Study of longitudinal phase space for typical beam injector via analytical method

Abstract

Longitudinal phase space (LPS) manipulation for high-brightness electron beams is critical for successful development of photocathode injectors, especially those are expected to generate ultra-short bunches. Compared with commonly used schemes involving dedicated devices and complicated peripheral sub-systems, a convenient approach for LPS linearization, which is based on adjusting injecting RF phase, has advantages in the typical injectors those consisting of RF cavities and a drift tube. Therein, instead of conventional higher-order harmonic cavities, natural evolutions in the following drift space have been applied to compensate nonlinearity of the LPS from the injector. Since adequate characterizations for the LPS are of importance to promote the application of such approach, elaborate analytical derivations from a new view have been conducted to demonstrate the manipulation scheme, and numerical simulations have been performed to further validate the theoretical results. Contributions of inevitable phase slippages have also been analyzed via analytical and numerical methods. Additionally, to cross-check the analysis results, multi-particle simulations have been performed as well. All of the results indicate that the LPS of the typical injector can be linearized through the natural evolutions during the drifting process. Then such method presents to be a conceivable supplement to conventional LPS manipulation approaches.