Fast response in the ripple trapped ion distribution to abrupt changes in a radial electric field in tokamaks

摘要

In the absence of a radial electric field E_r, there is a large deficit in the number of energetic deeply ripple blocked ions near the outer edge of a tokamak. It is shown numerically that the deficit is rapidly filled(in < 100μs)by the onset of an inward E_r and that the filling results from modifications in the ion drift orbits, connecting the inner undepleted regins to the nearly empty ripple loss region. The increase in the neutral particle flux from the ripple blocked ions, observed at an L-H transition, is reproduced using two independent numerical methods by turning on a large E_r.