Coherent synchrotron radiation free longitudinal bunch shaping using transverse deflecting cavities

Abstract

Longitudinal bunch shaping is gaining increasing attention due to the large impact it has on modern accelerators. The existing methods for controlling the density profile fall into three categories: laser shaping, emittance exchange, or correlations between the energy and one of the other coordinates. These methods require either (i) dispersive elements (e.g., dipole magnet), which generate coherent synchrotron radiation, or (ii) shaping near the cathode, which can distort the profile due to space-charge effects. These collective effects significantly decrease shaping quality as the bunch charge increases. None of the existing methods are currently capable of shaping high-charge bunches. In this paper, we introduce a transverse deflecting cavity-based shaping method to avoid the impact of collective effects on the shaping process. In this method, a transverse deflecting cavity introduces the z-x correlation, and a transverse mask tailors the longitudinal density profile. This method provides high-quality shaping regardless of charge level and preserves the beam quality.