Study of plasma current effect on divertor power footprint widths through experiments and modeling in EAST L-mode plasmas

Integrated studies of the scaling of divertor power footprint widths with plasma current in Experimental Advanced Superconducting Tokamak (EAST) L-mode plasmas are carried out through experiments and modeling. The divertor power widths, which consist of the scrape-off layer power decay length lambda(q) and the heat spreading S, are calculated from the measurements of divertor Langmuir probes (div-LPs) and scrape-off layer plasma simulation (SOLPS). A strong inverse scaling of both lambda(q) (mm) and S (mm) from the div-LP with plasma current I-p (MA) is demonstrated, with the regressions being lambda(q) = 4.37I(p)(-1.04 +/- 0.075) and S = 2.31I(p)(-0.997 +/- 0.047). However, a much weaker inverse scaling of lambda(q) with I-p is shown by the measurement of outer mid-plane reciprocating probes, which gives lambda(q,RP) = 6.56I(p)(-0.31 +/- 0.056). It indicates that the connection length may have played a stronger role in the negative scaling of lambda(q) with I-p than radial transport. A similar conclusion can also be drawn from a comparison of the simulation of the plasma current scan with a set of fixed radial transport and another set of coefficient modified by I-p. This indicates that plasma configuration with a longer connection length is a better L-mode operational scenario for diverted tokamaks. Published by AIP Publishing.