Behavior of low-impedance relativistic electron diodes in converging magnetic gradients

The behavior of a large-area field emission diode located in a 4:1 converging magnetic gradient is described. Evidence is presented that this technique significantly reduces the early-time L/R decay into the nominal 3/4 Ω space-charge-limited impedance characteristic. The elimination of late-time plasma closure in the diode gap is also demonstrated. Due to these characteristics, a significant reduction in the time-averaged diode impedance and an improvement in the pulse-line--diode energy transfer efficiency has been obtained: thereby permitting first observations of efficient matching to a sub-ohm pulsed electron accelerator