Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1MHz

D. Rauner, S. Mattei, S. Briefi, U. Fantz, A. Hatayama, J. Lettry, K. Nishida, M. Q. Tran

Research output: Chapter in Book/Report/Conference proceedingConference contribution

1 Citation (Scopus)

Abstract

The power requirements of RF heated sources for negative hydrogen ions in fusion are substantial, which poses strong demands on the generators and components of the RF circuit. Consequently, an increase of the RF coupling efficiency would be highly beneficial. Fundamental investigations of the RF efficiency in inductively coupled hydrogen and deuterium discharges in cylindrical symmetry are conducted at the lab experiment CHARLIE. The experiment is equipped with several diagnostics including optical emission spectroscopy and a movable floating double probe to monitor the plasma parameters. The presented investigations are performed in hydrogen at a varying pressure between 0.3 and 10 Pa, utilizing a conventional helical ICP coil driven at a frequency of 1MHz and a fixed power of 520W for plasma generation. The coupling efficiency is strongly affected by the variation in pressure, reaching up to 85% between 1 and 3 Pa while dropping down to only 50% at 0.3 Pa, which is the relevant operating pressure for negative hydrogen ion sources for fusion. Due to the lower power coupling, also the measured electron density at 0.3 Pa is only 5 · 1016 m-3, while it reaches up to 2.5 · 1017 m-3 with increasing coupling efficiency. In order to gain information on the spatially resolved aspects of RF coupling and plasma heating which are not diagnostically accessible, first simulations of the discharge by an electromagnetic Particle-In-Cell Monte Carlo collision method have been conducted and are compared to the measurement data. At 1 Pa, the simulated data corresponds well to the results of both axially resolved probe measurements and radially resolved emission profiles obtained via OES. Thereby, information regarding the radial distribution of the electron density and mean energy is provided, revealing a radial distribution of the electron density which is well described by a Bessel profile.

Original languageEnglish
Title of host publication5th International Symposium on Negative Ions, Beams and Sources, NIBS 2016
EditorsDan Faircloth
PublisherAmerican Institute of Physics Inc.
ISBN (Electronic)9780735415492
DOIs
Publication statusPublished - 2017 Aug 9
Event5th International Symposium on Negative Ions, Beams and Sources, NIBS 2016 - Oxford, United Kingdom
Duration: 2016 Sep 122016 Sep 16

Publication series

NameAIP Conference Proceedings
Volume1869
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

Other5th International Symposium on Negative Ions, Beams and Sources, NIBS 2016
CountryUnited Kingdom
CityOxford
Period16/9/1216/9/16

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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    Rauner, D., Mattei, S., Briefi, S., Fantz, U., Hatayama, A., Lettry, J., Nishida, K., & Tran, M. Q. (2017). Investigation of the RF efficiency of inductively coupled hydrogen plasmas at 1MHz. In D. Faircloth (Ed.), 5th International Symposium on Negative Ions, Beams and Sources, NIBS 2016 [030035] (AIP Conference Proceedings; Vol. 1869). American Institute of Physics Inc.. https://doi.org/10.1063/1.4995755