Authors: G.J. Kramer, M. Podestŕ, L. Cui,
N.N. Gorelenkov, B. Grierson, and R. Nazikian
Abstract: We show that the degradation of fast-ion
confinement in steady-state DIII-D discharges is quantitatively
consistent with predictions based on the effects of multiple
unstable Alfvén eigenmodes on beam-ion transport. Simulation and
experiment show that increasing the radius where the magnetic
safety factor has its minimum is effective in minimizing beam-ion
transport. This is favorable for achieving high performance
steady-state operation in DIII-D and future reactors. A comparison
between the experiments and a critical gradient model, in which
only equilibrium profiles were used to predict the most unstable
modes, show that in a number of cases this model reproduces the
measured neutron rate well.
Submitted to: Nuclear Fusion
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