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 Er, 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 <100 μs) by the onset of an inward Er and that the filling results from modifications in the ion drift orbits, connecting the inner undepleted regions 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 Er.