Numerical analysis of surface produced H- ions by using two-dimensional particle-in-cell method

Area of Science:

• Plasma Physics
• Ion Source Technology
• Computational Physics

Background:

• Negative ion sources are crucial for fusion energy and industrial applications.
• Understanding ion production mechanisms on surfaces is key to optimizing source performance.
• Previous studies lack detailed simulation of surface production effects on plasma parameters.

Purpose of the Study:

• To investigate the impact of negative hydrogen (H-) ion production on the plasma grid (PG) surface.
• To analyze the correlation between H- production rate and ion/electron current densities.
• To examine the role of H- ions in maintaining plasma quasi-neutrality.

Main Methods:

• Utilized a 2D particle-in-cell (PIC) simulation model.
• Simulated the negative ion source environment, focusing on the PG surface interactions.
• Varied the H- ion production rate to observe effects on plasma parameters.

Main Results:

• Increased H- ion production per time step enhanced H- ion current density.
• Electron current density decreased with a higher H- production rate on the PG surface.
• Plasma quasi-neutrality in the bulk plasma near the PG is primarily sustained by positive hydrogen (H+) and H- ions.

Conclusions:

• The simulation results align with experimental observations in negative ion sources.
• Surface H- production significantly influences the plasma grid's electrical characteristics.
• H- ions play a vital role in stabilizing the bulk plasma near the plasma grid.