Abstract
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 $\ensuremath{-}35\ifmmode^\circ\else\textdegree\fi{}$, 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.
Highlights
The Kombinierte Null Grad Struktur (KONUS) beam dynamics [1,2,3] has been developed since 1980
If the bunch center particle is injected at phases around zero degree but with a surplus energy Wcs;0 like shown in Figs. 6 and 8, all bunch particles are moving towards negative phases, and this allows the use of acceleration rf phases rather close to the crest of the wave along the first few gaps of each zero degree KONUS section
This article explains for the first time the concept of the KONUS beam dynamics in detail and demonstrates the high-current beam capabilities including an error study
Summary
The Kombinierte Null Grad Struktur (KONUS) beam dynamics [1,2,3] has been developed since 1980. This was the first RFQ–IH-DTL combination with an energy range of the IH cavity from 300 A keV up to 1.4 A MeV and at A/q values up to 8.5, corresponding to U28þ from the Caprice ECR source [8]. In the case of a high current, high duty factor proton, and deuteron acceleration (like needed for intense neutron sources, for example), beam halo formation plays an important role. In such cases, well-aligned DTLs of the Alvarez type based on a negative synchronous phase
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