Numerical studies of transport in the Columbia Non‐neutral Torus

The confinement of pure electron plasmas in the Columbia Non‐neutral Torus (CNT) stellarator is limited by the presence of unconfined orbits. The existence of a very large electric field across magnetic surfaces should preclude such unconfined orbits. However variations in the electric potential on magnetic surfaces, inherent to the CNT equilibrium, add to the complexity of the trajectories and lead to bad orbits. We have written a code using magnetic coordinates to integrate the electron drift trajectories in the electric and magnetic fields expected in CNT equilibria. Results of such calculations are presented showing that there exists unconfined orbits in CNT if the potential is not constant on surfaces.