Estimate of eddy current effects in APTRON

Eddy currect effects should be considered in a accelerator with magnets ramping with a large repetition frequency. Field components like dipolar, quadrupolar and sextupolar ones and heating effects induced by eddy current effects will affect the chromaticities, tunes, resonance， etc. The field components and their effects on beam parameters in the ring are evaluated for difference ramping curves and ramping frequencies. The most important effect is found to be from sextupolar component in the frequency range of proton therapy, and other components will play more important roles when the repetition frequency increases. Accordingly, the ramping curve for operation is selected as a sinusoidal curve with ramping time of 0.7 s.