Abstract
Localized CO2 laser repairing of surface damage on fused silica optics has been successfully applied in high-power laser system in the field of controllable nuclear fusion. In order to accurately predict the surface topography evolution and to reveal the intrinsic physical mechanism during the process of laser mitigation, experiments of localized CO2 laser mitigation were firstly carried out to analyze the features of mitigated craters under different laser powers. Then a multi-physics coupled mathematical model was developed based on the fluid control equation, heat and mass transfer equation and material phase transition kinetics to investigate the thermodynamic and kinetic behaviors of laser interaction with silica. The model considered the effects of Marangoni convection, gravity, capillary force and vaporization recoil pressure, as well as the nonlinear variation of physical parameters of silica material with respect to temperature. The results showed that with the increase of laser power, the material ablation and the appearance of raised rim occurred simultaneously. The depth of the mitigated crater increased sharply when the threshold for material ablation was attained, while the lateral dimension increased linearly. The vaporization recoil pressure was found to be the dominant factor for the formation of Gaussian crater with the raised rim feature. The capillary force caused the material at the edge of the molten pool to have a tendency to reflow after laser shutting down, but it was too small to change the surface topography. This work could significantly contribute to the understanding of laser mitigation process, which laid the foundation for the accurate prediction and evaluation of surface quality of CO2 laser repaired fused silica surface.
Original language | English |
---|---|
Article number | 102936 |
Journal | Results in Physics |
Volume | 16 |
Early online date | 10 Jan 2020 |
DOIs | |
Publication status | Published - 31 Mar 2020 |
Funding
This work was supported by the National Natural Science Foundation of China (Grant Nos. 51775147 , 51705105 ); Science Challenge Project (Grant No. TZ2016006-0503-01 ); Young Elite Scientists Sponsorship Program by CAST (No. 2018QNRC001), China Postdoctoral Science Foundation funded project (Grant Nos. 2018T110288, 2017M621260); Self-Planned Task (Grant Nos. SKLRS201718A, SKLRS201803B) of State Key Laboratory of Robotics and System (HIT).
Funders | Funder number |
---|---|
China Association for Science and Technology for the Young Elite Scientists Sponsorship Program | |
National Natural Science Foundation of China | 51705105, 51775147 |
China Postdoctoral Science Foundation | 2017M621260, 2018T110288 |
Harbin Institute of Technology | |
China Academy of Space Technology | 2018QNRC001 |
State Key Laboratory of Robotics and System | |
Science Challenge Project of China | TZ2016006-0503-01 |
Keywords
- CO laser
- Damage mitigation
- Fused silica
- Physical mechanism
- Surface topography evolution
ASJC Scopus subject areas
- General Physics and Astronomy