Particle-in-cell simulations of plasma accelerators and electron-neutral collisions

We present 2D simulations of both beam- driven and laser- driven plasma wakefield accelerators, using the object- oriented particle- in- cell code XOOPIC, which is time explicit, fully electromagnetic, and capable of running on massively parallel supercomputers. Simulations of laser- driven wakefields with low (similar to 10(16) W/cm(2) ) and high (similar to 10(18) W/cm(2)) peak intensity laser pulses are conducted in slab geometry, showing agreement with theory and fluid simulations. Simulations of the E- 157 beam wakefield experiment at the Stanford Linear Accelerator Center, in which a 30 GeV electron beam passes through 1 m of preionized lithium plasma, are conducted in cylindrical geometry, obtaining good agreement with previous work. We briefly describe some of the more significant modifications to XOOPIC required by this work, and summarize the issues relevant to modeling relativistic electron- neutral collisions in a particle- in- cell code.