Experimental Signatures of Homoclinic Tangles in Poloidally Diverted Tokamaks
By T. E. Evans, R K W Roeder, J. Carter, B. Rapoport, M. Fenstermacher, C. Lasnier. 2005
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Small non-axisymmetric perturbations of poloidally diverted tokamaks create edge stochastic magnetic field lines that connect to material surfaces such as those in the divertors. Separatrix structure calculations show that the distribution of stochastic field lines on the vessel walls is closely related to the topology of homoclinic tangles formed in the perturbed system. Since these tangles prescribe how the stochastic fields are organized, they are of significant practical interest in tokamak experiments. Experimental measurements of heat and particle distributions on plasma facing surfaces sometimes show split peak patterns that are consistent with the presence of stochasticity and homoclinic tangles. These split peaks are often observed during locked modes and other types of edge instabilities. They are also observed when perturbation fields from magnetohydrodynamic control coils are pulsed during a plasma discharge. Numerical modeling of the perturbation field from these control coils shows that the homoclinic tangle produced by a coil pulse is not always large enough to produce the splitting patterns observed. Nevertheless, there is a clear correlation between the coil pulses and the appearance of the split profiles. These results suggest the presence of the plasma amplification mechanism that enhances the size of the non-resonant homoclinic tangles.
Subfields: Astronomy and Astrophysics, Biomedical Engineering, Nuclear and High Energy Physics
View Paper: https://www.semanticscholar.org/paper/5f714063bbed81164d330e24ccdb1ab8799e24fa
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Citations in the corpus
- Overview of the results on divertor heat loads in RMP controlled H-mode plasmas on DIII-D (2009, methodology): “This has been observed in different experiments including limiter [19–21] and divertor plasmas [17, 11].”