High peak current operation of x-ray free-electron laser multiple beam lines by suppressing coherent synchrotron radiation effects

Toru Hara,Kenji Fukami,Osamu Morimoto,Hitoshi Tanaka,Kazuaki Togawa,Masamichi Yoshioka,Hirokazu Maesaka,Chikara Kondo,Taichi Hasegawa,Takahiro Inagaki,Yuji Otake,Shingo Nakazawa

doi:10.1103/physrevaccelbeams.21.040701

Abstract

The parallel operation of multiple beam lines is an important means to expand the opportunity of user experiments at x-ray free-electron laser (XFEL) facilities. At SPring-8 Angstrom free-electron laser (SACLA), the multi-beam-line operation had been tested using two beam lines, but transverse coherent synchrotron radiation (CSR) effects at a dogleg beam transport severely limited the laser performance. To suppress the CSR effects, a new beam optics based on two double bend achromat (DBA) structures was introduced for the dogleg. After the replacement of the beam optics, high peak current bunches of more than 10 kA are now stably transported through the dogleg and the laser pulse output is increased by a factor of 2--3. In the multi-beam-line operation of SACLA, the electron beam parameters, such as the beam energy and peak current, can be adjusted independently for each beam line. Thus the laser output can be optimized and wide spectral tunability is ensured for all beam lines.

Highlights

x-ray free-electron laser (XFEL) have distinctive characteristics such as high peak intensity, short pulse duration and coherence [1,2,3,4,5,6,7]
To suppress the coherent synchrotron radiation (CSR) effects, a new beam optics based on two double bend achromat (DBA) structures was introduced for the dogleg
After the replacement of the beam optics, high peak current bunches of more than 10 kA are stably transported through the dogleg and the laser pulse output is increased by a factor of 2–3

Summary

INTRODUCTION

XFELs have distinctive characteristics such as high peak intensity, short pulse duration and coherence [1,2,3,4,5,6,7]. In order to mitigate this drawback, multi-beam-line operation has been tested at SACLA by distributing the electron beam to multiple beam lines from bunch to bunch [12]. For the multi-beam-line operation, the electron bunches from the SACLA linear accelerator are alternately sent to the two XFEL beam lines, BL2 and BL3 [12]. For the single beam line operation of SACLA, the electron bunches are longitudinally compressed to 10–15 fs (FWHM) and the peak current reaches more than 10 kA. When these high peak current bunches pass through the dogleg, the electron beam orbit instability and projected emittance. In order to avoid the degradation of the electron beam quality, a new beam optics is introduced to the BL2 dogleg beam transport

CANCELLATION OF CSR EFFECTS

NEW BEAM SWITCHYARD AND DOGLEG BEAM TRANSPORT

MULTI-BEAM-LINE OPERATION

Findings

SUMMARY