Modelling of lower hybrid current drive in self-consistent elongated tokamak equilibria

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The stability properties of non-inductively driven, reversed shear type current profiles that may be achieved for Alcator C-Mod tokamak-like parameters (aspect ratio R/a=3) are examined. It is found that without a conducting wall, the best stability results (ON up to 3.7) are achieved for highly triangular plasmas (b = 0.7) at qmin=2.2, for relatively broad pressure profiles (p(0)/pavg = 2.8) and large values of rmin/a(= 0.75). For elliptical or circular cross-section plasmas with little triangularity, the stability limits are significantly lower (QNmax=2.2).Finally, more peaked pressure profiles (p(0)/payg = 4.5) have lower beta limits than broader profiles.1

Section: 3 )mentioning

confidence: 99%

Negative magnetic shear modes of operation in the Alcator C-Mod tokamak near the beta limit

Bonoli

Porkoláb

Ramos

et al. 1997

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“…As explained earlier, ICRF is applied to a given plasma either for heating or driving currents, both of which will unavoidably have an effect on the equilibrium itself. First attempts to evolve the equilibrium have been undertaken in [11]. These authors studied lower hybrid current drive scenarios and allowed for a current density variation determined by a simplified model comprising a unidimensional Fokker-Planck code coupled to a ray tracing method.…”

Section: Introductionmentioning

confidence: 99%

Ion cyclotron resonance heating with consistent finite orbit widths and anisotropic equilibria

Jucker

Graves

Cooper

et al. 2011

Minority ion cyclotron resonance heating is studied using the self-consistent numerical model SCENIC. This model includes 3D geometries with full shaping and anisotropic pressure effects, warm contributions to the dielectric tensor and full orbit effects. It evolves the equilibrium, wave field and hot particle distribution function iteratively until a self-consistent solution is found. We will show applications to JET-like two-dimensional equilibria with minority heating scenarios. The effects due to different heating locations on the hot particle distribution function, the hot dielectric tensor and the equilibrium will be studied for symmetric wave injection. Finally, the RF-induced particle pinch is investigated using asymmetric wave injection.

“…3 was to isolate (in a parametric sense) the effect of the temperature variation in the weak damping limit. Prior studies of LHCD have achieved MHD equilibria consistent with the LH current drive source by iterating between an MHD solver and the current drive calculation [Bonoli, 1990] [Devoto, 1992]. These studies indicate that the LH current density profile changes primarily due to changes in the poloidal magnetic field as the MHD equilibrium is re-solved.…”

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confidence: 99%

Modelling of the EAST lower-hybrid current drive experiment using GENRAY/CQL3D and TORLH/CQL3D

Yang

Bonoli

Wright

et al. 2014

Abstract:The coupled GENRAY-CQL3D code has been used to do systematic ray-tracing and Fokker-Planck analysis for EAST Lower Hybrid wave Current Drive (LHCD) experiments. Despite being in the weak absorption regime, the experimental level of LH current drive is successfully simulated, by taking into account the variations in the parallel wavenumber due to the toroidal effect. The effect of radial transport of the fast LH electrons in EAST has also been studied, which shows that a modest amount of radial transport diffusion can redistribute the fast LH current significantly. Taking advantage of the new capability in GENRAY, the actual Scrape Off Layer (SOL) model with magnetic field, density, temperature, and geometry is included in the simulation for both the lower and the higher density cases, so that the collisional losses of Lower Hybrid Wave (LHW) power in the SOL has been accounted for, which together with fast electron losses can reproduce the LHCD experimental observations in different discharges of EAST. We have also analyzed EAST discharges where there is a significant ohmic contribution to the total current, and good agreement with experiment in terms of total current has been obtained. Also, the full-wave code TORLH has been used for the simulation of the LH physics in the EAST, including full-wave effects such as diffraction and focusing which may also play an important role in bridging the spectral gap. The comparisons between the GENRAY and the TORLH codes are done for both the Maxwellian and the quasi-linear electron Landau damping cases. These simulations represent an important addition