High power neon seeded JET discharges: Experiments and simulations

A series of neon seeded JET ELMy H-mode pulses is considered from the modeling as well as from the experimental point of view. For two different Ne seeding rates and two different D puffing gas levels the heating power, P-heat, is in the range 22-29.5 MW. The main focus is on the numerical reconstruction of the total radiated power (which mostly depends on the W concentration) and its distribution between core and divertor and of Z(eff)(which mostly depends on the Ne concentration). To model self-consistently the core and the SOL two input parameters had to be adjusted case by case: the SOL diffusivity, D SOL, and the core impurity inward pinch, v(pinch). D-SOL had to be increased with increasing Gamma(Ne) and the level of v(pinch) had to be changed, for any given Gamma(Ne), according to the level of P-heat : it decreases with increasing P-heat. Since the ELM frequency, f(ELM), is experimentally correlated with P-heat, (it increases with P-heat) the impurity inward pinch can be seen as to depend on f(ELM). Therefore, to maintain a low v(pinch) level (i.e. high f(ELM)) Gamma(Ne)/P-heat should not exceed a certain threshold, which slightly increases with the Gamma(D) puffing rate. This might lead to a limitation in the viability of reducing the target heat load by Ne seeding at moderate Gamma(D), while keeping Z(eff) at acceptably low level. (C) 2016 Published by Elsevier Ltd.