US2752503A - Isotope separators - Google Patents

Isotope separators Download PDF

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Publication number
US2752503A
US2752503A US469784A US46978454A US2752503A US 2752503 A US2752503 A US 2752503A US 469784 A US469784 A US 469784A US 46978454 A US46978454 A US 46978454A US 2752503 A US2752503 A US 2752503A
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Prior art keywords
ions
plates
arc
electrons
circumferential
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Expired - Lifetime
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US469784A
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English (en)
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Slepian Joseph
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Individual
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Priority to NL201949D priority Critical patent/NL201949A/xx
Priority to DENDAT1070850D priority patent/DE1070850B/de
Priority to NL113583D priority patent/NL113583C/xx
Priority to BE542860D priority patent/BE542860A/xx
Priority to US469784A priority patent/US2752503A/en
Application filed by Individual filed Critical Individual
Priority to CH341145D priority patent/CH341145A/de
Priority to GB31880/55A priority patent/GB797558A/en
Priority to FR1139710D priority patent/FR1139710A/fr
Application granted granted Critical
Publication of US2752503A publication Critical patent/US2752503A/en
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D59/00—Separation of different isotopes of the same chemical element
    • B01D59/44—Separation by mass spectrography
    • B01D59/48—Separation by mass spectrography using electrostatic and magnetic fields
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J19/00—Details of vacuum tubes of the types covered by group H01J21/00
    • H01J19/68—Specified gas introduced into the tube at low pressure, e.g. for reducing or influencing space charge
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J49/00—Particle spectrometers or separator tubes
    • H01J49/02—Details
    • H01J49/10—Ion sources; Ion guns
    • H01J49/12—Ion sources; Ion guns using an arc discharge, e.g. of the duoplasmatron type

Definitions

  • My invention in its broader aspects is based on the realization that the electromagnetic mass separator, acting on the isotopes in ionized form, offers means for obtaining substantial quantities of separate isotopes while consuming substantially less power than for gas difiFusion separators.
  • the process of electromagnetic mass separation has been encountered in mass spectrographs.
  • An electromagnetic mass separator with Whichthis object may be accomplished must meet two basic conditions. First, a su-ificient number of ions must be deposited per unit time on collectors from which the collected mass may be readily removed to provide a substantial mass or quantity of the material when the apparatus operates over a. shorttime interval. Second, the material must be distributed over the collector, so that there is a substantial enrichment during each operation of the apparatus, or the isotope to be separated in a predetermined region of the collector.
  • an electromagnetic mass separator including a source of ions capable of delivering a substantial quantity of material per unit time in which a large proportion of the ions and of electrons shall flow to a collector from which the material may be readily removed.
  • Another specific object of my invention is to provide an electromagnetic mass separator in which the ions and electrons shall be so distributed over the collector that during each operation of the apparatus there shall be a substantial enrichment of the isotope to be separated in predetermined regions of the collector.
  • An incidental object of my invention is to provide a novel arc discharge device particularly for producing a discharge rich in ions.
  • the electromagnetic separator to which my invention relates includes a generally cylindrical. vessel having conductive bases and circumferential walls, the bases capable of being insulated from the circumferential walls.
  • This vessel is maintained in a very high vacuum, less than micron, and at its center an arc is produced which carries substantial current, amperes or more, made up principally of electrons from the cathode, and to a smaller extent, of ions of the material from the anode and a space-charge neutralizing density of electrons also from the anode.
  • the bases of the vessel may be made up of a number of insulated sections which may be at two or more different. potentials. Among these sections are rings of small diameter coaxial with the are. A high magnetic field is impressed longitudinally on the cylindrical vessel and electric fields are impressed within the vessel between electrodes within the vessel. Usually, also, a negative potential is impressed on the rings.
  • My invention arises from the discoveries first, that with a field of relatively low intensity impressed in the region of, the are, for example by impressing a negative potential on the rings, the ions of the isotopes to be separated are projected with space-charge neutralizing electrons in substantial quantities into the evacuated space surrounding the arc, and, second, that effective separation of the isotopes may be produced by impressing in this space.
  • circumferential fields of constant polarity that is, fields produced by direct current potentials.
  • the projection of substantial quantities of ions in the evacuated space occurs because under the action of the relatively low electric field and the magnetic field impressed, the discharge from the arc into the space includes'not only ions, but electrons which are charged oppositely, and supply a charge per unit volume equal and-opposite to that of the ions.
  • the space charge produced by the ions of the isotopes within the space is effectively neutralized, by that of the electrons, and the ions and the equally and oppositely space-charged electrons flow into the space in substantial quantities.
  • the electrons are readily displaced in the direction of the magnetic field, and the random collisionswith the ions produce rapid reversals in the up and down motion (that is, the motion axially to the cylinder) of the electrons.
  • the electrons cannot escape because of thepotential which is applied to the ring-shaped upper and lower electrodes bounding the magnetic field, and they acquire a random energy equal to a large part of the total energy of the positive ions.
  • the electron Because of the smallness of mass of the electron, the electron will have a random velocity in the direction of the magnetic field several hundred times the velocity of the ion.
  • the electron velocity in the directions perpendicular to the magnetic field is also large, since these velocities are random to, coming from the same collisions with positive ions. But, in these directions, because of the low mass of the electron, the path of the electron is bent into small nearly closed curves by the action of the magnetic field.
  • the electrons move rapidly up and down but do not escape because of the negative potential 'on the ring electrodes, a small number of positive ions escape at the ring electrodes, but their mass is 'so great, they form a space-charge there so that a sheath forms there which separates the negative potential on the ring electrodes, from the lower (less negative) potential of the space adjacent.
  • the electrons circulate up and down (axially) with high velocities past the ions, and in the directions perpendicular to the magnetic field, they circulate with similar high velocities but in tight smal spirals, and these spirals are open just enough so that the electrons accompany the ions in their motions.
  • the ions themselves acquire a random energy through this interchange with the electrons. Their random energy is equal to that of the electrons and has a large part of their mean energy. Hence, if the electrical field is largely radial, only a modest enrichment of parts of the deposit is obtainable because of the large proportion which the random motion of the ions is to the mean motion. My observations during more than ten years of the motion of ions and electrons in magnetic fields completely confirm this.
  • the circumferential electric fields are set up between two or more radial sets of electrodes or slats between which D. C. potentials are impressed.
  • These radial electrodes or slats are set with one end as near to the are as is practicable, and with the other end at the extreme outer end of the vacuum vessel.
  • the initial radial electric field extends from the are out to the inner edge of the radial electrodes, and is applied by impressing the negative potential to the inner rings of the upper and lower plates, the positive end being connected to the anode of the arc. inner edges of the radial slats.
  • a direct potential is applied between the alternate radial electrodes.
  • This potential is in accordance with the preferred practice of my invention, independent of The rings extend to the positive ions appears just at the surface of the negative electrode, and a space charge of negative electrons appears at the positive electrode, and these thin space charges limit the electric field in the space between the electrodes to a little more than that corresponding to Hv, where v is the mean radial velocity of the ions at any point, and H is the magnitude of the magnetic field.
  • Figure 1 is a view partly in side elevation and partly in section showing an embodiment of my invention
  • Fig. 2 is a view in section taken along lines IIII of Fig. 1;
  • Fig. 3 is a fragmental view in section of the electrodes used in the practice of my invention.
  • Fig. 4 is a diagrammatic view showing the trajectories of the ions in the practice of my invention.
  • Fig. 5 is a diagrammatic view showing the relationship between the forces on the ions in the practice of my invention.
  • Fig. 6 is a diagrammatic view illustrating a modification of my invention
  • Fig. 7 is a diagrammatic view showing another modification of my invention.
  • Fig. 8 is a diagrammatic view showing still another modification of my invention.
  • Fig. 9 is a diagrammatic view of a further modification of my invention.
  • the apparatus shown in Figs. 1 and 2 includes a vacuum chamber 11 which is connected to a system of vacuum pumps (not shown) through an exhaust tube 13 and the potential between the rings and the arc electrode;
  • the radial electrodes or slats float electrically relative to the arc electrodes.
  • This potential on the radial slats sets up two oppositely directed circumferential fields, which would draw currents through the mass of ions and electrons brought up to the radial electrodes by the initial radial electric field. These currents are of such a sign that they cause the ions and electrons to be accelerated by the uniform magnetic field outwardly on one side of the negative plates, and inwardly on the other side of the negative plates. The ions and electrons then proceed outwardly in the alternate spaces between the plate electrodes.
  • the ions enter the circumferential fields with a mean velocity (which is nearly radial) and a random velocity, which nearly equals the radial mean velocity.-
  • the currents which are drawn to the plates by the D. C. potential between them is limited, since a space charge of is capable of being evacuated so that the pressure within this chamber is less than 1 micron.
  • the chamber 11 is of generally circularly cylindrical form having conducting bases 15 and 17 and a wall 19, the bases being provided with centrally disposed insulator inserts 21 and 23, and the wall 19 being provided with insulator inserts 25 and 27 and with an opening 29 into which the exhaust tube 13 is sealed.
  • the vacuum chamber is preferably grounded.
  • electrode holders 31 and 33 are passed.
  • the lower holder 31 is dimensioned to receive the positive electrode 35 which emits the ions, and the space-charge-neutralizing electrons
  • the upper holder 33 is dimensioned to receive the negative electrode 37.
  • the holders are provided with suitable facilities (not shown in detail) for connection to a power supply. This supply must be adequate to produce an are between the electrodes 35 and 37 and must be suitably regulated to assure that the arc is properly maintained.
  • the negative electrode 37 may be a cored carbon made by manufacturers of such electrodes in the United States, such as National Carbon Company of Cleveland, Ohio. It is a carbon rod 41 (Fig. 3), with its center drilled out, and having within it a core of oxides of the rare metal earths 173. Other electrodes may be used, however. All that is required is that it serve as a source of electrons; that is, as a cathode of an arc supplying large currents of the order of amperes of electrons.
  • a conducting ring 45 and 47 is suspended from each of the inserts 21 and 23 in the bases.
  • a conductor 49 and 51 is sealed through each insert and includes facilities (not shown in detail) for impressing a potential between the conducting rings and the electrode holders.
  • the studs 65 by which the segments are suspended are of insulating material, so that the segments may be insulated from the bases.
  • each respective plate 67 or 69 nearest the radial plates 71 through 77 takes on a potential near the potential of the nearest radial plate and the other circumferential plates take on gradually chang ing intermediate potentials, or the circumferential plates nearest the radial plate may each be conductively connected to the nearest radial plate.
  • a pair of conducting vertical slats 71 and 73, and 75 and 77 extend radially on both sides of the arc electrodes 35 and 37. These slats are suspended from insulating brackets 79 and 81 which are suspended from the bases 15 and 17 and are secured to the slats by insulating bolts 83. Conductors 91 and 97 are connected to slats 71 and 77, and to a common lead through the insert 25, and conductors 93 and 95 are connected to slats 73 and 75 and to a common lead through insert 27, these inserts being in the circumferential wall 19 and serve for impressing a potential between the slats. Each.
  • the slats extends inwardly to a point very near to the arc electrodes 35 and 37, the edges of the slats adjacent the rings 45 and 47 extending between the rings.
  • the slats 71, 73, 75, and 77 extend to a region near the cylindrical sections 67 and 69.
  • the slats are mounted just between the two segments 61 and 63, and 61' and 63 suspended from each of the bases 15 and 17, respectively.
  • the chamber 11 is mounted within an electromagnet 101.
  • the north and south poles 103 and 105 respectively, extend over the bases 15 and 17, respectively, and are spaced a short distance from the bases.
  • a vacuum chamber 11 having an ex ternal diameter of about 48 inches and somewhat less than 3 feet high.
  • This chamber has a volume of about 50 cubic feet and is evacuated by a system including a 20-inch oil difiusion pump, an 8-inch oil duffusion booster pump, and a 105 cubic foot per minute Kinney mechanical pump.
  • the slats have aheight somewhat less than 3 feet and a width somewhat less than 48 inches.
  • the spacing between the slats 71, 73, 75, and 77 is about A; inch, and the insulating brackets 79 and 81 between the slats are of relatively small dimensions.
  • the magnet has pole faces (103 and 105) which are about, 3 feet in diameter and are spaced approximately 3 feet apart.
  • the magnet is 12 /2 feet high, 13 feet long, and 4" feet wide.
  • the iron of the magnet weighs 90 tons, and the magnet is excited by a winding 107 having copper coils weighing 11 tons.
  • the magnet is adapted to be excited by 2,000 amperes, and when so excited, its flux in the center of the gap between the pole faces is about 10,000 gauss.
  • the energy for the arc is derived from a direct current supply having a voltage of 250 volts, and the current supplied through the arc is usually of the order of 10 amperes throughout most of my experiments, although this current has been as high as amperes, and may be more.
  • the arc voltage fluctuates between 20 volts and 100 volts.
  • the arc is fired in the usual manner by bringing the arc electrodes 35 and 37 into contact and separating them.
  • a motor (not shown), properly geared to one of the electrodes, usually the anode, is provided.
  • the movable electrode holder is sealed through a so-called Wilson seal, so that it may be moved backward and forward, and to a small extent sideways in all directions.
  • the motor is controlled from a suitable thyraton circuit to maintain the arc.
  • the chamber 11 is grounded.
  • a direct current potential of about 30 volts is impressed between the rings 45 and 47 and the anode electrode 35.
  • a direct current potential of about 200 or 300 volts is impressed between each pair of coextensive plates 71 and 75, and 73 and 77, one plate 73 and 75 on each side of the arc electrodes being electrically negative, and the other plate 71 and 77 being electrically positive.
  • the supply of the potentials between the slats 71 through 77 is insulated from the are potential supply and the supply of the potential between the positive electrode 35 and the rings 45 and 47. Circumferential electric fields are, thus, produced between the slats 71 and 75, and 73 and 77.
  • the various potentials are impressed be tween the arc electrodes 35 and 37, the rings 45 and 47 and the positive electrode 35 and the slats 71 through 77, and an arc is fired between the arc electrodes.
  • This are operates between the cathode electrode 37 and the eroded surface 107 (Fig. 3) of the anode electrode 35, producing ions of the isotopes to be separated and electrons.
  • the ions andv the electrons are projected into the space in which the circumferential fields are produced by the slats 71 through 77.
  • the lighter ions as we shall see, are pushed in the direction of the negative electrode, and the heavier ions are pushed in the direction of the positive electrodes. When they reach the surrounding cylindrical electrode, they deposit out, with the deposit at the positive end, the richer in heavy ions, and with the deposit at the negative end the richer in lighter ions.
  • V'o is the circumferential velocity acquired by the ion in the time t. Cancelling Hevo against eEo, and integrating Now letting x be a small radial distance travelled by the ion in time t,
  • each of the slats 71 through 77 is subdivided into a plurality of insulated sections 71a through 71d through 77a through 77d on which progressively higher potentials are impressed.
  • the potentials are such that the field E is sufiicient to satisfy the requirement that eE is greater than Hevo.
  • the electric cirvc,urrrf ererrtial field is produced by separate radial slats 201 and 203 at an angle rather than by pairs or sets of slats.
  • the circumferential electric field is produced by impressing potentials of opposite polarity on adjacent sector plates 61 and 63, and 61 and 63.
  • This modification does not include radial plates such as 71, 73, 75, 77, or 71a through 77d.
  • This modification does include the circumferential plates 67, 69, but these are omitted in Fig. 8 for clarity.
  • the circumferential plates 67,v 69 are omitted and instead there are radial plates 301. These plates 301 may be suspended from the end plates 61, 63, 61, 63', the suspensions. being either insulated or conducting.
  • the plates 301 permit the apparatus to be evacuated more readily than plates 67, 69.
  • the plates 301 facilitate the separation, since uncharged material will pass between them and only charged material will be collected by them.
  • an arc discharge device including an evacuated chamber having therein a first electrode and a second electrode, means for impressing a potential between said electrodes adequate to produce an are therebetween such that said first electrode is electrically negative relative to said second electrode, and means for impressing a magnetic field coaxial with said electrodes, the said combination being characterized by a first electrode consisting of a conducting material surrounding a core of electron emissive material.
  • Apparatus for separating isotopes of a material including means for producing an are including ions of said isotopes and means for impressing a magnetic field along said arc, the said apparatus being characterized by means for impressing circumferential electric fields about said arc, each said field being maintained at the same polarity.
  • Apparatus according to claim 6 characterized by the fact that the circumferential fields are produced by conducting plates extending radially from the are between which direct current potentials are impressed.
  • Apparatus according to claim 6 characterized by the fact that the circumferential fields are produced by a plurality of sets of plates each set consisting of a plurality of plates extending edge to edge radially from the arc, said plates being insulated from each other and corresponding plates of adjacent sets having potentials impressed therebetween which increase progressively with the radial distance from the arc.
  • Apparatus according to claim 9 characterized by the fact that the adjacent edges of successive plates of each set overlap.
  • Apparatus according to claim 9 characterized by the fact that the aggregate radial length of the plates of each set is large compared to the distance from the are of the edge of the plate adjacent the arc.
  • Apparatus according to claim 13 characterized by the fact that the segmental plates overlap at their edges.
  • Apparatus according to claim 6 characterized by the fact that space of the arc and the circumferential fields is bounded by a plurality of end-to-end circumferential conducting plates extending in the direction of the magnetic field, said plates being insulated from each other.
  • Apparatus according to claim 6 characterized by the fact that space of the arc and the circumferential fields is bounded by a plurality of radial conducting plates, said plates being insulated from each other.
  • Apparatus according to claim 7 characterized by the fact that the space of the arc and the radial plates is bounded by a plurality of end-to-end circumferential conducting plates extending in the direction of the magnetic field, between the outside edges of the radial plates, said plates being insulated from each other.
  • Apparatus according to claim 17 characterized by means connecting the respective circumferential plates nearest the radial plates to the radial plates to which they are nearest. 7 i
  • Apparatus according to claim 13 characterized by the fact that the space of the arc and the segmental plates is bounded by a plurality of end-to-end circumferential conducting plates extending in the direction of the magnetic field, between the outside edges of the segmental plates, said plates being insulated from each other.
  • Apparatus according to claim 19 characterized by means connecting the respective circumferential plates :nearest the segmental plates to the segmental plates to which they are nearest.
  • Apparatus according to claim 6 characterized by the fact that the space potential with reference to the arc of each point Within the space of the circumferential field is substantially proportional to the radial distance of said point from the arc.

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  • Chemical & Material Sciences (AREA)
  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Plasma & Fusion (AREA)
  • Analytical Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electron Tubes For Measurement (AREA)
  • Physical Or Chemical Processes And Apparatus (AREA)
US469784A 1954-11-18 1954-11-18 Isotope separators Expired - Lifetime US2752503A (en)

Priority Applications (8)

Application Number Priority Date Filing Date Title
NL113583D NL113583C (fr) 1954-11-18
BE542860D BE542860A (fr) 1954-11-18
NL201949D NL201949A (fr) 1954-11-18
DENDAT1070850D DE1070850B (fr) 1954-11-18
US469784A US2752503A (en) 1954-11-18 1954-11-18 Isotope separators
CH341145D CH341145A (de) 1954-11-18 1955-11-07 Einrichtung zur Trennung von Isotopen
GB31880/55A GB797558A (en) 1954-11-18 1955-11-08 Improvements in or relating to the separation of isotopes in electric and magnetic fields
FR1139710D FR1139710A (fr) 1954-11-18 1955-11-17 Séparateurs d'isotopes

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US469784A US2752503A (en) 1954-11-18 1954-11-18 Isotope separators

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US2752503A true US2752503A (en) 1956-06-26

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US469784A Expired - Lifetime US2752503A (en) 1954-11-18 1954-11-18 Isotope separators

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US (1) US2752503A (fr)
BE (1) BE542860A (fr)
CH (1) CH341145A (fr)
DE (1) DE1070850B (fr)
FR (1) FR1139710A (fr)
GB (1) GB797558A (fr)
NL (2) NL201949A (fr)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1133917B (de) * 1957-06-24 1962-07-26 Joseph Slepian Einrichtung zur Isotopentrennung mit elektrischen und magnetischen Feldern
US3047717A (en) * 1956-03-31 1962-07-31 Iwata Giichi Focusing mass spectrometer
US3226542A (en) * 1961-12-07 1965-12-28 Ass Elect Ind Mass spectrometer arc-type ion source having electrode cooling means

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3047717A (en) * 1956-03-31 1962-07-31 Iwata Giichi Focusing mass spectrometer
DE1133917B (de) * 1957-06-24 1962-07-26 Joseph Slepian Einrichtung zur Isotopentrennung mit elektrischen und magnetischen Feldern
US3226542A (en) * 1961-12-07 1965-12-28 Ass Elect Ind Mass spectrometer arc-type ion source having electrode cooling means

Also Published As

Publication number Publication date
FR1139710A (fr) 1957-07-04
CH341145A (de) 1959-09-30
GB797558A (en) 1958-07-02
NL113583C (fr)
BE542860A (fr)
NL201949A (fr)
DE1070850B (fr)

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