Suppression of Coherent Synchrotron Radiation-Induced Emittance Growth in a Multi-Bend Deflection Line

TL;DR

This paper presents a novel QBA deflection structure optimized via reverse lattice design to effectively suppress CSR-induced emittance growth in high-brightness electron beam transport, ensuring high beam quality.

Contribution

The study introduces a simplified optimization method for CSR suppression using reverse lattice design and derives a general solution for transverse CSR effects in QBA structures.

Findings

QBA structure effectively suppresses CSR effects at high peak currents.

Simulation shows minimal emittance growth with large deflection angles.

General conditions for CSR suppression in isochronous structures are established.

Abstract

Preserving beam quality during the transportation of high-brightness electron beams is a significant and widespread challenge in the design of modern accelerators. The importance of this issue stems from the fact that the quality of the beam at the accelerator's output is crucial for various applications, including particle colliders, free-electron lasers, and synchrotron radiation sources. The coherent synchrotron radiation (CSR) effect can degrade beam quality when a bunch is deflected. Therefore, developing a structure that effectively suppresses the CSR effect, especially for the short bunches is critically important. This involves protecting both the transverse emittance and the longitudinal profile to ensure the production of a high-quality beam. In this study, an optimization based on the reverse lattice of the beamline is proposed. This method can simplify the optimization process. Based on this approach, the Quadruple Bend Achromat (QBA) deflection structure has been designed and optimized. Then we have derived a general solution to completely suppress the impact of steady-state CSR on the transverse plane for different topologies of QBA. Furthermore, a general condition is proposed for suppressing displacements caused by CSR in sequence drifts for isochronous structures. Simultaneously, QBA has proven to be the simplest structure that can simultaneously suppress both types of CSR effects. Simulation results for bunches with a peak current of up to $3000A$ show almost no change in transverse emittance for a large angle deflection.