Experimental design for observation of long beam-plasma instabilities

Abstract

Depending on the electron beam parameters there can appear three beam-plasma instabilities which might be critical in beam-driven plasma wakefield accelerators. Those three instabilities are the self-modulation instability (SMI), hose instability (HI), and current filamentation instability (CFI) or for a long beam, oblique two-stream instability (OTSI), respectively. In majority of the cases, the classification of these instabilities is not clear unless any seed for an instability is given. As an experimental design, we suggest a simple switching method among the three instabilities by sweeping beam transverse emittance and radial size. Particularly, we investigate the mixed case of SMI and HI, and discuss the resonant condition of HI.