Precision laser-based decontamination of microcavities

The removal of oil-based contaminants from microcavities with narrow apertures and comparatively long axial dimensions presents a number of challenges in an industrial production line environment. Traditional solvent-based approaches are costly to implement, inefficient in cleaning such microcavity geometries, and increasingly unacceptable from an environmental standpoint. An attractive alternative is to employ high-energy laser pulses to selectively remove the contaminants without introducing damage to the component undergoing the cleaning procedure. This paper will present results of initial ablation trials on example industrial oil-based organic contaminants whose residues within microcavities in steel-based components are to be removed. At present, higher order lines from a frequency tripledrquadrupled Nd:YAG laser are used to study the optimum fluence for removal of the oil-based contaminant without inflicting damage to the steel. Absorption spectroscopy of the contaminant fluid indicates that photon wavelengths shorter than ;370 nm will interact with the material. Initial results show that the required intensity at 355 nm )25 Jrcm2. also damages the type of steel under investigation, but that exposure to even single pulses at 266 nm ;100 mJrcm2. shows adequate removal of the contaminant without significant damage to the steel. Monitoring of the removal process is achieved through exploitation of the blue fluorescence of the oil-based contaminant that occurs as a result of ultraviolet pumping. q1998 Elsevier Science B.V.