Beam dynamics investigations for the second injection beamline of MESA

Abstract

The project MESA (Mainz Energy-Recovering Superconducting Accelerator) is an unique electron accelerator placed at the Johannes Gutenberg University in Mainz, Germany. MESA will be a recirculating machine that achieves energy recovery in superconducting accelerating structures through multiple turns. The goal of the MESA project is to conduct experiments in many fields, such as particle physics, nuclear physics and other fundamental research. The accelerator has two different laser-driven electron sources (polarized and unpolarized) operating at 100 kV . The main polarized source STEAM (Small Thermalized Electron-source at Mainz) allows to produce spin-polarized electron beam and has been operating since the end of 2023. A second source MIST (MESA Injector Source Two) is planned for construction in the future. The peculiarity of the second source is that it was designed to produce electron beam with a high charge in the bunch. In future, this source and double Mott polarimeter will be arranged on the same height above the MESA main injector beamline. Therefore, a special parallel shifting beamline is required to transport a highly charged electron beam from the source MIST to the main MESA beamline. This work is dedicated to the design of such a transport channel. Simulations shown that the designed channel allow to compress and transport electron beam to the first acceleration section of MESA with up to 10mA of average current, which corresponds to charge of 7.7 pC in a bunch for an operating frequency 1.3 GHz.