A NEW APPROACH TO SCALING OF THE SCRAPE-OFF LAYER AND DIVERTOR PLASMA IN JET

An analytical model of the SOL/divertor magnetic geometry is applied to JET. Exponential decay lengths, lambda, are related to differences in magnetic fluxes and are expressed in terms of lambda at midplane. Consistent values of lambda are usually obtained from Langmuir probes in the SOL or in the divertor, and with Lyman-alpha and Balmer-alpha profiles in the divertor. Scaling of lambda is presented: it is only slightly affected by [n(e)], by X-point to target distance and by input power (other than the usual changes OMEGA double-line arrow pointing right L double-line arrow pointing right H); it increases strongly with B(phi), especially in H-mode.