Single-turn extraction from a K110 AVF cyclotron by flat-top acceleration.

Area of Science:

• Nuclear Physics and Accelerator Technology
• Particle Beam Manipulation
• Microbeam Formation

Background:

• The Japan Atomic Energy Agency's AVF cyclotron (K=110) requires improved ion beam characteristics for microbeam applications.
• Existing extraction methods limit energy spread reduction and extraction efficiency.
• Flat-top (FT) acceleration is a promising technique to enhance beam quality.

Purpose of the Study:

• To implement single-turn extraction using a flat-top (FT) acceleration system in the AVF cyclotron.
• To reduce the energy spread of ion beams for microbeam formation.
• To increase the extraction efficiency of the cyclotron.

Main Methods:

• Designed and implemented a FT resonator using MAFIA code, operating at the fifth-harmonic frequency (55-110 MHz).
• Coupled the FT resonator to the main resonator via a coupling capacitor.
• Accelerated various ion beams (e.g., 220 MeV Carbon, 260 MeV Neon, 45 MeV Hydrogen) using FT acceleration with harmonic modes h=1 and h=2.
• Observed clear turn separation of beam bunches at the extraction region for over 200 revolutions.
• Confirmed single-turn extraction using a beam chopping system.
• Measured energy spread using an analyzing magnet.

Main Results:

• Achieved high extraction efficiency exceeding 95%.
• Successfully demonstrated single-turn extraction, confirmed by beam bunch counting.
• Reduced the energy spread of a 260 MeV Neon beam from ΔE/E=0.1% to 0.05% via FT acceleration and single-turn extraction.
• Observed clear beam bunch separation at the extraction region.

Conclusions:

• Single-turn extraction with FT acceleration effectively reduces ion beam energy spread.
• The developed FT resonator is compact, power-efficient, and covers the required frequency range.
• This technique significantly enhances extraction efficiency and beam quality for microbeam applications.