Relativistic electron beam transport in high pressure gases: a warm fluid treatment of nose physics

At the beam head of an ultrarelativistic electron beam propagating through an initially neutral dense gas, the radial defocusing electrostatic force is nearly cancelled by the self-magnetic pinching force. The beam head is thus almost force fee and suffers Nordsieck expansion at a rate governed by the beam emittance. Downstream, owing to the axial inductive electric field driven in the secondary plasma, beam electrons lose energy and spread out. This ohmic erosion combines with that of Nordsieck. The authors have carried out a numerical study of the beam. The warm fluid treatment of the nose physics allows the beam to have its profile distorted while being less time consuming than a particle code.<>