High rejection ruby filter for laser light scattering experiments

A rejection filter against stray ruby laser light in scattering experiments is described. It consists of an array of sixty-four ruby crystal cubes with a doping of up to 2.3 wt. % of chromium oxide. The filter is 15 mm thick. Suppression factors of more than 10(6) are achieved with individual cubes (5 x 5 x15 mm(3)), the effective overall suppression of the assembled array being 10(4). The filter facilitates Raman calibration of the lidar Thomson scattering system of the JET tokamak.