Device for scanning a beam of charged particles

A device for scanning a beam of charged particles over the surface of an exit window of a vacuum chamber coupled with a charged particle accelerator, comprising longitudinal and cross-sectional scanning electromagnets to deflect the beam of charged particles along the length and width of the exit window, respectively, and longitudinal and cross-sectional scanning current generators to energize the respective electromagnets, characterized in that the device further comprises a variable delayer (7) whose output is connected with the synchronizing input of the cross-sectional scanning current generator (6) and whose input is connected with the longitudinal scanning current generator (5), so that pulses arrive at the input of the variable delayer (7) at the moments when the current in the windings of the longitudinal scanning electromagnet (1) reaches its peak, which variable delayer provides N delay times different from each other by a .DELTA.t value and set in succession as the pulses arrive at its input, the values N and .DELTA.t being determined from the following relationships:

• .DELTA.t.ltoreq.d/2f.sub.1 L;
• N.gtoreq.1/f.sub.2 .DELTA.t
• where
• d--diameter of the charged particle beam,
• f.sub.1 --frequency of the longitudinal scanning,
• f.sub.2 --frequency of the cross-sectional scanning,
• L--value of maximum deflection of the beam along the length of the exit window.