Measurement of and hypothesis for particle influx and density peaking in a tokamak plasma

The particle influx, density peaking, and a concomitant change of the poloidal magnetic field Bθ, occurring after the particle source rate at the boundary is reduced from an earlier higher rate, are measured in an inductively driven tokamak plasma. A hypothesis is proposed to interpret the measurement: in neoclassical theory the toroidal electric field that drives the coupled transport in the Onsager relation is an inductive field; it is the differential field in a nonuniform resistive toroidal electric field, Eηj(r). The transport is nonlocal and not at the steady state because the boundary and initial conditions of Eηj(r) must be satisfied; neoclassical theory describes the transport due to perturbations on the steady state. That state, determined by the absence of the coupled transport in the Onsager relation, is uniform resistive dissipation: Eηj=const. The source of the perturbation is the particle source just outside the boundary.