Scaling of H-mode energy confinement withIpandBTin the MAST spherical tokamak

Abstract
The dependences of energy confinement on plasma current and toroidal magnetic field have been investigated in the MAST spherical tokamak in H-mode plasmas. Multivariate fits show that the dependence of energy confinement time on plasma current I-p is weaker than linear while the dependence on toroidal magnetic field B-T is stronger than linear, in contrast to conventional energy confinement scalings. These I-p and B-T dependences have also been confirmed by single parameter scans. Transport analysis indicates that the strong B-T scaling of energy confinement could possibly be explained by weaker q and stronger nu(*) dependence of heat diffusivity in comparison with conventional tokamaks.