Charged Particle Sources
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Laser cutting has generally three forms: fusion cutting, sublimation cutting, and photochemical ablation. Fusion cutting involves melting of the base material, which is then ejected using a high-pressure assist gas. The assist gas may be an inert gas, in which case the energy for melting is provided entirely by the laser beam. It may also be oxygen (or air), which reacts with the base metal, and the resulting exothermic reaction provides additional energy to enhance the process. Sublimation cutting is often achieved using a pulsed laser beam. It is a process in which the workpiece material is vaporized along the cutting seam. Sublimation cutting is limited to thin sections since more energy is required to remove a unit volume of material as compared to fusion cutting. However, it has the advantage of a narrower kerf width and higher edge quality. Photochemical ablation mainly utilizes ultraviolet laser, and it works effectively for organic compounds. This is because the ultraviolet photons have a energy range between 3.5 and 6.5 eV, which corresponds to the energy levels of organic molecular bonding. Hence, organic compounds tend to absorb ultraviolet radiation efficiently.