Plasma current

Introduction

Large Rogowski coil on tokamak GOLEM serves as sensor of electric current driven through plasma column and conducting chamber. Signal picked up by the coil is a superposition of these two signals, since the coil encircles both the chamber and the plasma. Thus, in order to obtain the information on plasma current, the cross-talk of current in chamber has to be eliminated. The theory of the measuring is here. Moreover, several small Rogowski coils are used for measuring currents flowing in conducting wires.

Elimination of the vessel current

The Rogowski coil is outside the stainless steel chamber, thus it measures not only the plasma current, but also the current through the tokamak liner \(I_{liner}\). Hence, the plasma current \(I_{pl}\) should be determined as

\[ I_{pl} = I_{measured} - I_{liner} \]

The resistance of the liner is \(R_{liner} = 9.7\) m\(\Omega\) so the current through the liner can be determined from the Ohm’s law:

\[ I_{liner} = \frac{U_{loop}}{R_{liner}} \]

Inductance of the chamber is 0.57 \(\mu\)H.

(Precise values are in pygolem database called “chamber_inductance” and “chamber_resistance”)

Pictures