PoS - Proceedings of Science
Volume 444 - 38th International Cosmic Ray Conference (ICRC2023) - Gamma-ray Astronomy (GA)
Performance Evaluation of “XRPIX” Event-Driven SOI Pixel Detector for Cosmic MeV Gamma-ray Observation
M. Hashizume*, Y. Suda, Y. Fukazawa, T. Go Tsuru and A. Takeda
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Pre-published on: August 18, 2023
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Abstract
Cosmic MeV gamma-ray observations are important for elucidating physics in high-energy objects such as gamma-ray bursts and active galactic nuclear jet blazars, for detecting nuclear gamma-rays in supernova explosions, and for advancing multi-messenger astronomy. However, there has been no progress since the COMPTEL detector on board the CGRO satellites in the 1990s, and a satellite for MeV gamma-ray observations is essential. Compton scattering is the dominant interaction between MeV gamma-rays and matter. The minimal way to reconstruct the arrival direction of an incident gamma-ray is to utilize both the deposit energy and hit position measured in both the scatterer and absorber, giving an event circle. The circle can be reduced to an arc if the initial direction of the Compton scattered electron is measured. Thus such an electron-tracking Compton camera is expected to improve the source sensitivity by reducing background events. Therefore, our goal is to enable more accurate Compton imaging by using an event-driven SOI pixel detector “XRPIX” as a scatterer in an electron-track Compton camera. The pixel size of XRPIX is as small as 36 um square, so it is expected to capture electron trajectories for scattering of gamma-rays of several hundred keV. In this contribution, we report on the evaluation of the depletion layer thickness of XRPIX8.5, which can be fully depleted at room temperature, the sensor response when irradiated with gamma-rays such as 662 keV of Cs-137 and 511 keV of Na-22, and a method for estimating the direction of scattered electrons.
DOI: https://doi.org/10.22323/1.444.0873
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