High field side lower hybrid wave launch for steady state plasma sustainment

Bonoli, P. T.; Wallace, G.; Shiraiwa, S.; Baek, Seung Gyou; Doody, J.; Greenwald, M.; LaBombard, B.; Leccacorvi, R.; Filar, Krzysztof; Lin, Y.; Marmar, E.; Meneghini, O.; Palmer, Timothy R.; Parker, R.; Porkoláb, M.; Sorbom, Brandon; Vieira, R.; White, Anne; Whyte, D.G.; Wright, J. C.; Wukitch, S.J.

doi:10.1088/1741-4326/aae7e9

Cited by 20 publications

(15 citation statements)

References 47 publications

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“…Fluctuations may therefore be important in understanding the observed SOL absorption of LH waves, particularly at high line averaged densities. Launching at a region with significantly lower density fluctuation amplitudes such as the high field side of a tokamak [59] may therefore be beneficial for increased LHCD efficiency at high densities.…”

Section: Discussionmentioning

confidence: 99%

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Lau¹,

Martin²,

Shiraiwa³

et al. 2020

Nucl. Fusion

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The effects of synthetic turbulence on lower hybrid (LH) wave field magnitude and polarization are studied on Alcator C-Mod. Three synthetic turbulence models are evaluated to assess the impact of filaments, holes, and periodic fluctuations on the LH wave electric fields. For all three cases, the synthetic turbulence can greatly impact the LH wave magnitude and polarization. Back scattering, interference and edge/SOL absorption of the LH wave is observed. This impact is shown to depend on the wavelength and amplitude of the fluctuations. The strongest effect appears for fluctuations at high amplitudes and wavelengths comparable to the LH wavelength. This synthetic turbulence model can be used as inputs into a synthetic diagnostic to calculate the lower hybrid wave field magnitude and direction measured by dynamic Stark effect spectroscopy. It will be shown that fluctuations at these high amplitudes and wavelengths may explain the experimentally measured results. The effect of fluctuations on modifying LH polarization are also shown to be anti-correlated with SOL power losses, similar to recently observed experimental trends on Alcator C-Mod. These SOL losses may have detrimental impact on LHCD efficiency.

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Section: Discussionmentioning

confidence: 99%

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Lau¹,

Martin²,

Shiraiwa³

et al. 2020

Nucl. Fusion

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“…The potential benefits of the HFS location are detailed in Ref. 16. The empirical scaling laws for LHRF antenna net power density predict 20 to 40 MW/m 2 at 4.6 GHz (Refs.…”

Section: Radiofrequency Designmentioning

confidence: 99%

Multiphysics Simulations of a Steady-State Lower Hybrid Current Drive Antenna for the FSNF

Wallace

Bohm

Kessel

2021

Fusion Science and Technology

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The Fusion Nuclear Science Facility (FNSF) is a proposed tokamak reactor with the mission to investigate operation of a fusion reactor in a nuclear environment. The high neutron fluence component of the FNSF mission requires steady-state operation for extremely long pulses (t pulse , months) at full power. Plasma sustainment and current drive will be critical components of a successful FNSF. COMSOL Multiphysics® software is used for combined radiofrequency (RF) and thermal simulations of the lower hybrid current drive antenna system. These simulations consider the resistive RF losses in the antenna including realistic surface roughness and a range of potential materials. The thermal analysis adds volumetric nuclear heating, plasma heat flux on leading edges, and electromagnetic radiation from the plasma to the RF heating calculated by COMSOL. Additional neutronics calculations have been performed to determine the impact of these antenna designs on activated waste disposal for the materials considered. The simulations show that it is technically feasible to implement a fully active multijunction (FAM) rather than a passive-active multijunction (PAM) style of antenna if the septum between adjacent waveguides is sufficiently wide and the thermal conductivity of the structural material is sufficiently high. The FAM has the benefit of higher achievable power density with respect to the PAM, which results in a more compact antenna with potentially lower impact on neutron shielding and tritium breeding. These considerations point to tungsten rather than steel as the preferred structural material in constructing the antenna.

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“…One feasible approach, which opens up * Author to whom any correspondence should be addressed. the accessibility window in high density plasmas, is that the LHW is launched from the high field side (HFS) [9]; however, the CD efficiency is still limited although the accessibility is improved. High harmonic fast waves (HHFW), also called 'helicon waves', with a frequency between ion cyclotron waves and the LHW can propagate into the center of the plasma without a density limit [10][11][12][13] because the HHFW's main absorption mechanism-electron Landau damping-is weaker than that of the LHW, such that the HHFW can provide an on-axis CD in low electron beta β e (= n e κT e /B 2 /2μ 0 ) [1] operation.…”

Section: Introductionmentioning

confidence: 99%

New synergy effects of the lower hybrid wave and the high harmonic fast wave current drive

Yin¹,

Zheng²,

Gong³

et al. 2022

Nucl. Fusion

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The combined drive current of the lower hybrid wave (LHW) and the high harmonic fast wave (HHFW) is studied for the first time, based on the use of low and higher β_e operational parameters in EAST. Broad and significant synergistic effects are found in the simulation, the local synergy factor reaching a factor of 4.3 in the off-axis region. The current drive (CD) efficiency is greatly improved, and the current profile is modified as a result of the synergy between the two types of waves . the LHW interacted with the resonant electrons in low parallel velocity region and pushes them into the adjacent resonance region of the high phase velocity wave (HHFW), the number of fast electrons resonant with the HHFW is increased dramatically, and the driven current is enhanced. Therefore the synergy effect strongly depends on the positional relational between the velocity resonance regions of the two waves. Moreover, the effects of the parallel refractive index and the wave power on the synergy effect are examined. Some problems well known in the single LHW CD or the HHFW CD may be overcome by the combined CD.

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High field side lower hybrid wave launch for steady state plasma sustainment

Cited by 20 publications

References 47 publications

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Full-wave model for the lower hybrid wave electric field vector with synthetic turbulence on Alcator C-Mod

Multiphysics Simulations of a Steady-State Lower Hybrid Current Drive Antenna for the FSNF

New synergy effects of the lower hybrid wave and the high harmonic fast wave current drive

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