Energy filter for charged particle beam apparatus.

摘要

An energy selecting filter comprising a structure of four hemispheres to be transpassed succesively by a beam of charged particles to be filtered. The structure is symmetrically with respect to a plane of symmetry in which the energy selecting element, such as slit or a knife-edge is introduced. In a charged particle beam apparatus such as a high resolution electron microscope the energy spread introduced by a source can adjustable be reduced to below for example 0,1 eV without introducing any beam deviation at the cost of only a small lengthening of the apparatus. <IMAGE>