Decontamination of CPA diffraction gratings

Summary form only given. The diffraction gratings are mounted in a vacuum chamber of the compressor. In these conditions the diffraction gratings and other gold coated mirrors illuminated by the laser beam are subjected to carbon contamination, especially on the place of the output beam. This reduces diffraction efficiency of the compressor. The cleaning method used at our 100 TW Ti:sapphire laser system is based on a radio frequency discharge in a mixture of oxygen and argon at low pressure.