Propagation of short electron pulses in underdense plasmas

Our program for an experimental plasma wake field accelerator (PWFA) to take place at the Argonne Wakefield Accelerator (AWA) facility, in the recently proposed blow-out regime relies on the propagation of an intense electron beam through an underdense plasma with a minimum of degradation. This paper presents a near-equilibrium model of beam propagation using the Maxwell-Vlasov equations governing the beam´s transverse behavior. Numerical results are presented which use this model simultaneously with the plasma electron cold fluid equations. A solenoidal magnetic field, which is necessary for high density plasma containment, also provides an initial beam equilibrium to begin the calculation. We compare the equilibrium model with a discrete beam particle simulation, which verifies the basic conclusions of the equilibrium model, and shows the collisionless damping approach to equilibrium in the beam head. The initial matching requirements for the beam´s entry into the plasma are examined. We also discuss the possibility of performing an adiabatic lens experiment