Development of In Situ Laser Blow Off Cleaning Setup for ADITYA Tokamak Window

Elemental compositional analysis was carried out on various portions (edges to center) of the film on the ADITYA tokamak window using X-ray diffraction, energy-dispersive X-ray analysis, scanning electron microscopy, and X-ray photoelectron spectroscopy. Optical transmission studies were carried out at various points along the length and breadth of the film. An automated tabletop setup was developed for cleaning the coating by back-side etching using an Nd:yttrium aluminum garnet laser operated at its second and third harmonics. Various experimental parameters were optimized so as to restore maximum transmission for the window. It was observed that a wavelength of 355 nm at an energy density of 1275 mJ/cm² and at a repetition rate of 10 Hz was found to be best suited for this application. It was possible to restore the transmission of the coated portion to the transmission level of bare window portions using this setup.