 Much denser plasmas can be created using inductive discharges, in which an inductive coil excited with a high-frequency signal induces an electric field within the discharge, accelerating electrons in the plasma itself rather than just at the sheath edge.Electron cyclotron resonance reactors and helicon wave antennas have also been used to create high-density discharges.Excitation powers of 10 kW or more are often used in modern reactors.