Initial operation of the NSTX phased array for launching high harmonic fast waves

Ryan, P. M.; Wilson, J. R.; Swain, D. W.; Pinsker, R. I.; Carter, M.D; Gates, D.; Hosea, J. C.; Mau, T. K.; Menard, J.E.; Mueller, D.; Sabbagh, S.A.; Wilgen, J. B.

doi:10.1016/s0920-3796(01)00269-1

Cited by 14 publications

(12 citation statements)

References 4 publications

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“…The NSTX HHFW system features a twelve-element antenna, six rf transmitters, a transmission system and a power dividing and decoupling network 6 .…”

Section: Description Of the Nstx Hhfw Systemmentioning

confidence: 99%

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

et al. 2003

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High Harmonic Fast Wave (HHFW) Heating has been proposed as a particularly attractive means for plasma heating and current drive in the high beta plasmas that are achievable in spherical torus (ST) devices. The National Spherical Torus Experiment (NSTX) [Ono, M., Kaye, S.M., Neumeyer, S., et al., Proceedings, 18 th IEEE/NPSS Symposium On Fusion Engineering, Albuquerque, 1999, (IEEE, Piscataway, NJ (1999.] is such a device. An rf heating system has been installed on NSTX to explore the physics of HHFW heating, current drive via rf waves and for use as a tool to demonstrate the attractiveness of the ST concept as a fusion device. To date, experiments have demonstrated many of the theoretical predictions for HHFW. In particular, strong wave absorption on electrons over a wide range of plasma parameters and wave parallel phase velocities, wave acceleration of energetic ions, and indications of current drive for directed wave spectra have been observed. In addition HHFW heating has been used to explore the energy transport properties of NSTX plasmas, to create H-mode discharges with a large fraction of bootstrap current and to control the plasma current profile during the early stages of the discharge.

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“…The NSTX HHFW system features a twelve-element antenna, six rf transmitters, a transmission system and a power dividing and decoupling network 6 .…”

Section: Description Of the Nstx Hhfw Systemmentioning

confidence: 99%

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

et al. 2003

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“…For reference, the NSTX HHFW system operates at 30 MHz, contains twelve straps for variable phasing, and possesses a boron-nitride Faraday shield (see Refs. [11] and [12] for details).…”

Section: Towards Identifying the Mechanisms Underlying Field-aligned mentioning

confidence: 99%

Towards identifying the mechanisms underlying field-aligned edge-loss of HHFW power on NSTX

Perkins

Ahn

Bell

et al. 2014

AIP Conference Proceedings

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Fast-wave heating will be a major heating scheme on ITER, as it can heat ions directly and is relatively unaffected by the large machine size unlike neutral beams. However, fast-wave interactions with the plasma edge can lead to deleterious effects such as, in the case of the high-harmonic fast-wave (HHFW) system on NSTX, large losses of fast-wave power in the scrape off layer (SOL) under certain conditions. In such scenarios, a large fraction of the lost HHFW power is deposited on the upper and lower divertors in bright spiral shapes. The responsible mechanism(s) has not yet been identified but may include fast-wave propagation in the scrape off layer, parametric decay instability, and RF currents driven by the antenna reactive fields. Understanding and mitigating these losses is important not only for improving the heating and current-drive on NSTX-Upgrade but also for understanding fast-wave propagation across the SOL in any fast-wave system. This talk summarizes experimental results demonstrating that the flow of lost HHFW power to the divertor regions largely follows the open SOL magnetic field lines. This lost power flux is relatively large close to both the antenna and the last closed flux surface with a reduced level in between, so the loss mechanism cannot be localized to the antenna. At the same time, significant losses also occur along field lines connected to the inboard edge of the bottom antenna plate. The power lost within the spirals is roughly estimated, showing that these field-aligned losses to the divertor are significant but may not account for the total HHFW loss. To elucidate the role of the onset layer for perpendicular fast-wave propagation with regards to fast-wave propagation in the SOL, a cylindrical cold-plasma model is being developed. This model, in addition to advanced RF codes such as TORIC and AORSA, is aimed at identifying the underlying mechanism(s) behind these SOL losses, to minimize their effects in NSTX-U, and to predict their importance in ITER.

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“…INTRODUCTION It has been proven that the high harmonic fast wave (HHFW) at 30 MHz can provide substantial plasma heating and current drive for the NSTX spherical tokamak operation [1][2][3][4][5]. However, the present antenna strap design [6] rarely achieves the design goal of delivering the full transmitter capability of 6 MW to the plasma. In order to deliver more power to the plasma, a new antenna strap design and its associated coaxial line feeds are being constructed.…”

Section: P Ryanmentioning

confidence: 99%

Simulation results for new NSTX HHFW antenna straps design by using microwave studio

Kung

Ellis

Brunkhorst

et al. 2009

2009 23rd IEEE/NPSS Symposium on Fusion Engineering

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Abstract-Experimental results have shown that the high harmonic fast wave (HHFW) at 30 MHz can provide substantial plasma heating and current drive for the NSTX spherical tokamak operation. However, the present antenna strap design rarely achieves the design goal of delivering the full transmitter capability of 6 MW to the plasma. In order to deliver more power to the plasma, a new antenna strap design and the associated coaxial line feeds are being constructed. This new antenna strap design features two feedthroughs to replace the old single feed-through design. In the design process, CST Microwave Studio has been used to simulate the entire new antenna strap structure including the enclosure and the Faraday shield. In this paper, the antenna strap model and the simulation results will be discussed in detail. The test results from the new antenna straps with their associated resonant loops will be presented as well.

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Initial operation of the NSTX phased array for launching high harmonic fast waves

Cited by 14 publications

References 4 publications

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

Exploration of high harmonic fast wave heating on the National Spherical Torus Experiment

Towards identifying the mechanisms underlying field-aligned edge-loss of HHFW power on NSTX

Simulation results for new NSTX HHFW antenna straps design by using microwave studio

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