Patent GB-1160598-A (GB)
Title: Apparatus for Positioning Specimens in Electron Microscopes or Electron Diffraction Cameras
IPC: H01J37/20
Filed: 1967-11-03
Abstract: 1,160,598. Electron microscopes. AUSTRALIA, COMMONWEALTH SCIENTIFIC & INDUSTRIAL RESEARCH ORGANIZATION. 3 Nov., 1967 [7 Nov., 1966], No. 50177/67. Heading H1D. Apparatus for manipulating specimens within an electron microscope or electron diffraction camera, and which permits a specimen, from outside the vacuum envelope, to be displaced in three perpendicular directions and tilted about two perpendicular axes, includes a translatable structure which may be adjustably displaced in three perpendicular directions and which includes a seat for a specimen holder, which specimen holder includes a body with respect to which a tiltable specimen support member may be tilted about two perpendicular axes by a pair of movable members mounted on the body, the arrangement being such that when the specimen holder is inserted into the seat the pair of movable members operatively engage control members which are mounted on the translatable structure and by which the tilting of the specimen may be adjusted. The arrangement is mounted within a circular housing 21 by a member 66 mounted on a column 43 which is secured to a disc 27. The disc 27 is mounted in the housing in a groove 25 which permits limited horizontal slidable movement in any direction, the position of the disc being adjustable by two assemblies mounted at right angles to one another (Fig. 4, not shown), each consisting of a tag 30 secured to the disc and engaging, by means of a ruby ball 34 and a knife-edge respectively, a corresponding toggle pin 36 and thrust rod 35, the thrust rods being operable from outside the microscope envelope, and the tags being biased against the ball and knife edge by a spring 39 acting along a line bisecting the angle between the two tags. A member 66, Figs. 7 and 10, is vertically slidable upon column 43, its vertical position being adjusted by the slidable engagement within the recess 63 of a member 61 mounted on and vertically movable, from outside the envelope, along a screwed rod (50, Figs. 3 and 5, not shown). Member 66 carries a pair of pivotally mounted rocker arms 89, 90 which are each engaged at one end by a respective screwed rod 94, 95, operable from outside the envelope by a pair of universally jointed and telescopic shafts 101, 102, to pivot the arms against the upward biasing action of the spring 111. A convergent dovetail slideway 88, Fig. 10, in the member 66 permits the insertion to a standard position, of a correspondingly shaped member 82, Fig. 7, to which a ring 72, Figs. 7 and 12, is attached. The ring 72 has a downwardly extending conical stem 73, at the bottom of which a specimen ring 74 is mounted by three arms 76, 78, which extend along the stern and are held thereagainst by a plastics collar 79 mounted around them towards their lower end, which collar is a close sliding fit within the aperture 124 in the disc 27. The ring 74 may be tilted about two perpendicular axes by oppositely directed movement along their length of the two arms 76, produced by rocking the semi-circular yoke 77, to which arms 76 are pivotally attached, about the screw 75, Fig. 12, by which the yoke is pivoted to the plate 72 within the recess 58, and by movement along its length of arm 78, respectively. Rocking of yoke 77 and movement of arm 78 are produced by the spring-biased plungers 83, 84, the tops of which are positioned to be engageable by the rocker arms 89 and 90 when the member 82 is inserted into the slideway 88. The specimen is removed by disengaging rocker arms 89, 90 from the plungers 83, 84 and raising member 44 up the column 43 until the open-sided socket 112 on the plate 82 is on a level with an extractor rod (113, Fig. 9, not shown) having a lug at its end which may be inserted through the socket 112, and thereafter rotated through 90 degrees to engage the socket upon withdrawal of the rod, permitting removal of the plate 82 and attached specimen holding arrangement (Fig. 9, not shown) into an air-lock. The member 82 and ring 72 are connected by thermally insulating components, and a thermally conductive plate (121, Figs. 8, 9, and 11, not shown) having copper leads attached is mounted on, but thermally insulated from, member 66, the plate being shaped to engage the ring 72 when the member 82 is in its inserted position, whereby, by placing the copper leads in a liquid nitrogen bath, stem 73 may be cooled to reduce contamination.