Geant4 simulation of the residual background in the ATHENA Wide Field Imager from protons deflected by the Charged Particle Diverter
Date Issued
2022
Author(s)
Galgóczi, Gábor
•
Breuer, Jean Paul
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•
Zlámal, Jakub
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Werner, Norbert
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Čalkovský, Vojtěch
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Boudin, Nathalie
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Ferreira, Ivo
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•
von Kienlin, Andreas
•
•
•
•
Perinati, Emanuele
Abstract
X-ray telescopes opened up a new window into the high-energy universe. However, the last generation of these telescopes encountered an unexpected problem: their optics focused not only X-rays but low-energy (so called soft) protons as well. These protons are very hard to model and can not be distinguished from X-rays. For example, 40% of XMM-Newton observations is significantly contaminated by soft proton induced background flares. In order to minimize the background from such low-energy protons the Advanced Telescope for High ENergy Astrophysics (ATHENA) satellite introduced a novel concept, the so called Charged Particle Diverter (CPD). It is an array of magnets in a Hallbach design, which deflects protons below 76 keV before they would hit the Wide Field Imager (WFI) detector. In this work, we investigate the effect of scattering of the deflected protons with the CPD walls and the inner surfaces of the WFI detector assembly. Such scattered protons can loose energy, change direction and still hit the WFI. In order to adopt the most realistic instrument model, we imported the CAD model of both the CPD and the WFI focal plane assembly. Soft protons corresponding to ≈2.5 hours of exposure to the L1 solar wind are simulated in this work. The inhomogeneous magnetic field of the CPD is included in the simulation. We present a preliminary estimate of the WFI residual background induced by soft proton secondary scattering, in the case of the optical blocking filter present in the field of view. A first investigation of the volumes responsible for scattering the protons back into the field of view is reported.
Coverage
Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray
All editors
den Herder, Jan-Willem A.; Nikzad, Shouleh; Nakazawa, Kazuhiro
Series
Volume
12181
Start page
185
Conferenece
Space Telescopes and Instrumentation 2022: Ultraviolet to Gamma Ray
Conferenece place
Montréal, Québec, Canada
Conferenece date
July 17-23, 2022
Issn Identifier
0277-786X
Rights
open.access
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