A conceptual pre-injector design for the KEK-ERL test accelerator

A conceptual design for a test accelerator based on an energy recovery scheme is under way in developing a next generation light source at KEK. A high bright electron beam will be delivered from the test accelerator with a maximum energy of 200 MeV using 1.3 GHz superconducting accelerating cavities installed in two cryomodules. It is of great importance to design a pre-injector that can generate an electron beam with exceptionally high brightness and low emittances. A new simulation code is being developed to simulate the beam dynamics of the electron beam and to optimize the beam characteristics at the pre-injector. The simulation code describes semi-analytically the two-dimensional (transverse and longitudinal) beam dynamics of the electron beam based on a well-known envelope equation taking into account the space charge effect. The purpose of this code is not to rigorously simulate the particle dynamics, as is done by the particle tracking code “Parmela”, but rather to quickly optimize the design parameters of the accelerator components and beam characteristics themselves. This code has been validated by comparison with the results obtained from the “Parmela” code using the pre-injector design parameters. In this report, the development and some numerical results obtained from this new simulation code are presented in detail.