Grazing angle proton scattering: effects on Chandra and XMM-Newton X-ray telescopes

Abstract

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Update on the use of Geant4 for the Simulation of low-energy protons scattering off X-ray Mirrors at grazing incidence angles

“…The Firsov scattering process in Geant4 has enabled us to address concerns raised in [4] with regard to a probable under-prediction of damaging proton fluences at the focal plane of the XMMNewton and Chandra telescopes. We have revised the XMMNewton simulation to include this new process for the relevant ranges of incident angle.…”

“…The most sensitive region of the CCD, i.e., the buried channel is at a silicon equivalent depth of m to the incident protons, i.e., it is behind the optical filter and the top layers of the CCD for the front illuminated case. The range of 100 keV protons in silicon is in the order of 0.92 m [3], [4], thus only incident protons with energy above 100 keV can reach the sensitive region of the CCD and cause damage. The fact that the incident proton spectrum is very steep [3]- [5], implies that the majority of the damaging protons are of energy just above keV.…”

“…The XMM-Newton Geant4 model was progressively enhanced to include all of the optical components that protons could interact with and further analysis performed [5], [6]. Recently, it has been reported that the multiple scattering process underlying the XMM-Newton Geant4 model does not provide the correct treatment for protons of energies in the critical range 30-710 keV scattering at grazing incident angles [4]. The authors make a convincing case that the fluence of protons with the most damaging energies keV would have been underestimated if only multiple scattering is considered and propose an alternative treatment based on the scattering angle distribution formulated by Firsov [7] and the energy loss as observed in the somewhat limited experimental data available.…”

Impact of space protons and electrons scattering through the IXO telescope mirrors

“…Previous studies [1] [2][3] [4] have shown how low energy protons can reach the focal plane of Xray space telescopes by grazing angle scattering through the optics elements. As a consequence, imaging and spectrographic detectors can experience a deterioration of their performances, for example with a decrease of charge transfer efficiency (CTE) induced by non-ionizing energy loss (NIEL).…”

Framework for a Geant4-based simulator of the radiation background and detector responses of the space X-ray observatory Suzaku (Astro-E2)

“…For the purpose of the radiation environment study, Monte Carlo simulations [2]- [4] with MCNPX [5] and Geant4 [6] and the study of physics models [7] for Chandra and XMM-Newton observatories were carried out, and succeeded in explaining the degradation as being due to damage by background protons propagating through the X-ray telescope optics by grazing incidence scattering processes. These studies supplied significant information about the on-orbit radiation background that was not known before the accident because Chandra and XMM-Newton have atypical orbits for X-ray observation satellites.…”