Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while exte...Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.展开更多
The orientation angle is an important parameter that reflects the structure of molecules at interfaces. In order to obtain this parameter, second order nonlinear spectroscopic techniques including second harmonic gene...The orientation angle is an important parameter that reflects the structure of molecules at interfaces. In order to obtain this parameter, second order nonlinear spectroscopic techniques including second harmonic generation （SHG） and sum frequency generation-vibrational spec- troscopy （SFG-VS） have been successfully applied through analysis of the nonlinear signal from various polarizations. In some SHG and SFG-VS experiments, total internal reflection （TIR） configuration has been adopted to get enhanced signals. However, the reports on the detailed procedure of the polarization analysis and the calculation of the orientation angle of interracial molecules under TIR configuration are still very few. In this paper, we mea- sured the orientation angles of two molecules at the hexadecane-water interface under TIR and Non-TIR experimental configurations. The results measured from polarization analysis in TIR configuration consist with those obtained from Non-TIR configuration. This work demonstrates the feasibility and accuracy of polarization analysis in the determination of the orientation angle of molecules at the interfaces under TIR-SHG configuration.展开更多
文摘Secondary electron emission(SEE)has emerged as a critical issue in next-generation accelerators.Mitigating SEE on metal surfaces is crucial for enhancing the stability and emittance of particle accelerators while extending their lifespan.This paper explores the application of laser-assisted water jet technology in constructing high-quality micro-trap structures on 316L stainless steel,a key material in accelerator manufacturing.The study systematically analyzes the impact of various parameters such as laser repetition frequency,pulse duration,average power,water jet pressure,repeat times,nozzle offset,focal position,offset distance between grooves,and processing speed on the surface morphology of stainless steel.The findings reveal that micro-groove depth increases with higher laser power but decreases with increasing water jet pressure and processing speed.Interestingly,repeat times have minimal effect on depth.On the other hand,micro-groove width increases with higher laser power and repeat times but decreases with processing speed.By optimizing these parameters,the researchers achieved high-quality pound sign-shaped trap structure with consistent dimensions.We tested the secondary electron emission coefficient of the"well"structure.The coefficient is reduced by 0.5 at most compared to before processing,effectively suppressing secondary electron emission.These results offer indispensable insights for the fabrication of micro-trap structures on material surfaces.Laser-assisted water jet technology demonstrates considerable potential in mitigating SEE on metal surfaces.
文摘The orientation angle is an important parameter that reflects the structure of molecules at interfaces. In order to obtain this parameter, second order nonlinear spectroscopic techniques including second harmonic generation （SHG） and sum frequency generation-vibrational spec- troscopy （SFG-VS） have been successfully applied through analysis of the nonlinear signal from various polarizations. In some SHG and SFG-VS experiments, total internal reflection （TIR） configuration has been adopted to get enhanced signals. However, the reports on the detailed procedure of the polarization analysis and the calculation of the orientation angle of interracial molecules under TIR configuration are still very few. In this paper, we mea- sured the orientation angles of two molecules at the hexadecane-water interface under TIR and Non-TIR experimental configurations. The results measured from polarization analysis in TIR configuration consist with those obtained from Non-TIR configuration. This work demonstrates the feasibility and accuracy of polarization analysis in the determination of the orientation angle of molecules at the interfaces under TIR-SHG configuration.
