Multistage CSR microbunching gain development in transport or recirculation arcs

TL;DR

This paper introduces a multistage analysis method for microbunching gain development in accelerator arcs, revealing complex amplification stages and linking optics patterns with gain functions, validated by Vlasov and tracking simulations.

Contribution

It extends the stage gain concept to characterize microbunching development, enabling comparison of optics impacts and revealing multistage amplification in transport arcs.

Findings

Up to 6th stage amplification observed in transport arcs.

Multistage microbunching gain development differs from typical chicanes.

Vlasov analysis agrees well with tracking simulations.

Abstract

Coherent synchrotron radiation (CSR) induced microbunching instability has been one of the most challenging issues in the design of modern accelerators. A linear Vlasov solver has been developed [1] and applied to investigate the physical processes of microbunching gain amplification for several example lattices [2]. In this paper, by further extending the concept of stage gain as proposed by Huang and Kim [3], we develop a method to characterize the microbunching development in terms of stage orders that allow the quantitative comparison of optics impacts on microbunching gain for different lattices. We find that the microbunching instability in our demonstrated arcs has a distinguishing feature of multistage amplification (e.g, up to 6th stage amplification for our example transport arcs, in contrast to two-stage amplification for a typical 4-dipole bunch compressor chicane). We also try to connect lattice optics pattern with the obtained stage gain functions by a physical interpretation. This Vlasov analysis is validated by ELEGANT [4] tracking results with excellent agreement.