A high-current light-ion injector for tandem accelerators

Area of Science:

• Accelerator Physics
• Plasma Physics
• Ion Source Technology

Background:

• Tandem accelerators require reliable sources for negative ion beams, including hydrogen (H), deuterium (D), and helium (He).
• Efficient production of these negative ions is crucial for various applications, such as fusion research and materials science.
• Existing ion source technologies face challenges in achieving high currents and optimizing yields for specific ion species.

Purpose of the Study:

• To develop and construct a dual-source injector system for tandem accelerators.
• To achieve high negative ion currents for H, D, and He.
• To optimize the production and transport of He(-) ions for enhanced accelerator performance.

Main Methods:

• Designed and built a dual-source injector featuring a central vacuum enclosure housing two multicusp ion sources.
• Employed direct negative extraction for H(-) and D(-) ion production.
• Utilized differentially pumped vacuum sections and optimized extraction geometry for He(-) production and transport, including charge exchange optimization.

Main Results:

• Achieved several milliamperes (mA) of H(-) and D(-) beam currents via direct negative extraction.
• Optimized He(-) yield by managing space charge effects and minimizing neutralization losses during charge exchange.
• Obtained over 10 mA of He(+) and approximately 50 microamperes (µA) of He(-) using lithium (Li) as a charge exchange medium, with potential for over 100 µA using sodium (Na).

Conclusions:

• The developed dual-source injector is a capable system for producing high-current negative ion beams of H, D, and He.
• The optimization strategies for He(-) production, including vacuum pumping and charge exchange, significantly enhance ion yield.
• The system demonstrates potential for further improvements, particularly for He(-) currents, by exploring different charge exchange media.