Investigation of low energy space charge dominated beam bunching

摘要

The dynamics of low energy space-charge-dominated beam bunching is studied self-consistently considering different beam distributions in the transverse phase space and a uniform distribution in longitudinal direction with a Gaussian energy spread. We have developed a 3D Particle-in-Cell (PIC) code for this purpose. The evolution of rms beam size and emittance growth during the bunching has been obtained. The average behaviour of the rms beam size and relative increase in the bunch current agrees with the results of disc-envelope equation model. The detail investigation of evolution of rms emittance in the transverse direction shows considerable increase in the emittance of the bunch at the time focus even in the case of KV distribution. The relative increase of current in the different portions of the bunch is found to be almost independent of transverse beam distribution. Simulations indicate considerable emittance growth with the nonlinearity of space charge force caused due to non-uniform beam distribution in transverse phase space and energy spread in the longitudinal direction.%Space charge effect; Particle-in-cell method; Bunching; Emittance growth