Global simulation of ion temperature gradient instabilities in a field-reversed configuration

Bao, Jian; Lau, Calvin; Zhang, Lin; Wang, H. Y.; Fulton, Daniel; Dettrick, Sean; Tajima, T.

doi:10.1063/1.5087079

Cited by 8 publications

(19 citation statements)

References 39 publications

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Section: Perpendicular Transportmentioning

confidence: 99%

“…Perpendicular turbulent transport is modeled using the 3D PIC codes ANC [17,18], GTC [19] and GTC-X [20]. In previous simulations [20][21][22], a gyrokinetic particle push was used, necessitating the removal of magnetic null regions from the simulation domain. Nevertheless, nonlinear simulations find qualitative agreement in fluctuation spectrum with experimental Doppler back scattering (DBS) measurements [23].…”

Section: Perpendicular Transportmentioning

confidence: 99%

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Simulation of equilibrium and transport in advanced FRCS

Dettrick¹,

Barnes²,

Ceccherini³

et al. 2021

Nucl. Fusion

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The advanced beam-driven FRC is a field reversed configuration (FRC) with the addition of neutral beam (NB) injection, electrode biasing, and magnetic expander divertors. The resulting configuration has novel features that make it necessary to revisit many key results in FRC theory. Three of these features include (i) a large energetic ion population, (ii) in-principle capability to adjust the electric field and rotation profiles, and (iii) a combination of magnetic and electrostatic confinement of electrons in the SOL. In some fueling scenarios the electron density profile may exhibit a significant peak outside of the separatrix. To explore these features a hybrid fluid/kinetic equilibrium model has been used to reconstruct typical experimental profiles of the C-2W experiment. Results indicate that the energetic ions provide at least 50% of the total plasma pressure. These equilibrium profiles have been used as initial conditions for global, cross-separatrix, turbulent transport simulations using the 3D electrostatic particle-in-cell code ANC. Electrostatic fluctuations were found to nonlinearly saturate at an amplitude which is an order magnitude lower than that observed previously. The tokamak turbulence code GTC code has also been extended to handle FRC physics in the new GTC-X version, which has been used to perform simulations of turbulent transport in the SOL relevant to electrode biasing. It is found that equilibrium E × B flow shear significantly decreases ion temperature gradient saturation amplitude and ion heat transport. Also in the SOL, a 1D2V continuum code has been developed and applied to parallel electron heat transport. Results show the formation of pre-sheath potential and reduction of parallel electron heat loss close to the ideal ambipolar limit, a result which has been validated by experimental diagnostics. These transport modifications caused by the three novel configuration features help to explain the remarkable plasma performance of the C-2W experiment.

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Section: Perpendicular Transportmentioning

confidence: 99%

Section: Perpendicular Transportmentioning

confidence: 99%

Simulation of equilibrium and transport in advanced FRCS

Dettrick¹,

Barnes²,

Ceccherini³

et al. 2021

Nucl. Fusion

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“…( 56) gives the zonal electric as a function of ψ while the guiding center equations of motion in cylindrical coordinates (Eqs. [41][42][43][44] require the R and Z components of the zonal field. Hence we simply do a coordinate transformation to obtain E R and E Z i.e.…”

Section: Verification Of Zonal Flows In the Core Regionmentioning

confidence: 99%

“…A particular feature of GTC-X is the use of a cylindrical coordinate system for the advancement of the particle dynamics, which allows particle motion in arbitrary shaped flux surfaces including the magnetic separatrix and the magnetic X-point in the tokamak. GTC-X in its present form is an electrostatic code, which has been applied to simulate ion temperature gradient instability in the FRC geometry, which has no toroidal magnetic field 42 .…”

Section: Introductionmentioning

confidence: 99%

Kinetic particle simulations in a global toroidal geometry

Singh

Kuley

et al. 2019

Physics of Plasmas

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The gyrokinetic toroidal code (GTC) has been upgraded for global simulations by coupling the core and scrapeoff layer (SOL) regions across the separatrix with field-aligned particle-grid interpolations. A fully kinetic particle pusher for high frequency waves (ion cyclotron frequency and beyond) and a guiding center pusher for low frequency waves have been implemented using cylindrical coordinates in a global toroidal geometry. The two integrators correctly capture the particle orbits and agree well with each other, conserving energy and canonical angular momentum. As a verification and application of this new capability, ion guiding center simulations have been carried out to study ion orbit losses at the edge of the DIII-D tokamak for single null magnetic separatrix discharges. The ion loss conditions are examined as a function of the pitch angle for cases without and with an electric field. The simulations show good agreement with past theoretical results and with experimentally observed feature in which high energy ions flow out along the ion drift orbits and then hit the divertor plates. A measure of the ion direct orbit loss fraction shows that the loss fraction increases with the ion energy for DIII-D in the initial velocity space. Finally, as a further verification of the capability of the new code, self-consistent simulations of zonal flows in the core region of the DIII-D tokamak were carried out.

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“…Edge plasma simulations have attracted significant attention in recent years due to their connection to, e.g., the high confinement regime of tokamak plasmas; the prediction of the divertor heat-flux width of ITER 10 ; edge localized mode (ELM) control 11 . In order to simulate the edge physics, besides comprehensive physics models 12,13 , numerical schemes such as finite element methods for unstructured meshes in XGC 5, 14 , GTS 4 and GTC/GTC-X 15,16 and multiple patches of structured meshes in JOREK 11 have been developed in order to treat the open field line (OFL) region. While whole plasma simulations for neoclassical transport, ELMs and micro-turbulence have been reported and various numerical schemes have been developed for treating the OFL geometry 5, 10,11,15,17,18 , there is still space to understand the features of different schemes, such as the particle-in-Fourier method (cf.…”

Section: Introductionmentioning

confidence: 99%

Development and testing of an unstructured mesh method for whole plasma gyrokinetic simulations in realistic tokamak geometry

Lauber

Hayward-Schneider

et al. 2019

Physics of Plasmas

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In this work, we have formulated and implemented a mixed unstructured mesh-based finite element (FE)-Fourier decomposition scheme for gyrokinetic simulations in realistic tokamak geometry. An efficient particle positioning (particle-triangle mapping) scheme for the charge deposition and field scattering using an intermediate grid as the search index for triangles has been implemented and a significant speed-up by a factor of ∼ 30 is observed as compared with the brute force scheme for a medium-size simulation. The TRIMEG (TRIangular MEsh based Gyrokinetic) code has been developed. As an application, the ion temperature gradient (ITG) mode is simulated using the simplified gyrokinetic Vlasov-Poisson model. Our simulation and that using the ORB5 code for the DIII-D Cyclone case show reasonable agreement. As an additional application, ITG simulations using an ASDEX Upgrade equilibrium have been performed with density and temperature gradient profiles similar to the Cyclone case. Capabilities of the TRIMEG code for simulations with realistic experimental equilibria in the plasma core and in the whole plasma volume with open field lines are demonstrated.

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Global simulation of ion temperature gradient instabilities in a field-reversed configuration

Cited by 8 publications

References 39 publications

Simulation of equilibrium and transport in advanced FRCS

Simulation of equilibrium and transport in advanced FRCS

Kinetic particle simulations in a global toroidal geometry

Development and testing of an unstructured mesh method for whole plasma gyrokinetic simulations in realistic tokamak geometry

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