Combined zero degree structure beam dynamics and applications

The combined zero degree structure (KONUS) is a quasiperiodic structure. It was developed for the low-energy part of multigap drift tube linacs with H-type cavities. Their rf efficiency depends very much on a low electrical capacity of the drift tube structure, while in E-type structures like the Alvarez-DTL this is a minor effect. Therefore, instead of having quadrupole singlets integrated in voluminous drift tubes, KONUS allows one to develop a separated function drift tube linac (DTL) with a large voltage gain between two lenses. Very low beam injection energies can be realized, as the drift tube lengths can range down to around 10 mm. One KONUS period consists of a triplet lens, a rebuncher with a few gaps at a synchronous phase around -35 degrees, and the main multigap acceleration designed for a hypothetical zero degree synchronous particle. The longitudinal beam dynamics along this main acceleration section and the layout of the quadrupole triplet channel are explained in detail. Two examples for pulsed high current proton and heavy ion acceleration are included.