Last update:
Apr 1, 2000
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Low-Energy Proton Effects on Detectors on X-Ray Astronomy Missions
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Eamonn Daly1,
Petteri Nieminen1,
Hugh Evans1,
Ramon Nartallo1,
Alain Hilgers1,
John Sorensen1,
Pete Truscott2,
Fan Lei2,
Simone Giani3,
John Apostolakis3,
Laszlo Urban4,
Stefano Magni5
- ESA
- DERA
- CERN
- KFKI
- INFN
Speaker:
Petteri Nieminen
X-ray astronomy in space relies on the focussing of X-ray photons by low-angle
scattering from shaped "shells". In most cases the "optics" consist of two sets
of nested concentric shells with shapes near to sections of cones. Two grazing-incidence scatters
result in focussing of the X-rays on the shell axis. ESA's XMM mission has three mirror modules of
outer diameter 70 cm, each consisting of 58 nested shells which focus the X-rays onto CCD detectors
some 7 m from the mirrors. The shells' configuration precludes any direct line-of-sight of space
through the mirror system.
CCD detectors are known to be radiation sensitive and much attention is given to
shielding them against radiation penetrating spacecraft structural materials. However, it has been
found that protons of energies in the range of hundreds of keV to a few MeV can scatter at low
angles through the mirror shells. These protons, because of their low energy can produce a high
non-ionising dose in unshielded CCDs and are therefore a potential threat. This paper discusses the
efforts made in the context of the XMM mission to simulate the processes involved in the transport
of protons and generation of non-ionising dose in CCD's.
The tools used for this analysis included the Geant4 Monte-Carlo toolkit and the TRIM
code. Geant4 was used for fully three-dimensional calculations while TRIM was used to examine
details of the low angle scattering.
Presentation:  | Short Paper:  |
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