Characteristics of global energy confinement in KSTAR L- and H-mode plasmas

Abstract

We evaluate the characteristics of global energy confinement in KSTAR (tau(E, KSTAR)) quantitatively in three ways; firstly by comparing it with multi-machine scalings, secondly by deriving multiple regression equations for the L- and the H-mode plasmas, respectively, and lastly by comparing confinement enhancement of the H-mode phase with respect to the L-mode phase in each discharge defined as H-exp. The KSTAR database exhibits tau(E, KSTAR) of similar to 0.04 to similar to 0.16 s and of similar to 0.06 to similar to 0.19 s in L-mode and in H-mode plasmas, respectively. The multiple regression equations derived by statistical analysis present the similar dependency on P-L and higher dependency on I-p compared with the multi-machine scalings, however the dependency on kappa in both L- and H-mode plasmas draw the negative power dependency of kappa(-0.68) and kappa(-0.76) for H-mode and for L-mode database, respectively on the contrary to the positive dependency in all multi-machine empirical scalings. It is found that the energy confinement of both L-mode and H-mode of the discharges with H-exp > 1.5 can be well-predicted by multi-machine scalings, tau(E, 89L) and tau(E, 92H). Apart from this, the H-mode confinement with 1.5 < H-exp < 2.0 is well-predicted by using the multi-machine empirical L-mode scaling tau(E, 89L).