FAST-RESPONSE IN THE RIPPLE TRAPPED ION DISTRIBUTION TO ABRUPT CHANGES IN A RADIAL ELECTRIC-FIELD IN TOKAMAKS

In the absence of a radial electric field E-r, there is a large defici t in the number of energetic deeply ripple blocked ions near the outer edge of a tokamak. It is shown numerically that the deficit is rapidl y filled tin <100 mu s) by the onset of an inward E-r and that the fil ling results from modifications in the ion drift orbits, connecting th e inner undepleted regions to the nearly empty ripple loss region. The increase in the neutral particle flux from the ripple blocked ions, o bserved at an L-H transition, is reproduced using two independent nume rical methods by turning on a large E-r.