External Electron Injection for the AWAKE Experiment

We summarize and explain the realization of witness particle injection into wakefields for the Advanced WAKefield Experiment (AWAKE). In AWAKE, the plasma wakefields are driven by a self-modulating relativistic proton bunch. To demonstrate that these wake-fields can accelerate charged particles, we inject a 10-20 MeV electron bunch produced by a photo-injector. We summarize the experimental challenges of this injection process and present our plans for the near future.