Beam tuning and bunch length measurement in the bunch compression operation at the cERL

TL;DR

This paper demonstrates effective bunch compression at cERL using phase space manipulation, with a diagnostic system based on coherent transition radiation, achieving a 250 fs bunch length at 2 pC charge.

Contribution

It introduces a diagnostic system for bunch length measurement and tuning, validating the bunch compression technique in a compact ERL test accelerator.

Findings

Achieved RMS bunch length of 250±50 fs at 2 pC

Validated the tuning procedure for bunch compression

Confirmed the design parameters for future ERL applications

Abstract

Realization of a short bunch beam by manipulating the longitudinal phase space distribution with a finite longitudinal dispersion following an off-crest accelera- tion is a widely used technique. The technique was applied in a compact test accelerator of an energy-recovery linac scheme for compressing the bunch length at the return loop. A diagnostic system utilizing coherent transition radiation was developed for the beam tuning and for estimating the bunch length. By scanning the beam parameters, we experimentally found the best condition for the bunch compression. The RMS bunch length of 250+-50 fs was obtained at a bunch charge of 2 pC. This result confirmed the design and the tuning pro- cedure of the bunch compression operation for the future energy-recovery linac (ERL).