Non-inductively driven currents in JET

Challis, C.; Cordey, J.G.; Hamnén, H.; Stubberfield, P.M.; Christiansen, J.; Lazzaro, E.; Muir, D.G.; Stork, D.; Thompson, E.

doi:10.1088/0029-5515/29/4/002

Cited by 171 publications

(174 citation statements)

References 17 publications

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“…Beam drive of current has been predicted by theory (see e.g. [6][7][8] and observed in many experiments (e.g., in TFTR [9,10], DIII-D [11,12], JET [13,14], JT-60U [15][16][17], for an overview see [18]). In most of these experiments the beam driven current was located on-axis, including those with N-NBI [16,17].…”

Section: Current Profile Modification By Off-axis Nbi On Asdex Upgradementioning

confidence: 99%

Interaction of energetic particles with large and small scale instabilities

Günter

Conway

Graca³

et al. 2007

Nucl. Fusion

124

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Beyond a certain heating power, measured and predicted distributions of NBI driven currents deviate from each other even in the absence of MHD instabilities. The most reasonable explanation is a redistribution of fast NBI ions on a time scale smaller than the current redistribution time. The hypothesis of a redistribution of fast ions by background turbulence is discussed. Direct numerical simulation of fast test particles in a given field of electrostatic turbulence indicates that for reasonable parameters fast and thermal particle diffusion can indeed be similar. -High quality plasma edge density profiles on ASDEX Upgrade and the recent extension of the reflectometry system allow for a direct comparison of observed TAE eigenfunctions with theoretical ones as obtained with the linear, gyrokinetic, global stability code LIGKA. These comparisons support the hypothesis of TAE-frequency crossing the continuum at the plasma edge in ASDEX Upgrade H-mode discharges. -A new fast ion loss detector with 1 MHz time resolution allows frequency and phase resolved correlation between the observed losses and low frequency magnetic perturbations such as TAE modes and rotating magnetic islands.Whereas losses caused by TAE modes are known to be due to resonances in velocity space, by modelling of the particle drift orbits we were able to explain losses caused by magnetic islands as due to island formation and stochasticity in the drift orbits.

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Section: Current Profile Modification By Off-axis Nbi On Asdex Upgradementioning

confidence: 99%

Interaction of energetic particles with large and small scale instabilities

Günter

Conway

Graca³

et al. 2007

Nucl. Fusion

124

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“…For this, all current sources have been considered, including the NBI driven component, which is about 15% of the total plasma current. NBI power deposition profiles have been taken from PENCIL code calculations [25]. The neoclassical ion heat transport is calculated using NCLASS, a transport code inside JETTO.…”

Section: Simulation Set-upmentioning

confidence: 99%

Numerical analysis of the impact of the ion threshold, ion stiffness and temperature pedestal on global confinement and fusion performance in JET and in ITER plasmas

Baiocchi

Mantica

Tala

et al. 2012

Plasma Phys. Control. Fusion

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Numerical analysis of the impact of the ion threshold, ion stiffness and temperature pedestal on global confinement and fusion performance in JET and in ITER plasmas Baiocchi, B.; Mantica, P.; Tala, T.; Corrigan, G.; Joffrin, E.; Kirov, K.; Naulin, Volker Published in: Plasma Physics and Controlled FusionLink to article, DOI: 10.1088/0741-3335/54/8/085020 Publication date: 2012 Document VersionPublisher's PDF, also known as Version of record Link back to DTU Orbit Citation (APA): Baiocchi, B., Mantica, P., Tala, T., Corrigan, G., Joffrin, E., Kirov, K., & Naulin, V. (2012) Abstract Understanding the impact of micro-instabilities on the global plasma performance is essential in order to make realistic predictions for relevant tokamak scenarios. The semi-empirical transport model CGM is a useful tool to this scope because it depends explicitly on the threshold and the stiffness level, two key parameters of turbulent transport as driven by the ITG/TEM instabilities. The CGM then makes it possible to vary separately the transport variables and to see the quantitative effect of their changes on the global plasma performance. This paper focuses on the impact that four parameters (ion temperature gradient threshold, ion temperature gradient stiffness, height of the temperature pedestal and input power) have individually on the global confinement. Parameters for JET hybrid plasmas and prospective ITER plasmas are used. For JET plasmas changing the ion temperature gradient stiffness from typical low values (characterized by χ s = 0.1) to high values (χ s = 2) leads to variations in the H factor up to 30%. Varying the ion temperature gradient threshold within the interval of the realistic values 3-7 causes changes in H 98 between 20% and 30%. The effect of the temperature pedestal height is very considerable (over 50% of H 98 variation changing the temperature pedestal height from 1 to 3 keV), in agreement with the previous investigations. H 98 is found to slightly decrease with increasing power (from 20 to 60 MW of injected NBI power) for high stiffness and to remain constant in the case of low stiffness. For ITER plasmas the variation of the H factor has qualitatively similar trends, but the variations with respect to changes in stiffness and threshold are smaller. However, very important changes are found for the values predicted by the fusion power in these plasmas.

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“…[16][17][18][19][20] The neoclassical bootstrap current arises from the particle orbit excursion across radial pressure gradient. It has been known that source of the current is mostly the trapped particles, but the current is carried mostly by the passing particles via collisional coupling between trapped and passing particles.…”

Section: Introductionmentioning

confidence: 99%

Bootstrap current for the edge pedestal plasma in a diverted tokamak geometry

Koh

Chang

et al. 2012

Physics of Plasmas

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The edge bootstrap current plays a critical role in the equilibrium and stability of the steep edge pedestal plasma. The pedestal plasma has an unconventional and difficult neoclassical property, as compared with the core plasma. It has a narrow passing particle region in velocity space that can be easily modified or destroyed by Coulomb collisions. At the same time, the edge pedestal plasma has steep pressure and electrostatic potential gradients whose scale-lengths are comparable with the ion banana width, and includes a magnetic separatrix surface, across which the topological properties of the magnetic field and particle orbits change abruptly. A driftkinetic particle code XGC0, equipped with a mass-momentum-energy conserving collision operator, is used to study the edge bootstrap current in a realistic diverted magnetic field geometry with a self-consistent radial electric field. When the edge electrons are in the weakly collisional banana regime, surprisingly, the present kinetic simulation confirms that the existing analytic expressions [represented by O. Sauter et al., Phys. Plasmas 6, 2834] are still valid in this unconventional region, except in a thin radial layer in contact with the magnetic separatrix. The agreement arises from the dominance of the electron contribution to the bootstrap current compared with ion contribution and from a reasonable separation of the trapped-passing dynamics without a strong collisional mixing. However, when the pedestal electrons are in plateau-collisional regime, there is significant deviation of numerical results from the existing analytic formulas, mainly due to large effective collisionality of the passing and the boundary layer trapped particles in edge region. In a conventional aspect ratio tokamak, the edge bootstrap current from kinetic simulation can be significantly less than that from the Sauter formula if the electron collisionality is high. On the other hand, when the aspect ratio is close to unity, the collisional edge bootstrap current can be significantly greater than that from the Sauter formula. Rapid toroidal rotation of the magnetic field lines at the high field side of a tight aspect-ratio tokamak is believed to be the cause of the different behavior. A new analytic fitting formula, as a simple modification to the Sauter formula, is obtained to bring the analytic expression to a better agreement with the edge kinetic simulation results. V C 2012 American Institute of Physics.

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Non-inductively driven currents in JET

Cited by 171 publications

References 17 publications

Interaction of energetic particles with large and small scale instabilities

Interaction of energetic particles with large and small scale instabilities

Numerical analysis of the impact of the ion threshold, ion stiffness and temperature pedestal on global confinement and fusion performance in JET and in ITER plasmas

Bootstrap current for the edge pedestal plasma in a diverted tokamak geometry

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