US2850635A - Regulator for calutron ion source - Google Patents

Description

Sept. 2, 1958 B, F. MILLER REGULATOR FOR C'ALUTRON ION SOURCE 4 Sheets-Sheet 1 Filed Aug. 28, 1945 INVENTOR. Bum-0 E MILLER BY %J M B. F. MILLER REGULATOR FOR CALUTRON ION SOURCE Sept. 2, 1958 Filed Aug. 28, 1945 4 Sheets-Sheet 2 N-m H UH v INVENTOR. Bum-0N F. M/LLE'E AIT ORNE Y 1*- 2, 1.953 B. F. MlL LER 2,850,635

REGULATOR FOR CALUTRON ION SOURCE Filed Aug. 28, 1945 4 Sheets-Sheet 3 AG. POWER SUPPLY INVEN TOR.

E :3 Y Bum-0N F M/LLEE F 3? M4 M ATTORNEY.

Sept. 2,1958 B. F. MILLER 2,350,635

REGULATOR FOR CALUTRON ION SOURCE Filed Aug. 28, 1945 4 Sheets-Sheet 4 A.C. POWER SUPPLY I I l i i I Y l l I i I I INVENTOR. F I E 4 I Basra/v F/V/LLEE AITOR NEY.

United States Patent REGULATOR FOR CALUTRON ION SOURCE Burton F. Miller, Berkeley, Calif., assignor to the United States of America as represented by the United States Atomic Energy Commission Application August 28, 1945, Serial No. 613,160

7 Claims. (Cl. 250-41.9)

This invention relates to improvements in electric discharge devices and circuit arrangements therefor, and more particularly to ion sources and circuit arrangements therefor as applied to calutrons of the type disclosed in the copending applications of Ernest 0. Lawrence, Serial No. 557,784, filed October 9, 1944, now Patent No. 2,709,222 granted on May 24, 1955 and Serial No. 536,401, filed May 19, 1944, now Patent No. 2,714,644 granted August 2, 1955.

A calutron is a device for increasing the proportion of a selected isotope in an element containing a plurality of isotopes in order to produce the element enriched with the selected isotope. Such a calutron essentially cornprises means for vaporizing a quantity of material containing the element that is to be enriched with the selected isotope; means for subjecting the vapor to ionization, whereby at least a portion of the vapor is ionized, so that ions of the different isotopes are produced; electrical means for segregating the ions from the un-ionized vapor and for accelerating the segregated ions to relatively high velocities; magnetic means for deflecting the ions along curved paths, the radii of curvature of the paths of the ions being proportional to the square roots of the masses of the ions, whereby the ions are concentrated in accordance with their masses; and means for deionizing and collecting the ions of the selected isotope thus concentrated, thereby to produce a deposit of the element enriched with the selected isotope.

The apparatus is especially useful in producing uranium enriched with U In the previously-mentioned copending application, Serial No. 536,401, there is disclosed a calutron of the multiple beam type, including, as shown in Figures 24, 25, and 26 thereof, an ion source unit provided with an arc block having a number of arc chambers formed therein. In this source unit, each arc chamber is provided with electron emitting structure individual thereto which is utilized to ionize the vapor contained in the associated arc chamber.

Likewise, the instant application pertains to a calutron of the multiple beam type including an ion source unit provided with a plurality of arc blocks, each having an arc chamber formed therein. In this source unit, however, the electron emitting devices are provided with power supplies common to all of them, together with circuits adapted for regulating each individual are. In another aspect, the conductors to two or more electron emitting devices may be combined electrically in such manner as'to reduce the total number of heavy electrical conductors.

One object of this invention is to provide, in a calutron ion source unit, an improved cathode circuit and are regulator arrangement.

Another object of the invention is to provide a regulated calutron multiple ion source unit requiring a reduced number of electrical conductors connected thereto.

Another object of the invention is to provide a "ice calutron ion source apparatus employing a plurality of independently regulated ion generators.

Another object of the invention is to provide a calutron ion source unit including a plurality of cathodes with an improved arrangement for controlling the emissions thereof.

Another object of the invention is to provide a calutron ion source unit with an improved circuit for regulating the arc current by utilizing a saturable reactor.

A further object of the invention is to provide a calutron ion source unit with an improved circuit utilizing an indirectly heated cathode.

Further objects of the invention will appear from a reading of the following detailed description of apparatus embodying the invention.

In the accompanying drawings, forming part of the specification,

Figure 1 is a diagrammatic plan view of a calutron comprising an improved ion source employing a plurality of independently regulated ion generators;

Fig. 2 is a vertical sectional view of the calutron taken along the line 22 of Fig. 1;

Fig. 3 is a schematic wiring diagram of the ion source filament supply, are supply and regulator incorporated in the calutron shown in Fig. 1;

Fig. 4 is a schematic wiring diagram of an alternate ion source filament supply, are supply and regulator adapted to a calutron having the arc cathodes at a common potential.

Referring now more particularly to Figs. 1 and 2, there is illustrated a calutron 10 comprising magnetic field structure, including upper and lower pole pieces 11 and 12 provided with substantially parallel spaced-apart pole faces, and a tank 13 disposed between the pole faces of the pole pieces 11 and 12. The pole pieces 11 and 12 carry windings, not shown, which are adapted to be energized in order to produce a substantially uniform and relatively strong magnetic field therebetween, which magnetic field passes through the tank 13 and the various parts housed therein. The tank 13 is of tubular configuration, being substantially arcuate in plan, and comprising substantially fiat parallel spaced-apart top and bottom walls 14 and 15, upstanding curved inner and outer side walls 16 and 17, and end Walls 18 and 19. The end walls 18 and 19 close the opposite ends of the tubular tank 13 and are adapted to be removably secured in place, whereby the tank 13 is hermetically sealed. Also, vacuum pumping apparatus 20 is associated with the tank 13, whereby the interior of the tank 13 may be evacuated to a pressure of the order of 10- to 10- min. Hg. Preferably, the component parts of the tank 13 are formed of steel, the top and bottom Walls 14 and 15 thereof being spaced a short distance from the pole faces of the upper and lower pole pieces 11 and 12 respectively, the tank 13 being retained in such position in any suitable manner, whereby the top and bottom Walls 14 and 15 constitute in efiect pole pieces with respect to the interior of the tank 13, as explained more fully hereinafter.

The removable end wall 18 suitably supports the ion source unit 21 provided with a charge receptacle 22. Communicating arc blocks 23a, 23z, are provided to the ion source unit 21. An electric heater 24 is arranged'in heat exchange relation with the charge receptacle 22 and is adapted to be connected to a suitable source of heater current supply, whereby the charge receptacle 22 may be appropriately heated, the charge receptacle 22 being formed of stainless steel or the like. The are blocks 23a, 23z, are formed, at least partially, of brass or the like and have upstanding slots 25a, 25z, formed in the front walls thereof remote from the charge receptacle 22. Thus, the arc blocks 23a, 232, are of hollow construetion, the cavities in arc blocks 23a, 23z, communieating with the interior of the charge receptacle 22.

Also the removable end wall 18 carries filaments 26a,

26z, adapted to be connected through busses 27 and 28 to a suitable source of filament current supply Thefilaments 26a, 26z, overhang the upper end of their respective arc blocks 23a, 23z,- and are arranged in alignment with respect to the upperjendofthe cavity formed therein. Between the filaments 26a, 26z, and their respective arc blocks 23a, 23;, are arranged in alignment the respective control electrodes 29a, 29z, and the respective arc cathodes; 30a, 30z. The are blocks 23a, 232, carry anodes 31a, 31z, respectively, disposed adjacent the lower end thereof and arranged in alignment with respect to the cavity formed therein.

Also, the arc blocks 23a, 23z, carry collimating elec- "trodes 32a, 321, respectively, adjacent the upper ends thereof, each of the collimating electrodes 32:1, 321 having an elongated collimating slot 33a, 33 z, respectively, formed therethrough'and arranged in alignment with respect to the electron emitting portions of the arc cathodes 30a, 302:, respectively, as Well as with the anodes 31a, 31z, respectively and the cavities formed in the arc blocks 23a, 23z, respectively.

Thecontrol electrodes 29a, 2%, the arc cathodes 30a, 30z, the collimating electrodes 32a, 321, and the anodes 31a, 31z, are electrically connected to the are 7 supply and regulator apparatus 34, The, positive terminal 35 of the arc supply and regulator apparatus 34 is grounded and is thereby associated with the positive terminal of a suitable source of decelerating electrode celerating electrode supplyg while the ion decelerating structure 37, the tank liner 38, and the ion collector assembly'39 are connected to the negative ungrounded terminal of the decelerating electrode supply. This requires that the ion accelerating structure 36, the ion decelerating structure 37, the tank liner 38, and the ion collector assembly 39 be electrically insulated from the component parts of the'tank 13. Thus the tank liner 38 supply, as explained more fully hereinafter. Also, the W V tank 13 is grounded. The filament'busses 27 and 28 are adapted to beoperatively connected to the arc supply and regulator apparatus 34, as shown in Figs. 3 and 4 a and described more fully hereinafter.

Further, the removable end wall 18 carries anion accelerating structure 36 formed at least partially of tungsten or the like, and disposed, in spaced-apart relationwith respecttothe wall of the arcblocks23a, 23z,

in which the slots 25a, 25z, respectively,;areformed. The negative terminal of the source 60, of accelerating elcc:

trode voltage supply is connected to the lion accelerating structure 36-and the positive terminal is connected tothe ion decelerating structure 37' together with the negative terminal of the source 61 of the decelerating electrode a voltage supply, the positive terminal of the latter'source 61 being connected to the arc block 21 and also grounded. The ion decelerating structure:37 is electrically connected to a tank liner 38. Both the ion decelerating structure 3 7 and the tank liner 38 are suitably supported in'and disposed between the ion decelerating structure 37 and the ion collector assembly 39 constitutes an electrostatic 4111,41; of theion collector assembly 39 through-the; slits 42a, 42;, and 4311, 432.. Considering now the general principle of operation of the calutron 10, a charge comprising a compound of the elementto be treated is placed in the charge receptacle 22, the compound of the elemcnt mentioned being one which may be readily vaporized. The end-walls 18 and 19 are securely attached to the open ends of the tank'13,

whereby the tank 13 is hermetically sealed. The various 5 electrical connections are completed and operation of the vacuum pumping apparatus 20 associated with the tank 13 is initiated, When a pressure of the order of 10- to 10- mm. Hg is established Within the tank 13,- the electric circuits for the windings, not shown, associated with the polepieces 11 and 12 are energized and adjusted, whereby a predetermined magnetic field is established therebetween traversing the tank 13. The electric "circuit for the heater 24 is energized, whereby the charge in the charge'receptacle 22 is heated and vaporelectrically insulated from the tank 13; 'A suitable source 7 of decelerating electrode voltage supply 61, as mentioned above, is adapted to be'connected with its positiveterminal operativelyassociated :with the .ion source unitv 21 and its negative terminal operatively associated with the ion decelerating structure 37 and the tank liner 38.'

The removable end wall 19 suitably supports an elec- 'trically. insulated ion collector assembly 39 formed of stainless steel .or the like, and provided with pairs of laterally spacedea'partcavities' or .pockets 40a 211M141,

401' and 41z, which respectively communicate withp'airs 1 of aligned slots 42a and 43a, 42 z and '43z, formed in the wall of the collector block 39 disposed remote from the removable end wall 19;. It is noted that the pockets 4011, 402 are adapted to receive one ofthe constituent isotopes of an element, and the pockets 41a, 412 another of the constituent isotopes, which have been separated in the calutron'10, .as explained more fully hereinafter.

Finally, the .ion collector assembly 39 iselectrically connected to thetank liner 38, the ion decelerating struc-f. ture 37, and the ungrounded jnegativetterminal of the decelerating electrode supply. Thus it will be understood that the ion source. unit 21 and the tank '13 are connected to the positive grounded'terminal of the de,-.

ized. The vapor fills the charge receptacle 22-and is condueted'into the communicating cavities formed in the a The A. C. power supply circuit is a are blocks 23a,'23z. energized, whereby busses 27 and 28 are energized and the filaments 26a; 262 are heated and rendered electronemissivea a 7 a V The cathode bombardment voltage'supply is operatively connected-between the filamentary cathodes 26a, 26z'and the arc cathodes 30a, 30z with the negative terminal of the .cathode'bombardment voltage supply associated with the filaments 26a, 26 and the positive terminal asso ciated ,with the arc cathodes 3041, 301 as further de scribed hereinafter This bombardment voltage. supply causes the electrons emitted from the electron emissiv'e portions of the filaments 2661,2623 to be accelerated and bombard the arc cathodes 30a, 3(iz. The intensity of this bombardment can be controlled by the voltage of the control electrodes 29a, 29z as further described hereinafter. 7 V

This electronbomba'rdment of the arc cathodes 36a,"

30; raises their temperature to the thermionic emission point.

tive terminal associated withthe anodes 31:1,,31z.

This are voltage supply causes an arc ischarge to strike between'the electron temitting portions of the arc cathodes 30:1, 302 and their-respective anodes 3 1d, 31:,

with electron streams proceeding from the electron emitting .portions of thear'c cathodes 30a, 3Gz through the collimating slots 33g, 333 respectively formed in the collimating electrodes 32a, 32z respectively'to the anodes 31a, 31;;resp'e'ctively. These electron streams may be controlled in intensity .bynieans of :the arc supply and regulator 34 and its; controls. as described hereinafter."

i The collimating. slots 7 33a, ssz, r formed in the collimat- An arc voltage supply is operatively connectedbetween the are cathodes 30a, 30z and the anodes 31a, v 31z, with the negative terminal of the arc voltage supply associated with thearc cathodes 30a, 30z and the posiing electrodes 32a, 32z, respectively, define the cross sections of the streams of electrons proceeding into the arc blocks 23a, 23 respectively, whereby each arc discharge has a ribbon-like configuration and breaks up the molecular form of the compound of the vapor to a considerable extent, producing positive ions of the element that is to be enriched with the selected one of its isotopes.

The electric circuit between the arc blocks 23a, 23z, and the ion accelerating structure 36 is completed, the ion accelerating structure 36 being at a high negative potential with respect to the arc blocks 23a, 232, whereby the positive ions in the arc blocks 23a, 23z are attracted by the ion accelerating structure 36 and accelerated through the voltage impressed therebetween.

The positive ions then come under the influence of the ion decelerating structure 37 and are decelerated thereby so as to reduce their velocity. In this manner the final velocity of the ions will depend upon the voltage of the decelerating electrode supply and will not depend upon the voltage of the accelerating electrode supply.

More particularly, the positive ions proceed from the cavities formed in the arc blocks 23a, 23z through the slots 25a, 25 formed in the walls thereof, across the space between the ion accelerating structure 36 and the adjacent walls of the are blocks 23a, 232, through the slits 44a, 44 respectively, formed in the ion accelerating structure 36, across the space between the ion decelerating structure 37 and the ion accelerating structure 36 and thence through the slits 45a, 45z in the ion decelerating structure 37.

The high velocity positive ions form vertical upstanding ribbons or beams proceeding from the cavities formed in the are blocks 23a, 23z through the slots 25a, 25z, respectively, the aligned slits 44:1, 442,, respectively, and the aligned slits 45a, 45z.

As previously noted the ion collector assembly 39 and the tank liner 3% are electrically connected to the ion decelerating structure 37, whereby there is an electric-fieldfree path for the high velocity positive ions disposed between the ion decelerating structure 37 and the ion collector assembly 39 within the tank liner 38. The high velocity positive ions are deflected from their normal straight-line path and from a vertical plane passing through the slots 25a, 25z and the aligned slits 45a, 45z, respectively, due to the effect of the relatively strong magnetic field maintained through the space within the tank 13 through which the positive ions travel, whereby the positive ions describe arcs, the radii of which are proportional to the square roots of the masses of the ions and consequently of the isotopes of the element mentioned. Thus, ions of the relatively light isotope of the element describe interior arcs of relatively short radius and are focused through the slots 42:2, 422 into the pockets 40a, 401, respectively, formed in the ion collector assembly 30; whereas ions of the relatively heavy isotope of the element describe exterior arcs of relatively long radius and are focused through the slots 43a, 43g into the pockets 41a, 411, respectively, formed in the ion collector assembly 37. Accordingly, the ions of the relatively light isotope of the element are collected in the pockets 40a, tz and are de-ionized to produce a deposit of the relatively light isotope of the element therein; while the ions of the relatively heavy isotope of the element are collected in the pockets 41a, 412 and are deionized to produce a deposit of the relatively heavy isotope of the element therein.

After all of the charge in the charge receptacle 22 has been vaporized, all of the electric circuits are interrupted and the end wall 18 is removed so that another charge may be placed in the charge receptacle 22 and subsequently vaporized in the manner explained above. After a suitable number of charges have been vaporized in order to obtain appropriate deposits of the isotope of the element in the pockets 40a, 40z and 41a, 411 of the ion collector assembly 39, the end wall 19 is removed and the deposits of the collected isotopes in the pockets 40a, 401: and 41a, 41z in the ion collector assembly 39 are reclaimed.

Of course, it will be understood that the various dimensions of the parts of the calutron 10, the various electrical potentials applied between the various electrical parts thereof, as well as the strength of the magnetic field between the pole pieces 11 and 12, are suitably correlated with respect to one another, depending upon the mass numbers of the several isotopes of the element which is to be treated therein. In this connection reference is again made to the previously-mentioned copending application, Serial No. 557,784, filed October 9, 1944, now Patent No. 2,709,222 granted on May 24, 1955, for a complete specification of a calutron especially designed for the production of uranium enriched with the isotope U By way of illustration, it is noted that when the calutron 10 is employed in order to produce uranium enriched with U the compound of uranium which is suggested as a suitable charge in the charge receptacle 22 is UCl as this compound may be readily vaporized and the molecular form of the vapor may be readily broken up to form positive ions of uranium. In this case, uranium enriched with U is collected in the pockets 40a, 402, of the ion collector assembly 39 and uranium comprising principally U is collected in the pockets 41a, 41z of the ion collector assembly 39. Also, it is noted that from a practical standpoint, the deposit of uranium collected in the pockets 40a, 40z of the ion collector assembly 39 contains considerable amounts of U in view of the fact that this isotope comprises the dominant constituent of normal uranium. Furthermore, the deposit of uranium collected in the pockets 40a, 402, of the ion collector assembly 39 contains a considerably increased amount of U in view of the fact that it is not ordinarily feasible to separate U and U in the production of relatively large quantities of uranium enriched with U for commercial purposes. Accordingly, in this example the uranium deposited in the pockets 40a, 402 of the ion collector assembly 39 is considerably enriched, both with respect to U and U and considerably impoverished with respect to U as compared with natural or normal uranium.

Referring now to Fig. 3 of the drawing in detail it will be observed that the terminals 1, E, M, O, R, X, B shown in Fig. 3 connected to the schematically illustrated apparatus 34 correspond to similarly designated terminals used in the apparatus 34 illustrated in block form in Fig. 1. These terminals are connected to a pair of ion sources with the electrodes thereof shown in diagrammatic illustrations in the block designated by the reference numeral 48. The apparatus 34 may be designated as the filament supply, are supply and regulator and includes the transformer 49 with the secondary thereof connected to the bus bars 27 and 28, which are connected to the ion generaitor filaments 26a, 26z so that these filaments are supplied with alternating current for the heating thereof. Only one pair of bus bars 27 and 28 is employed to supply heating current to a plurality of filaments. The bus bar 28 is connected to the negative terminals of the batteries 46 and 56, the positive terminal of the battery 46 being connected to the negative terminal of the battery 47 and the positive terminal of the battery 56 being connected to the positive terminals of the rectifiers 55a, 55z. The positive terminal of the battery 47 is connected to the calutron ground designated by reference numeral 35, to the ion generator anodes 31a, 312: and to the ion generator arc current collimating electrodes 32a, 32z. The positive terminal of the battery 46 and the negative terminal of the battery 47 are connected to the resistors 50a and 50z. These resistors are provided with variable contactors and function as are current control rheostats for the arc currents of the ion generators. The other terminals of these arc current control resistors are connected to the bombardment cathodes 30a. 3oz, respectiyely. These'bombardmentcath odes 30a, 30za're' also'connected to resistors 51a, 51

respectively and through these to the rectifiers'53a, 535

respectively, the negative terminals of the'rectifiers 53a,

532 being connected to the D. 'C. control windings of the saturable reactors 54a, 541, respectively. The other 'the A. C. power supply which also energizes the transformer 49. A pair of protective rectifiers 52a, 52 are connected around the rectifiers 53a, 53z and the control windings 54a, 54z,rrespectively to the terminal 47b of the battery 47, for the purpose of protecting the control windings of these saturable reactors from excessive D. C. control currents which may be fed to the control windings as a result of abnormal ion generator arc currents flowing through the resistors 50a, Stlz, respectively.

Having set forth the physical connections of the ion generators and associated current supplies and controls, the operation of the apparatus shown in Fig. 3 will now be described. a a p 7 Inasmuch as the battery 46 is connected with its negative terminal to the filament 26a and its positive terminal to'the resistor 50:: which, in turn, is connected to the bombardment cathode 300, the bombardment. current flowing from positive to negative will flow from the positive terminal of the battery 46 through the variable 7 contactor associated with the resistor 50a, through the 7 terminal to the resistor 50a, feeds the arc current from its positive terminal'to the arc anode 31a and from the arc cathode 30a through the resistor 5021 to the negative terminal of this battery. From the foregoing it is seen 7 that the bombardmentcurrent flows through the resistor 50a in'one direction and the arc current flows through this same resistor 50a in the opposite direction so that if'these currents are not equal a net current will'result' with a' corresponding potential drop across the resistor. Ifno arc current flows through the resistor 50a and only I the bombardment current flows therethrough,then the resistor terminal connected to the positive terminal of the rectifier 53a will be negative and no current can flow through this rectifier and through the D. C. control winding of the saturable reactor 54a. However, if both bombardment current and are current flow through the resistor 50a and the net current therethrough isthat resulting from alargerarc current then the lower terminal of this resistor, that is, the terminal connected to the recti fier 53a through resistor 51a will assume a positive polarity. However, no current can flow through. the rectifier 53a andthe'D. C. control winding of the saturable reactor54a even when the proper polarity is potential is exceeded current will flow through the rectifier 53a and the control winding of the reactor 54 1 to reduce the inductance of the reactor 54a and thereby reduce the reactance of thisrcactor to alternating current so that the rectifier 55a has a greater A. C. potentialapplied thereto. As a result the D. C. output potential of this rectifier is increased and a higher negative potential is applied to the control grid 29a between the filament 26a and the bombardment cathode 30a and the current between this filament 26a and the bombardment cathode 39a is decreased. Consequently the emission of the bombardment cathode 3 3:: is decreased, the'arc current flowing to the anode 31a through the resistor Stla is decreased and the potential drop across this resistor a is decreased with the result that the D. C. control current through the rectifier 53a and the control winding of the saturable reactor 54a is decreased. Thereupon, the DC. output voltage of the rectifier 55a is decreased and the apparatus through this operation adjusts itself automatically to substantially constant arc current for the purpose of ionizing the material fed into the ion generator apparatus betweenrthe bombardment cathode and the anode.

In the foregoing the operation of one of the ion generators only was taken up in detail and it will of course be apparent that the adidtional generator or generators and associated circuits will function in the same manner as the circuit described hereinbefore.

It will be observed that auxiliary battery 56 is con- :nected with its negative terminal to thenegative terminal of the battery 46 supplying the cathode bombardment current. The positive terminal of this battery 56is connected to the positive terminals of the D. C outputs of the rectifiers 55a, 55 This battery is not essential'but 'is employed for the purpose of facilitating voltage ad-- justments and its polarity may be reversed if desired. Likewise the polarities of the rectifiers may be reversed and instead of applying a negative potential on the control grids 29a, 2% with respect to the filaments 26a, 26z, respectively, a positive potential may be applied thereto with respectto the filaments. The polarity applied to these gridswith respect to the filaments depends upon;

among other things, the size of the slot openings therein since it is obvious that the size of these openings Wlll control the mu or amplification of the structure. In other words, if the slot opening is of a certain size'it may be.

desirable to use a positive potential on the respect to the'filament whereas if this opening is larger than the aforesaid size it may be desirable to apply a negative potential on the grid with respect to the filament.

Another embodiment of this invention is shown schematically in Fig. 4 and it will be observed that here terminals I, E, Ma,'Mz, 0, RB are provided to the apparatus applied to the. rectifier from the potential drop across the resistor 50a unless. this potential drop exceeds the potential of the battery 47 between the terminal 47a and the negative terminal of this battery since these po- 'a certain predeterminedpotential as outlined hereinbefore' and this potential drop may be controlled by varying the tap of the resistor 50:: manually sothat difierent values ofarc currents throughgthis resistor may be used to exercise automatic controli .When 'this predetermined 34 so that terminals Ma andMz are employed instead of one terminal M of apparatus 34 in Fig.3 and the functions of terminals 0 and X of Fig. 3 are consolidated into fone ter'minal O in Fig. 4. The transformer 49 in this case also supplies the filament heating current to the filaments;26a, 26 through the bus bars 27 and 28. 'Likewise, a battery 46 having-its negative terminal connected to the bus bar 23 is employed to supply the bombardment 7 current between the bombardment cathodes 39a, 302 and the filaments 26a, 26z, respectively. The positive terminal of the battery 46 is connected to the negative terminal of the arc current supply battery 47 and the positive terminal of this battery 47' is connected to the anodes 31a, 311 and the collimating electrodes 32a, 32z through the arc current control rheostats Sea, 50x, respectively. Rectifiers- SSa, 55 are connected'with their negative output terminals to grid electrodes 2%,292 respectively and with the a positive output terminals together to the positive terminal of grid bias battery 55 to one side of the secondaryof the filament transformer'49. The A. C. inputs of the rectifiers 55a, 55z are connected to the A. C windings; of the saturable reactors 54a, 54z, respectively. The

9. D. C. control windings of these saturable reactors 54a, 54g are connected with one terminal thereof to the ion generator anodes 31a, 31z, respectively, and the other terminals of these D. C. control windings are connected together to the negative terminal of the battery 56, the positive terminal of this battery being connected to the calutron ground 35' and to the positive terminal of the battery 47.

The operation of the apparatus shown in Fig. 4 is as follows:

The battery 46 supplies the bombardment current for the bombardment cathodes 30a, 30z and this bombardment current, of course, flows between these bombardment cathodes and the filaments 26a, 262, respectively, through the grids 29a, 29z, respectively. The are current which functions to ionize the material supplied to the ion generators flows between the anodes 31a, 31z and the respective bombardment cathodes 30a, 30 when these cathodes are heated by bombardment to be electron emissive. This arc current flows through the resistors 56a, Stlz from the arc current supply 47 thereby producing IR drops across these resistors 50a, 50z depending of course upon the magnitudes of the resistors and the currents flowing therethrough.

The battery 55 which is connected with its negative terminal tothe filaments 260:, 261 and with its positive terminal to the positive terminal of the rectifiers 55a, 552 provides a high positive bias to the grids 29a, 29z with respect to the filaments 26a, 262, respectively, and these grids 29a, 29z are operated well in the saturation zone of the grid voltage-bombardment current characteristic so that substantial reductions in the positive grid voltages of the grids 29a, 2% is necessary before these grids exercise control of the bombardment current passing therethrough from the filaments 26a, 26 to the bombarded electrodes 3521, SM, respectively. It will be observed that the polarity of the battery 55 is in opposition to the rectifiers 55a, 55z and, therefore, these rectifiers 55a, 55 may be used to vary the effective value of the voltage of the battery 55 on the grids 29a, 292, respectively, as will be more fully described hereinafter. Since the D. C. control windings of the saturable reactors 54a, 54z are connected to the control rheostats 50a, 50z, respectively, the IR drops across these rheostats will be applied to the control windings of these saturable core reactors. When control currents flow through these D. C. windings the reactances of these reactors are decreased and therefore the alternating current potentials applied to the rectifiers 55a, 55z are individually increased so that the D. C. outputs of these rectifiers are increased thereby varying the potentials of the control grids 29a, 29.2, respectively, with respect to the filaments 26a, 26z, respectively, in opposition to the grid bias battery 55. The voltage of the battery 55 is suficient to drive the grids 29a, 29z substantially positive with respect to their associated filaments so that a substantial reduction of the efiective value of the potential of the battery 55, by virtue of the increase in the output of the rectifier 55a, for control of grid 29a and rectifier 55z for control of grid 292:, is necessary before these grids are effective in decreasing the bombardment currents of the bombardment cathodes 30a, 38 respectively. This is necessary so that a substantial arc current flows between the bombardment cathode and the anode of each ion generator before the respective grid electrodes start exercising control. When the grid electrodes start exercising control and reduce the bombardment cathode currents the temperatures of the bombardment cathodes 30a, 302 are decreased so that electron emissions from these bombardment cathodes are decreased and the arc current between the bombardment cathodes Stla, 302 and the anodes 31a, 312,, respectively, are decreased. Decreasing these are currents produces lower potential drops across the control resistors 59a, 50z, respectively, so that control currents flowing through the D. C. windings of the re- 10 actors 54a, 54z are decreased and the A. C. potential applied to rectifiers 55a, 551 are caused to decrease since the reactances of the reactors are increased. In this manner the arc currents to the ion generators are stabilized around some predetermined values automatically.

It will be observed that the arc current control rheostats 50a, 502 may be manually adjusted if desired since the contactors thereof are variable and the arc currents of the ion generators may thereby be manually varied.

Furthermore, while from the foregoing description of the operation of the ion generators and associated circuits shown in Fig, 4 were set forth with respect to both ion generators shown, it is obvious that this control is individual and the arc current through one of the generators may be varied automatically independently of the automatic control of the arc current through the other.

While there has been described what is at present considered to be the two preferred embodiments of the invention, it will be further understood that various modifications may be made therein, and it is intended to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

I. A regulator for a calutron ion source comprising in combination an ion source having an anode, a bombardment cathode, a grid and a filament, a pair of primary feeders for supplying heating current to said filament, a variable impedance device having a direct-current control winding and an alternating-current impedance winding, a rectifier having its output connected between said filament and said grid for supplying a bias potential to said grid with respect to said filament, a source of alternating current for said rectifier, said source of alternating current being connected to said rectifier through the alternating-current impedance winding of said impedance device, and means for supplying current to said direct-current control winding of said impedance device in accordance with the current supplied to said anode so that the bias potential of said grid is changed to decrease the bombardment current to said bombardment cathode when the anode current increases beyond a predetermined range.

2. A regulator for a calutron ion source comprising in combination an ion source having an anode, a bombardment cathode, a grid and a filament, a pair of primary feeders for supplying heating current to said filament, a variable impedance device having a direct-current control winding and an alternating-current impedance winding, a source of grid bias voltage for said grid for biasing said grid beyond saturation, a rectifier having its output connected between said filament and said grid for supplying negative bias potential to said grid with respect to said filament, a source of alternating-current for said rectifier, said source of alternating-current being connected to said rectifier through the alternating-current winding of said impedance device, and means for supplying current to said directcurrent winding of said impedance device in accordance with the current supplied to said anode so that the negative bias of said grid is increased to decrease the efiect of said source of grid bias potential and to decrease the bombardment current to said bombardment cathode when the anode current increases beyond a predetermined range.

3. A regulator for a calutron ion source comprising in combination an ion source having an anode, a bombardment cathode, a control electrode and a filament, wall structure for defining an arc chamber between said anode and said bombardment cathode, said are chamber having an atmosphere to be ionized therein, a pair of primary feeders for supplying heating surrent to said filament, a rectifier for supplying a bias potential to said control electrode and being connected between said filament and said control electrode, a saturable reactor connected to control the output of said rectifier in accordance with the current to said anode to maintain said current substantially constant through the control of the bombard ment current to said bombardment cathode from said filament. r t a i a 4. A regulator for a calutron ion source comprising in combination 'an ion source having an anode, a bombardment cathode, a control electrode and a filament, wall structure for defining an arcchamber between said anode an'd said bombardment cathode, said are chamber having' an atmosphere to be ionized therein, a pair ofpri-t mary'feeders for supplying heating current to said filatment, a rectifier for supplying a bias potential to said control electrode and being connected between said filament and said control electrode, a saturable reactor having-a winding connected to the input of said rectifier and having another Winding energized substantially, in accordance with the current to said anodeto' control the bias of said control electrode to maintain said current sub- 'stantially constant through the control of the Lbombardment current to said bombardment cathode from said filament.

5; A regulator for a calutron ion source comprising in combination an ion source having an anode, a bombardtial connected between said filament and said control -electrode, a saturable reactor connected to control said source of control electrode bias potential, said saturable reactor having a'direct current control winding connected to be energizedin accordance with the potential drop across said resistor to control the reactance of said saturable reactor for varying the bias to said control elec-' trode. a a r 6. A regulator for a calutron ion source comprising in combination an ion source having an anode, a bombardment cathode, a filament and a grid between said filament r with the net potential drop across said resistor to control 1'2 and said cathode, a source of biasvoltage comprising a rectifier having its output connected between said grid and said filament, a saturable reactor having .a directcurrent control winding and an alternating-current impedance winding, said alternating-current impedance winding being connected in series with the, input of said 'sourceof 'grid bias voltage, an arc current supply, a resistor connected in series with said cathode and the negative terminal of said are current supply, the positive terminal of said are current supply being connected to 7 said anode, a direct-current bias voltage supply connected in opposition to the polarity of said rectifier, said directcurrent control winding being connected to saidresistor so that the arc current passingthrough said resistor operates to control the reactance of said saturable reactor.

7. A regulator for a calutron ion source comprising in combination an ion source having an anode, a bombardment cathode,,a control electrode and a filament, said control electrode being positioned between said filament and said bombardment cathode for controlling the bombardment of the cathode, wall structure for defining an arc chamber between said anode and said bombardment cathode, said are chamber having an atmosphere to be ionized therein, a source of arc currentsupply connected betweensaid bombardment cathode and said anode,*a source of bombardment cathode current supply, aresistor connected in series with said arc current supply 'and said cathode and in series with said bombardment cathode current supply and said cathode, a-source-ofl control-electrode-bias potential connected between said filament and said control electrode, a saturable reactor connected to control said source of control electrode bias potential, said saturable reactor having a direct current control winding connected to be energized in accordance the ,reactance of said saturable reactor for varying the bias to said control electrode.

References Cited in the file of this patent UNITED STATES PATENTS 1,628,678 7 Morrison May 17, 1927

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