title: Radiofrequency antenna for suppression of parasitic discharges in a helicon plasma thruster experiment.
abstract: A radiofrequency (rf) antenna for helicon plasma thruster experiments is developed and tested using a permanent magnets helicon plasma source immersed in a vacuum chamber. A magnetic nozzle is provided by permanent magnets arrays and an argon plasma is produced by a 13.56 MHz radiofrequency helicon-wave or inductively-coupled discharge. A parasitic discharge outside the source tube is successfully suppressed by covering the rf antenna with a ceramic ring and a grounded shield; a decrease in the ion saturation current of a Langmuir probe located outside the source tube is observed and the ion saturation current on axis increases simultaneously, compared with the case of a standard uncovered rf antenna. It is also demonstrated that the covered antenna can yield stable operation of the source.
authors.affiliation: Department of Electrical Engineering and Computer Science, Iwate University, Morioka 020-8551, Japan. kazunori@iwate-u.ac.jp
authors.forename: Kazunori
authors.initials: K
authors.lastname: Takahashi