Angle-resolved scatter measurements of laser-damaged DKDP crystals using a bidirectional scatter diagnostics

We built a bi-directional scatter diagnostic to measure and quantify losses due to scattering and absorption in harmonic generation crystals (DKDP) for the National Ignition Facility. The diagnostic performs angle-resolved photometry at 351 nm, and is capable of both near-specular transmission and large angle scatter measurements. In the near-specular configuration, the transmission can be measured with variable acceptance angle ranging from +/- 65 (mu) rad up to +/- 60 mrad. A silicon photo detector and a scientific- grade CCD camera quantify total energy and energy distribution. A linear swing arm detection system enables large angle scatter measurements of 360 degree(s), in principal, with step sizes as small as 0.01 degree(s) and variable collection angle ranging from 1 to 20 mrad. The design of this instrument and its application to the measurement of optical scatter from laser damage and final finishing process of DKDP are discussed.