Scaling of the marginal beta(p) of neoclassical tearing modes during power ramp-down experiments in ASDEX Upgrade
Based on the models describing the behaviour of neoclassical tearing modes (NTMs), fits for the seed-island triggered excitation and disappearance of these modes at small beta-values have been tested for an extended parameter range in the rho(pi)*-(υ) over bar (ii) plane in ASDEX Upgrade. The disappearance of NTMs at the marginal beta(p,marg) during power rampdown phases provides input for a direct comparison with models without the influence of the seed-island size. It has been found that for low q(95) the NTM remains present until the HL-transition, whereas for higher q(95) the mode decays well in H-mode. Scalings for the onset and the marginal beta(p) for the (3/2)-NTM and the analysis of marginal beta(p) for the (2/1)-NTM are presented.