# 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”)