skip to main content
OSTI.GOV title logo U.S. Department of Energy
Office of Scientific and Technical Information

Title: Generation of harmonic frequencies and their effects in present day ICRF systems

Abstract

The whole TEXTOR-94 ICRF system circuit has been analyzed, partially modelled and studied at the fundamental operating frequency and, more important, at harmonic frequencies thereof. It has been found that without appropriate measures, present day systems and especially the TEXTOR ICRF system are prone to spurious generation of power at the second harmonic frequency. This leads either to erroneous activation of the reflected power safety protection or to highly increased (in some cases doubled) voltages in the transmission lines and antennas. As the voltage standing waves at the second harmonic displace the total voltage maxima in the transmission lines and antennas, this also explains why arcs are not always found at the expected voltage maxima for the fundamental frequency. The model is also able to give additional explanations why the ASDEX-Upgrade ICRF system has dramatically improved its power handling capabilities after the introduction of the '3dB coupler reflection compensation scheme'. The output of one of the TEXTOR transmitters has been fitted with a quarter wave length shorted stub which has no effect on the operation at the fundamental frequency but which effectively shorts out the second harmonic. It has to be noted that eg. the Tore Supra RDL antennas aremore » fitted with such a stub in the feeding transmission line whose function is to enter cooling water into the transmission line system. Hence, this could be the explanation of the apparent higher than average power handling capabilities of the TS antenna system. Experimental results clearly indicate a much improved operational power handling capability on plasma and an increased voltage stand-off when conditioning this antenna pair on vacuum. Limits have yet to be explored but already remarkable is the fact that since the installation of the quarter wavelength stub the reflected power safety system has been activated only once and furthermore so in poorly matched conditions.« less

Authors:
;  [1]
  1. Laboratorium voor Plasma Fysica-Laboratoire de Physique des Plasmas Associatie 'EURATOM-Belgische Staat'-Association -EURATOM-Etat Belge - Koninklijke Militaire School-Ecole Royale Militaire Renaissancelaan 30-B-1000 Brussels-30, Av. de la Renaissance (Belgium)
Publication Date:
OSTI Identifier:
21210507
Resource Type:
Journal Article
Journal Name:
AIP Conference Proceedings
Additional Journal Information:
Journal Volume: 485; Journal Issue: 1; Conference: 13. topical conference on radio frequency power in plasmas, Annapolis, MD (United States), 12-14 Apr 1999; Other Information: DOI: 10.1063/1.59707; (c) 1999 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); Journal ID: ISSN 0094-243X
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; AMPLIFIERS; ANTENNAS; ASDEX TOKAMAK; ELECTRIC POTENTIAL; HARMONIC GENERATION; ICR HEATING; PLASMA; PLASMA PRODUCTION; POWER TRANSMISSION LINES; REFLECTION; REFLECTIVITY; RF SYSTEMS; STANDING WAVES; TEXTOR TOKAMAK; TORE SUPRA TOKAMAK; WAVELENGTHS

Citation Formats

Durodie, F., and Vervier, M. Generation of harmonic frequencies and their effects in present day ICRF systems. United States: N. p., 1999. Web. doi:10.1063/1.59707.
Durodie, F., & Vervier, M. Generation of harmonic frequencies and their effects in present day ICRF systems. United States. doi:10.1063/1.59707.
Durodie, F., and Vervier, M. Mon . "Generation of harmonic frequencies and their effects in present day ICRF systems". United States. doi:10.1063/1.59707.
@article{osti_21210507,
title = {Generation of harmonic frequencies and their effects in present day ICRF systems},
author = {Durodie, F. and Vervier, M.},
abstractNote = {The whole TEXTOR-94 ICRF system circuit has been analyzed, partially modelled and studied at the fundamental operating frequency and, more important, at harmonic frequencies thereof. It has been found that without appropriate measures, present day systems and especially the TEXTOR ICRF system are prone to spurious generation of power at the second harmonic frequency. This leads either to erroneous activation of the reflected power safety protection or to highly increased (in some cases doubled) voltages in the transmission lines and antennas. As the voltage standing waves at the second harmonic displace the total voltage maxima in the transmission lines and antennas, this also explains why arcs are not always found at the expected voltage maxima for the fundamental frequency. The model is also able to give additional explanations why the ASDEX-Upgrade ICRF system has dramatically improved its power handling capabilities after the introduction of the '3dB coupler reflection compensation scheme'. The output of one of the TEXTOR transmitters has been fitted with a quarter wave length shorted stub which has no effect on the operation at the fundamental frequency but which effectively shorts out the second harmonic. It has to be noted that eg. the Tore Supra RDL antennas are fitted with such a stub in the feeding transmission line whose function is to enter cooling water into the transmission line system. Hence, this could be the explanation of the apparent higher than average power handling capabilities of the TS antenna system. Experimental results clearly indicate a much improved operational power handling capability on plasma and an increased voltage stand-off when conditioning this antenna pair on vacuum. Limits have yet to be explored but already remarkable is the fact that since the installation of the quarter wavelength stub the reflected power safety system has been activated only once and furthermore so in poorly matched conditions.},
doi = {10.1063/1.59707},
journal = {AIP Conference Proceedings},
issn = {0094-243X},
number = 1,
volume = 485,
place = {United States},
year = {1999},
month = {9}
}