FACET Beam Ionization Injection Technique Advantages and Challenges*

Beam-driven Plasma Wakefield Accelerators (PWFAs) can sustain accelerating gradients that surpass those of standard accelerators. In the PWFA technique called “Beam Induced Ionization Injection” (BIII) a mismatched beam excites the wakefields while performing betatron oscillations. During each betatron cycle, the beam space charge fields exceed the high ionization thresholds of gas impurities and inject their electrons into the wake’s accelerating phase. By correctly positioning the impurity gas, it is possible to produce a single, high-quality accelerated beam. Moreover, if the impurity section encompasses several cycles, a multi-colored beam of electrons with narrow energy spread can be generated. Although BIII can produce low energy spread beams through beam-loading, the required charge ionizes and injects an additional low quality “inception beam”. Here we will discuss different BIII scenarios modeled with Particle in Cell code OSIRIS [R.A.Fonseca et al., LNCS (2331) 342, 2002]. We will show the BIII formation of single accelerated beams, multi-colored beams and the impact of “inception beams” on beam quality.