Impurities have been injected into Heliotron E in order to study the transport properties of currentless plasmas. In ECH-produced plasmas, the observed impurity transport can be described by purely anomalous diffusion, with a coefficient of the order of D = 2000–5000 cm2 ·s−1. During neutral beam operation, the impurity transport can be characterized by considerably weaker diffusion, combined with inward convection. Convection velocities as large as a few hundred centimetres per second are inferred.
Suppression of anomalous impurity transport in NBI-heated W7-X plasmas
Observation of enhanced ion particle transport in mixed H/D isotope plasmas on JET