Coupling between multiple antennas through a plasma cylinder

The coupling physics between multiple antennas separated axially along a plasma cylinder is investigated. Experiments are carried out on a recently built device: Physics ANd Thruster oriented HElicon Research (PANTHER), with an upgrade of second-stage antennas. Mutual induction currents are measured in detail. It is found that the existence of plasma column going through these antennas increase the coupling effects among them significantly. Theoretical analyses from the perspectives of transformer and magnetic permeability and moment confirm the reasonability of this phenomenon. This work is of particular interest for electrodeless plasma source or thruster which employs multiple antennas for ionisation and acceleration.