Publications Details

Controlling hollow relativistic electron beam orbits with an inductive current divider

Swanekamp, S.B.; Richardson, A.S.; Angus, J.R.; Cooperstein, G.; Hinshelwood, D.D.; Ottinger, P.F.; Rittersdorf, I.M.; Schumer, J.W.; Weber, B.V.; Zier, J.C.

A passive method for controlling the trajectory of an intense, hollow electron beam is proposed using a vacuum structure that inductively splits the beam's return current. A central post carries a portion of the return current (I₁), while the outer conductor carries the remainder (I₂). An envelope equation appropriate for a hollow electron beam is derived and applied to the current divider. The force on the beam trajectory is shown to be proportional to (I₂-I₁), while the average force on the envelope (the beam width) is proportional to the beam current I_b = (I₂ + I₁). The values of I₁ and I₂ depend on the inductances in the return-current path geometries. Proper choice of the return-current geometries determines these inductances and offers control over the beam trajectory. As a result, solutions using realistic beam parameters show that, for appropriate choices of the return-current-path geometry, the inductive current divider can produce a beam that is both pinched and straightened so that it approaches a target at near-normal incidence with a beam diameter that is on the order of a few mm.