Calibration of the AXAF-HRC UV/ion shields at the Osservatorio Astronomico DI Palermo G.S. Vaiana: IV - UV rejection measurements
The AXAF-HRC UV/ion shields have to provide high UV rejection from diffuse background and bright UV sources (e.g. rejection greater than 10(superscript 7) at wavelength longer than approximately 300 angstrom for the HRC-I). In the framework of the AXAF-HRC calibration program we have conducted UV (300 - 2500 angstrom) and FUV/visible (1900 - 10,000 angstrom) transmission measurements on the baseline design UV/ion shields based on Lexan and aluminum. The results of these measurements, here reported, have shown that the baseline design UV/ion shields did not meet the scientific requirements of UV opacity and as a consequence, the UV/ion shields were redesigned. UV tests of new UV/ion shields, based on new materials, is in progress.