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Magnetic Surface Function Equdibrium point (saddle) X-point Equihbrium point (center) 0-point Contour plot Separatrix 1-45 I 3-6. Magnetic surface of circular helical device No symmetry! No analytic magnetic surface function! Consider: Magnetic surface of linear helical device + perturbation 1)The X-point and the separatrix still remain? No. Separatrix breaks and ergodic (chaotic) structure appears. 2) The toruses around the O-point still remain? YES. KAM torus theory shows an existence of stable torus orbit.

Vi. o o - o ? o Lb z ............................... Liz..................... -0 . e I .................... 4 I :: ................. k... a :"""" + ............................ z........ LE ............................................... .............................................. - us? 1-5 2 Schematic view of divertor leg Heat flux Because of special structure of magnetic field lines, hit points of plasma on divertor plate are discrete. 1-53 c I Asymmetry of heat flux 8: direction of divertor plate r: distance between center and cross point 2 e l 0 1.

One cleaning method that is being highly considered is the introduction of oxygen into the confinement vessel while heating the first wall. O and CO/02 which than can be removed by the tritium clean-up system. A major drawback to this approach is that in order to get an acccptablc removal rate of the co-deposited carbon layer (> 2 x d h r for carbon) the wall temperature of the reactor will need to be heated to 350°C. I n addition, this process loads the wall with O? that will need to be removed before tokamak operations re-commence.