Current scaling of plasma confinement

The dependence of global confinement properties in a Tokamak upon global plasma parameters has been well established empirically and is often represented by for example the ITER89P scaling law for L-mode plasmas τE = 0.048 a0.3 R1.2 n0.1 Iφ0.85 Bφ0.2 P-0.5 κ0.5 A0.5 τE is the confinement time which scales with respectively minor-major radius, density, current field, power, plasma elongation and ion mass. The dependence of local confinement, the local thermal diffusivity χ, upon local values of representation plasma parameters, i.e. χ = χ(x, n, Bp, s, Bφ, T, κ, A, Lj,) is however not very well known; x is a flux surface label, 0 ≤ x ≤ 1, Bp the poloidal field, T the temperature, s the shear and Lj denotes scale lengths like (∇n/n)-1. The scalings that are best determined are those with Iφ, n and P; the origin of such scalings must arise from the Bp, s, n, T and Lj scalings of χ. (author) 3 refs., 4 figs