A novel discharge control method for megawatt-level NNBI RF ion sources

Area of Science:

• Plasma Physics
• Fusion Energy Engineering
• Accelerator Technology

Background:

• Efficient power coupling and high-density negative ion beam extraction are crucial for Radio Frequency (RF) driven Negative ion based Neutral Beam Injection (NNBI) systems.
• Current NNBI systems face challenges in optimizing power transfer efficiency and simplifying filter magnetic field designs.

Purpose of the Study:

• To propose and verify a novel discharge control method for NNBI RF ion sources.
• To improve power transfer efficiency of the RF ion source power supply.
• To simplify the design of the NNBI filter magnetic field.

Main Methods:

• Analysis of the RF ion source inverter power supply design.
• Investigation and simulation of a frequency-tuning-based impedance matching control method.
• Proposal of a pulsed power modulation technique to optimize electron temperature distribution.

Main Results:

• The proposed inverter power supply demonstrates fast frequency adjustment for dynamic impedance matching.
• Efficient RF power coupling into the ion source is achieved, improving electromagnetic compatibility.
• Reduced arcing incidents in the excitation coil were observed.

Conclusions:

• The novel discharge control method enhances RF power coupling efficiency in NNBI systems.
• Pulsed power modulation simplifies NNBI filter magnetic field design and reduces engineering complexity.
• This approach addresses critical challenges in high-power RF-driven negative ion sources.