Efficient coupling of thermal electron Bernstein waves to the ordinary electromagnetic mode on the National Spherical Torus Experiment

Taylor, G.; Efthimion, P. C.; LeBlanc, B.; Carter, M. D.; Caughman, J. B. O.; Wilgen, J. B.; Preinhaelter, J.; Harvey, R. W.; Sabbagh, S. A.

doi:10.1063/1.1891065

Cited by 24 publications

(15 citation statements)

References 28 publications

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“…Recently, obliquely-viewing, dual polarization radiometry has been employed on NSTX to evaluate the coupling efficiency of 16-18 GHz thermal EBW emission [10]. An EBW coupling efficiency 80±20% was achieved in good agreement with ~ 65% coupling efficiency predicted by a numerical model that included a 1-D full wave calculation of the EBW mode conversion layer, radiometer antenna pattern modeling and 3-D EBW ray tracing and deposition modeling [19].…”

Section: Ebw Coupling Calculations and Measurementsmentioning

confidence: 62%

“…Another goal of NSTX EBW research is to establish a viable and resilient technique for efficiently coupling rf power to EBWs in the plasma. Recent radiometric thermal EBW emission data acquired on NSTX [10] support efficient EBW coupling via O-mode launch oblique to the confining magnetic field [11]. These thermal EBW coupling experiments and the associated numerical EBW modeling research support the design and implementation of a proof-of-principle, 1 MW, 28 GHz EBW heating and CD system planned for NSTX.…”

Section: Introductionmentioning

confidence: 99%

“…Assuming that the EBWCD system needs to generate ~ 100 kA of plasma current [2], that the microwave coupling efficiency to EBWs is 90% [10] and that the waveguide transmission loss is 10-15%, 4 MW of microwave source power would be needed in order to deliver the necessary 3 MW of EBW power into the plasma. Four EBW steerable mirror launchers will couple microwave power into the plasma.…”

Section: Plans For Ebwcd On Nstxmentioning

confidence: 99%

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Electron Bernstein Wave Research on the National Spherical Torus Experiment

Taylor¹,

Bers²,

Bigelow³

et al. 2005

AIP Conference Proceedings

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Abstract. Off-axis electron Bernstein wave current drive (EBWCD) may be critical for sustaining non-inductive high β NSTX plasmas. Numerical modeling results predict that the ~ 100 kA of offaxis current needed to stabilize a solenoid-free high β NSTX plasma could be generated via Ohkawa CD with 3 MW of 28 GHz EBW power. In addition, synergy between EBWCD and bootstrap current may result in a 10% enhancement in CD efficiency with 4 MW of EBW power. Recent dualpolarization EBW radiometry measurements on NSTX confirm that efficient coupling to EBWs can be readily accomplished by launching elliptically polarized electromagnetic waves oblique to the confining magnetic field, in agreement with numerical modeling. Plans are being developed for implementing a 1 MW, 28 GHz proof-of-principle EBWCD system on NSTX to test the EBW coupling, heating and CD physics at high rf power densities.

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Section: Ebw Coupling Calculations and Measurementsmentioning

confidence: 62%

Section: Introductionmentioning

confidence: 99%

Section: Plans For Ebwcd On Nstxmentioning

confidence: 99%

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Electron Bernstein Wave Research on the National Spherical Torus Experiment

Taylor¹,

Bers²,

Bigelow³

et al. 2005

AIP Conference Proceedings

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“…A promising EBW scenario is identified at 28 GHz with the O-X-B coupling scenario where the EBW emission measurements suggests an efficient coupling of EBW for this scenario. (68) O-X-B coupling appears to be more suitable for high power EBW experiments since it is only mildly sensitive to variation in the edge density gradient and the coupling resiliency can be further improved by polarization adjustments. NSTX plans to develop a 1 MW 28 GHz EBW system as at high priority in the near future.…”

Section: Electron Bernstein Waves For Current-profile Control -mentioning

confidence: 99%

Status and Plans for the National Spherical Torus Experimental Research Facility

Ono

Bell

et al. 2005

IEEJ Trans. FM

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An overview of the research capabilities and the future plans on the MA-class National Spherical Torus Experiment (NSTX) at Princeton is presented. NSTX research is exploring the scientific benefits of modifying the field line structure from that in more conventional aspect ratio devices, such as the tokamak. The relevant scientific issues pursued on NSTX include energy confinement, MHD stability at high β, non-inductive sustainment, solenoid-free start-up, and power and particle handling. In support of the NSTX research goal, research tools are being developed by the NSTX team. In the context of the fusion energy development path being formulated in the US, an ST-based Component Test Facility (CTF) and, ultimately a high β Demo device based on the ST, are being considered. For these, it is essential to develop high performance (high β and high confinement), steady-state (non-inductively driven) ST operational scenarios and an efficient solenoid-free start-up concept. We will also briefly describe the Next-Step-ST (NSST) device being designed to address these issues in fusion-relevant plasma conditions.

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“…Electron Bernstein wave heating (EBWH), using the O-X-B double mode conversion scheme, was successfully demonstrated in the W7-AS stellarator [12], with injection into a high density high (HDH) confinement mode. Electron Bernstein emission (EBE) measurements in spherical, low aspect-ratio tokamaks and in reversed field pinches are reported in [13][14][15]. High field side (HFS) launch Bernstein wave heating was demonstrated in a tokamak using the X-B scheme [16], but this scheme is limited by the left-hand X-mode cut-off in practical applications.…”

Section: Introductionmentioning

confidence: 99%

Electron Bernstein wave heating of over-dense H-mode plasmas in the TCV tokamak via O-X-B double mode conversion

et al. 2007

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This paper reports on the first demonstration of electron Bernstein wave heating (EBWH) by double mode conversion from ordinary (O-) to Bernstein (B-) via the extraordinary (X-) mode in an over-dense tokamak plasma, using low field side launch, achieved in the TCV tokamak H-mode, making use of its naturally generated steep density gradient. This technique offers the possibility of overcoming the upper density limit of conventional EC microwave heating. The sensitive dependence of the O-X mode conversion on the microwave launching direction has been verified experimentally. Localized power deposition, consistent with theoretical predictions, has been observed at densities well above the conventional cut-off. Central heating has been achieved, at powers up to two megawatts. This demonstrates the potential of EBW in tokamak H-modes, the intended mode of operation for a reactor such as ITER.

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Efficient coupling of thermal electron Bernstein waves to the ordinary electromagnetic mode on the National Spherical Torus Experiment

Abstract: Efficient coupling of thermal electron Bernstein waves (EBW) to ordinary mode (Omode) electromagnetic radiation has been measured in plasmas heated by energetic neutral beams and high harmonic fast waves in the National Spherical Torus Experiment (NSTX)

Cited by 24 publications

References 28 publications

Electron Bernstein Wave Research on the National Spherical Torus Experiment

Electron Bernstein Wave Research on the National Spherical Torus Experiment

Status and Plans for the National Spherical Torus Experimental Research Facility

Electron Bernstein wave heating of over-dense H-mode plasmas in the TCV tokamak via O-X-B double mode conversion

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