Influence of fast ion loss on the radial electric field in Wendelstein VII-A

A theoretical model for the simultaneous determination of the radial electric field and the fast ion loss is developed and applied to Wendelstein VII-A. The value of the radial electric field obtained with this model is closer to experimental values than that obtained with a purely neoclassical calculation. The loss rate of fast ions, which is also determined, is in the range of values found in experiments