2013 Volume 8 Pages 1406167
High-power electromagnetic waves propagating in a negative-permeability space were investigated theoretically and experimentally, and they generated overdense plasmas successfully. Theoretical analysis predicted that high-density plasmas with negative permittivity can form via saddle-node bifurcations within an adequate electric field. To confirm theoretical predictions, using metamaterials with negative permeability achieved by magnetic resonances, we injected microwaves with several hundreds of watt into a waveguide filled with a low-pressure discharge gas. Langmuir probe measurement revealed that a generated plasma is well beyond the cutoff density for the wave frequency of 2.45 GHz, and indicated transition between positive-permittivity (low-electron-density) and negative-permittivity (overdense) states.