Measurement and simulation of the impact of coherent synchrotron radiation on the Jefferson Laboratory energy recovery linac electron beam

C C Hall,B E Carlsten,R Li,S Benson,D Douglas,C D Tennant,S G Biedron,S V Milton,A L Edelen

doi:10.1103/physrevstab.18.030706

Abstract

In an experiment conducted on the Jefferson Laboratory IR free-electron laser driver, the effects of coherent synchrotron radiation (CSR) on beam quality were studied. The primary goal of this work was to explore CSR output and effect on the beam with variation of the bunch compression in the IR recirculator. Here we examine the impact of CSR on the average energy loss as a function of bunch compression as well as the impact of CSR on the energy spectrum of the bunch. Simulation of beam dynamics in the machine, including the one-dimensional CSR model, shows very good agreement with the measured effect of CSR on the average energy loss as a function of compression. Finally, a well-defined structure is observed in the energy spectrum with a feature in the spectrum that varies as a function of the compression. This effect is examined in simulations, as well, and a simple explanation for the variation is proposed.

Highlights

The Thomas Jefferson National Accelerator Facility (JLAB) energy recovery linac (ERL) IR free-electron laser (FEL) driver [1] consists of a superconducting radio frequency (SRF) linac, allowing for cw operation, and a recirculating transport system
We have shown the results of measurements of the impact of coherent synchrotron radiation (CSR) on the electron beam quality of the JLAB IR FEL as it varies with bunch compression
Very good agreement is seen between these measurements and simulations performed by using a 1D CSR model

Summary

Introduction

The Thomas Jefferson National Accelerator Facility (JLAB) energy recovery linac (ERL) IR free-electron laser (FEL) driver [1] consists of a superconducting radio frequency (SRF) linac, allowing for cw operation, and a recirculating transport system. This recirculation of the beam back to the linac, after it has passed through the magnetic wiggler, used to generate an IR free-electron laser, allows for recapture of the rf energy before the beam is dumped. The IR FEL can operate at a repetition rate of 75 MHz with a charge per bunch of up to 135 pC providing up to 10 mA of average current and a beam energy of 160 MeV.

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