US2418903A - Electron optical instrument with adjustable specimen support - Google Patents

Description

F. E. RUNGE 2,418,903

April 15, 1947.

ELECTRON OPTICAL INSTRUMENT WITH ADJUSTABLE SPECIMEN SUPPORT Filed Aug. 51, 1943 MN m lull .Illl

QNNW @Rm .II III Han/ ZZ.

attorney '1 ment.

Patented Apr. 15, 1947 UNITED STATES PATENT OFFICE 2,418,903 ELECTRON OPTICAL INSTRUMENT ADJUSTABLE SPECIMEN snrron'r Frank E. Runge, Haddon Heights, N. 3.,- assignor to Radio Corporation of; America, a corporation of Delaware Application August 31, 1943, Serial No 500,620

(Cl. 250"49.5l

'7 Claims.

an electron image thereof, and has special reference to the provision of an improved specimenholder for such instruments.

In operating an electron diffraction camera, or a transmission type electron microscope, it is often desirable to explore the specimen with the electron beam in order that the more interesting portions of the specimen may be viewed. Since in electron optical instruments of the general character described the electron beam passes in an undeviating path from its source to the target, the desired exploration can only be achieved by orienting the specimen-holder with respect to the beam. The present invention is predicated upon an appreciation of the fact that the ideal specimen-holder would be one capable of being moved in all directions with respect to the electron beam,

without breaking the vacuum within the instru- While certain specimen-holders of the prior art are capable of numerous adjustments certain of the adjustments could heretofore be made only when the vacuum is broken. (As to this, see U. S. Patent 2,275,284.)

Accordingly, the principal object of the present invention is to provide an improved specimenholder for'electron optical instruments of the general character described and one including a specimen mount capable of being oriented'in all directions without breaking the vacuum in any part of the instrument in which it is used.

Another and important object of the invention is to achieve the foregoing advantages in a readily removable and compact specimen-holder, and one further characterized by its ease of assembly and by the simplicity and. accuracy of its adjustments.

Still another object of the present invention is to provide an adjustable specimen-holder having interchangeable specimen mounts for use with various types of specimens and in different types of electron optical instruments.

Certain preferred details of construction together with other objects and advantages will be apparent and the invention itself will be best understood by a reference to the fOllOWiIlg specification and to the accompanying drawing,

wherein: v I

Figure 1 is a sectional elevation of an adjustable specimen-holder constructed in accordance with the present inventionand shown mounted for use in an electron optical instrument,

Figure 2 isan end view, with the beam forming diaphragm removed looking into the leading end Ofthe specimen-holder of Fig. 1, and

Figure-3 is a sectional view of an alternative form of fixture for the specimen-holder of Fig. 1.

In Fig. 1, l designates generally an electron optical instrument containing a centrally located vertical conduit 3 having an electron axis A-A which is surrounded by magnetic coils 5 and l for directing the electrons downwardly from a source (not shown) along the said axis to a viewing chamber (not shown) The'relative arrangement of the coils 5 and 1 forms no part of the present invention though it may here be mentioned that when the instrument here illustrated is to be used as a transmission type electron microscope only the coil '5 is energized (in which case it may comprise the projection lens of the microscope). On-the other hand'whe'n, as in the instant case, the instrument is used as an electron diffraction camera only the coil '1 is energized.

Interposed in the path of the electrons which travel along the axis A-A is a diaphragm 9, which has a beam-forming aperture ta therein, and beneath thesaid diaphragm there is a specimen mo'un't H to which a crystalline or other opaque specimen lid is cemented, or otherwise affixed. As willh'erein'aft'er more fully appear, the diaphragm 9 is immovably supported, and the specimen mount ii is adjustably supported, by a'plug-like structure 13 which is removable as a unit from a core or conduit it which extends through the instrument along an axis which is normal to theel'ectron axis A-A.

Before proceeding with a des'criptionof the removable plug-like structureor holder 13 upon which the diaphragm .9 and specimen mount H are supported, attention is called to the fact that that part of the bore 15 which'liest'o the left of the electron axis A -A contains a slid'ably mounted cup-shape'valve ll which-may be moved inwardly to a position whereat its leading circular edge abuts a similarly shaped gasket I9 on the inner end of a cylinder 2! within Which'the plug i3 is contained. The vacuum tight seal thus formed permits the plug l3 to be withdrawn from the cylinder 2| without breaking the vacuum in the electron conduit 3. In order to facilitate the removal of air from the confines of the cylinder 2|, both the cylinder and the plug i3 therein may be provided with registered holes 23 and the body or housing of the microscope may be provided with a port (not shown) in line with the said holes, through which the air may be removed prior to opening the valve H.

The cylinder 2| within which the plug or holder i3 is contained is held in the bore I5 by means of a gland bushing 25 which is provided with a number of circumferentially spaced screws 21 which engage screw holes in the casing of the microscope. A so-called Woodruff key 29 holds both the cylinder 2| and plug l3 against rotation. It will be observed that the rounded edge of the key 29 is received in a slot 3| on the outer surface of the plug l3 and that (as shown in Fig. 2) the said slot extends to the inner or leading end of the plug. Hence, the plug can be inserted within the cylinder 2| (and the cylinder within the bore IE) only when the slot 3! is in register with the key 29.

The holder or plug l3 which carries both the rigidly supported diaphragm 9 and the adjustable specimen mount H is held in the cylinder by means of a handwheel 33 which has a dependent externally threaded collar 330. which engages the complementarily threaded inner surface of the gland bushing 25. Torque applied in the clockwise direction to the handwheel 83 through its handles or spokes 3'5 serves to screw up the collar 33a in the gland bushing 25 and causes a compression force to be applied to a gasket 31' through an annulus 39 which is keyed against rotation on the surface of the plug l3 contiguous the inner periphery of the wheel.

The projecting portion of the plug I3 is provided, in addition to the handwheel 33, with three thumbwheels 4|, 43 and 45, respectively, which operate to control theorientation of the specimen mount H with respect to the electron axis AA of the microscope or diffraction camera i. Exactly how these thumbwheels operate to efiect such movements of the holder M will be apparent from the following:

The specimen mount II isremovably affixed to the inner end of a flexible rod 41 which is supported within the plug 13 in a manner to permit .of its being both rotated about and moved slidably along an axis which is substantially normal to the electron axis AA. The axial movement of this red 41 is controlled by the thumbwheel. 4| and its rotary movement is controlled by the thumbwheel 43. An externally threaded splined sleeve 49 which is held ,on the outer end of the.

rod 41 by a washer and nut 5| serves to move the said rod to the left or to the right as determined by the direction-in which the thumbwheel 4| is rotated. The wheel 43, on the other hand, imparts its rotary movement directly to the said rod 4'! through a hub 53 upon which the said wheel is slidably splined.

The third thumbwheel 45 operates through a second slidably mounted rodj55 and a tiltable carriage 51 to impart a flexing force to the flexible rod 41 upon whichthe specimen mount H is afiixed- The details of the tiltable carriage 5? are shown more clearly in the-end view (Fig. 2) wherein this T-shape member is shown pivotally supported adjacent to its-lower end between two ball bearings 59 and "59a contained in separate 4 inwardly extending slots GI and Bid in the rigid platform or extension l3a. of the plug l3 which supports the diaphragm 9. (In Fig. 2 the diaphragm 9 has been removed from its seat in the platform Ilia, but see Figs. 1 and 3.) Two pointed screws 6| and 6M, seated in the platform 53a, confine the balls 59, 59a in their holes and urge them into frictional supporting engagement with the opposite sides of the upstanding base of the T. The upper rod 55 which controls the movement of this T-shape carriage 57 is received in a holein the crossarm of the T and is secured therein by two oppositely extending set screws 65, 65a. The lower rod 47, upon which the specimen-holder H is mounted, has a sliding fit in a hole provided for the purpose in the base of the T, adjacent to its'pivot point. It will thus be apparent that when the thumbwheel 45 is turned to move the control rod 41 axially (to the left or to the right, as viewed in Figs. 1 and 3), the carriage 5? will be tilted in the same direction on its pivot (i. e. the balls 59 and 58a) and, as a result, the lower rod 41 will have a flexing force applied thereto along the section thereof which passes through the lower end of the said carriage 5?. The flexure in the rod 41 producedby the tilting movement of the carriage 5? is localized by reducing the diameter of the said rod adjacent to its leading end, as indicated at 41a. (Fig. 1).

As the rod M is flexed the specimen-support l i on the end thereof is tilted with respect to the electron axis AA; hence, the portion of the specimen Ha which ispresented to the electron" beam may be changed at willsimply by turning the thumbwheel 45 which controls the movement of the carriage 5?. The axial and rotatable move ments imparted to the flexible rod 41 by the thumbwheels d! and 43, respectively, are substantially unaffected by the angular position of the carriage 5'1 and this makes it practical to provide calibrations on the periphery of each of the thumbwheels ii, 43, 45 to indicate the relative position of the specimen at any given moment.

It is, of course, important to prevent air from leaking into the electron conduit 3 through the specimen-holder 3 and, to prevent such leakage, vacuum tight seals of a special construction are provided where the slidable control rods 41 and 55 pass to the exterior of the instrument.

Since these seals for the rods 41 and 55 are of duplicate construction, a description of one will serve as a description of both. r

As shown in Fig. 1, the'rod 55 passes through a grommet 61, a metal washer 69 and a'coil spring H which are contained in a bore, pro vided for the purpose, in the body |3 of the holder.

, This bore communicates through a passageway 73 with 'a second bore l5 which will be understood to contain a. filling of oil having a'low vapor pressure. The grommet or gasket" 61 is constituted of synthetic rubber (e. g. neoprene or hycar) or other suitable elastic material;

ond spring, about the leading end of the rod 55 and which bears against the tiltable carriage 51,

has been found to contribute to the-smooth op'- In either case, the

eration of the saidv carriage and shaft 55 but is not a necessary adjunct to the operation of the vacuum tight seal above described.

The shape or form of the specimen mount affixed to the end of the shaft il will ordinarily'be dictated by the kind of specimen to be examined and by the type of instrument used in its examination. Thus, while the flat surfaced plate H shown in Fig. 1 is recommended as a support for. a crystalline specimen whose surfaces, are to be examined in an electron diifraction camera, when the specimen comprises a. powder-like substance or a transparent object which is to be examined in a transmission type microscope the use of a foraminous support, such, for example, as the one shown in Fig. 3, is recommended.

In Fig. 3 a small metal screen II (which will be understood to contain the specimen embedded in a collodion or similar film, not shown) is supported in a removable cap 19 which is fitted over the end of a hollow fixture Bl on the end of the adjustable control rod 41. Other types and forms of fixtures and supports will suggest themselves to those skilled in the art of electron microscopy.

From the foregoing it Will be apparent that the present invention provides an improved specimen-holder which is capable of being oriented in all directions without breaking the vacuum in any part of the instrument in which it is used, and is further characterized by its ease of assembly and by the simplicity and accuracy of its adjustments.

What is claimed is:

1. In an electron optical device having an electron axis, a flexible rod supported within said device and extending to the exterior thereof, said rod terminating at its inner end adjacent to said electron axis, a support for a specimen mounted on said flexible rod adjacent to the said inner end thereof, and means extending to the exterior of said device for causing a flexing force to be applied to said flexible rod whereby to tilt said specimen-support with respect to said electron axis.

2. In an electron optical device having'an axis along which electrons travel in the form of a beam, a flexible rod mounted to permit of movement along its axis within said device, said rod extending to the exterior of said device and terminating at its inner end adjacent to said electron axis, a specimen-support mounted on said flexible rod adjacent .to the said inner end thereof, means adjacent to the outer end of said rod for moving said rod axially whereby to move said specimen-support into and out of the path of said electron beam, and means extending to the exterior of said device for causing a flexing force to be applied to said flexible rod, Wherebyto tilt said specimen-support with respect to said electron axis.

3. In an electron optical device having an axis along which electrons travel in the form of a beam, a flexible rod mounted to permit of rotatable movement about and longitudinal movement along its axis within said device, said rod extending to the exterior of said device and terminating at its inner end adjacent to said electron axis, a specimen-support fixedly mounted on said flexible rod adjacent to the said inner end thereof, means operatively connected to said rod adjacent to its outer end for moving said specimen-support in the path of said beam and for rotating said support in said path, and separate means extending to the exterior of said device for causing a flexing force to be applied to-said-flexible. rod Whereby'to tilt said specimenholder with respect to said electronaxis.

4'. In an electron optical device having an electron axis along which electrons travel in the form of a beam and a second axis which intersects 'said first mentioned axis, a flexible rod mounted within said device to permit of rotatable movement about and axial movement along said second mentioned axis, said flexible rod extending to the exterior of said device and terminating at its inner end adjacent to the point of intersection of said axes, a specimen-support fixedly mounted on said flexible rod adjacent to the said inner end thereof, means for moving said rod axially whereby to move said specimen-support With respect to the point of intersection of said axes, means for rotating said rod and hence said specimen-support about said second mentioned axis in the path of said electron beam, and means extending to the exterior of said device for applying a flexing force to said rod adjacent to its said inner end whereby to tilt said specimen-support with respect to said electron arms.

5. The combination with an electron optical device having a first conduit through which electrons pass from a source to a target and a second conduit which communicates with said first mentioned conduit, of a holder for adjustably mounting a specimen within said electronic device so as to be impinged by said electrons and operable to adjust the point of impact at any point on the surface of said specimens as well as the angle of incidence of said beam on the surface of said specimen, said holder comprising a plug-like structure adapted to be received within said second mentioned conduit and containing a flexible control rod terminating at its inner end adjacent to the point of intersection of said first and second conduits, a support for a specimen fixedly mounted on said control rod adjacent to the said inner end thereof and extending into said electron conduit when said plug is received within said second conduit, means adjacent to the outer end of said plug for moving said rod axially whereby to move said specimensupport across the path of said beam, means adjacent to said outer end of said plug for ro-tating said rod and hence said specimen-support in the path of said electron beam, and means operably connected to the inner end of said flexible rod and extending to the outer end of said plug for applying a flexing force to said rod whereby to tilt said specimen-support with respect to said electron beam.

6. In an electron optical device having an axis along which electrons travel in the form of a beam, a carriage supported for tiltable movement adjacent to said axis, a flexible rod supported adjacent to its inner end, for axial movement on said carriage and extending to the exterior of said electron optical device, a support for a specimen mounted on said flexible rod adjacent to the said inner end thereof, means exterior of said device for moving said flexible rod axially whereby to move said specimen-support into and out of the path of said electron beam, and separate means extending to the exterior of said device for tilting saidcarriage to flex said rod and thereby tilt said specimen-holder with respect to said electron axis.

7. In combination, an evacuated envelope containing a part to be oriented within said envelope, 3, rod-like member mounted for movement with in said envelope and extending to the exterior thereof for controlling the movement of said part, an elastic bushing about said rod,means' REFERENCES CITED The following references are of record in the file of this patent:

8,. UNITED STATES PATENTS Number Name Date 4 2,267,769 Von Ardenne Dec. 80, 1941 2,003,387 Ott June 4, 1935 2,272,843 Hillier Feb. 10, 1942 OTHER REFERENCES Page 353 of Zeit. Fur Physik, vol. 115, March,

1940, Von Ardenne, Uber ein Universal-Elecktrarenmikroskop etc. 250-495.

Page 556 of Review of Scientific Instruments, vol. 12, Nov. 1941, 250-495.

Images