Modelling of deuterium emission in high density divertor plasmas in JET

Simulations of neutral deuterium emission from high density Ohmic and L-mod e JET divertor discharges with the EDGE2D/NIMBUS codes are presented. At hi gh density the codes fail to reproduce quantitatively the steady increase o f divertor D-0 emission with rising plasma density observed in the experime nt. However, good agreement is obtained with the measured D-gamma/D-alpha r atio in inner and outer divertor despite the total plasma volume recombinat ion being small in the simulations. The asymmetry between inner and outer d ivertor detachment is found to depend on the strength of the charge exchang e momentum losses. Recombination alone is not sufficient to obtain strong d etachment in the inner divertor. Measurements of Ly(beta)/D-alpha emission profiles across the JET divertor show signs of Lyman radiation reabsorption in the inner divertor at high density. The first attempt at including dive rtor plasma opacity corrections self-consistently in EDGE2D/NIMBUS simulati ons of high density JET L-mode discharges is presented. The effect of opaci ty on the simulated deuterium emission and on the 2D plasma solution is dis cussed. (C) 1999 JET Joint Undertaking, published by Elsevier Science B.V. All rights reserved.