DIVERTOR SCALING LAWS FOR TOKAMAKS

The breakdown of two body scaling laws is illustrated by using the two dimensional plasma code UEDGE coupled to an advanced Navier-Stokes ne utrals transport package to model attached and detached regimes in a s implified geometry. Two body similarity scalings are used as benchmark s for runs retaining non-two body modifications due to the effects of (i) multi-step processes altering ionization and radiation via the exc ited states of atomic hydrogen and (ii) three body recombination. Prel iminary investigations indicate that two body scaling interpretations of experimental data fail due to (i) multi-step processes when a signi ficant region of the plasma exceeds a plasma density of 10(19) m(-3) o r (ii) three body recombination when there is a significant region in which the temperature is less than or equal to 1 eV while the plasma d ensity is greater than or equal to 10(20) m(-3). These studies demonst rate that two body scaling arguments are often inappropriate in the di vertor and the first results for alternate scalings are presented.