Dynamics of runaway electrons in lower hybrid current drive plasmas in the HT-7 tokamak

In lower hybrid current drive (LHCD) plasmas with non-zero loop voltage, the fast electron tail can act as a seed population of runaways. The runaways are found to be enhanced in the presence of lower hybrid (LH) waves when the fast electron tail extends above the critical velocity for electrons to run away. In runaway discharges, the LH waves may suppress runaway electrons due to the drop in the electric field linked to the non-inductive current drive. In this paper, the behaviour of runaway electrons in an extensive range of LHCD plasmas is presented.