Abstract: So as to position a device, such as an eddy current probe support inside a cylindrical cavity with radial perforations opening into said cavity, a device (36) is proposed, said device including a pole (50) orientated parallel to the axis of the cavity. This pole may occupy different pre-established indexing positions in rotation and in translation inside the cavity by means of a mechanism (42, 44, 54, 58, 60). In each of these indexing positions, an active head (98), mounted at the extremity of the pole (50) by means of a pantograph (66) and a cladding arm (100), is able to move in a specific active zone on the lower wall of the cavity. To this effect, the active head is clad by the arm (100) and is equipped with autonomous thrustors controlling its movement.