Characteristics of a transient axial mode from the formation of anode plasma in a gigawatt-class L-band magnetically insulated transmission line oscillator

Abstract

An experimental result of a gigawatt-class L-band magnetically insulated transmission line oscillator (MILO) shows the generation of a transient axial mode pertaining to an anode plasma effect in the circuit of the MILO. The transient axial mode between the desired π mode and the 5π/6 mode causes the output power to become eccentric. When the electrons impact onto the metallic surface, plasma exists on the surface of the anode due to the electron-impact distortion process. As a result, the anode plasma causes the emitted current to increase the neutralization near the cathode. The increase of the current induces faster and stronger magnetic insulation, which lowers the drift velocity and suppresses the mode earlier during the beam pulse. After the 5π/6 mode, which initially interacts with the electron beam, remains as a transient axial mode for a very short time, it shows the capability to convert to the π mode, which is more stable and slowly grows.