Contamination Monitoring Approaches For EUV Space Optics

Abstract

We present a summary of contamination monitoring methods currently being used on extreme ultraviolet (EUV) astronomy instruments and in EUV calibration facilities at the Space Sciences Laboratory, U.C. Berkeley. Methods include measurement of contamination -induced optical degradation on EUV witness samples as well as measurement and characterization of contamination on non -optical hardware. EUV witness samples, fabricated in the same manner as novel grazing incidence EUV telescope mirrors, are measured for reflectivity and scattering in the EUV range of 80 to 900 A to characterize the optical degradation effects of contamination in the EUV and to provide a basis for molecular contamination requirements of EUV instruments. Particle size distributions on cleanroom surfaces and particulate models are used to develop particulate contamination requirements of EUV instruments. Non -optical hardware on EUV astronomy payloads is then processed to minimize the potential to transfer contaminants to sensitive EUV space optics, and is monitored for particulate and molecular contamination by a variety of methods. We compare the efficiency and accuracy of these monitoring methods and recommend guidelines for contamination monitoring activities, and for developing allowable contamination requirements for various phases of instrument processing, including fabrication, assembly and testing.