and after scattering source photons by 90 degrees, producing a ~53.3 keV beam with nearly 100% polarization. Measurement results were compared to Geant4-based Monte-Carlo simulations, and the agreement achieved provided a robust benchmarking of the simulation framework (Aoyagi, et al., 2024). The simulation framework is then used to study in-flight performance, including determining the response to a 100% polarized beam with a given source spectrum – the so-called “modulation factor”. These simulations incorporate the detailed mirror response, as characterized with synchrotron beams at SPring-8 in Japan.