Optimization design of magnetic filter for the prototype RF negative ion source at ASIPP.

Area of Science:

• Plasma Physics
• Fusion Energy Technology
• Ion Source Development

Background:

• RF negative ion sources are critical for fusion energy applications.
• Existing magnetic filter fields in prototype sources exhibit poor gradient and uniformity, leading to plasma unevenness.
• Nonuniform plasma affects negative ion loss, electron coextraction, and beam alignment.

Purpose of the Study:

• To design and analyze an improved magnetic filter field for RF negative ion sources.
• To enhance plasma uniformity and reduce electron coextraction.
• To optimize magnetic field parameters for better ion source performance.

Main Methods:

• Development of a negative RF ion source test facility at ASIPP.
• Utilizing a finite element analysis method to calculate magnetic field distribution.
• Comparing several design cases for the magnetic filter field.

Main Results:

• The proposed magnetic filter field, using permanent magnets and Plasma Grid (PG) current with return wires, offers improved uniformity.
• The final design achieves a more uniform magnetic field within 70 mm above the PG.
• The field strength is approximately 5 mT with an integral BdL quantity exceeding 1.2 mTm.

Conclusions:

• The new magnetic filter field design significantly improves plasma uniformity in RF negative ion sources.
• This advancement is expected to reduce negative ion loss and electron coextraction.
• The optimized magnetic field configuration is beneficial for fusion applications.