Recent measurements of the electric potential profile and fluctuations in ECRH and NBI plasmas on TJ-II stellarator

摘要

Heavy Ion Beam Probe diagnostics is used in TJ-II stellarator to study directly the plasma electric potential with audgood spatial (up to 1cm) and temporal (up to 2 µs ) resolution. Low density (ne = (0.3…0.5)×1019 mud–3) ECRH plasma inudTJ-II is characterized by positive plasma potential (ϕ(0) = +600…+ 400 V). At higher densities the minor area of theudnegative electric potential appears at the edge. This area increases with the density, finally makes potential fullyudnegative. This tendency is affected by ECRH power and deposition area. The NBI plasmas are characterized byudnegative electric potential in the full plasma column from the center to the edge, (ϕ(0) = -300…-600 V). These resultsudshow the clear link between plasma potential, temperature, density and particle confinement.