A 2D Particle in Cell model for ion extraction and focusing in electrostatic accelerators

Area of Science:

• Plasma Physics
• Fusion Energy
• Beam Technology

Background:

• Negative ions are essential for generating high-energy neutral beams used in plasma heating for fusion energy research.
• Ion extraction involves plasma sheath formation near the Debye length, while acceleration occurs over larger distances.

Purpose of the Study:

• To develop and implement a numerical model simulating both ion extraction and acceleration phases.
• To integrate particle-in-cell (PIC) and finite element methods (FEM) for comprehensive modeling.
• To investigate the transition between beam and plasma regions.

Main Methods:

• A novel numerical code combining PIC for space charge and FEM for field solving was developed.
• The model incorporates hypotheses for the beam-plasma transition to simulate both regions concurrently.
• The code was tested using the NIO1 negative ion source geometry.

Main Results:

• The implemented numerical model accurately simulates negative ion extraction and acceleration.
• The code's results show good agreement when compared with established ray tracing codes.
• The model provides insights into the complex physics of ion beam formation in fusion devices.

Conclusions:

• The developed numerical model offers a robust tool for studying negative ion beam generation.
• This work advances the understanding of plasma heating mechanisms in fusion devices.
• The validated model can aid in optimizing negative ion source performance.