PoS - Proceedings of Science
Volume 395 - 37th International Cosmic Ray Conference (ICRC2021) - GAD - Gamma Ray Direct
Measuring the Cosmic X-ray Background accurately
H. Li*, N. Produit and R. Walter
Full text: pdf
Pre-published on: July 31, 2021
Published on: March 18, 2022
Measuring the Cosmic X-ray Background (CXB) is a key to understand the Active Galactic Nuclei population, their absorption distribution and their average spectra. However, hard X-ray instruments suffer from time-dependent backgrounds and cross-calibration issues. The uncertainty of the CXB normalization remain of the order of 20\%. To obtain a more accurate measurement, the Monitor Vsego Neba (MVN) instrument was built in Russia but not yet launched to the ISS. We follow the same ideas to develop a CXB detector made of four collimated spectrometers with a rotating obturator on top. The collimators block off-axis photons below 100 keV and the obturator modulates on-axis photons allowing to separate the CXB from the instrumental background. Our spectrometers are made of 20 mm thick CeBr$_{3}$ crystals on top of a SiPM array. One tube features a $\sim$20 cm$^2$ effective area and more energy coverage than MVN, leading to a CXB count rate improved by a factor of $\sim$10 and a statistical uncertainty $\sim$0.5\% on the CXB flux. A prototype is being built and we are seeking for a launch opportunity.
DOI: https://doi.org/10.22323/1.395.0589
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