Dynamics of the major disruption of a DIII-D plasma

Kruger, Scott; Schnack, D. D.; Sovinec, C. R.

doi:10.1063/1.1873872

Cited by 26 publications

(22 citation statements)

References 25 publications

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“…Non-axisymmetric with perfectly conducting walls Disruption simulations using NIMROD assume a perfectly conducting wall, [8][9][10] which is an inconsistent boundary condition for a plasma being driven into a wall. The NIM-ROD disruption simulations focus on effects that arise from the breakup of the internal magnetic surfaces, such as disruption mitigation by massive gas injection.…”

Section: A Axisymmetricmentioning

confidence: 99%

“…Although the axisymmetric simulations of ITER disruptions assume force balance, the non-axisymmetric simulations, which include magnetic islands, [6][7][8][9][10] not only retain Alfvénic effects, which would be important only if force balance failed, but more importantly have a tight intertwining of the equilibrium and transport calculations. Existing non-axisymmetric simulations use unphysical boundary conditions though the effect is mitigated by specifying important plasma parameters heuristically rather than determining their dependence through boundary conditions.…”

Section: Introductionmentioning

confidence: 99%

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Theory of tokamak disruptions

Boozer

2012

Physics of Plasmas

134

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Section: A Axisymmetricmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Theory of tokamak disruptions

Boozer

2012

Physics of Plasmas

134

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“…Nonlinear MHD codes have been utilized to study phenomena such as growth rates for nonlinearly coupled modes, the effects of multiple tearing mode harmonics at the same rational surface, nonaxisymmetric effects, effects of magnetic field line stochasticity, and the dynamic evolution of coupled modes leading to a disruption. [24][25][26] …”

Section: Model For Neoclassical Tearing Modesmentioning

confidence: 99%

Integrated simulations of saturated neoclassical tearing modes in DIII-D, Joint European Torus, and ITER plasmas

Halpern¹,

Bateman²,

Kritz³

2006

Physics of Plasmas

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tokamak discharges in order to investigate the adverse effects of multiple saturated magnetic islands driven by neoclassical tearing modes ͑NTMs͒. Simulations are carried out with a predictive model for the temperature and density pedestal at the edge of the high confinement mode ͑H-mode͒ plasma and with core transport described using the Multi-Mode model. The ISLAND module, which is used to compute magnetic island widths, includes the effects of an arbitrary aspect ratio and plasma cross sectional shape, the effect of the neoclassical bootstrap current, and the effect of the distortion in the shape of each magnetic island caused by the radial variation of the perturbed magnetic field. Radial transport is enhanced across the width of each magnetic island within the BALDUR integrated modeling simulations in order to produce a self-consistent local flattening of the plasma profiles. It is found that the main consequence of the NTM magnetic islands is a decrease in the central plasma temperature and total energy. For the DIII-D and JET discharges, it is found that inclusion of the NTMs typically results in a decrease in total energy of the order of 15%. In simulations of ITER, it is found that the saturated magnetic island widths normalized by the plasma minor radius, for the lowest order individual tearing modes, are approximately 24% for the 2 / 1 mode and 12% for the 3 / 2 mode. As a result, the ratio of ITER fusion power to heating power ͑fusion Q͒ is reduced from Q = 10.6 in simulations with no NTM islands to Q = 2.6 in simulations with fully saturated NTM islands.

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“…Particularly, a stochastic magnetic field with the topological structures like the ones in Figs. 1 leads to poloidally and toroidally localized heat and particle deposition patterns on the wall (see, e.g., [21]) similar to those in ergodic divertor tokamaks (see, e.g., [18]). …”

mentioning

confidence: 99%

“…. ) that lead to a large-scale magnetic stochasticity (see, e.g., [19][20][21][22] and references therein). The heat and particle transports in the strongly chaotic magnetic field causes the fast temperature drop and ceases the plasma current.…”

mentioning

confidence: 99%

Mechanism of runaway electron beam formation during plasma disruptions in tokamaks

et al. 2015

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A new physical mechanism of formation of runaway electron (RE) beams during plasma disruptions in tokamaks is proposed. The plasma disruption is caused by a strong stochastic magnetic field formed due to nonlinearly excited low-mode number magnetohydrodynamic (MHD) modes. It is conjectured that the runaway electron beam is formed in the central plasma region confined inside the intact magnetic surface located between q = 1 and the closest low-order rational magnetic surfaces [q = 5/4 or q = 4/3, . . . ]. It results in that runaway electron beam current has a helical nature with a predominant m/n = 1/1 component. The thermal quench and current quench times are estimated using the collisional models for electron diffusion and ambipolar particle transport in a stochastic magnetic field, respectively. Possible mechanisms for the decay of the runaway electron current owing to an outward drift electron orbits and resonance interaction of high-energy electrons with the m/n = 1/1 MHD mode are discussed.The runaway electrons (REs) generated during the disruptions of tokamak plasmas may reach a several tens of MeV and may contribute to the significant part of postdisruption plasma current. The prevention of such RE beams is of a paramount importance in future tokamaks, especially in the ITER operation, since it may severely damage a device wall [1][2][3][4][5].The mitigation of REs by massive gas injections (MGI) and externally applied resonant magnetic perturbations (RMPs) have been extensively discussed in literature (see, e.g., Refs. [6-8] and references therein). However, no regular strategy to solve this problem has been developed because up to now the physical mechanisms of the formation of REs during plasma disruptions are not well understood. In spite of the numerous dedicated experiments to study the problem of runaway current generation during plasma disruptions in different tokamaks (see, e.g., [7][8][9][10][11][12][13][14][15]) no clear dependence of RE formation on plasma parameters has been established. These numerous experiments show the complex nature of plasma disruption process especially the formation of RE beams.One of the important features of the formation of RE beams is the irregularity and variability of the beam parameters from one discharge to another one. This is an indication of the sensitivity of RE beam formations on initial conditions which is the characteristic feature of nonlinear processes, particularly, the chaotic system. Therefore one expects that ab initio numerical simulations of the RE formation process may not be quite productive to explain it because of complexity of computer simulations of nonlinear processes [16]. The problems of numerical simulations of plasma disruptions is comprehensively discussed in [17].In this work we propose a new physical mechanism of formation of RE beams during plasma disruptions in tokamaks. It is based on the analysis of numerous experimental results, mainly obtained in the TEXTOR tokamak and the ideas of magnetic field stochasticity [18]. The mecha...

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Dynamics of the major disruption of a DIII-D plasma

Cited by 26 publications

References 25 publications

Theory of tokamak disruptions

Theory of tokamak disruptions

Integrated simulations of saturated neoclassical tearing modes in DIII-D, Joint European Torus, and ITER plasmas

Mechanism of runaway electron beam formation during plasma disruptions in tokamaks

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