An electron injector for the Electron-Ion Collider based on proton-driven plasma wakefield acceleration
We describe an electron bunch injector scheme based on proton-driven plasma wakefield acceleration for the Electron-Ion Collider. The proton bunches are assumed to have the same energy as those used in the EIC, and the polarized electron source is that used in the current EIC design. We describe the different elements making up the injection scheme and give an estimate for the performance. Using a novel top-up injection scheme for electrons, the charge in the ring is accumulated over many injection events, avoiding deleterious beamloading in the proton-driven wakefield stage and allowing the polarization in the ring to be maintained. Our initial study indicates that for electron bunches at 10 GeV, 1160 bunches can be stored in the ring over a 10-hour period with an average bunch charge of 19.3 nC and an average polarization of 75.8 %, representing 69 % of the EIC design specification for charge and exceeding the specification for polarization. Operation at 18 GeV is achieved by shortening the electron beam lifetime to increase the average polarization. Paths to improve upon these results are identified.