Coupling between JET pedestal ne–Te and outer target plate recycling

Abstract

Systematic scans using D2 gas puffing and impurity-seeding (Ne, N2) have been carried out on ELMy-H and Advanced-Tokamak-like discharges to study power deposition amelioration at the divertor target plates in preparation for the JET ITER-Like Wall (ILW). Hereby it has been discovered that the recycling ion fluxes Idiv to the outer target plate exhibit a clear connection to pedestal ne and Te, whereby the Dα photon flux ΦDα from the outer divertor serves here as an approximate measure of Idiv. ΦDα can be expressed as (ne/Te)β with β=2.5/3 depending on the scenario (EH/AT). This coupling between SOL and pedestal across the edge transport barrier (ETB) is associated with a close connection between ne and Te in the ETB over the entire range of operational parameters, with the slope of logTe vs. logne being ∼0.9/1.24 for ET/AT scenarios, respectively.