The Filters for EPIC: Optimized Design

EPIC will be the focal plance imaging and medium-spectroscopy detector, based on CCD technology, which will fly on board the ESA mission XMM. EPIC has been planned to observe a wide variety of X-ray sources in the energy range 0.1 10keV. However, the X-ray emission from any source is often coupled to a strong optical/UV emission, which could degrade the EPIC spectral resolution. In order to overcome this problem, the camera-head will include a few ultra-thin filters, which can be placed in front of the CCDs to optimally reduce the optical/UV flux. After a brief description of the problem from the theoretical point of view, the technical and scientific requirements of EPIC filters are presented here. The best light attenuators and plastic carriers are reviewed and discussed. Finally, the flight filter design is outlined.