Mitigation Techniques for Witness Beam Hosing in Plasma - Based Acceleration

We present three methods for mitigating the hosing of the witness beam in plasma wakefield acceleration (PWFA) experiments. We will look at a specific case with parameters similar to what will be used in FACET-II (Facility for Advanced Accelerator Experimental Tests). First, we examine adding an energy chirp to the witness beam and how the loading of the beam affects the growth of the energy spread. Next, we look at how an asymmetric (elliptical) drive beam can suppress the hosing of the witness beam by making the focusing force vary along the propagation direction. Finally, we look at the regime where ion collapse from the drive beam suppresses the hosing of the witness beam.