High resolution energy-selecting electron beam apparatus

9) An electron-optical apparatus for use in an electron microscope or a microanalyzer comprising:

• energy-dispersing optical elements such as magnetic or electrostatic prisms, which create an energy dispersed electron beam;
• quadrupoles which adjust first order focus trajectories of said electron beam;
• at least two sextupole lenses acting on said energy-dispersed electron beam in at least two Z locations at which said beam is energy-dispersed and at which the ratios of the extents of the beam in the X direction and in the Y direction are different,
• whereupon chromatic defocus and chromatic astigmatism of said electron beam become adjustable and can be set to zero as needed for chromatic aberrations correction.

12) A method of energy-selecting an electron beam in an electron microscope, said method comprising the steps of:

• dispersing said electron beam in energy using a magnetic or electrostatic prism or prisms;
• magnifying an energy dispersion of said electron beam using a first-order magnifying element such as a quadrupole or quadrupoles or a round lens or lenses;
• selecting a subset of electron energies within said electron beam using an energy-selecting slit;
• de-magnifying said energy dispersion using further first-order focusing elements arranged approximately in a minor-symmetric arrangement with said first-order magnifying elements, such that said energy dispersion of said electron beam is exactly or approximately cancelled,
• whereupon the energies of said electron beam are selected without reducing the intensity of said beam any more than necessary due to the cutting out of unwanted energies.