A mode converter to generate a Gaussian-like mode for injection into the VENUS electron cyclotron resonance ion source

Journal Article · Sat Feb 15 00:00:00 EST 2014 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.4832064· OSTI ID:22253913

Benitez, J.; Hodgkinson, A.; Strohmeier, M.; Todd, D. ^[1]; Plaum, B. ^[2]; Thuillier, T. ^[3]

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1. Nuclear Science Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720 (United States)
2. Institut für Grenzflächenverfahrenstechnik und Plasmatechnologie (IGVP), Stuttgart (Germany)
3. Laboratoire de Physique Subatomique et de Cosmologie, Université Joseph Fourier Grenoble 1, CNRS/IN2P3, Institut Polytechnique de Grenoble, 53 rue des martyrs 38026 Grenoble cedex (France)

A number of superconducting electron cyclotron resonance (ECR) ion sources use gyrotrons at either 24 or 28 GHz for ECR heating. In these systems, the microwave power is launched into the plasma using the TE{sub 01} circular waveguide mode. This is fundamentally different and may be less efficient than the typical rectangular, linearly polarized TE{sub 10} mode used for launching waves at lower frequencies. To improve the 28 GHz microwave coupling in VENUS, a TE{sub 01}-HE{sub 11} mode conversion system has been built to test launching HE{sub 11} microwave power into the plasma chamber. The HE{sub 11} mode is a quasi-Gaussian, linearly polarized mode, which should couple strongly to the plasma electrons. The mode conversion is done in two steps. First, a 0.66 m long “snake” converts the TE{sub 01} mode to the TE{sub 11} mode. Second, a corrugated circular waveguide excites the HE{sub 11} mode, which is launched directly into the plasma chamber. The design concept draws on the development of similar devices used in tokamaks and stellerators. The first tests of the new coupling system are described below.

• OSTI ID: 22253913
• Journal Information: Review of Scientific Instruments, Vol. 85, Issue 2; Conference: ICIS 2011: 14. international conference on ion sources, Giardini-Naxos, Sicily (Italy), 12-16 Sep 2011; Other Information: (c) 2013 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

70 PLASMA PHYSICS AND FUSION TECHNOLOGY
ECR HEATING
ECR ION SOURCES
ELECTRON CYCLOTRON-RESONANCE
GHZ RANGE 01-100
MICROWAVE AMPLIFIERS
MICROWAVE RADIATION
MODE CONVERSION
PLASMA
TOKAMAK DEVICES
WAVEGUIDES