Abstract: In order to provide exceptionally high beam deflection speed in apparatus utilizing a magnetically deflected electron beam, such as an electron microscope or an electron beam welding machine, a ferro-magnetic yoke having opposed internal poles arranged to be positioned on opposite sides of the beam is provided with a pair of beam deflection coils on each pole, one coil of each pair being connected in a series circuit including a coil of the other pair and in a sense such that the voltage induced in one pair of coils by a collapsing deflection current in the other pair assists the rising deflection current in the first mentioned pair.