CHARGED PARTICLE BEAM APPARATUS, SCANNING ELECTRON MICROSCOPE, AND METHOD OF OPERATING A CHARGED PARTICLE BEAM APPARATUS

A charged particle beam apparatus (100) is described. The charged particle beam apparatus includes a first vacuum region (121) in which a charged particle beam emitter (105) for emitting a charged particle beam (102) along an optical axis (A) is arranged, a second vacuum region (122) downstream of the first vacuum region and separated from the first vacuum region by a first gas separation wall (132) with a first differential pumping aperture (131), wherein the first differential pumping aperture (131) is configured as a first beam limiting aperture for the charged particle beam (102); and a third vacuum region (123) downstream of the second vacuum region and separated from the second vacuum region by a second gas separation wall (134) with a second differential pumping aperture (133), wherein the second differential pumping aperture (133) is configured as a second beam limiting aperture for the charged particle beam (102). Further described are a scanning electron microscope and a method of operating a charged particle beam apparatus.