Optical materials for output windows of large-scale e-beam-pumped KrF lasers

Summary form only given. E-beam-pumped KrF lasers are very promising drivers for inertial confinement fusion due to their high efficiency, short radiation wavelength and a large bandwidth, as well as to principle feasibility to operate with repetition rate of a few Hz at multi-kilojoule energy level. One of the problems to be developed for reliable rep-rate KrF laser operation is a stability of output laser windows. In addition to intense UV laser light they would be exposed to fluorine etching (it is contained in a working gas mixture), and to irradiation by bremsstrahlung X-rays and energetic scattered electrons. A number of optical materials such as fused silica (SiO/sub 2/), calcium fluoride (CaF/sub 2/), magnesium fluoride (MgF/sub 2/), and synthetic leucosapphire (Al/sub 2/O/sub 3/) have been comparatively examined in regard of chemical resistance to fluorine, nonlinear and ionizing-radiatian-induced absorption at KrF laser radiation wavelength of 248 nm.