The bifurcated nature of the potential profile of a toroidal helical plasma is investigated in CHS using a heavy ion beam probe.The measurements reveal that three main branches of potential profile exist in ECR heated plasmas with a low density of e ≈ 0.5 × 1019m-3.The branches with higher central potential exhibit a rather strong radial electric field shearthat should result in fluctuation reduction and formation of a transport barrier.An analysis of the pulsating behaviour in the potential suggests the existence of a fine structure in the potential profiles between the main branches. Lissajous and histogram expressions are useful in extracting the bifurcation characteristics of the potential structure.
Detection of an electron beam in a high density plasma via an electrostatic probe