PLASMA FLUCTUATIONS AND PROBE SHEATH

The edge plasma parameters are monitored using electrical probes in the Castor tokamak (R = 0.4 m, a = 85 mm, Btor = 1 1.2 T, Ipl = 5 20 kA, ne 1019m3). For this, a single Langmuir probe is modified using Stangeby’s idea [1] and a so called double-pin-plate probe is designed. We have shown that the influence of the plasma potential and density fluctuations on a probe can be suppressed using signals describing the plasma parameters in front of a planar probe. 1