The folded waveguide: a high frequency rf launcher

Haste, G. R.; Baity, F. W.; Barber, G. C.; Bigelow, T.; Carter, M.D.; Goulding, R. H.; Hoffman, D. J.; Ryan, P. M.; Shepard, T. D.

doi:10.1016/0920-3796(94)90045-0

Cited by 11 publications

(10 citation statements)

References 10 publications

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“…The MAntIS code has been used to model very complicated antenna structtu'es, such as the folded waveguide [5,6], by superimposing many basic current elements. However, to illustrate the use of some of the code's features, a simple current strap with feeders and finite phase velocity v¢ along the main strap is presented here.…”

Section: Resultsmentioning

confidence: 99%

“…This coupling is far below the design requirement and demonstrates the difficulties involved in using a standard loop antenna design to couple power to the FT-U plasma. Extensive modelling using MAntIS for a folded waveguide launching structure has shown the folded waveguide technology to be a possible solution to the problem of large electric fields when coupling RF power to the FT-U plasma [5,6]. where j m,n is defined by Eq.…”

Section: Resultsmentioning

confidence: 99%

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Multiple Antenna Implementation System (MAntIS)

D¹,

Batchelor²,

Jaeger³

1993

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The MAntIS codewas developed as an aidtothedesignofradiofrequency (RF) antennas forfusion applications. The codesolves fortheelectromagnetic fields in threedimensions • near the antenna structure with a realistic plasma load. Fourier analysis is used in the two dimensions that are tangential to the plasma surface and backwall. The third dimension is handled analytically in a vacuum region with a general impedance match at the plasma-vacuum interface. The impedance tensor is calculated for a slab plasma using the ORION-lD code [JAEGER, E.F., BATCHELOR, D.B., WEITZNER, H., Nuclear Fusion 28 (I988) 53] with all three electric field components included and warm plasma correct._ons. The code permits the modelling of complicated antenna structures by superposing currents that flow on the surfaces of rectangular parallelepipeds. Specified current elements have feeders that continuously connect the current flowing from the ends of the strap to the feeders. The elements may have an arbitrary orientation with respect to the static magnetic field. Currents are permitted to vary along the length of the current strap and feeders. Parameters that describe this current variation can be adjusted to approximately satisfy boundary conditions on the current elements. The methods used in MAntiS and results for a preliminary loop antenna design are presented.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Multiple Antenna Implementation System (MAntIS)

D¹,

Batchelor²,

Jaeger³

1993

Self Cite

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“…The second feeder option permits both standing wave and traveling wave currents with wavelength 2aw to flow on the feeder elements. This option has been used primarily for folded waveguide modeling [7,8].…”

Section: Appendix: Amentioning

confidence: 99%

“…This boundary condition is equivalent to a conducting backwaU for standing waves where _ = 0, but it permits power carried by the traveling wave to flow through the backwall when _ ¢ 0. This combination has been used to model folded waveguide antenna structures [7,8] primarily for _ = 0. In terms of these Region I eoeftieients, the electric fields in Region I along with the particular solutions for existing feeder options are given by Eq.…”

Section: Appendix: Amentioning

confidence: 99%

Three-dimensional effects for radio frequency antenna modeling

Carter¹,

Batchelor²,

Stallings

1994

AIP Conference Proceedings

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Electromagneticfield calc_ationsforradio frequency(rf)antennas in two dimensions (2-D) neglectfinite antenna lengtheffects as wellas thefeedersleadingto the main current. strap.Comparisons with experimentsindicate that these 2-D calculations can overestimate the loadingof the antenna and fail to givethe correctreactive behavior.The 2-D calculationsalsopredictthat the returncurrentsin the sidewalls of the antenna structuredepend stronglyon plasma parameters,but thisprediction isalsosuspectbecause of experimental evidence. To study the validity of the 2-D approximation,the MultipleAntenna Implementation System (MAntIS) has been used to perform 3-D modeling of the power spectrum, plasma loading,and inductancefora relevant loop antenna design.Effects on antenna performance caused by feedersto the main currentstrap,conductingsidewalls, and finite phase velocity are considered.The plasma impedance matrix for the loadingcalculation is generatedby use of the ORION-ID code. The 3-D model isbenchmarked with the 2-D model in the 2-D limit. For finite-length antennas,inductance calculations are found to be in much more reasonable agreement with experiments for 3-D modeling than for the 2-D estimates. The modeling shows that the feeders affect the launchedpower spectrum in an indirect way by forcingthe drivenrf currentto returnin the antenna sidewalls ratherthan in the plasma as in the 2-D model. Thus, the feedershave much more influence than the plasma on the currentsthatreturnin the sidewall. It has alsobeen found thatpoloidaldependenciesin the : plasma impedance matrix can reducethe loadingfrom that predictedin the 2-D model. For some plasma parameters,the combined 3-D effects can lead to a reductionin the predicted loading by as much as a factorof 2 from that given by the 2-D model.

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“…A relationship between the polarizing plate magnetic field and internal electric fields can be estimated using the MANTIS code and also the numerical codes. Laboratory measurements of the FWG fields can be used to check these results [8].…”

Section: Fwg-plasma Interactionmentioning

confidence: 99%

RF modeling and design of a folded waveguide launcher for the Alcator C-Mod tokamak

Bigelow

Fogelman

Baity

et al.

15th IEEE/NPSS Symposium. Fusion Engineering

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The folded waveguide (FWG) launcher is being investigated as an improved antenna configuration for plasma heating in the ion cyclotron range of frequencies (ICRF). A development FWG launcher was successfully tested at Oak Ridge National Laboratory (ORNL) with a low-density plasma load and found to have significantly greater power density capability than current strap-type antennas operating in similar plasmas. To further test the concept on a high density tokamak plasma, a collaboration has been set up between ORNL and Massachusetts Institute of rechnology (MIT) to develop and test an 80-MHz, 2-MW FWG on the Alcator C-Mod tokamak at MIT.The radio frequency (rf) electromagnetic modeling techniques and laboratory measurements used in the design of this antenna are described in this paper.A companion paper [l] describes the mechanical design of the FWG.

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The folded waveguide: a high frequency rf launcher

Cited by 11 publications

References 10 publications

Multiple Antenna Implementation System (MAntIS)

Multiple Antenna Implementation System (MAntIS)

Three-dimensional effects for radio frequency antenna modeling

RF modeling and design of a folded waveguide launcher for the Alcator C-Mod tokamak

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