Angular distributions of surface produced H(-) ions for reflection and desorption processes.
M Wada1, T Kasuya1, T Kenmotsu2
1Graduate School of Science and Engineering, Doshisha University, Kyotanabe, Kyoto 610-0321, Japan.
The Review of Scientific Instruments
|March 6, 2014
Summary
Simulating hydrogen flux on plasma grids reveals incident angle impacts particle reflection and desorption. Larger angles increase reflection but decrease desorption yield of negative hydrogen ions.
Area of Science:
- Plasma Physics
- Materials Science
- Surface Science
Background:
- Understanding particle interactions with plasma-facing components is crucial for fusion energy research.
- Surface modifications and incident angles significantly influence sputtering and desorption yields.
- Cesium-covered Molybdenum (Mo) is a relevant material for plasma grids.
Purpose of the Study:
- To investigate the effect of hydrogen flux incident angle on collision cascades in Cs-covered Mo plasma grids.
- To analyze the energy distribution of negative hydrogen (H-) ions leaving the surface.
- To quantify changes in reflection and desorption coefficients with varying incident angles.
Main Methods:
- Utilized a numerical simulation code, "Atomic Collision in Amorphous Target."
- Incorporated the threshold energy for H- ion surface escape.
- Analyzed angular distributions and coefficients for reflection and desorption components.
Main Results:
- Incident angle of hydrogen particles tilts the angular distribution of the reflection component.
- Larger incident angles have a minimal effect on the angular distribution of the desorption component.
- Increased angle of incidence (from surface normal) leads to a higher reflection coefficient.
- Increased angle of incidence (from surface normal) leads to a lower desorption yield.
Conclusions:
- The incident angle of hydrogen flux is a critical parameter influencing particle dynamics at plasma grid surfaces.
- Simulation results provide insights into optimizing plasma grid performance by controlling incident angles.
- The energy threshold for H- ion escape affects the energy distribution, differentiating it from neutral hydrogen atoms.
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