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Publication numberUS2633539 A
Publication typeGrant
Publication dateMar 31, 1953
Filing dateJan 14, 1948
Priority dateJan 14, 1948
Publication numberUS 2633539 A, US 2633539A, US-A-2633539, US2633539 A, US2633539A
InventorsAltar William
Original AssigneeAltar William
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Device for separating particles of different masses
US 2633539 A
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Description  (OCR text may contain errors)

W. ALTAR March 31, 1953 DEVICE FOR SEPARATING PARTICLES OF DIFFERENT MASSES Filed Jan. 14, 1948' LOW Mega zfve Vo/zfaye H/yh lVeya five 75 Reservoh' V0 H W of No/ecu/es INVENTOR W/'///'am 14/ tax v I 4 ATTORN BYKN Patented Mar. 31, 1953 DEVICE FOR SEPARATING PARTICLES OF DIFFERENT MASSES William Altar, Pittsburgh, Pa., assignor, by mesne assignments, to the United States of America as represented by the United States Atomic Energy Commission Application January 14, 1948, Serial No. 2,337

16 Claims. 1 My invention relates to arrangements for separating particles of different mass from mixtures thereof and, in particular, relates to an arrangement for separating isotopes of the chemical elements. Its operation depends upon a particularly effective method of imparting widely different velocities to particles of even very slightly different mass, and then utilizing the difference in velocity for effecting physical separation of the particles.

One object of my invention is, accordingly, to provide a novel arrangement and method for separating, from mixtures thereof, particles which differ from each other in mass.

Another object of my invention is to provide a novel and improved arrangement and method for causing electrified particles having different masses to be physically separated from each other.

Still another object of my invention is to provides, novel and improved method of producing widely different accelerations between particles having masses which differ from each other.

Another object of my invention is to provide a novel arrangement and method for producing widely different velocities as between ions having only slightly different masses.

A further object of my invention is to provide a novel arrangement and method for segregating from mixtures thereof different isotopes of the same chemical element.

Other objects of my invention will become apparent upon reading the following description, taken in connection with the drawings, in which the single figure is a diagrammatic showing of one form of apparatus in which the prin-' ciples of my invention may be embodied;

Referring in detail to the drawings, a vacuum-tight chamber I may be considered to be subdivided into five different chambers 2, 3, 4,

chamber 5 and the ion-collecting chamber 6 may conveniently be of conducting material.

The chamber 2 is provided at one end with an y em ss e gaih d o any typ The walls} known in the art to be suitable as a source of a concentrated electron beam. The chamber 2 is likewise provided with an offtake 9 to a vacuum pump of sufficient capacity to maintain the desired vacuum in the above-mentioned system of chambers, even when a desired quantity of gaseous ions is allowed to flow into the chamber in the immediate vicinity of the cathode 8 through a duct ll leading from a reservoir of molecules of the substances which it is desired to separate from each other. In front of the cathode 8 there is provided a series of diaphragms l2, l3 and M of a type known in the art to be suitable for producing a concentrated beam of ions or other charged electrical particles; The diaphragms l2, I3 and I4 are connected to a suitable source [5 of direct-current potential which has one ter-" minal connected to the cathode 8 and also, preferably, to ground. The wall of the chamber 2 opposite to the end containing the cathode 8 is pierced with an aperture which is aligned with similar apertures in the plates l2, l3 and 14. It will readily be evident that if the diaphragm I2 is positive relative to the cathode 8, electrons will be accelerated in the space in front of the latter, and that these will ionize any molecules which have been allowed to flow into the chamber 2 through the duct ii. If the diaphragms l3 and M are negative in potential relative to the oathode 8, they will accelerate positiveions thus produced by the electron stream along a path passing through their apertures and through the aperture in the end wall of the chamber 2 which is adjacent the chamber 3.

A high negative potential is imparted to the chamber 3 relative to the cathode 8, and the end wall of the chamber 3, which is adjacent the chamber 2, is provided with an aperture which is aligned with the apertures in the diaphragms l3 and I4. Such a system of electrical potentials will produce a narrow beam of positive ions accelerated to a high velocity which will pass into the interior of the chamber 3. Where it is desired to produce a stream of negatively charged ions or negatively charged electrified particles,

it will be obvious to those skilled in the art that the potentials of the diaphragms l3 and I4 and chamber 3 and provided with a pair of apertures I1 and 18 in its end walls which are aligned with the apertures in the diaphragms l3 and i4 and in the end walls of the chambers 2 and 3, as abovedescribed. A narrow space intervenes between the respective end of the cylinder 16 and the adjacent end walls of the chamber 3, and a source of alternating potential-"2| which.may; ion (EX- ample, have. an amplitude of 1000-volts: and a frequency of 70 me. per second, is connected between the cylinder l6 and the chamber sub-- stantially at one end thereof 3. It will be evident from the foregoing description that an alternating voltage will be set up in the" spaces between the end walls of the cylinder-16: and:

those of the cylinder 3, but thatthe'spaceinthe.

interior of the cylinder l6willabevirtually an:

electric-field-free space in which any electrified particles entering through theapertures in one end of the cylinder [6 will move without acceleration or deceleration until they pass. through the aperture in the opposite end of the cylinder I6.

The endwall-of the chamber 3, which .is .remote from the chamber 2,.isprovided withanaperture aligned witht-he-apertures l1 and; i8, and the above-described-arrangement will be seen. to be such thata beam. of..elect'rifiedparticles emanating in. front: of the cathode 8' will" be. passed throughthe aperturesimthe. diaphragms i3 and. M, the apertures ILa-ndJa andintothe interior of the decelerating: chamberAl. The. end wall of the chamber 4,, which is. adjacent. the. chamber. 5, is oLmetal. andis. provided witl'ran. aperture 22.- which. is. alignedwith. the. apertures l1 and 3.. This end. wall. is-..impressed'.by. a suitable voltage source:.(not.shown) with; a.negative voltage: which is muchrlower. thanthat :irnpressed on. the: chamber. 3.. It will. be. seen. to result from this arrangement that theelectrifiedparticles in the above-mentioned beam-willlpass. through the aperture: zzfwith amuch :lower-veloc ity'than that which .they' possessedwhile. passing.

through. the cylinder "5-.

The electrifiedparticles,-. when about to pass through the: apertures-in. the: end. wall. or. thechamber. 3 whichis adjacentrthe; chamberfi, will.-

have a kinetic energy. corresponding-.to-theproduct of. their electrical. charge by; the voltage-0f: the cylinder 31relative: tothe cathode 8.: Since. the electrical charge produced on ions. in .front of the cathode 8'-will,- inegeneral be the same even though. the ions. differ. fromreach other in. mass, thevelocities oithe. ions whenthey. enter the chamber 3s wilLbe. inversely. proportionaLto the square roots of their respective masses. How.- ever, one of the principal problemsto. be. solved by my above-described arrangement'lissthe separation of ions; such. as isotopes. of the: same.- element, which. differ from. each: other. only slightlyin mass. In such cases;.the. velocity .oiionsof'. each particular. isotope. will.be.-.the same,. and.

the velocity. of.difierent.isotopes wilL. diffier from. each other only slightly,.the-velocitiesofldifferent. isotopes. being: inversely proportionalto the square root. of their respective masses.

In the space betweenthe'end wallotthe chambar 3 and the adjacent aperture |'|-,the iOIlSIWill be subjected to an alternating electricfieldhav ing the frequency of the source Ziwhich williurther accelerate or; decelerate-themin. an. amount dependingupon theinstantaneeusvalue: and sign of this electricfield. The ionswilll then pass through the field-freespace. alongthe-axisoi. the. cylinder l6 andwill arriveat the aperture. (8 with the same velocity that theyhadon. leaving. the aperture] 1-. However, thetime. at mhthey arrive at the aperture l8 will obviously depend upon the respective velocities with which they pass through aperture I1, and as has just been stated above, this velocity will difier for isotopes of different mass, and will also differ even as between .isotopes-. o the .same.-mass which pass through theraperture [hat different'times in the cycle of the voltage impressed by the source 2|.

The source 2| impresses an electric field on the space between the aperture l8 and the aperture iF-w-hibh iseXactIy eQual and in the same direction as'the electric field impressed on the ions just. before: they pass; through the aperture l1. Asa resnlt eachaion will leave the aperture 19 with arvelocity-which depends upon the relative phasertofTthe electric field between the apertures l8 and .IQ and .the electric field in front of the aperture IT at theinstant of passing; and this relative phase will depend in turn on the time consumed by the ion traversing the distance from the. aperture ilto .the aperture. Hi. In accordancewith the.foregoingconsiderations.the length of thechamber 3.-is;.selected-..to be. substantially equal to. the. lengthof axhalf -integral. number of cycles...of-.the'-frequencyof'the source 2| so that itispossible.to.causeionshavingrthe mass of one isotope to. traverseithe. distance between. the apertures. l1;- and. .l.8..in...some' half-integral number; oilcycl'esoithe' source 2.1 ';.-b'ut,. on the other hand, electrifiedparticles, such as other isotopes.

havingmasses which .difierirom that of the firstmentionedisotope willlhave. different velocities in. passing throughtithe: chamber. 16 and will correspondingly enterthe. electric held. between apertures. 18.. andimlwhenrthe latter hasa difierent phase. .f'romthat of-l the electric field; in front. of. theiaperture ll'whenthey pass through it... Thus, .,thei.ions; of. the. selected. isotope first mentioned will enter the decelerating chamber 4 withthesamevelocity.thatthey hadinentering the. chamber 3.; .but..alll other isotopes will .have differentvelocities. from those that. they. had. in entering the chamber 3. The. effect. of. the. passage through the chamber 3 is thus to differentiate from. each. other. the. velocities. oi. different isotopes, or other.electricaLparticles. having identical chargesbut. difierenti masses.

Within the decelerating, chamber 4, the. electrified. particles .aresubjected to .an-electric field whichrtends to greatly slowthemdcwn, nearly but. not quitert'o zero. velocity.-. It can beshown.

that the residual velocities...with.. whichthe par..- ticles. pass through..-the aperture. 22' will. differ very. greatly. as. between. isotopes or. other. particles of. evenslightly; diiierent mass.

. After, passing. throughthe. aperture. 22, the particles. pass. through; amagneti'c. field. of con: stant' magnitude which.isperpendicularto. the direction. inwhich. they. are. moved; Such a magneticfield. will..cause..moving. particles. to be deflected. intdcurvedlpathsthe curvature of. the.

pathdepending upon. the velocity. with which.

they are. moving. aswell; asmtheir. masses. Thus, twoisotopes. passing throughthe aperture 22, even. if..of nearly the same...mass,, wi1l.have,..in accordance with. the foregoing description, widely, different. velocities and. will. correspondingly. follow. paths. of: widely different. curvature inthechamber. 5. Thecollecting; chamber 6 is provided .with.anaperturecorresponrling inposition. torthe. path. followed. by. the. isotope which it is desired. to collect All. such. isotopes will, therefore, pass. intothe collecting chamber. 6, whileall other isotopesor charged electrical particles will be seatteredabout. on the walls ofthe chamber 5 or on the exterior walls chamber 6.

Since the velocity with which two difierent isotopes pass through cylinder 16 is, as'above stated, inversely proportional to the square root of their respective masses, the time they consume in passing from the aperture H to the aperture 18 will be proportional to the square root of their respective masses. It is obviously possible to so select the frequency of the source 2| that the time thus consumed by the desired isotope is an odd number of half periods of the source 2|, but the time consumed by an undesired isotope is an even number of half periods of, the source 2|. Under such circumstances,

of the the velocity with which the first isotope passes through the aperture I9 is the same as that with which it entered the chamber 3, but the velocity with which the undesired isotope enters the aperture [9 is less than that with which it entered the chamber 3 by an amount corresponding to twice the alternating voltage of the source 21. This affords an effective means of Widely differentiating the velocities of egress of two. isotopes, or other electrically charged particles, entering the chamber 3 with substantially identical velocities.

While I have described an arrangement in which the number of ions passing through the apertures in the diaphragms I3 and I4 is substantially constant with time, it is also within the scope of my invention to pulse the voltage impressed on the diaphragm i2 relativeto the cathode 8 at the same periodicity as that of the source 2 l, or otherwise to modulate the ion beam. The phase of such pulses relative to the source 2| should be made such that an undesired isotope will never enter chamber 3 at a time when the voltage impressed by the source 21 is zero. By the expedient of pulsing the ion beam, it is possible to insure that the net velocity change suffered by an undesired isotope in passing through the alternating fields at the opposite ends of cylinder l6 has a desired value, since the phases of both the alternating electric fields through which the particle passes are fixed and predetermined quantities.

I claim as my invention:

1. In combination with a means for producing a beam of moving electrified particles, means for passing said particles consecutively through two alternating electric fields, means for decelerating by-a predetermined amount said particles after passing through the second of said fields, and means for separating from each other such of said particles as have different velocities after said deceleration.

2. In combination with a source of electrically charged particles, means for establishing an electric field having a direct-current component and an alternating-current component for accelerating said particles to a relatively high velocity, means providing a field-free space traversed by said. particles subsequent to said acceleration, means for decelerating said particles by an electric field having a direct-current component slightly smaller in magnitude than said directcurrent component of said first electric field, and having an alternating component of substantially thesame frequency and magnitude as said alternating component of said first electric field,.the directions of all said electric fields being substantially parallel, and means for separating said particles in accordance with their respective vetric field.

3. In combination with a source of electrically charged particles, means for establishing an electric field having a direct-current component and an alternating-current component for accelerating said particles to a relatively high velocity, means defining a field-free space traversed by said particles subsequent to said acceleration, the time spent in traversing said field-free space being some odd number of halfperiods of said alternating current, means for decelerating said particles by an electric field having a direct-current component slightly smaller in magnitude than, and opposed to, said direct-current component of said first electric field, and having an alternating component of substantially the same frequency and magnitude as said alternating component of said first electric field, the directions ofall said electric fields being substantially parallel, and means for separating said particles in accordance with their respective velocities after passing through said second'electric field.

4. In combination with a means for producing a beam of moving electrified particles, means for passing said particles consecutively through two substantially cophasal equal alternating electric fields-which are substantially parallel to the direction of motion of said particles, means for decelerating by a predetermined amount said particles after passing through the second of said fields, and means for separating from each other such of said particles as have different velocities after said deceleration.

5. In combination with a means for producing a beam of moving electrified particles, means for passing said particles consecutively through a first alternating field, a field-free space and a second alternating field, said alternating fields being substantially synchronized and having substantial components parallel to the direction of motion of said particles, the time spent in traversing said field-free space being some integral number of half-periods of said alternating fields.

6. In combination with a means for producing a beam of moving electrified particles, means for passing said particles consecutively through a first alternating field, a field-free space and a second alternating field, said alternating current fields being synchronized and having substantial components parallel to the direction of motion of said particles, the time spent in traversing said field-free space being such that said alternating current fields respectively produce changes of velocity which are substantially equal but of opposite algebraic sign in certain of said particles.

'7. In combination with a means for producing a beam of moving electrified particles, means for passing said particles consecutively through two substantially cophasal equal alternating current fields which are substantially parallel to the-direction of motion of said particles, and means for separating from each other such of said particles as have different velocities after passing through said two alternating electric fields.

8. In combination, means for producing a rapidly moving stream of electrified particles, a first chamber having conductive walls, a second 'chamberhaving conductive walls insulatingly een thrones sa d second chamb r, readies electrode for said particles outside said fii stghan i: means i9 intere ting h fill fi i ih l p o ntia d a e qe V ves th ax s. be en s id fir t air of anert i esend i -rimrr s as a subt tial cor asal nd e ua alt iaa sch m tial difierencealong the agi s; between said second p ir f p ures.

9- In o ination. mean o P e ne rapidly v n tr m. le tr fi d a ticl s fi h mb r hav n conduc i Wa a ec n cham e ha in c ndi ir W s nsu i s v supp rted wi hin a first ch mb a firs pa per e al ned ith sai b a n h espec ive wallsf aid first an econ c amb rs, a secon pa r ofa r res nthe w ll-s i: t sa two ham ers and ali ned w th the P Of sa d beam throu h said second ch mber, me ns for parati g sai artic s. of d f er nt velocity after thei issue through said second pair of apertures, a receiver electrode for said particles out side said first chamber, and means for impressing an alternating acceleration on each particle as it traverses said first pairof apertures and for impressing an alternating.acceleration of substantially equal and opposite magnitude on said particle as it traverses said second pair of apertures.

10. In combination, means for producing a rapidly moving stream of electrified particles, 2. first chamber having conductive walls, a second chamber having conductive walls insulatingly supported within said first chamber, a first pair of apertures aligned with said beam in the respective walls ofsaid firstand second chambers, a second pair-of apertures in the walls of the said two chambers and aligned with the path of said beam through said second chamber, means for separating said particles of different velocity after they issue through said second pair of apertures, a receiver electrode for said particles outside said first chamber, means for impressing an alternating acceleration on each particle as it traverses said first pair of apertures and for impressing an alternating acceleration of substantially equal and opposite magnitude on said particle as it traverses said second pair of apertures, and means for applying a decelerating force to the particles of said beam after they issue from said second pair of apertures.

11. In combination, a first cylindrical chamber having conductive walls, and coaxial therewith a second cylindrical chamber having conductive walls positioned inside said first chamber, the end walls of said second chamber being separated from the end walls of said first chamber by relatively narrow gaps and said second chamber being insulatingly supported within said first chamber, a first pair of apertures in one pair or adjacent end walls of said chambers, a second pair of apertures in the other pair of end walls of said chambers, all said apertures being positioned on the common axis of said chambers, means for impressing an alternating voltage between said two chambers, means for projecting a stream of electrified particles along the common axis of said two chambers, and a receiver electrode for said electrified particles which have passed through said second set of apertures.

12. Incom'bination, afirst cylindrical chamber having conductive walls, and coaxial therewith a second cylindrical chamber having conductive walls positioned inside said first chamber, the end walls of said second chamber being separated from the end walls of said first chamber by I813:-

i-re n r o s ts nd. ai set edchar e being msaiseugiy supported within said st chamber, a first pair of apertures in one, pair of adjacent end walls of said chambers, a second pair of apertures in 'the other pair of end walls. of said chambers, all said. apertures being positioned on the common axis of'said chambers, means for impressing an alternating voltage'b'e tween said two chamber'sQmeanS for. projecting a stream of electrified particles along theconimon axis of said two chambers, and, meansfor separating particles of different velocities 'i'iisaid stream after they have issued f roin said second pair of apertures. V v

13. In combination, a first cylindrical chamber having conductive walls, and coaxial therewith a second cylindrical chamber havin wnductive Walls positioned inside said first chamber, the d w l f aid se nd chamb being sep ate from the end walls of said first chamber. b relatively narrow gaps and said second chamber being ins ti s up t d W th n sai first chamber, a first pair of apertures in one pair of adjacent end Walls of said chambers, a second pair of apertures in the other pair of end walls of said chambers, all said apertures being, 1305i tioned on the common axis of said chambers, means for impressing an alternating voltage between said two chambers, means for projecting a stream of electrified particles along the common axis of said two chambers, means for applying a decelerating force to said electrified particles after they have passed through said second pair of apertures, and means for separating from each other such of said particles as have different velocities after being subjected to said decelerating force.

14. Apparatus for separating from each other electrified particles having substantially equal electric charges, but difierent masses which com.- prises means for, accelerating said particles by means of a first electric field having a directcurrent component and an alternating current component, said direct-current component con sisting of intermittent pulses having the same frequency as said alternating-currentcomponent, a region substantially tree irorn accelerating or decelerating forces disposed in the path of said particles, means for subjecting said particles to a second electric field having a direct-current component slightly smallerthan and opposed t0 said direct-current component of said first field and having an alternating component of sub stantially the same amplitude and frequency as said alternating component of said first electric field, the directions of all said electric fields being substantially parallel, and means for separating from each other particles having different velocities after passing through said second electric field.

1.5. In combination with a stream of charged particles having difierent velocities, means for imparting to said particlesa periodieacceleration in a direction parallel to their reassess path traversed by said particles afte r s'a id acceleration which is substantially free fronijf orc'e s producing acceleration in said direction and which has a length such that some of said particles traverse it in a time substantially canal to a half-period of said periodic "acceleration, and means for imparting to said particles'a periodic deceleration in said direction which is substantially equal and opposite'to'said periodic acceleration.

16. Means for separating from each other electrified particles having equal electric charges and difierent masses which comprises accelerating the particles of desired mass to a predetermined speed, passing them consecutively through two electric fields oscillating at the same high frequency and spaced apart within a resonant cavity which resonates at said frequency; the fields being of such strength, dimensions and spacing relative to each other that particles traversing the said fields at the predetermined speed will undergo substantially equal changes of their velocities but of opposite algebraic sign, and means for separating from each other particles having different direction or speed of motion after passing through the second electric field.

WILLIAM ALTAR.

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

UNITED STATES PATENTS Name Date Sloan July 30, 1935 OTHER REFERENCES Number

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US2009457 *Apr 11, 1932Jul 30, 1935Research CorpMethod and apparatus for producing high voltage
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US2758214 *Dec 16, 1952Aug 7, 1956Jr William E GlennTime-of-flight mass spectrometer
US2769093 *Sep 8, 1953Oct 30, 1956Beckman Instruments IncRadio frequency mass spectrometer
US2817032 *Mar 5, 1954Dec 17, 1957Dwight W BatteauGaseous-discharge method and system
US2836750 *Jan 6, 1956May 27, 1958Licentia GmbhIon source
US2911532 *Mar 26, 1956Nov 3, 1959Beckman Instruments IncIon collector for mass spectrometry
US2946919 *Sep 18, 1957Jul 26, 1960CsfIon sources using a high-frequency field
US2969480 *Apr 29, 1959Jan 24, 1961Commissariat Energie AtomiqueIon sources
US3155593 *Jan 19, 1960Nov 3, 1964CsfApparatus for producing neutrons by collisions between ions
US3571642 *Jan 17, 1968Mar 23, 1971Atomic Energy Of Canada LtdMethod and apparatus for interleaved charged particle acceleration
US4535235 *May 6, 1983Aug 13, 1985Finnigan CorporationApparatus and method for injection of ions into an ion cyclotron resonance cell
US4581533 *May 15, 1984Apr 8, 1986Nicolet Instrument CorporationMass spectrometer and method
US4739165 *Feb 27, 1986Apr 19, 1988Nicolet Instrument CorporationMass spectrometer with remote ion source
US4801848 *May 11, 1987Jan 31, 1989Quantum Diagnostics Ltd.For producing broadband radiation
US7247847May 29, 2002Jul 24, 2007Ilika Technologies LimitedMass spectrometers and methods of ion separation and detection
Classifications
U.S. Classification250/290, 315/5.41, 313/600, 313/161, 313/230
International ClassificationH01J49/34, H01J49/38, H01J49/00
Cooperative ClassificationH01J49/004, H01J49/40, H01J49/30
European ClassificationH01J49/30, H01J49/00T, H01J49/40