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°, 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.

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Additive manufacturing (AM or “3D printing”) has become a powerful tool for the rapid prototyping and manufacturing of complex part geometries. Especially interesting for the world of particle accelerators is the process of the 3D printing of stainless steel (and copper) parts. We present a first prototype of a 43 MHz IH-type linac cavity with an internal drift tube structure manufactured by metal 3D printing. The prototype cavity has been constructed to act as a proof-of-concept for the technology. In this paper we present the concept of the cavity as well as first results of vacuum testing and materials testing.