TUNABLE AMPERE PHASE PLATE FOR CHARGED PARTICLE IMAGING SYSTEMS

A phase shifting device for a charged particle imaging system includes means for passing an electric current in a direction that has a nonzero component parallel to at least one section of the imaging beam. Preferably, the electric current is passed parallel along the section of the imaging beam. The amount of phase shift then centrosymmetrically depends on the distance between the electric current axis and the imaging beam axis. The magnetic field produced by the electric current exhibits the same effect on the phase of the beam as a localized charge according to the prior art.