The Impact of statistical models on scalings derived from multi-machine H-mode threshold experiments

McDonald, D. C.*; Meakins, A. J.*; Svensson, J.*; Kirk, A.*; Andrew, Y.*; Cordey, J. G.*; Takizuka, Tomonori; ITPA H-mode Threshold Database Working Group*

The H-mode power threshold is estimated from the International threshold database by the ordinary least square log-linear regression (OLS), the errors-in-variables log-linear orthogonal regression and the generalized maximum-likekihood (M-L) method. A chi-squared analysis shows that none of the studied models are entirely consistent with the data, indicating that further refinement of the physical and statistical model is required. For ITER-like parameters, a M-L analysis shows a predicted threshold of 38.4 MW, compared with 31.1 MW for the OLS.