Report from KEK (High gradient study results from Nextef)

TL;DR

This report details high gradient testing of CLIC prototype structures at KEK, highlighting the performance of undamped and damped structures, with the undamped T24 meeting CLIC requirements and the damped TD24 showing improvements over previous models.

Contribution

First comprehensive high gradient test results of KEK's CLIC prototype structures, comparing undamped and damped designs and their performance characteristics.

Findings

T24 undamped structure achieved low breakdown rate and rapid processing.

TD24 damped structure showed improved performance over TD18.

Further R&D efforts are ongoing to enhance high gradient performance.

Abstract

Most up-to-date high gradient test of the CLIC prototype structures as of September 2011 is described in this report. The "T24" undamped structure showed fast processing time, still-decreasing breakdown rate and its breakdown rate was estimated to be as low as the CLIC requirement. The "TD24" damped structure showed not so excellent high gradient performance as undamped "T24" but the characteristics was much improved than the damped "TD18" structure with higher magnetic field. Further R&D is needed and we present some of the present efforts at KEK.