Simultaneous DC measurements of ion current density and electron temperature using a tunnel probe

19th International Summer School on Vacuum, Electron and Ion Technologies

Gunn, J.P.^1 ; Dejarnac, R.^2 ; Stöckel, J.^2

CEA, IRFM, Saint-Paul-Lez-Durance

F-13108, France^1

Institute of Plasma Physics, Czech Academy of Sciences, Prague

182 00, Czech Republic^2

关键词: Dc measurements;    Ion current density;    Kinetic modeling;    Magnetized plasmas;    Measurements of;    Sheath expansion;    Simultaneous measurement;    Single electron;   

Others  :  https://iopscience.iop.org/article/10.1088/1742-6596/700/1/012018/pdf
DOI  :  10.1088/1742-6596/700/1/012018

来源: IOP

【 摘 要 】

The tunnel probe is a concave Langmuir probe designed to operate in strongly magnetized plasma. Due to its shape, the tunnel probe is immune to sheath expansion effects and thus provides absolutely calibrated measurements of the parallel ion current density. A two-dimensional, self-consistent kinetic model is employed to model the flow of charges within the cavity of the tunnel probe. The calculation predicts that the distribution of the ion flux onto the inner conductors depends on the electric field inside the tunnel, which in turn depends on the electron temperature. Therefore, if the tunnel is divided into two negatively biased collectors, it is possible to use the simulation results to determine the electron temperature from the measured ion current ratio. This means that a DC-biased tunnel probe can be used to provide fast, simultaneous measurements of the parallel ion current density and the electron temperature without collecting a single electron. Measurements in the CASTOR and Tore Supra tokamaks agree well with the numerical simulations.