The characterization and optimization of NIO1 ion source extraction aperture using a 3D particle-in-cell code

Area of Science:

• Plasma Physics
• Ion Source Technology
• Surface Production

Background:

• The geometry of extraction grid apertures significantly impacts negative ion transport and extraction efficiency in hybrid negative ion sources.
• Optimizing these apertures is key to enhancing ion source performance.

Purpose of the Study:

• To develop and utilize a 3D particle-in-cell/Monte Carlo collision model to investigate the influence of a new single aperture design on negative ion optimization.
• To determine the optimal geometric parameters of the aperture for maximizing negative ion production and extraction probability.

Main Methods:

• Development of a three-dimensional particle-in-cell/Monte Carlo collision model simulating the extraction region around a single aperture.
• Modeling included parts of the source and acceleration regions up to the extraction grid (EG) middle.
• Analysis of negative ion density in the yz plane.

Main Results:

• The dimensions of flat and chamfered parts, along with the slope of the chamfered section, were found to be critical factors.
• These geometric features maximize the product of production rate and extraction probability for surface-produced negative ions.
• Optimal geometry allows for the best extraction grid (EG) field penetration.

Conclusions:

• The study successfully identified key geometric parameters for optimizing negative ion extraction.
• The developed model provides a valuable tool for designing improved hybrid negative ion sources.
• Specific aperture geometry significantly enhances the efficiency of negative ion transport and extraction.