Patent GB-1162732-A (GB)
Title: Electron Beam Column
IPC: H01J29/52
Filed: 1967-08-01
Abstract: 1,162,732. Electron beam apparatus. INTERNATIONAL BUSINESS MACHINES CORP. 1 Aug., 1967 [29 Aug., 1966], No. 35206/67. Heading H1D. In a device, which may be readily disassembled, for generating focusing, and accrately directing an electron beam-for use, for example, in electron microscopes, data recording systems, or electron beam cutting, welding, and etching apparatus-all the beam-forming elements, including polepieces and beam-diameterlimiting aperture assemblies, are mounted within and slidably removable from a straight tube of non-magnetic material around which electromagnetic coils for the polepieces are mounted. In the arrangement shown, a beam from the cathode assembly 6 is directed on to and scanned over a memory element 17, by being projected through the alignment coils 25 and 26; the aperture assemblies 85, 87, 89 and 91; the polepieces assemblies 86 and 88 of magnetic lenses 10 and 11; the vernier focusing coil assembly 59 which co-operates with lens 12 to focus the beam in the plane of the memory element; the blanking assembly 90 consisting of electrostatic plates 103 and 104, which permit the beam to be diverted to miss the opening of the final aperture assembly 91; the dynamic focusing coil 14; and the deflecting coil 16. The coil assemblies for the magnetic lenses are separated by spacers 46 and 47, and lenses 10 and 11 each include non-magnetic inserts 35a 97 and 40a, 100, respectively. The structure is assembled by sliding the aperture assemblies, polepiece assemblies 86 and 88, and blanking assembly 90, along the inside of the non- magnetic tube 66, where they are maintained in position between spring clips 92 and 93. The various coil assemblies are slid over the tube 66 and within the outer housing 9 and are compressed between an end flange 48 secured to one end of housing 9, and a clamping ring 50, which is removably held within the housing by a plurality of radially extending screws 51, the axially extending screws 54 permitting the coil assemblies to be pressed against one another. The housing 18 for the memory element 17 is clamped to flange 48, and housing 19 for the cathode assembly 6 is clamped to the end flange 68 of the tube 66. Tube 66 is positioned within housing 9 by one or more members 75 which are pivotally mounted on pins 76 secured to the clamping ring 50, and the inner ends of which engage in recesses 78 in the wall of the tube 66; adjustment of screws 80, which engage against the bevelled outer ends 81 of members 75, cause the latter to pivot anti-clockwise and press the tube 66 forward so that its other end abuts against the plate 71 clamped between the polepiece 43 and the housing 18. Hermetic sealing is ensured by ring seals 69, 70, and 74. Electrical contact to the aperture and blanking assemblies is achieved by conductors passing through insulating sleeves mounted on the wall of tube 66 and projecting on the inside and the outside of the tube to contact spring contacts on the beamforming members within the tube, and conductive portions of the coil assemblies outside the tube, when the apparatus is fully assembled (Fig. 3, not shown). The aperture assemblies incorporate heating coils to reduce the deposition of contamination upon the surfaces exposed to the beam. The memory element 17 is of electron-sensitive or thermoplastic film.