Wang, L. Emma, P. Qiang, J. Raubenheimer, T.O. TUP066 space-charge wakefield linac optics undulator 2015 2015-12 The beam dynamics codes ELEGANT and IMAPCT have many users. We use these two codes for the design of LCLSII. Both codes use a 1D model for the coherent synchrotron radiation (CSR) in bend magnets. In addition, IMPACT has a 3D space-charge model, while ELEGANT uses a 1D model. To compare the two codes, especially the space-charge effects, we systematically benchmark the two codes with different physics aspects: wakefields, CSR and space-charge forces.