Lcls beam dynamics studies with the 3-D parallel impact-T code

We present the beam dynamics studies with the 3-D parallel Impact-T code on the linac coherent light source (LCLS) injector system. The physics model and recent additions of the Impact-T code are reviewed, and the space charge simulation studies are described. Simulation results show that for the normal design parameters of the LCLS with a smooth laser profile, the space charge effects above 135 MeV are negligible. However, the electron bunch can form a very-high current spike after the bunch compressor. In this case space charge still play an important role in affecting the beam quality in both longitudinal and transverse directions.