Aachen PK 2003 – scientific programme

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K: Kurzzeitphysik

K 4: Laser applications

K 4.5: Talk

Thursday, March 20, 2003, 16:15–16:30, F04

Rapid Excimer Laser Cleaning of Plane Objects — •Karl-Heinz Steglich and Hermann Harde — Universität der Bundeswehr Hamburg, Lasertechnik und

Sensitive surfaces like pigment lacquer, finishing varnish, art paintings or plastics are precarious to clean due to the danger of damaging the top layer which may have a protective function or artistic merit. So it is essential only to remove the contamination itself or, if necessary, some very thin coating without affecting or destroying the underlying structure.

For such kind of gentle laser applications we set up a prototype machine based on a KrF excimer laser. It rapid adaptation of the pulse energy is achieved by passing the radiation through a computer controlled attenuator followed by a beam forming system to ensure homogeneous irradiation at the target with intensity variations smaller 5%. The rectangular laser beam cross section (2x2 mm) is scanned by galvo mirrors across the surface covering an area up to 50 cm² . For larger sections the object is precisely shifted to follow-up positions, from which further scans are performed. The computer controlled shifting and scanning ensures a homogeneous treatment of the surface with a face rate of up to 6 cm²/s . This automation guarantees a uniform, complete and fast processing.

The device is preferentially designed to operate with plane objects. Examples of laser treated targets, which were radioactively, biologically or environmentally contaminated, will be presented, demonstrating the homogeneous and efficient cleaning function.