Title: Mitigation of microbunching instability in x-ray free electron laser linacs

Abstract

The microbunching instability seeded by small initial density modulation and driven by collective effects can cause significant electron beam quality degradation in next generation x-ray free electron lasers. A method exploiting longitudinal mixing derived from the natural transverse spread of the electron beam through a dispersive bending magnet was proposed to suppress this instability several years ago [Phys. Rev. Lett. 111, 054801 (2013)PRLTAO0031-900710.1103/PhysRevLett.111.054801]. Instead of using bending magnets to introduce the transverse-to-longitudinal coupling, which will lead to an inconvenient deflection of the downstream beam line, in this paper, we propose a scheme to mitigate the microbunching instability by inserting a quadrupole magnet inside a bunch compressor of the accelerator. This results in transverse-to-longitudinal phase space mixing and large slice energy spread that can efficiently mitigate the growth of the microbunching instability through the major accelerator section. Finally, at the exit of the accelerator, a dogleg section is used to restore the emittance and slice energy spread before entering the undulator radiation section. Multiparticle simulations show that the transverse space charge, structure wakefield, and the coherent synchrotron radiation effects will have a relatively small impact on this scheme.

Authors:

Li, Biaobin; Qiang, Ji

Publication Date:

Thu Jan 09 00:00:00 EST 2020

Research Org.:

Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Sponsoring Org.:

USDOE Office of Science (SC); China Scholarship Council

OSTI Identifier:

1581856

Alternate Identifier(s):

OSTI ID: 1603593

Grant/Contract Number:  

AC02-05CH11231

Resource Type:

Published Article

Journal Name:

Physical Review Accelerators and Beams

Additional Journal Information:

Journal Name: Physical Review Accelerators and Beams Journal Volume: 23 Journal Issue: 1; Journal ID: ISSN 2469-9888

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

43 PARTICLE ACCELERATORS; relativistic multiple-particle dynamics