THE OPTICAL UV FILTERS FOR THE EPIC EXPERIMENT/

EPIC, the European Photon Imaging Cameras is an experiment based on co oled CCDs on board the ESA X-ray Multi Mirrors satellite due to be lau nched in 1999. Since CCD's are sensitive to radiation other than X-ray s, namely Optical and UV light, filters are necessary to prevent this radiation from reaching the detector sensitive area. Three types of fi lters were developed, to be used alternatively depending on target sou rce. Here we report on the medium and thin filters developed by MOXTEK Inc. in Orem, Utah, while the thick ones, developed at the MaxPlanck- Institut fur Extraterrestrische Physik (MPE, Germany) have been descri bed elsewhere. The two filters: described here, have a 1600 Angstrom P olyimide substrate coated with 400 Angstrom and 800 Angstrom aluminium for the thin and medium filter, respectively. After manufacturing, th e filters have been submitted to an intensive qualification and calibr ation programme at MOXTEK. Further calibrations, transmission measurem ents and performance stability, have been carried our or are in progre ss at one of the EPIC Institutes (Osservatorio Astronomico di Palermo) .