John G. Leopold - Video Lecture

John G. Leopold - Video Lecture

IVS-IPSTA 2020 Online Conference December 13, 2020

Morning Plasma Session
Session chair:
Yoav Hadas

RAFAEL, Israel

A split-cathode as a novel type of virtual electron source for relativistic magnetrons

John G. Leopold

Pulse power and plasma laboratory, Faculty of Physics, Technion, Israel


In relativistic magnetrons coaxial with the cathode, the plasma evolving from the cathode exploding emission surface propagates towards the magnetron anode causing pulse shortening of the generated high-power microwaves. It is possible to place a cathode upstream from the magnetron body and use only the magnetized beam as the electron source. An elegant solution to use this electron beam is to use a new type of structure: A split cathode. The cathode with its emitting surface placed upstream from the magnetron, is held on axis by a rod. A reflector, i.e. a conducting circular plate, is placed downstream from the magnetron and is attached to the cathode by an additional thin conducting axial rod. This entire structure is at, or near the cathode potential, so the beam is decelerated near and reflected from the reflector surface. The electrons are trapped in the space between the cathode and the reflector, and the connecting rod does not emit electrons because the beam screens it. The accumulating charge in this split cathode becomes the relativistic magnetron’s electron source.