Electron thermal confinement in a partially stochastic magnetic structure

Abstract

Using a high-repetition-rate Thomson scattering diagnostic, we observe a peak in electron temperature T e coinciding with the location of a large magnetic island in the Madison Symmetric Torus. Magnetohydrodynamic modeling of this quasi-single helicity plasma indicates that smaller adjacent islands overlap with and destroy the large island flux surfaces. The estimated stochastic electron thermal conductivity (%30 m 2 =s) is consistent with the conductivity inferred from the observed T e gradient and ohmic heating power. Island-shaped T e peaks can result from partially stochastic magnetic islands.

First observation of plasma healing via helical equilibrium in tokamak disruptions

“…However, the difference in thermal conductivity χ e does exist between fully and partially developed stochastic fields. For example, the measured χ e reaches ∼900 m 2 s −1 in a fully stochastic RFP field [34], but is an order-of-magnitude smaller in the partial stochastic field [35]. When the stochastic field partially heals in the core, a higher landing temperature T e,l than the usual T e,l [6] determined by the balance between P Ohm and P rad during the CQ is observed, as shown in figure 7(b).…”