Scaling of H-mode energy confinement with I p and B T in the MAST spherical tokamak

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 ν * dependence of heat diffusivity in comparison with conventional tokamaks.