Observation of Confined Current Ribbon in JET Plasmas

Solano, E.R.; Lomas, P. J.; Alper, B.; Xu, G. S.; Andrew, Y.; Arnoux, G.; Boboc, A.; Barrera, L.; Belo, P.; Beurskens, M.; Brix, M.; Crombé, Kristel; Luna, E. de la; Devaux, S.; Eich, T.; Gerasimov, S.; Giroud, C.; Harting, D.; Howell, D. F.; Huber, A.; Kocsis, G.; Korotkov, A.; Löpez‐Fraguas, A.; Nave, M. F. F.; Rachlew, Elisabeth; Rimini, F.; Saarelma, S.; Sirinelli, A.; Pinches, S. D.; Thomsen, H.; Zabeo, L.; Zarzoso, D.

doi:10.1103/physrevlett.104.185003

Cited by 39 publications

(60 citation statements)

References 18 publications

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“…We have concentrated our efforts in the domain where J BS at the edge is large, which tends to coincide with the region where low n = 1 structures dominate (corresponding to the upper half of the graph in figure 8). In our opinion, these structures constitute a very realistic model for the OM observed on JET (Solano 2010) and the EHO detected on DIII-D and other tokamaks (Burrell et al 2005;Suttrop et al 2005;Hu et al 2015). A detailed analysis of the equilibrium state for large edge J BS indicates that a parallel helical current density ribbon forms just outside the q = 3 rational surface with a radial extent that aligns with the vanishing magnetic shear region associated with the flat spot in the q-profile caused by the bootstrap current.…”

Section: Discussionmentioning

confidence: 99%

“…We interpret these deformations as indicative of the development of an external kink/peeling mode that saturates at finite amplitude. The distortions observed are symptomatic of the edge harmonic oscillation (EHO) (Burrell et al 2005) first reported on DIII-D, but subsequently observed on many other machines (Suttrop et al 2005;Hu et al 2015), and the outer mode (OM) measured on JET (Solano et al 2010). The shape of the last closed magnetic flux surface on TCV at four different cross-sections projected onto a single toroidal plane for β N = 1, 1.49, 1.99 and 2.47 are presented in figure 4.…”

Section: -D Equilibrium Numerical Simulations: Nonlinearly Stable Stmentioning

confidence: 99%

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A 3-D MHD equilibrium description of nonlinearly saturated ideal external kink/peeling structures in tokamaks

et al. 2015

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Novel free boundary magnetohydrodynamic equilibrium states with spontaneous three-dimensional (3-D) deformations of the plasma-vacuum interface are computed. The structures obtained look like saturated ideal external kink/peeling modes. Large edge pressure gradients yield toroidal mode number n = 1 distortions when the edge bootstrap current is large and higher n corrugations when this current is small. Linear ideal MHD stability analyses confirm the nonlinear saturated ideal kink equilibrium states produced and we can identify the Pfirsch-Schlüter current as the main linear instability driving mechanism when the edge pressure gradient is large. The dominant non-axisymmetric component of this Pfirsch-Schlüter current drives a near resonant helical parallel current density ribbon that aligns with the near vanishing magnetic shear region caused by the edge bootstrap current. This current ribbon is a manifestation of the outer mode previously found on JET (Solano 2010). We claim that the equilibrium corrugations describe structures that are commonly observed in quiescent H-mode tokamak discharges.

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Section: Discussionmentioning

confidence: 99%

Section: -D Equilibrium Numerical Simulations: Nonlinearly Stable Stmentioning

confidence: 99%

A 3-D MHD equilibrium description of nonlinearly saturated ideal external kink/peeling structures in tokamaks

et al. 2015

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“…It is possible that ambipolar electron particle flux is responsible for extremely good plasma confinement in snakes or current filament. [22][23][24][25] The electron particle flux is…”

Section: Kinematic Effects Of Parallel Mass Flowmentioning

confidence: 99%

“…Using Eqs. (25) and (26) and changing independent variables from w; h; E; l ð Þto p f ; h; E; l ð Þ , we recast Eq. (A1) as…”

Section: Acknowledgmentsmentioning

confidence: 99%

Neoclassical theory inside transport barriers in tokamaks

Shaing

Hsu

2012

Physics of Plasmas

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Inside the transport barriers in tokamaks, ion energy losses sometimes are smaller than the value predicted by the standard neoclassical theory. This improvement can be understood in terms of the orbit squeezing theory in addition to the sonic poloidal E Â B Mach number U p;m that pushes the tips of the trapped particles to the higher energy. In general, U p;m also includes the poloidal component of the parallel mass flow speed. These physics mechanisms are the corner stones for the transition theory of the low confinement mode (L-mode) to the high confinement mode (H-mode) in tokamaks. Here, detailed transport fluxes in the banana regime are presented using the parallel viscous forces calculated earlier. It is found, as expected, that effects of orbit squeezing and the sonic U p;m reduce the ion heat conductivity. The former reduces it by a factor of jSj 3=2 and the later by a factor of RðU 2 p;m Þ expðÀU 2 p;m Þ with RðU 2 p;m Þ, a rational function. Here, S is the orbit squeezing factor.

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“…ELMs deposit large, localized and impulsive heat loads that can damage the divertor. A quiescent regime with edge harmonic oscillations (EHO) or broadband MHD activity is observed in some DIII-D [4][5][6][7][8][9][10][11], JT-60U [12,13], JET [14] and ASDEX-U [15], discharge scenarios. These ELM-free discharges have the pedestal-plasma confinement necessary for burning-plasma operation in ITER [11].…”

Section: Introductionmentioning

confidence: 99%