Plasma resistivity profile measurement from an external radio-frequency magnetic coil

Plasma resistivity is obtained by measuring the change in circuit behavior from a simple loop placed externally to the plasma. The loop is part of a series-driven oscillator that can be tuned over a wide range of frequencies with a very low internal impedance. By varying the frequency, and observing both the detuning and loading of this circuit, the location and resistance of the screening currents can be determined. A two-dimensional resistive magnetohydrodynamic code calculation is performed to obtain both the plasma interaction with the oscillating field as well as the effects of nearby conductors. The plasma resistance in the numerical calculations is adjusted to match the data from the experiment and, in this way, obtain a measure of the plasma resistivity profile.