X‐ray damage to optical components using a laser‐plasma source

X‐ray damage to optical surfaces consisting of melting, fracturing, cracking, and cratering is produced, and then analyzed using interference contrast microscopy and stylus profilometery. The test samples are irradiated by 0.5–1.6 keV x rays at fluence levels up to 5.5 cal/cm2. The x rays originate from L‐shell transitions in copper ions, produced when 1.25‐μm‐thick targets are irradiated at 1.3 kJ energy by a 1.054 μm wavelength laser. The x‐ray emission is found to be nearly isotropic over 2π sr, while the plasma mass‐flow distribution is peaked along the laser axis. Hence, contamination of the test sample by target debris or plasma is greatly reduced by placing the samples off axis from the laser beam, in addition to the use of beryllium shields.