AbstractA three-dimensional complex trajectory is imposed on the heavy ion beam probe (HIBP) particle orbits in heliotron/torsatron devices. A pair of two-dimensional beam deflectors for primary and secondary beam lines are equipped in the Compact Helical System (CHS) HIBP, which makes it possible to measure the plasma potential at almost all plasma radii. A plasma observation point is determined by a set of four deflector voltages. Experimental verification for these observation points is necessary in such a complex configuration. In this study, a movable detector and a gas ionization method have been used to find these deflector voltages. Calibration procedures for these methods are described in detail. The movable detector is also used to optimize the focusing condition of the primary beam in the plasma region.