ELECTROMAGNETIC FILTER FOR SEPARATING ELECTRON BEAMS Russian patent published in 2007 - IPC H01J37/147 H01J37/28 

FIELD: raster electron microscopy; electromagnetic filters for spatial separation of primary and secondary electron beams.

SUBSTANCE: proposed filter has eight sector electrodes disposed within cylinder made of dielectric and nonmagnetic material. Electrodes are made of ferromagnetic material in the form of eight cylindrical segments having separation angle of 30 and 60 degrees and function at the same time as magnetic poles. Four magnetic poles are disposed on outer surface of cylinder at separation angle of 60 and 120 degrees. Round diaphragms with central bore placed on butt-ends of filters are made of conducting ferromagnetic material, one of diaphragms having four or more symmetrically disposed holes for bringing out secondary electron beam. Deviation of secondary electron beams is more than 20 deg. in absence of primary electron beam axis deviation throughout entire length of filter.

EFFECT: minimized aberration of primary electron beam.

1 cl, 2 dwg