Latest results on the H-mode threshold using the international H-mode threshold database

This is an analysis of the H-mode threshold physics by the International H-mode Threshold Database Working Group. The data from 10 different tokamaks world-wide are combined in an attempt to determine the physics of the H-mode transition as well as the scaling of the plasma parameters relevant to the H-mode transition to future magnetic fusion devices. The input power required to achieve H-mode is fitted with log-linear regressions of global plasma parameters such as density, toroidal magnetic field and plasma size. An attempt to cross-validate this analysis method is made by removing each tokamak in turn and recalculating the fit. Based on these global scalings, the hysteresis in the threshold power can be defined in terms of how far away from the threshold scaling plasma parameters can be obtained and remain in H-mode. Local edge temperatures and densities are also analysed at the H-mode threshold in an attempt to find a scaling with plasma parameters. Changes in divertor geometry also have strong effects on the H-mode threshold, so scalings are compared for open and closed diverters.