Laser-assisted cleaning of beryllium-containing mirror samples from JET and PISCES-B

• Be-contaminated JET mirrors have been laser-cleaned in vacuum.
• The removal of the mixed-material layers was only successful for thin ones.
• Laboratory-prepared Be layers were removed successfully from metal mirrors.
• No preference for a particular wavelength range is apparent.

A set of seven polycrystalline mirror samples retrieved from the JET tokamak has been cleaned in vacuum using a pulsed laser system. The surfaces of samples exposed to plasma during 2008–2009 campaigns as part of the second phase of a comprehensive first mirror test contained a mixture of carbon, beryllium and tritium. For this reason, the samples were treated in a vacuum chamber constructed specially for this purpose. In some cases mirrors show an increase of the specular reflectivity after cleaning, though beryllium and carbon deposits were not fully removed. Additionally, three samples coated in PISCES-B with a 110–120 nm beryllium layer were subjected to laser cleaning tests as well.