Design of a 3 GHz Accelerator Structure for the CLIC Test Facility (CTF 3) Drive Beam

TL;DR

This paper discusses the design and testing of a 3 GHz accelerator structure for the CLIC test facility, focusing on high-current drive beam requirements and innovative damping techniques.

Contribution

It introduces two novel accelerator structure concepts, Tapered Damped Structure and Slotted Iris - Constant Aperture, with prototype testing results.

Findings

Successful full-power testing of the Tapered Damped Structure prototype

Development of the SICA structure prototype in progress

Effective higher-order mode damping achieved with SiC loads

Abstract

For the CLIC two-beam scheme, a high-current, long-pulse drive beam is required for RF power generation. Taking advantage of the 3 GHz klystrons available at the LEP injector once LEP stops, a 180 MeV electron accelerator is being constructed for a nominal beam current of 3.5 A and 1.5 microsecond pulse length. The high current requires highly effective suppression of dipolar wakes. Two concepts are investigated for the accelerating structure design: the "Tapered Damped Structure" developed for the CLIC main beam, and the "Slotted Iris - Constant Aperture" structure. Both use 4 SiC loads per cell for effective higher-order mode damping. A full-size prototype of the TDS structure has been built and tested successfully at full power. A first prototype of the SICA structure is being built.