Abstract
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 shear
that 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.