Effects of space charge in a compact superconducting energy recovery linac with a low energy

The Energy Recovery Linac (ERL) is one of the candidates for the next generation light sources, which is based on the 1.3 GHz superconducting radio frequency (SRF) linear accelerator. The ERL can produce high brilliance synchrotron radiation and a short pulse beam. We investigated the beam dynamics in the compact-Energy Recovery Linac (c-ERL) with a beam energy of 35 MeV, which is a prototype of the 5 GeV ERL at KEK. One of the main goals of our studies on the c-ERL is the emittance compensation in the merger section to achieve an emittance smaller than 1.0 mm mrad.In the case of the early commissioning phase, the injector system produces electron bunches of 5 MeV with a repetition rate of 1.3 GHz. The compensation of the emittance growth due to the space charge effect was investigated in order to achieve a small emittance at the exit of the merger. We discuss the results of a method to compensate the emittance growth which is based on beam envelope matching between the betatron function and the linear dispersion induced by the space charge force. We investigated the space charge effect when the beam energy in the superconducting RF section was changed. The effect of space charge in the arc section was also investigated. It is shown that the space charge effect in the c-ERL is an important source of distortion of the optics function. In this paper, we show the results on the analysis of the effect of space charge in the compact-ERL at KEK which has a low-energy beam.