Chandra and XMM-Newton missions showed that X-ray telescopes are able to focus soft protons (100keV-1MeV) with grazing incident angles as well as photons. This unexpected phenomenon, that caused the damage of Chandra CCD and reduction of XMM observation time, need to be carefully considered in the design of the next generation of X-ray missions planned for working in the Lagrangian point L-2, as ATHENA. In this environment, in fact, the geomagnetic field is not strong enough to shield the telescope from soft solar protons. The rate of focused protons can be evaluated from simulations introducing realistic models of the physical phenomenon.
The IASF Palermo has a long experience in the production of ray-tracing codes able to simulate the optics transmission either for input photons or protons in the X band. The main activities of IASF Palermo researchers are:
- production of sets of mathematical functions and numerical tables that starting from theoretical model or from experimental data allow to compute the proton reflection efficiency and the scattering angles as function of the input energies and directions of protons.
- production of a ray-tracing code able to simulate the transmission at the focal plane of grazing incident protons in order to evaluate its contribution to the total background.