Helicon Plasma Discharge in a Toroidal Magnetic Field of the Tokamak

A helicon wave plasma (HWP) discharge in an experimental advanced superconducting tokamak device with a toroidal magnetic field of 2 T is investigated. The HWP with an electron density of
$10^{12}\ \hbox{cm}^{-3}$
was produced with two 4-turn flat spiral antennas in series that are perpendicular to the toroidal magnetic field and driven by a 13.56-MHz radio-frequency (RF) source at a power of 1500 W, a toroidal magnetic field of 2 T, and a pressure (helium) of 1 Pa. The increase of the toroidal magnetic field from 0.5 to 2 T, the increase of the RF power from 500 to 1500 W, and the decrease of the pressure (helium) from 1 to 0.01 Pa were found to improve the plasma uniformity from the CCD images.