High-current H₂ ⁺ beams from a filament-driven multicusp ion source

Area of Science:

• Particle Accelerators
• Plasma Physics
• Nuclear Physics

Background:

• The IsoDAR experiment requires high-purity, high-current proton beams for neutrino discovery.
• Existing ion sources face challenges in meeting the stringent beam requirements for IsoDAR.
• Multicusp ion sources offer potential for high brightness and purity.

Purpose of the Study:

• To develop and test a new multicusp ion source (MIST-1) for the IsoDAR experiment.
• To achieve record steady-state currents of H2+ with high purity.
• To validate the performance of MIST-1 for RFQ direct injection.

Main Methods:

• Systematic measurements of MIST-1 performance by varying discharge voltage, current, and gas pressure.
• Characterization of beam emittance and species purity.
• Comparison of experimental results with high-fidelity simulations.

Main Results:

• MIST-1 produced record 1 mA steady-state H2+ current with 80% purity.
• Optimal operating regime identified at low pressure, high discharge current, and high voltage.
• Measured combined species emittance <0.05 π-mm-mrad (rms, normalized) for a 0.95 mA beam.
• Experimental results show good agreement with simulations.

Conclusions:

• MIST-1 demonstrates the feasibility of using multicusp ion sources for IsoDAR.
• The source design and performance pave the way for 5 mA H2+ (10 mA proton equivalent) continuous wave beams.
• This advancement is crucial for compact cyclotrons and underground physics experiments.