%0 Journal Article %1 chu.2002 %A Chu, M. S. %A Parks, P. B. %D 2002 %I AIP %J Physics of Plasmas %K i-mhd tokamak nested current_hole current_reversal equilibrium %N 12 %P 5036-5042 %R 10.1063/1.1521714 %T On tokamak equilibria with a zero current or negative current central region %U http://link.aip.org/link/?PHP/9/5036/1 %V 9 %X Several tokamak experiments have reported the development of a central region with vanishing currents (the current hole). The straightforward application of results from the work of Greene, Johnson and Weimer Physics of Fluids 14, 671 (1971) on a tokamak equilibrium to these plasmas leads to the apparent singularities in several physical quantities including the Shafranov shift and casts doubts on the existence of this type of equilibria. In this paper, the above quoted equilibrium theory is re-examined and extended to include equilibria with a current hole. It is shown that singularities can be circumvented and that equilibria with a central current hole do satisfy the magnetohydrodynamic equilibrium condition with regular behavior for all the physical quantities and do not lead to infinitely large Shafranov shifts. Isolated equilibria with negative current in the central region could exist. But equilibria with negative currents in general do not have neighboring equilibria and thus cannot have experimental realization, i.e., no negative currents can be driven in the central region.

@article{chu.2002, abstract = {Several tokamak experiments have reported the development of a central region with vanishing currents (the current hole). The straightforward application of results from the work of Greene, Johnson and Weimer [Physics of Fluids 14, 671 (1971)] on a tokamak equilibrium to these plasmas leads to the apparent singularities in several physical quantities including the Shafranov shift and casts doubts on the existence of this type of equilibria. In this paper, the above quoted equilibrium theory is re-examined and extended to include equilibria with a current hole. It is shown that singularities can be circumvented and that equilibria with a central current hole do satisfy the magnetohydrodynamic equilibrium condition with regular behavior for all the physical quantities and do not lead to infinitely large Shafranov shifts. Isolated equilibria with negative current in the central region could exist. But equilibria with negative currents in general do not have neighboring equilibria and thus cannot have experimental realization, i.e., no negative currents can be driven in the central region.}, added-at = {2009-02-27T02:47:51.000+0100}, author = {Chu, M. S. and Parks, P. B.}, biburl = {https://www.bibsonomy.org/bibtex/22619277194841618209a6cba000b9abb/prodrigues}, description = {Extends an old formalism used to describe i-mhd equilibria with nested flux surfaces in order to handle a region with a current hole (zero current densities and constant pressure). It claims that a match can be found between the current hole and a regular equilibria via a contact boundary, but no equilibria can be found if the toroidal current reverses its sign other than isolate ones.}, doi = {10.1063/1.1521714}, interhash = {ae1d572e5ce068272960f9db3d57c11a}, intrahash = {2619277194841618209a6cba000b9abb}, journal = {Physics of Plasmas}, keywords = {i-mhd tokamak nested current_hole current_reversal equilibrium}, number = 12, pages = {5036-5042}, publisher = {AIP}, timestamp = {2009-02-27T02:47:52.000+0100}, title = {On tokamak equilibria with a zero current or negative current central region}, url = {http://link.aip.org/link/?PHP/9/5036/1}, volume = 9, year = 2002 }