APF or KONUS drift tube structures for medical synchrotron injectors-a comparison

Tumor therapy with light ion beams like carbon out of a synchrotron is a topical accelerator application. In all designs the layout of the injector linac is an important factor with respect to construction and operation costs as well as to the operation performance of such a medical facility. Two alternative linac approaches which keep the number of components and setting parameters as low as possible are discussed. In both cases the interdigital H-type drift tube structure is used for acceleration of C⁴⁺ ions from 0.3 MeV/u to 7 MeV/u. The “Combined Zero Degree Structure” KONUS is used in one design; the other approach is “Alternating Phase Focusing” APF without any magnetic quadrupoles for transverse focusing. Both designs were investigated with the LORASR code. As the same linac should also provide protons with beam intensities of a few mA, the comparison was extended towards the capability of accelerating intense ion beams