Particle-in-cell simulation of parasitic absorption of lower hybrid power in edge plasmas of tokamaks

Rantamäki, Karin; Pättikangas, Timo; Karttunen, Seppo; Litaudon, X.; Moreau, D.; Bibet, P.

doi:10.1088/0741-3335/41/9/305

Cited by 10 publications

(12 citation statements)

References 8 publications

(14 reference statements)

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“…This is justified because the low-n part does not interact with the cold edge plasma. The details of the calculation of coupled power are presented in Refs [13,22].…”

Section: Coupling a Pic Code With Swanmentioning

confidence: 99%

“…The absorbed power and the deposition profiles were calculated from the changes in kinetic energy of the electrons, as has been explained in Refs [13,19]. Figure 2 shows the absorption profiles at three different power levels.…”

Section: Power Dependence Of Absorptionmentioning

confidence: 99%

“…On Tore Supra the heat flux on the guard limiter increases from 1 to ∼2 MW/m 2 for plasma conditions indicating densities from 0.5×10 18 to 1.0×10 18 m −3 [12]. The density dependence of parasitic absorption was studied with particle-in-cell (PIC) simulations in Refs [13][14][15][16]. The absorbed power fraction was found to increase slightly with density.…”

Section: Introductionmentioning

confidence: 99%

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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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“…This is justified because the low-n part does not interact with the cold edge plasma. The details of the calculation of coupled power are presented in Refs [13,22].…”

Section: Coupling a Pic Code With Swanmentioning

confidence: 99%

Section: Power Dependence Of Absorptionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…it has been proposed that such hotspots are induced by the parasitic absorption of the injected lower hybrid wave (LHW) in the scrapeoff layer (SOL) resulting from the interactions of electrons and lower hybrid modes with high parallel refractive index n of the launched spectrum [11][12][13][14][15][16][17][18]. As indicated by the launched LHW power spectrum, although primary inci dent power is carried by low n modes, there is a small portion of power carried by high n modes [11,19].…”

Section: Interactions Of Plasma and Guard Limiter In Front Of Lower H...mentioning

confidence: 99%

Interactions of plasma and guard limiter in front of lower hybrid wave antenna on EAST tokamak

Xiang

Men

et al. 2019

Nucl. Fusion

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The hotspots on the guard limiters of the lower hybrid wave (LHW) antenna on EAST tokamak not only cause serious damage to the guard limiters, but also strongly degrade the plasma performance due to enhanced impurity productions. In published studies, the heat flux to the limiters is assumed to be carried to limiter walls by electrons which can absorb a small amount of the launched wave energy via interactions with the lower hybrid modes of high parallel refractive index , and the effects of the sheaths formed in front of the limiter surface are ignored. In this work, the heat fluxes to the limiter surfaces are obtained consistently by conducting one-dimension particle-in-cell (PIC) simulations. For the plasma between two guard limiters, while the ions are assumed to be Maxwellian, the electrons are described by using the Fisch model, whose velocity distribution function (VDF) has a resonant plateau in the superthermal region formed by the electron and LHW interaction. Secondary electron emission (SEE) from the limiter surfaces is taken into account by considering two kinds of wall materials, carbon and tungsten. It is found that the sheath potential drop is significantly raised due to the presence of fast electrons. As a result, both ion and electron heat fluxes to the limiters are strongly enhanced compared to those in a Maxwellian plasma, which increases the wall temperature and gives rise to hotspots. The heat flux to the guard limiters increases with the width of the resonant plateau of the electron VDF (i.e. the electron energy). With the enhancement of the sheath potential drop, the physical sputtering yield from the primary and impurity ions on limiter surfaces is found to be significant, which may affect the plasma confinement and discharges.

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Particle-in-cell simulation of parasitic absorption of lower hybrid power in edge plasmas of tokamaks

Cited by 10 publications

References 8 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

Interactions of plasma and guard limiter in front of lower hybrid wave antenna on EAST tokamak

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