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Abstract

Highly elongated tokamak equilibria may have high critical beta and long confinement times, even at aspect rations about 4 required for reactors such as INTOR, if scaling laws determined at elongations K <or= 1.8 extrapolate to higher K. The MHD equilibria are calculated with a free boundary code which requires shaping coil currents as input. The MHD input parameters are specified as p' = C-1PHI**L and TT' = C-2PHI**M. In a circular plasma with B-T = 2.2 T and I-p = 0.33 x 10**6 Amps, L = M = O.5 gives a ratio of edge to central safety factors of q-e/q-c = 1.8. With input values of L = M = 0.5, R-o = 0.68, a = 0.18, B-o = 0.8T, a free boundary K = 4/1 racetrack equilibrium is obtained with I-p = 1.00 x 10**6 Amps at q-e = 2.0. When compared with the circular equilibrium at the same edge q, the increase in I/B-o indicates a (1+K**2)/2 scaling. The central flux surface is more elongated and has a q of 2.1. Equilibria of this type have been computed for a wide range of beta-pol. Racetrack equilibria with K = 4 have been obtained with L = M = 1.0, but the central flux surface elongation is considerably reduced, and q-e/q-c = 5 at low beta-pol. With more peaked profiles, L = M = 1.5, racetracks with K = 4/1 have not been obtained. Instead, the flux function develops a separatrix resulting in equilibria with an expanded boundary divertor.

Additional information

Authors: HOFMANN F, CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS,ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (SWITZERLAND);MARCUS F B CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS,ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (SWITZERLAND), CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS,ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (SWITZERLAND)
Bibliographic Reference: WRITE TO CONFEDERATION SUISSE, CENTRE DE RECHERCHES EN PHYSIQUE DES PLASMAS, ECOLE POLYTECHNIQUE FEDERALE DE LAUSANNE (SWITZERLAND), MENTIONING REPORT LRP 235/84, 1984
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