A device for modulating the intensity of a charged particle beam emitted along an axis, comprises 4×N consecutive deflection systems, with N=1 or 2, with the deflection systems being positioned along the axis of said particle beam, and being capable of deflecting the beam relative to the axis in the same direction, with alternating directions of deflection, for two consecutive systems, means for applying a force for deflecting the beam for each deflection system and for varying the applied force; two collimators each having a slot with an opening that increases in width from the center towards the periphery, located respectively between the first and second deflection systems and between the third and fourth deflection systems, with the opening of the slot of the first collimator facing towards one side of the emission axis of the beam, with the opening of the slot of the second collimator facing towards the opposite side of the emission axis of the beam.