US2417213A - Device for indirect heating of materials - Google Patents

Description

March 11, 1947. R. G, PlCARD DEVICE FOR INDIRECT HEATING OF MATERIALS Filed Dec. 28, 1944 mm R mm Ul m m m Rn Patented Mar. 11, 1947 DEVICE FOR INDIRECT HEATING OF MATERIALS Robert G. Pica-rd, Collingswood, N. 1., assignor to Radio Corporation of America, a corporation of Delaware Application December 28, 1944, Serial No. 570,091

6 Claims.

The present invention relates to the indirect heating of materials and more particularly to a means for raising the temperature of specimens while under examination in electron microscopes, electron difii'action cameras, or other vacuum equipment.

In the examination of specimens in a vacuum, such as electron microscopes, the temperature of the specimen generally remains substantially constant, which is entirely satisfactory under most observation conditions, but leaves the observer uninformed as to how a specimen reacts when its temperature is raised above that existing in the vacuum chamber. In other words, it is important to know the effect of abnormal temperature upon a material or specimen under ob servation.

Some of the objects of the present invention are: to provide a device for raising the temperature of a specimen in a vacuum chamber so that it can be examined in this heated condition; to provide means for indirectly heating a specimen in a vacuum chamber; to provide an indirect heating unit which can be readily mounted in an electron microscope or electron diffraction camera in a position to focus heat upon a specimen for examination purposes; and to provide other improvements as will hereinafter appear.

In the accompanying drawings, Fig. 1 represents a fragmentary axial section of the column of an electron microscope showing an indirect heating unit embodying one form of the present invention; Fig. 2 represents a perspective of the unit; and Fig. 3 represents a section on line III- III of Fig. 1.

Referring to the drawings, one form of the present invention comprises a casing l0 forming a chamber II to be evacuated and having a cap extension of reduced diameter to provide a Deripheral shoulder l2 to abut the gasket i3 and so prevent air leakage when the extension enters the specimen chamber l4 formed in the column l5 of the microscope or diffraction camera. When so assembled the gasket I3 is compressed between the shoulder l2 and the column 15 by atmospheric pressure when the chamber 1 4 is exhausted. The end of the cap extension is apertured and threaded for adjustably mounting a lens l6, preferably of the rock salt type or sylvite, for focusing the heat (infra-red) radiation upon the specimen. Source of heat may be focused on sp cimen by cap screw arrangement shown. A port I! is provided in the extension so that the chamber II is also evacuated with the specimen chamber id. The outer end of the casing is vacuum 2 sealed by a plate l8 which is welded or otherwise fastened in place in leak-proof relation.

For generating the heat to be radiated, current conducting wires 20 are led into the chamber II and there terminate in a filament 2|, preferably in the shape of a flat spiral which is located in juxtaposed relation to the lens IS. The wires 20 are in a circuit including a suitable source of current 23 and a variable resistance 24, the latter serving to control the heat developed in the filament 2!. When assembled for use as shown in Fig. l, the lens i6 is in close proximity to the specimen carried by the apertured end of the specimen holder 25 which enters the opposite side of the specimen chamber 14. The holder 25 locates the specimen in alignment with the beam of electrons from the electron gun 26, which is of well known form and enters an end of the microscope or diffraction camera column. Thus, while the specimen is subject to the normal heat of the projected electrons, it can also be heated at will by energizing the filament 2| thereby to raise the temperature of the specimen to allow it to be studied under the changed condition. By varying the resistance 24 the radiated heat can be controlled as desired.

The specimen holder 25 is moved into the posi tion of focus by means of the controlling meohanism 21, which may be of the type disclosed in the copending application Serial No. 500,620, filed August 31, 1943, by Frank E. Runge for "Electron-optical instruments. which is assigned to the same assignee as the instant application.

What is claimed is:

1. An indirect heating unit comprising a closed casing having an aperture in one end, said casing having a portion arranged to enter the evacuated chamber of an electron microscope and assume a position with said aperture in juxtaposed relation to a specimen, said portion having a port communicating with the interior of said chamber, a lens mounted in said aperture, an electrical filament in said casing aligned with said lens, and an electrical circuit including a source of current and leads connected to said filament.

2. 'An indirect heating unit comprising a closed casing having an aperture in one end, said casing having a portion arranged to enter the evacuated chamber of an electron microscope and assume a position with said aperture in juxtaposed relation to a specimen, said portion having a port communicating with the interior of said chamber a lens mounted in said aperture, an electrical spiral filament in said casing aligned with and parallel to said lens, and an electrical circuit including a source of current and leads connected to said filament.

3. An indirect heating unit comprising a closed casing having an aperture in one end, said casing having a portion arranged to enter the evacuated chamber of an electron microscope and assume a position with said aperture in juxtaposed relation to a specimen, said portion having a port communicating with the interior of said chamber a lens mounted in said aperture, an electrical spiral filament in said casing aligned with and parallel to said lens, an electrical circuit including a source of current and leads connected to said filament, and means in said circuit for varying the voltage applied to said filament.

4. In a device operating under vacuum conditions, the combination of an evacuated chamber, an electron gun arranged to project an electron beam into said chamber, a holder in said chamber for mounting a specimen in the path of said beam, and means including a source of heat to subject said specimen to radiated heat.

5. In a device operating under vacuum conditions, the combination of an evacuated chamber, an electron gun arranged to project an electron beam into said chamber, a holder in said chamber for mounting a specimen in the path of said beam, means including 9, source of heat to subject said specimen to radiated heat, and means to focus said supplemental heat upon said specimen.

6, In a device operating under vacuum conditions, the combination of an evacuated chamher, an electron gun arranged to project an electron beam into said chamber, a holder in said chamber for mounting a specimen in the path of said beam, means including a source of heat to subject said specimen to radiated heat, and means to control the temperature of said supplemental means.

ROBERT G. PICARD.

REFERENCES CITED The following references are of record in the file of this patent:

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