Lasers can remove coatings from surfaces through mechanisms such as photochemical decomposition, photothermal decomposition or ablation and photomechanical delamination or spallation.. In particular, solid state lasers, when operated in the sub 100 nsec pulse regime and irradiances of ~109 W/cm2, are very efficient at removing coatings through spallation . Under these circumstances and using a 1.06 micron Nd-YAG laser, up to a few 100 microns of material per pulse can be removed with minimal or no damage to the substrate, but the removal rate is dependent on coating pigment and substrate. This phenomena has motivated us to explore the application of high average power laser technology to the paint and other coating removal industry. The most celebrated of these applications is the removal of graffiti, but numerous other applications are being considered such as building restoration, automotive and airplane paint removal, hazardous/radioactive paint removal, engine part cleaning, concrete/masonry cleaning and even cleanup of fossils. Generally speaking, the technology works well for any application where there is a coating that is not chemically bonded to the substrate.

I will describe to you some of the efforts currently being explored at LLNL to develop commercial coating systems that will ultimately use 1 kW or higher compact lasers. Removal rates with these systems could be as high as 3000 to 5000 ft2 /hr. This is 30 to 50 times higher than that achievable with today's best high pressure baking soda slurry or steam removal technology. In addition, the residue of the process is flakes or dust, both of which are swept up easily using a vacuum system built into a delivery arm.

Commercial laser-based coating removal systems, in fact, are already available from several companies. However, these systems operate with off-the-shelf laser technology which is generally limited to 10 W maximum. At these power levels, the technology is not competitive except in a few niche areas where standard methods are not acceptable. Our technical challenge, therefore, is to develop affordable compact systems that can generate a few kW of average power. LLNL has developed high average power lasers for other applications and I will discuss our plan for modifying that technology for the coating removal application.

Dr. Matthews is Program Leader for the Medical Technology Program which is a joint program within the Laser, Engineering, and Defense and Nuclear Technology Directorates at Lawrence Livermore National Laboratory. This program unites ~50 scientists, engineers, technicians, graduate and postdoctoral students into a broad program which develops medical devices in collaboration with physicians and private companies.

Dr. Matthews is also an Adjunct Professor of Engineering at the University of California at Davis and at the Livermore Department of Applied Science Campus. He currently supervises 8 graduate and 5 postdoctoral students.

Dr. Matthews received his Ph.D. in Experimental Physics in 1974 from the University of Texas at Austin. Since that time, he has been performing research and managing scientists, engineers and technicians in broadly varying scientific projects involving development of lasers and radiation technology for science and industry. He has also worked in the physics department at Livermore and has held temporary positions at the Hahn Meitner Institut in Berlin, the Rutherford-Appleton Laboratory in Great Britain and Centre d'Etudes de Limeil near Paris. His fields of expertise include heavy-ion atom collision phenomena, Auger electron and x-ray spectroscopy of ions and atoms, spectroscopic diagnostics and studies of nonLTE plasmas, x-ray lasers, x-ray and optical imaging, and applications of lasers and optical technology to medical, scientific and industrial needs.

Dr. Matthews has written well over 180 publications in the scientific literature and holds numerous patents for applications of laser and imaging technology. He is generally considered to be the pioneer of the x-ray wavelength laser. He is a Fellow of the American Physical Society and the Optical Society of America and is a co-recipient of the 1990 Division of Plasma Physics Award for Excellence in Plasma Physics Research. He is a member of the American Physical Society, Optical Society of America, the Society of Photographical and Industrial Engineers and the Institute for Electrical and Electronics Engineers.

Directions to LLNL Visitor's Center: From I-580 in Livermore, exit at Vasco Road. Proceed south on Vasco Road; left onto Patterson Pass Road; right onto Greenville Road; right into the Visitor's Center Entrance at the intersection of Greenville Road and Lupin Way.