Cryostats for vacuum ultraviolet spectroscopy

Abstract

Two cryostats for vacuum ultraviolet spectroscopy are described, one for temperatures between 77 and 300 K, the other for a temperature of 4.2 K. They are designed so as to reduce to a minimum the rate of condensation of a solid contaminant film on to the cold samples from the residual vacuum of the system. At the lowest rate obtained, the absorption of L alpha radiation (121.6 nm) by the growing film increases by only 0.2% per hour. The nature of the contaminants is discussed.