Tangential magnetic field immersion of a hollow beam electron gun

Harris flow is one of a number of equilibrium electron beams requiring a launching method which imparts angular momentum to the stream. Immersion of the electron gun region in a magnetic field tangent to the cathode and orthogonal to the electron trajectories provides a means of rotation free of the defocusing and discontinuity effects of previous methods. Centrifugal-force spreading is eliminated by electric-field compensation in the gun. This compensation results in field lines at an angle to the stream edges and necessitates gun electrode design by a curvilinear flow method. An immersed gun of this kind has produced a stable Harris flow beam containing 86 per cent of the total energy in rotational motion. Anode transmission is in excess of 95 per cent.