KEK, Ibaraki
The J-PARC Main Ring should provide high beam power with strict limitation of the particle losses during the operation, including the injection and acceleration processes,caused by the machine imperfections and the space charge effects. The linear coupling resonance [1,1,43] has been identified as the most serious resonance for the MR operation, which leads to significant particle losses during the injection process. Effect of the sextupole resonances, caused by the machine imperfection, is much smaller. The 4th order resonances, mainly 4Qx, 4Qy and 2Qx-2Qy, excited by the space charge of the low energy beam, lead to additional particle losses. The correction procedure to minimize the effect of the sum coupling resonance [1,1,43] by using four independent skew quadrupole magnets has been studied. The particle losses for different machine operation scenario have been estimated, including the injection and acceleration processes. The study of the combined effect of the MR imperfections and the space charge of the beam with moderate beam power has been performed by using the PTC_ORBIT code, installed for the KEK super computer HITACHI SR11000.
Tech-X, Boulder, Colorado
KEK, Ibaraki
At low current, accelerators are dominated by their independent, separated-function magnets, and hence essentially all accelerator simulation codes have used not time but longitudinal distance, s, as the independent variable. The simulation of space-charge effects within this approach has been at best ad hoc, as it requires a (thoroughly approximate) transformation between a pancake of space charge at fixed s to a particle bunch at fixed t. We shall describe recent modifications to the accelerator simulation code PTC [1] that make it possible to, in effect, perform time-based particle tracking in a code that correctly handles the full geometry and wide dynamic range of current designs for FFAGs. In addition, we shall describe the associated space-charge computation and present initial results from simulations that cover a large energy gain in a model non-scaling FFAG.
[1] E. Forest, Y. Nogiwa, F. Schmidt, "The FPP and PTC Libraries", Proceedings of ICAP 2006.