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Introduction
------------

[Large Rogowski coil](/Diagnostics/Magnetic/RogowskiCoilArroundChamber/Theory/diagnostics_rogowski) 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](/Diagnostics/Magnetic/Theory/Rogowski_coil/index). Moreover, several [small Rogowski coils](/Diagnostics/Magnetic/RogowskiCoilArroundChamber/diagnostics_rogowski_small) are used for measuring currents flowing in conducting wires.


Elimination of the vessel current
---------------------------------

The Rogowski coil is outside the stainless steel [chamber](/Tokamak/Chamber/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](/SW/pygolem) called ["chamber_inductance"](http://golem.fjfi.cvut.cz/cgi-bin/data/10814/chamber_inductance) and ["chamber_resistance"](http://golem.fjfi.cvut.cz/cgi-bin/data/10814/chamber_resistance))

Pictures
--------

<a href="Photos/0113JK_TR/IMG_2190.JPG">
<img alt="Large Rogowski coil" width="300" align="middle"
     src="Photos/0113JK_TR/IMG_2190l_small.JPG">
<a href="Photos/0113JK_TR/IMG_2191.JPG">
<img alt="Placement of the Rogowski coil" width="300" align="middle"
     src="Photos/0113JK_TR/IMG_2191_small.JPG">
</a>