Multiple-energy operation with extended flattops at HIMAC

Multiple-energy operation with extended flattops for synchrotron accelerators is being developed at HIMAC. This operation uses synchrotron operation-patterns having a stepwise flattop. With these patterns, a beam would be initially accelerated to the maximum energy, and then successively decelerated to lower energies. Having extended the flattops and extracted beams during these flattops, heavy ions with various energies can be provided in a single synchrotron cycle. Since the extraction energy can be quickly changed by the accelerator, itself, no energy degrader will be required to control the depth dose-distribution. By applying this multiple-energy operation to our fast raster-scanning irradiation, we can considerably reduce the total irradiation time, and concurrently obtain excellent depth dose-distributions. Beam acceleration and extraction tests using this operation were made. Successful results of the tests proved the effectiveness of this multiple-energy operation with extended flattops in heavy-ion therapy.