Assessing Magnetic Insulation in a Crossed-Field Gap

Crossed-field devices (CFDs), which have an external magnetic field perpendicular to the electric field, are important in many applications, including high power microwaves and directed energy. One critical quantity for characterizing CFDs is the Hull cutoff (HC) magnetic field, which corresponds to the maximum magnetic field for an electron emitted from the cathode to reach the anode [1] . CFDs with magnetic fields above the HC are referred to as magnetically insulated. Theory demonstrated that placing ions in the gap increased the distance that an emitted electron traveled from the cathode [2] . Subsequent simulations demonstrated the loss of magnetic insulation for sufficiently high pressures [3] .