Design and Fabrication of Comparative Langmuir Ball-Pen Probe (LBP) for the Tokamak

Abstract

The first results of design and fabrication of comparative Langmuir Ball-Pen probe (LBP) for the IR-T1 tokamak were presented. Conventional Langmuir probe can’t measure the plasma potential precisely (due to temperature fluctuations). Therefore we used LBP for direct measurement of the plasma potential. First measurements show that the probe allows a modification of its collected electron and ion saturation currents. Regarding to the results, the ratio of R (up to down ion saturation currents) is close to one at a certain collector position (h = −0.7 mm). In this situation, the floating potential is very close to the plasma potential. Temporal and radial evolutions of plasma potential have been investigated and analyzed.