A system for measuring a particle beam includes a central and peripheral part and a front and back panel. The central part includes a system for producing a space charge zone to be passed through by a beam to be measured, charge carriers of a first and second type being generated by the beam when the latter passes through the space charge zone. The peripheral part includes a system for collecting at least one type of charge carrier from among the first or second type. The peripheral part surrounds the central part such that a particle beam can pass through the central part without passing through the peripheral part, an orifice being provided in back panel, in a region of the central part such that the thickness of the region, along a normal axis to the front panel is less than that of the peripheral part along the normal axis.