公开(公告)号：US3900808A

公开(公告)日：1975-08-19

申请号：US64862367

申请日：1967-06-26

申请人： ZERBST HELMUT ,  WEYL REINHARD ,  DIETRICH ISOLDE

发明人： ZERBST HELMUT ,  WEYL REINHARD ,  DIETRICH ISOLDE

IPC分类号： H01J37/141 ,  H01F7/00

CPC分类号： H01J37/1416 ,  Y10S505/871

摘要： A corpuscular ray device having a magnetic lens assembly. Although the invention is particularly applicable to objective lens assemblies of electron microscopes which operate under vacuum, it is also applicable to lens assemblies for ion microscopes, electron-diffraction devices, or other corpuscular ray apparatus wherein the rays are situated in tubular enclosures. The magnetic lens assembly includes a pair of shielding cylinders which are coaxial and spaced from each other, which are made of a superconductive material, and which have their common axis coinciding with a lens axis of the lens assembly, these shielding cylinders being surrounded by a lens winding which may also be made of a superconductive material and which serves to generate the magnetic field which is concentrated by the shielding cylinders in the region of the corpuscular ray. These shielding cylinders have directed toward each other a pair of end faces which are spaced from each other and define between themselves a lens gap which is devoid of any shielding components made of superconductive material. The aperture error constant of the lens assembly depends upon the maximum value of the field intensity in the lens gap and upon the field gradient along the lens axis in the lens gap. The magnitude of the lens gap is chosen in such a way that with a predetermined value of field intensity outwardly beyond the lens gap and the shielding cylinders the maximum value of the field intensity in the lens gap and the field gradient in the lens gap along the lens axis provide for the lens assembly an aperture error constant which is less than a predetermined value of aperture error constant.