Lower hybrid wave coupling and propagation in the presence of nonthermal edge electrons

Jacquet, P.; Demers, Y.; Fuchs, V.; Glaude, V.

doi:10.1063/1.873274

Cited by 7 publications

(22 citation statements)

References 10 publications

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“…Details of the coupling are presented in the Appendix. Fast electrons do not change significantly the power content of the high-n part of the spectrum [21]. Therefore, this model should not be too restrictive.…”

Section: Coupling a Pic Code With Swanmentioning

confidence: 98%

Estimation of heat loads on the wall structures in parasitic absorption of lower hybrid power

et al. 2000

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Parasitic absorption of the short wavelength modes of the LH spectrum is a probable reason for the hot spots seen in the grill region of several tokamaks. Experiments suggest that the heat loads on the wall structures depend on the coupled power. In this work, the parasitic absorption of LH power was studied with self-consistent particle-in-cell simulations. The launched spectra were obtained from the SWAN coupling code. The power and temperature dependences of the absorption in the near field of the LH grill were investigated with a series of simulations. The parasitic absorption was found to grow from 0.6 to 1.1% when the coupled power increased from 26 to 67 MW/m2. When the edge temperature rose from 12.5 to 100 eV, the absorption increased from 0.4 to 1.7%. The maximum kinetic energies were between 0.6 and 1.8 keV. Estimates for the heat loads and surface temperature of the grill limiter are also obtained. The absorption leads to heat loads between 1.5 and 13 MW/m2 and surface temperatures of 510-2390° C.

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Section: Coupling a Pic Code With Swanmentioning

confidence: 98%

Estimation of heat loads on the wall structures in parasitic absorption of lower hybrid power

et al. 2000

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“…The flux of fast electrons driven by LHCD in SOL plays a key role in generation of hot spots and the SOL currents as well as, due to the carried heat and electric charges, respectively. Some simulation tools, including the antenna-plasma coupling code, 17 particle in cell (PIC) simulation code, 18 were developed in order to calculate the fast electron flux driven by LHCD. In a theoretical study, 19 fast electron generation in a wide layer of several centimeters was investigated.…”

Section: Introductionmentioning

confidence: 99%

Fast electron flux driven by lower hybrid wave in the scrape-off layer

Wang

et al. 2015

Physics of Plasmas

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The fast electron flux driven by Lower Hybrid Wave (LHW) in the scrape-off layer (SOL) in EAST is analyzed both theoretically and experimentally. The five bright belts flowing along the magnetic field lines in the SOL and hot spots at LHW guard limiters observed by charge coupled device and infrared cameras are attributed to the fast electron flux, which is directly measured by retarding field analyzers (RFA). The current carried by the fast electron flux, ranging from 400 to 6000 A/m 2 and in the direction opposite to the plasma current, is scanned along the radial direction from the limiter surface to the position about 25 mm beyond the limiter. The measured fast electron flux is attributed to the high parallel wave refractive index n jj components of LHW. According to the antenna structure and the LHW power absorbed by plasma, a broad parallel electric field spectrum of incident wave from the antennas is estimated. The radial distribution of LHW-driven current density is analyzed in SOL based on Landau damping of the LHW. The analytical results support the RFA measurements, showing a certain level of consistency. In addition, the deposition profile of the LHW power density in SOL is also calculated utilizing this simple model. This study provides some fundamental insight into the heating and current drive effects induced by LHW in SOL, and should also help to interpret the observations and related numerical analyses of the behaviors of bright belts and hot spots induced by LHW. V C 2015 AIP Publishing LLC.

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“…To begin, we illustrate why, based on earlier calculations [6,7], it was generally accepted that fast electrons should only be generated within a few mm of the LH grill. Time-averaged SOL plasma profiles of figure 2, determined by reciprocating Langmuir probe measurements in Tore Supra shot 39547 in magnetic flux tubes that were not connected to the LH antenna, are used as input to our calculations.…”

Section: Introductionmentioning

confidence: 93%

“…It is now well documented, both by experiment [1][2][3][4] and theory [2,[5][6][7], that high n // components of the lower hybrid (LH) grill spectrum interact with tokamak edge electrons via linear as well as non-linear Landau damping (n // = k // c/ω is the parallel refractive index defined as the ratio of the speed of light to the parallel phase velocity of a given Fourier component of the LH wave spectrum). Resonant electrons absorb LH power and spread via resonance overlap throughout the stochastic region of velocity space forming a suprathermal population as depicted in figure 1.…”

Section: Introductionmentioning

confidence: 99%

“…It is therefore of practical importance to understand the radial extent of the fast electron population. The presentday understanding of the tokamak edge LH power absorption is based on the antenna calculations of Jacquet et al [6], which self-consistently include the LH-generated hot electrons, and on electron Landau damping results from 2D simulations of Rantamäki et al [7]. Both studies were carried out under the assumption of quiescent background plasma and predict a radial interaction zone of the order of a few millimeters adjacent to the grill mouth.…”

Section: Introductionmentioning

confidence: 99%

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Measurement and modelling of suprathermal electron bursts generated in front of a lower hybrid antenna

et al. 2016

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Measurements in the tokamak scrape-off layer show the existence of fast electrons as far as a few centimeters radially in front of a lower hybrid antenna grill, which is one order of magnitude further than earlier predictions of interaction zones not exceeding 5 mm in width (Rantamäki et al 2000 Nucl. Fusion 40 1477). The present contribution aims at understanding these experimental results on the basis of electron Landau damping in a turbulent scrape-off layer. A crucial guiding element from the experiments is the observation of temporal intermittency of the fast electron signal at positions radially away from the grill mouth at a rate comparable with the detachment rate of relatively hot and dense field-aligned plasma filaments, or ‘blobs,’ from the last closed flux surface. When the dynamic character of the scrape-off layer is taken into account, transient low density and low temperature states occur during which the Landau damping can be weak enough to allow the radiated spectrum to penetrate radially deep inward. When the lower hybrid wave intercepts a dense and hot ‘blob’ a few cm in front of the antenna, then strong damping of the high wave number components can occur. This is the scenario we propose for explaining the generation of fast electrons far away from the grill mouth.

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Lower hybrid wave coupling and propagation in the presence of nonthermal edge electrons

Cited by 7 publications

References 10 publications

Estimation of heat loads on the wall structures in parasitic absorption of lower hybrid power

Estimation of heat loads on the wall structures in parasitic absorption of lower hybrid power

Fast electron flux driven by lower hybrid wave in the scrape-off layer

Measurement and modelling of suprathermal electron bursts generated in front of a lower hybrid antenna

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