Controlled ablation of impurity deposition in fusion devices by using variable laser fluence within depth-of-focus of focusing lens

• Published in: Applied physics. B, Lasers and optics Lasers and optics, 2024-02, Vol.130 (2), Article 27
• Main Authors: Imran, Muhammad, Hu, Zhenhua, Ding, Fang, Sattar, Harse, Luo, Guang-Nan
• Format: Article
• Language: English
• Subjects: Ablation; Applied physics; Copper base alloys; Craters; Deposition; Depth of field; Diameters; Emission analysis; Engineering; Fluence; Impurities; Laser ablation; Laser applications; Lasers; Lenses; Morphology; Neodymium lasers; Optical Devices; Optics; Photonics; Physical Chemistry; Physics; Physics and Astronomy; Quantum Optics; Semiconductor lasers; Spectral emission; YAG lasers
• ISSN: 0946-2171; 1432-0649
• DOI: 10.1007/s00340-023-08165-x

The ability of laser pulse was tested for controlled ablation of the copper alloy (CuCrZr) and nanometer-thick impurity layer on the rear surface of a glass window. The target surface was moved across the focus point (FP) to vary the distance from the FP within the depth-of-focus (DOF) of the focusing lens. An Nd:YAG laser was used at its fundamental wavelength of 1064 nm in this experiment. The controlled ablation was performed to remove the impurity from the rear surface of a glass window that was taken from the H-port of the EAST tokamak. The morphology of the laser-produced craters was measured using the 3D laser scanning confocal microscope and scanning electron microscope. The depth and diameter of the craters varied according to the laser energy which focused on the unit area. The spectral intensity increases as the distance from the FP decreases. The threshold fluence values for ablation, ignition of the plasma, and spectral emission were investigated. The laser pulse energy focused before and after the FP resulted in different ablation behaviors, crater morphologies, and spectral intensity. The precise removal of impurities from the rear surface was performed at − 2 mm from the FP. The laser ablation with variable fluence can further improve the selective ablation of impurity deposition to investigate the surface of the plasma-facing components.