Sensitivity of the CSR Self-Interaction to the Local Longitudinal Charge Concentration of a Bunch

(TU-04) Presenting Author: Rui Li

R. Li  

Jefferson Lab

Recent measurements of the coherent synchrotron radiation (CSR) effect carried out at CERN and at Jefferson Lab indicate that the observed emittance growth and energy modulation due to CSR induced bunch self-interaction are often bigger than the results predicted from previous analyses and simulations based on a Gaussian longitudinal charge distribution. In this paper, by performing a model study, we show both analytically and numerically that when the longitudinal bunch charge distribution involves concentration of charges in a small fraction of the bunch length, enhancement of the CSR self-interaction beyond the Gaussian prediction could occur. The level of this enhancement is sensitive to the level of the charge concentration. Awareness and understanding of this sensitivity is important for the design of FEL accelerator drivers involving generation and transportation of high-peak current electron beams by bunch compression chicanes.