US2890340A - Calutron - Google Patents

Description

Unid j Safe Pate CALUTRON Willian! vlM. Brobeck, Berkeley, Edward J.,Lofg'en, Al- Bally, andRoliert L. Thornton, Berkeley, Calif., iassignsito the United States of America as represented by 4the UnitedStates Atomic Energy 'Commission Applicata@ July zs, 1946, Serial No. 685,646

' 9ct-aims. (ci. asti-41.9)

The present invention relates 'to the apparatus for treating a polyisotopic substance to produce a plurality of '-seg'regable (masses wherein the distribution of the constituent isotopes has beenaltered so that one of the masses produced is enriched with respect to'at least one isotope. -Th'e'purpose "of such treatment is to obtain a product characterized by an enhancement of the percentage of a 's"electedisotope. More specifically, the invention'relates to ya deviceknown in the art as a calutron, a term whose definition is any apparatus or machine where isotope separation or enrichment is achieved on a large scale yielding commercially usefulquantities of one or more isotopes, byappropriate separative action on gaseous ions with electrostatic or electromagnetic means or combinations of them.

The {foregoing definition has been takenv from U. S. Patent No. 2,709 ,222, which issued to Ernest O. Lawrence, `onli/ lay 24, 195,5. In that patent, the theory of isotopic 'separation'and the principles of operati'onof a calutron 'are fully set forth, and will not here be repeated.

'It may be stated generally, however, that the calutron to which this invention relates comprises essentially an evacuated tank disposed in a strong, substantially uni- 'for'm magnetic ield, and a transmitter and a receiver located withinthe tank.

The transmitter includes an ionizing arc chamber having an electron emitting cathode associated therewith. The arc chamber has an exit slit opening out into the tank,l and spaced from the slit are two mutually spaced accelerating electrodes carried at a relatively high negative potential with respect to the arc chamber. As a result ofthis potential difference, positive ions formed in the arc chamber are drawn out through the slit, and are projected'in a slightly divergent beam into the tank.

- continuous supply of material, the isotopes of which are'to be separated, is provided in the arc chamber. This may conveniently be accomplished by providing a charge reservoir in communication with the arc chamber, and the material or a suitable compound thereof may be provide'dinthe charge reservoir. The charge material may th'en be'heated, and its vapor caused to flow at a controlled fate into thev arc'chamber, where ions of the several isotopes -are formed -and projected into the beamv previously described.

rThe calutron described herein is particularly useful in the separation of U235 and Um, and a suitable charge material for this separation is UC14, a solid which may be caused to pass into the vapor phase by heating the compound in the charge reservoir. Alternatively, of course, the vcharge material may be a compound which isa gas at normal conditions and is 'supplied directly to the arc chamber at a controlled rate.

The beam of positive ions of the polyisotopic substance isvprojected through themagn'etic eld in a direction norrral tothe'lield,and the beamv is caused thereby to follow an arcuatepath wherein -the ions Yof theheavier isotope tend to concentrate in the region adjacent the outer perice riphery. From geometric considerations there results a substantial focusing of ions of the same isotope after approximately 180 of travel, and selective collection of isotopes may bemade at this location.

The present invention relates more particularly to an improved calutron having a plurality of ion transmitters and to a liner employed throughout the region traversed by the beams generated and including beam delimiting vanes for preventing the scattering of ions from one of the beams into another,

It is accordingly one object of this invention to provide an improved calutron having an increased capacity.

It is another object of this invention to provide a liner for a calutron of the type employing a plurality of beams which liner includes means for preventing the scattering of components of one of the beams into another.

lt is a feature of this invention that there is provided a calutron having a pair of beam transmitting units or source units each including a double beam source and a corresponding pair of receiver units each including a pair of receivers, and an electrostatic shield or liner extending from the sources to the receivers and including beam delimiting vanes for the proper segregation of the various beams.

Further objects and advantages will be apparent from the annexed specification in which:

vFigure l is a horizontal sectional View of a calutron embodying the present invention;

Fig. 2 is an enlarged section taken on the line 2-2 of Fig.l. v

Referring more particularly to the drawings, there is indicated a calutron comprising an evacuated vessel or tank 20 having an upper wall 21, a lower Wall 22, a rear wall 23, side walls 24 and a front wall or door 25. One of the side walls 24 is provided with a manifold 26 which in practice communicates with suitable pumping apparatus (not shown) by which the vessel 20 may be evacuated to the desired pressure. The pressure employed is of the order of 10-4-10-5 mm. of Hg.

The vessel 20 is positioned between the upper and lower pole faces, numbered 27 and 28 respectively, of a powerful electromagnet (not shown), by means of which a strong substantially uniform magnetic flux is caused to traverse the vessel 20.

As indicated, the front wall or door 25 comprises a number of sections, 29, 30, 31 and 32, respectively, each of which is secured by any suitable means in removable relation to the top and bottom walls 21 and 22, the corner posts 33 and 34 or to the intermediate upstanding posts 35.

The sections 29 and 30 each carry on their inner sides a dual ion generating mechanism indicated at 36, projecting into the vessel 20. As will ybe understood by those skilled in the art each of the ion generating mechanisms 36 includes means for generating a vapor of the material to be segregated and a pair of arc chambers (not shown) aligned with the source slits 37.

Each of the sections 29 and 30 similarly carries, by means of insulator-bushings 38, an accelerating mechanism indicated generally at 39. This accelerating mechanism includes a frame 40 carrying a pair of accelerating slit defining elements 41 aligned with the source slits 37, yand a shield 4Z engaging the forwardly extending box 43 framing an aperture 44 in the liner 45. A good mechanical and electrical connection is provided between the shield 42 and the box 43.

Suitable electrical connections (not shown) are provided, preferably through one of the bushings 38 by means of which the entire liner 45, the shields 42 and the accelerating mechanism 39 is maintained at a high negative potential with respect to the ion generating mechainsms 36, which are grounded.

As will be readily understood the last described mechanism will cause a beam of positive ions of the material to be treated to be withdrawn from each of the source slits 37, through'each of the slits defined by the accelerating slit dening elements 41, and projected into the liner 45. Each of the four beams so projected is indicated schematically as 43, 49, and 50 and 51 respectively.

The liner 45 as indicated is generally trapezoidal in cross-section and includes an upper wall 52, a lower wall 53, a rear wall 54, a front wall 55 and a pair of converging side walls 56 and 57.

A plurality of pin insulators 58 are provided and insulatedly support the liner 45 upon the bottom wall 22 of the vessel 20.

The liner 45 is also provided with a pair of openings 60 and 61 formed in its front wall 55 through which the beams may pass, as shown. The interior of the liner 45 is provided with a number of beam delimiting vanes. One of these, numbered 62, is positioned on the inner side of the front wall 55 and is inclined in the direction of travel of the beams. Along its innermost edge vthe vane 62 has suitably secured thereto a beam delimiting strip 63 of carbon, molybdenum or other material adapted to withstand bombardment by positive ions. The strip 63 is positioned so that its inner edge lies in a vertical line which intersects the inner edges of both beam 48 and beam 49. An altogether similar vane 64 but oppositely inclined with respect to the vane 62 is also carried by that wall 55 and has a similar beam delimiting strip 65 secured along its inner edge. The beam delimiting strip 65 is positioned so that its inner edge lies in a vertical line which intersects the inner edges of both beam 50 and beam 51.

The wall 55 is also provided adjacent its midpoint with a vane 66 extending inwardly therefrom in a direction perpendicular thereto. The vane 66 similarly carries a similar beam delimiting strip 67 whose innermost Vedge lies in a line intersecting the inner edges of both bea-m 48 and beam 51.

The rear wall 54 of the liner 45 is provided with a vane 68 extending perpendicular thereto into the liner and including a beam delimiting strip 69 whose inner edge is spaced slightly from or coincides with the outer edges of both beam 48 and beam 49.

The rear wall 54 similarly carries a vane 70 extending perpendicular thereto into the liner and including a beam delimiting strip 71 whose inner edge is spaced slightly from or coincides with the outer edges of both beam 50 and beam 51. The sections 31 and 32 each carry a pair of receiver-collector units 72, thus'providing a collector for each of the beams 48, 49, 50 and 51 as indicated. The collector units 72 each conventionally includes pockets for receiving and collecting de-ionized samples of the material being treated, and in accordance with the underlying principles of the calutron these samples will be either enriched or impoverished with respect to a given isotope of the polyisotopic material.

When the above described calutron is used, as is Contemplated, for the treatment of a polyisotopic element such as uranium and a suitable charge material such as UC14 is utilized, a variety of positive ions such as U+, U++, UCl+ and UCl++, etc., may be generated and it is generally impractical to attempt to collect more than one of these Varieties, in practice generally U+ ions. The beams numbered 4S, 49, 50 and 51 accordingly represent beam of U+ ions. It will be Aapparent from the foregoing that in this multiple source clutron there is provided a suitable beam delimiting strip 63, 65, 67, 69 or 71 adjacent either the inner or outer edge ofl each such beam and adapted to intercept and exclude fromA the collectors 72 any ions such as U++, UCl+ or UCl++ which may have been projected into the liner with the desired U+ ions. Furthermore, as only U+ ions which have taken an uninterrupted passage from the sources to the receivers without suffering scattering will conform to the beams indicated and hence have a focusing point after 180 of travel, the above enumerated vanes yand beam delimiting strips also serve to prevent contamination of the collected samples by excluding any such scattered ions.

The problem of excluding undesired ions from the collectors is increased in multiple source calutrons such as the present invention. In single beam units only the desired U+ ions should have the required trajectory to arrive at the collecting focus, but in multiple beam units undesired ions from one source unit may very Well have the desired energy, unless interrupted, to reach the co1- lecting foci provided for an entirely ditferent beam. accordingly it will be Iappreciated that the beam delimitmg vanes and strips enumerated serve the purpose of excluding undesired ions from a given source from reaching a different collector.

Furthermore by providing the inclined liner walls 56 and 57 closely adjacent the outer periphery of the beams, another provision is made for the exclusion of wideangle ions, which are caused to strike these Walls and become neutralized.

While there has been described what is at present consldered a preferred embodiment of the invention it will be apparent that various changes and modifications may be made therein without departing from the spirit of the invention and it is intended to cover all such changes and modifications as found within the true scope and spirit of the appended claims.

What is claimed is:

l. In a calutron, a pressure tight vessel having an insulated liner therein adapted to be maintained at a high negative potential, a plurality of independently mounted source units each comprising a plurality of ion generating mechanism and a corresponding plurality of independently mounted receiverunits each comprising a plurality of ion collectors.

2. In a calutron comprising a substantially fluid-tight vessel positioned between a pair of magnet poles, a plurality of ion transmitters in said vessel arranged to project a plurality of beams of ions in arcuate paths transversely of the magnetic field, a plurality of ion receivers respectively positioned within said vessel to receive the resulting curved beams, a hollow insulated liner in said vessel extending between the transmitters and receivers and carried at a high negative potential with respect to said vessel, said liner including a plurality of beam delimiting vanes respectively adapted to prevent ions from one beam scattering into a receiver positioned to receive ions from another of said beams.

3. The combination set forth in claim 2 in which at least one of said beam delimiting vanes is positioned substantially in a region of the intersection of the outer components of an adjacent pair of said beams.

4. The combination set forth in claim 2 in which at v least one of said beam delimiting vanes is positioned so 6. The combination set forth in claim 2 in which said plurality of beam delimiting vanes includes a vane positioned to intersect and scrape the inner edges of two of said beams, a vane positioned to intersect andY shave the outer edges of two of said beams and a vane positioned to intersect and shave the inner edges of another pair of said beams.

7. The combination set forth in claim 2 in which at least one of said beam delimiting vanes is positioned adjacent said receivers and intermediate the paths of two Of said ion beams.

8. In a calutron, a fluid-tight vessel, a pair of ion transmitters adapted to project across said vessel, a pair of double arcuate focused ion beams, a corresponding pair of double ion receivers located at the foci of said arcuate beams, and a liner within said vessel and having a plurality of beam delimiting vanes located respectively substantially in the regions of intersection of the inner and outer components of said beams.

9. In a calutron comprising a substantially fluid tight tank positioned between a pair of magnet poles, an ion transmitter in said tank arranged to project a beam of ions transversely of the magnetic eld, including ion velocity controlling electrodes carried at a high negative potential, and an ion receiver in said tank disposed to receive the resulting curved ion beam; a hollow insulating liner in said tank extending between said transmitter and receiver carried at the potential of said electrodes, said liner being generally trapezoidal in plan, and positioned with respect to the ion beams such that the inclined ends of the liner lie closely adjacent to the ion 10 beams.

No references cited.

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