Coupling between multiple coaxial antennas surrounding a plasma column produced by helicon antenna

Abstract

AbstractThe coupling physics between multiple coaxial antennas separated axially along plasma column produced by helicon antenna are investigated. Experiments are carried out on a recently built device, named Physics ANd Thruster oriented HElicon Research (PANTHER) with the upgrade of second‐stage antennas. Mutual induction currents on these antennas are measured for two cases: without plasma discharge and with plasma discharge, respectively. It is found that the existence of a plasma column going through these antennas increases the coupling effects among them significantly. Theoretical analyses from the perspectives of transformer and magnetic permeability and moment confirm the reasonability of this phenomenon. Equivalent circuit models and governing equations are provided for preliminary analyses, covering both single‐antenna‐driven cases and dual‐antenna‐driven cases. The effects of confining magnetic field and background pressure on the mutual coupling are shown as well. This work is of particular interest for electrodeless plasma source or thruster which employs multiple coaxial antennas for ionization and acceleration. The analogy of a plasma column going through multiple antennas to a magnetic core for a transformer is an innovative attempt.