An Ultra-Short Dense Paraxial Bunch of Sub-Relativistic Runaway Electrons

This letter reports new results on the formation of a paraxial flow of runaway electrons emitted in an elongated air gap near the tip of a conical steel cathode. In the axial magnetic field > 4 T, the peak current density of ≈ 0.6 kA/cm2 has been achieved in the bunch core with a 0.7 mm diameter. Similarly to the vacuum case, dependence of the bunch parameters on the magnetic field w...