Particle Beam Waist Location in Plasma Wakefield Acceleration

The role of beam waist location in interactions between a plasma and a particle beam is not yet fully understood. Nonlinear effects within the plasma make an analysis of such interactions difficult. I present five simulations in which I vary the waist location of a beam of ultra-relativistic electrons propagating through one meter of self-ionized lithium plasma. The simulation parameters are chosen to model the recent experiment 167 at the Stanford Linear Accelerator, relevant to the design of future plasma wakefield accelerating afterburners. I find that beams focused near the point of entry into the plasma propagate further into the plasma and accelerates witness particles to a greater maximum energy before disintegrating. These results could indicate that ion channel formation is dependent on the drive beam waist location and that the plasma accelerating medium can have an observable effect on the focusing of the drive beam.