Coupling Concept for Cross-Bar H-Type Cavities

Linear Accelerator

Abstract

The Cross-bar H-type cavities (CH-DTL) have been investigated in last two decades in different laboratories. They have promising features when comparing with conventional DTL structures in terms of field gradient, shunt impedance and costs. The KONUS beam dynamics allows to have short drift tube sections without focusing lenses, resulting in a limited number of gaps per CH – cavity. With the available 3 MW klystron, the short cavity structure will not use the full amplifier power and to RF - couple two single cavities seems an applicable solution to have more gaps per structure, without harming the beam dynamics.  This concept will be realized by coupling three resonators together and operating them as one structure at zero mode. In this paper, two identical CH – tanks - each with 13 gaps - will be coupled together with a coupling cell containing a quadrupole triplet and the results will be compared with theory. This type of cavity is called Coupled CH – cavity and is denoted as CCH. The design frequency and field distribution results from an optimization of the three coupled resonators and is described in this paper. The fine tuning will be done by fixed and movable tuners along the structure.