GB1281132A - Improvements in or relating to corpuscular beam apparatus - Google Patents

Abstract

1281132 Electron beam apparatus; ion beam apparatus SIEMENS AG 25 Sept 1970 [30 Sept 1969 (2)] 45756/70 Heading H1D [Also in Division G4] Corpuscular beam apparatus (i.e. electron or ion microscopes or diffraction apparatus) in which magnetic means are provided for the positioning of a component (e.g. object table, diaphragm, Hoppe zoned diaphragm or phase shifting plate, or foil) comprises a plurality of shifting magnet pairs 14 to 17 and locating magnet pairs, e.g. 7, 8, at least one magnet of each pair being an electromagnet, and control circuits to the electromagnets to cause the locating magnets to effect relatively large or small frictional holding forces, the latter during selective energization of the shifting magnet pairs to effect positioning. The magnets on the components may be permanent magnets. During positioning the rear magnets of each pair in the direction of motion may exert a larger repulsive force than the forward pairs. Stabilizing magnet pairs (35, 36) (Fig. 2, not shown) may be included to prevent rotation, and mutually opposite stabilizing pairs may exert identical attractive forces smaller than the shifting magnet forces, the polepieces also being further spaced than those of the shifting magnets. During object table 5 movement, the locating magnets repel so that surfaces 10, 11 are guiding surfaces, and during de-energization of the shifting pairs, the repulsive forces may be further increased. Subsequently on de-energization, gaps 50 and 51 close and the table weight effects high friction which may be increased by attraction of the polepieces of the locating magnets. Magnet coils secured to the apparatus may be isolated from the evacuated space, and energizing currents wobbulated to eradicate remanent effects. In Fig. 3 (not shown), clockwise rotation of potentiometer arm (69) causes sequential energization of the locating magnet coils (60, 61, 62) prior to energization of shifting magnet coils (63, 64) at position (71), then increased energization of the former prior to de-energization of the latter at position (74). The magnets may be polarity switched during de-energization of magnets 14 to 17. The control circuit may include means such as a wedge filter (Fig. 6, not shown) to generate an electrical signal corresponding to particular shifting magnet energizing currents to identify specific component positions, storing means, and means to energize according to the stored signal, e.g. as in machining several objects, the electromagnets on one side preferably being non-variably energized. For instance, in Fig. 14 (not shown) converter (111) converts signals determined by D.C. coil current i to suitable storage signals, e.g. binary, for store (110). Automatic repositioning in Fig. 6 (not shown) may be effected by controller (134) including a servo motion performing follow-up during differences between stored set point values S2<SP>1</SP> and actual values S2.