Abstract
We report the dependence of the lower divertor surface heat flux profiles, measured from infrared thermography and mapped magnetically to the mid-plane on loss power into the scrape-off layer (P-LOSS), plasma current (I-p), and magnetic flux expansion (f(exp)), as well as initial results with lithium wall conditioning in NSTX. Here we extend previous studies [R. Maingi et al., J. Nucl. Mater. 363-365 (2007) 196-200] to higher triangularity similar to 0.7 and higher I-p <= 1.2 MA. First we note that the mid-plane heat flux width mapped to the mid-plane, lambda(mid)(q) is largely independent of P-LOSS for P-LOSS >= 4 MW. lambda(mid)(q) is also found to be relatively independent of f(exp); peak heat flux is strongly reduced as f(exp) is increased, as expected. Finally, lambda(mid)(q) is shown to strongly contract with increasing I-p such that lambda(mid)(q) alpha I-p(-1.6) with a peak divertor heat flux of q(div), (peak) similar to 15 MW/m(2) when I-p = 1.2 MA and P-LOSS similar to 6 MW. These relationships are then used to predict the divertor heat flux for the planned NSTX-Upgrade, with heating power between 10 and 15 MW, B-t = 1.01 and I-p= 2.0 MA for 5 s.
