Practical Betatron Tune Behavior During Acceleration in Scaling FFAG Rings at KURNS

In scaling FFAG* accelerators, ideally, betatron tunes are fixed for each closed orbit concerned with the certain beam energy. Therefore, they should not vary during the acceleration. However, it is not the case since practical implementations of the magnetic field can not provide perfect scaling conditions. There are two types of radial scaling FFAG ring at Kyoto University Research Reactor Institute: one has no return yokes so called 'yoke free type' adopted by MAIN RING which has a large tune variations causing non negligible beam losses; the other has return yokes and filed clamps adopted by BOOSTER RING which has smaller tune variations compared with MAIN RING. We report the tune measurements and calculations based on 3-d magnetic field calculations about these two types of ring and discuss the scaling conditions in FFAG accelerators.
Proceedings of the 9th Int. Particle Accelerator Conf., IPAC2018, Vancouver, BC, Canada