CA1123784A - Isotopic separation - Google Patents
Isotopic separationInfo
- Publication number
- CA1123784A CA1123784A CA315,163A CA315163A CA1123784A CA 1123784 A CA1123784 A CA 1123784A CA 315163 A CA315163 A CA 315163A CA 1123784 A CA1123784 A CA 1123784A
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- isotopes
- species
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- isotope
- mixture
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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
- B01D59/50—Separation involving two or more processes covered by different groups selected from groups B01D59/02, B01D59/10, B01D59/20, B01D59/22, B01D59/28, B01D59/34, B01D59/36, B01D59/38, B01D59/44
Abstract
Description
3~ ~ ~
45,~32 ~AC~GROUND OF THE INYENTIOM
Field of the Invention:
.
This invention relates to isotope separation processes and more particularly to separation processes based upon selective isotopic excitation.
Descriptîon of the Prior Art:
Selected isotopic species are useful ~or many purposes including medical apparatus and treatment, tracer studies of chemical and biological processes, and as target materials and fuels for nuclear reactor application. Per-haps the largest present utilization is for nuclear reactors, which typically require, for example, fuel enriched in uranium-235.
The system most widely used today for isotopic separation is gaseous diffusion through a porous barrier, which requires a large, complex, and costly cascading net-work. More recently systems are being considered based upon technologies such as distillation and photo-ionization in the presence of magnetic and electric fields. Exemplary of the latter are U.S. Patent No. 3,772,519 in the name of R.
H. Levy et al. and U.S. Patent No. 3,443,o87 in the name of J. Robieux et al.
While such processes offer much promise for increas-ing the efficiency of isotopic separation processes, it is desirable to provide further alternatives, particularly with a view toward practical application.
SUMMARY OF THE INVENTION
This invention provides additional alternatives to existing and proposed isotope separation techniques. In 3 each of the preferred embodiments, an atomic or molecular ~k r~
45,~32 isotopic mixture is selectively irradiated so as to select-ively excite an isotopic species, preferably through photo-excitation by a laser.
In one embodiment a molecular isotopic species is selectively excited to a preselected internal energy and exposed to positive ions of a predetermined ionization energy. The sum of the internal and ionization energies is sufficiently high to cause a dissociative charge transfer process to occur, releasing as a fragment a positive ion form of the desired isotope. The positive ion is then separated from the balance of the mixture. Preferably, the sum of the ionization energy and the internal energy of the unexcited molecular species in the mixture is below the threshold energy for a dissociative charge transfer process between these constituents so as to decrease the probability for competing processes. This method is particularly appli-cable to the separation of uranium-235 in a mixture of U 35F6 and U233F6.
In another embodiment the positive ion form of the desired isotope, as summarized in the above paragraph, is ~,~ reacted with a negative ion form of the desired isotope to form a neutral species which is separated from the balance of the mixture. The negative ions are formed by addition-ally exposing the selectively excited molecular species to free electrons, thereby causing a dissociative electron attachment process.
Another embodiment exposes the selectively excited molecular isotopic species to another excited species such that the sum of the excitation energies is sufficient to cause a dissociative ionization process to occur, resulting 3~
45,832 in release of a positive ion of the selected isotope. The positive ion form is then separated from the balance of the constituents subsequent to the excitation transfer process by conventional magnetic, electrostatic, electromagnetic or chemical means, in addition to other separation means disclosed.
In other embodiments a near resonance charge transfer process is utilized to separate isotopes in an isotopic, preferably atomic mixture by exposing selectively excited isotopes to positive ions. The sum of the isotope excitation energy and the ionization energy is substantially e~ual to the ionization energy of the selected isotope, and the resulting resonance charge transfer process releases the selected isotopes as positive ions. The process is advan-tageously carried out in a discharge tube which creates an ambipolar diffusion field transverse to the tube axis.
Under the influence of the field, the desired positive isotope ions drift toward the tube periphery and can there-fore be separated from other constituents within the dis-charge tube. Separation can also be accomplished by flowing the products of the process through a curved passage and a magnetic field, thereby deflecting the desired ions to a collection area separate from the collection area for the balance of constituents.
Separation apparatus is also disclosed which can advantageously be used for such isotope separation processes and includes components positioned to enhance the reactions and efficiency of the processes. A discharge device, such as a pair of electrodes, acts upon a flowing gaseous species to form the initial ions and electrons. The isotopic molecu-lar or atomic species are injected into the flowing afterglow 45,832 region downstream of the discharge, mixing with the flowinggas, and are then selectively lrradiated by a ]aser. The i flowing products are directed along a curved centrifuge path, thereby being de~lected to dirfererlt degrees, and are then collected by segmented areas. In those instances where the desired isotope is in an ionic form, a magnetic field directed perpendicular to the flow velocity assists in the deflection, and hence enhances isotopic separation.
The advantages of the inventive embodiments are substantial and include alleviation of the need for an atomic beam as typical in other isotopic separation pro-cesses and apparatus. The invention further provides a convenient and practical means~ such as electrical dis-charge, for provision of atomic or molecular ion species, n e~a - ~bles meta stable3 or chemical radicals not otherwise readily ~, available for photochemical or other types of isotopic separation. Additionally, as a result of the discharge afterglow, the mean electron energy can be provided over a broad range, compatible with a large number of reaction processes, by varying the point of injection of the isotopic mixture downstream in the afterflow. Further, the energy spread of the electrons in the discharge afterflow at a selected downstream distance is smaller than that typically obtained with an electron beam. Also, the electron density obtainable is substantially higher than the density obtain-able with an ordinary electron beam in the same energy range. Complex electron beam formation apparatus is there-for alleviated. Additionally, where the discharge may provide photons of proper energy, a portion of the energy 3 required for the discharge can be extracted as a laser beam 3 ~ ~
~15,832 to be used for the selective excitation leading to enhance-ment in the charge and/or mass difference in the selected isotopic species, thereby increasing the overall system efficiency for isotopic separation.
It will be apparent to those skilled in the art that the various processes disclosed herein are not com-pletely efficient. Accordingly, it is to be understood that reference to the terms "separating", "collecting" and the like refer to increasing the concentration or enrichment of the selected isotopic species relative to the feed concen-tration. Similarly, reference to phrases such as "the balance of constituents" and the like refer to the various fragments, species and reaction products decreased in con-centration of the selected isotopic species. And, while the examples provided relate to actions directed primarily toward the desired isotopic species, it will also be appar-ent that actions can similarly be directed toward an unde-sired species and also provide isotopic separation.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages, nature and additional ~eatures of the invention will become more apparent from the following description taken in connection with the accompanying draw-ings in which:
Figure l is a block diagram of an isotope separa-tion process;
Figures 2 and 3 are schematic illustrations of apparatus in accordance with embodiments of this invention;
Figures 4 and 5 are perspective schematics of further apparatus in accordance with this invention; and 3 Figures 6 and 7 are schematic illustrations of 7o'~
45,832 additional embodiments of the apparatus of Figures 4 and 5.
DESCRIPTION OF TIIE PREFERRED EMBODIMENTS
According to the quasiequilibrium theory of uni-molecular decomposition of polyatomic ions, (see, ~or ex-ample, H. M. Rosenstock, M. B. Wallens~ein, A. L. Wahshaftig, and H. Eyring, Proc. Natl. Acad. Sci. USA 38, 667 (1952); H.
M. Rosenstock, Adv. Mass Spectrom. 4, 523 (1968); M. L.
Vestal, in "Fundamental Process in Radiation Chemistry", edited by P. Ansloos (Wiley, New York, 1968), pp. 59-118;
and A. L. Washshaftig, in "Mass Spectrometry", MTP Intnl.
, Review of Science, edited by A. Maccoll (Butterworths, London, 1972), Physical Chemistry Series One, Vol. 5, pp. 1-24), the fragmentation of such an ion is a function of its total internal energy and is independent o~ the means by which the ion state is arrived at prior to fragmentation.
For example, the dissociative charge transfer process can be written as ~ollows A + XY~ A + tXY ) ~ A + X + Y (1) where A denotes a positive ion, XY is a molecular compound, and the asterisk (*) denotes an excited state. The positive ion can also be that of a molecular compound, AB .
The total internal energy of the parent polyatomic ion (XY ) prior to decomposition consists of two parts: the thermal or internal energy of the neutral molecule XY and the ionization energy of A through transfer. The thermal e-nergy and the transferred energy are equivalent in promot-ing dissociation, since randomization of internal energy is assumed to be extremely fast, on the order of a few hundred vibrational periods, i.e., 10 12 sec., prior to dissociation.
Experimental evidence (W. A. Chupka, J. Chem.
3t7~4 l~5,832 Phys. 54, 1936, 1971; and C. Lifshitz and T. 0. Tiernan, J.
Chem. Phys. 59, 6143, 1~73) showed that the theory is essen-tially correct. In particular, Lifshitz and Tiernan have - found that fragmentation patterns of neopentane, 2-methyl-pentane, 2,3-dimethyl butane and n-octane all exhibit a - strong temperature dependence upon charge exchange with mercury ions ~Ig+. They observed a factor of two or more increase in the fractional abundance of the dissociated ions by increasing the temperature of the neutral molecules (XY) from 28C to 142C. The increase in the degree of fragmen-tation of XY to form X is believed to be the result of vibrational excitation of the molecule XY.
Accordingly, isotope separation can be accom-plished by employing a dissociative charge transfer process as exemplified in reaction (1) and modifying it so that positive ions of the desired isotopic species can be created selectively. This is performed by selective photo-excita-tion of the desired isotopic species followed by dissocia-tive charge transfer. Assuming for clarity that there are only two isotopic species in the target gas, then by virtue of the isotope shift in the absorption spectrum it is pos-sible to selectively excite one isotopic species over the other, hz~ + lxy + 2xy~ (lxy) + 2XY, (2) where h~ denotes the selectively exciting narrow band photo-irradiation of chosen wavelength for isotopic species lXY
and X and X denote different isotopes of an element, and so on throughout the specification.
Since the dissociative charge transfer process depends strongly on the internal excitation of the target ,t$~
4 5 , 8 3 2 molecule, the isotopic ionlc species lX can be created selectively via the following process A+ + (lXY)* + 2Xy_~A + (lXY ) + XY
~ ~ + lx+ + y + 2~y (3) Reaction (3) will occur if the following condition is met:
the sum of the ionization energy of A and the internal energy of ~lXY) is above the threshold energy needed for reaction ~1), while the sum of the energies of A and 2XY is below the threshold.
An example of photon enhancement of reaction (1) can be found in uranium hexafluoride (UF6) or sulfur hexa-fluoride (SF6). It is known that the threshold energy for SF5 from SF6 by electron impact is 15.7 + 3.8 eV, (see V.
H. Dibler and F. L. Mohler, J. Research Natl. Bureau Stand-ards, 40, 25, 1948) and that the ionization potential for argon is 15.68 eV, (R. C. Weast edited, "Handbook of Chem-istry and Physics", The Chemical Rubber Co., Cleveland, Ohio, 1968 p. E-59). It has also been found that at room temperature, the ~3 (943 cm 1) mode of vibration of SF6 is in resonance with the P(20) to P(30) lines, (and preferably the P(26) to P(30) lines) (~10.6~ m) of the carbon dioxide laser. It is therefore expected that the following reactions will occur:
h Y(0.117 eV) + SF6 ~(SF6) (4) where the SF6 is a gas at room temperature and Ar (15.68 eV) + (SF6) ~ SF5 (15.7 eV) + F (5) It will be recognized that reaction (5) is a resonance process. Since there is an isotope shift in the absorption spectrum of 32SF6 and 34SF6, then isotope separation of 32S
from 3 S is possible by selective excitation of the desired _g_ 3'~4 1~5, 832 isotopic species. SF5 is a stable ion and can be .separated and collected by conventional magnetic, electrostatic, electromagnetic, or chemical means, as well as by apparatus discussed hereinafter.
A block diagram of the exemplary dissociative charge transfer process for isotope separation is shown in Figure 1. Pure argon gas is introduced into the ionization zone 1 where the argon gas is ionized by either dc or ac discharge or by other means known in the art. The ionized argon gas flows into a reaction zone 2 where the isotopic molecu~Lar mixture of SF6 gas is injected from a gas source 3 at a controlled rate based upon the argon ion concentration, the gas flow rate and the intensity of a continuous wave (cw) C02 laser 4. For room temperature SF6 gas, the C02 laser 4 is operated on the P(20) to P(30), and preferably the P(26) to P(30) transitions of the C02 (001-100) band, - whereby 32SF6 will be selectively excited. The arrangement is preferably chosen such that the density ratio of Ar to 34SF6 in the reaction zone 2 is larger than the ratio of the cross section of excitation transfer (reaction (9)) to that of dissociative charge transfer (reaction (3)), as shown in (12). The dissociated ionic species 32SF5 from the reac-tion zone is then directed through an ion separator 5 where the positive ions are drawn in a direction different than the balance of constituents by electrostatic force resulting in isotope separation. In another mode of separation the desired isotopic species 32SF5 is neutralized through volume recombination with either electrons or negative ions.
The neutralized 32SF5 is then condensed out on the walls of a condenser 6. The temperature of the condenser wall is so ~3.,~3 ~l~3a~
45,832 adjusted such that 32S~5 is the selectlve condensate.
A relatively si}nple embodiment for utilizing a selective dissociative-charge-transfer process for isotope separation is illustrated in ~ig. 2. Neutral gas A is fed into a flowing afterglow tube 10 fro-rn one end. The tube 10 includes three basic regions. Gaseous discharge is estab-lished in region "a" where electrons and ions A are pro-duced. The discharge can be accomplished through any of a number of means such as by plates 12 which set up an elec-tric field in region "a". Electromagnetic wave, directcurrent, alternating current and microwave fields, among others, can also be utilized. The electrons and ions pro-duced are carried downstream by the flowing gas. At an appropriate point downstream, region "b", gaseous mixkure lxy + 2x~ is introduced into the flowing plasma through an inlet 14 and simultaneously radiation of proper frequency, for example, P(20) to P(30) lines of the CO2 laser, is used to selectively irradiate the mixture of S~6. The radiation is here shown as coming from a laser 16. The stable posi-tive product ions lX , produced in accordance with reaction(3), can be collected further downstream in region "c", through mechanical, chemical or the electrical process shown. The system illustrated has many degrees of freedom through adjustment of such parameters as the gas pressure and temperature, flow velocity, discharge intensity, iso-topic mixture feed density and laser intensity.
Electrons produced in the discharge also appear in the flowing afterglow. By proper location of the injection point of the isotopic mixture and hence selecting the proper energy of the electrons in the flowing afterglow, a selective 45,832 dissociative electr-on attachment process can also be accom-plished:
e + (lxy~ + 2xy-~lxy~~* + 2xy _~lX_ + y + 2xy (6) The negative product ions lX produced in accordance with reaction (6) and the positive product ions lX produced in accordance with reaction (3) will recombine readily. For example, in the case of sulfur hexafluoride SF5 + SF5 ~2SF4 + 2F (7) Accordingly, a simplified separation process can be utilized in region "c", such as cooling the reaction products to condense the enriched SF4 onto a removal surface.
For isotope separation of a uranium mixture, such as U235F6 and U238F6, similar dissociative charge transfer and dissociative electron attachment processes can be used. The threshold energy at which UF5 is formed from UF6 is 15.5 _ 0.7 eV (J. R. White and A. E. Cameron, Phys.
Rev. 71, 907, 1947). The argon ion is a preferred candidate for the process, although other ions can be utilized. As potential candidates for the primary positive ions A for any dissociative charge transfer process for isotope separa-tion, a whole spectrum of atoms and molecules with ioniza-tion potential ranging from as low as 3.87 eV (for cesium) to as high as 24.46 eV ~for helium) exist.
The processes taught can be Eurther extended to include a selective dissociative excitation transfer process for isotope separation. In reaction (3? a long-lived meta-stable excited species A is substituted for the positive ion A :
A + ( XY) + XY~ A + X + Y + e + XY (8) l~ere, the sum of the excitation energies of the species A
~ 3~8~ ~5,832 and (lXY) must be sufficient to cause reaction ~) to occur.
In any selective photon excitation process for isotope separation, a competing process to reduce the effect-iveness and overall efficiency of separation is the unde-sired excitation transfer, such as (lxy)~ + 2xy~ lxy + (2XY) (9) The cross section of this process has been found to be inthe range of 10 14 to 10 15 cm2. However, the dissociative charge transfer process, reaction (3), is also expected to be large where near energy resonance occurs, as illustrated in the example of Ar + (SF6) . In order to achieve a high separation factor in a practical device such as illustrated in ~ig. 2, the selective dissociative charge exchange rate of reaction (3) must be higher than the excitation transfer rate of reaction (9). This criteria is satisfied if [A ] ~ XY ] QDCT Vr1~[ XY ] [ XY] QXT Vr2, (10) where the brackets represent the particle density of the indicated species within a given reaction volume; QDCT and QXT are respectively the cross sections of the dissociative charge transfer process reaction (3), and the excitation transfer process reaction (9); and vr1 and vr2 are the relative velocities of the colliding partners in reactions (3) and (9), respectively.
The velocities are substantially equal, Vrl ~ Vr2, ( 11 ) and accordingly, a large separation factor can be achieved if [A ] > QXT (12) [ 2XY ] QDCT
45,832 Accordingly, once the cross sectlons QDCrll and QXT are accur-ately known, one can control the gas A flow rate, the dis-charge condition and the neutral lxy + 2XY injection rate so that reaction (12) is satisfied. Apparatus disclosed here-inafter, particularly with respect to Fig. 5, can be util-ized for carrying out the discussed reactions.
It has been found that atoms in an atomic isotopic mixture, such as U 35 atoms in a mixture including atoms of U 38, can be selectively ionized by a resonance charge transfer process following selecti~e excitation. The physi-cal separation of the ions from the balance of constituents of the process is preferably achieved by apparatus utilizing radial ambipolar diffusion techniques (P. C. Stangeby and J.
E. Allen, Nature 233, 472, 1971) or a combination of elec-trostatic and magnetohydrodynamic effects. This process advantageously eliminates the need for provision of an atomic beam of atoms, such as uranium atoms, as typically required.
It is known (J. B. Hasted, Advances in Atomic and Molecular Physics, Edited by D. R. Bates and I. Estermann (Academic Press, New York, 1968), p. 237) that the charge transfer cross section of A + B~ A + B +~E, whereQ E is the energy released (13) is very large ( 10 13 cm ) if QE~O. The neutral species B
in reaction (13) can be either in the ground state or in the excited states. For the exemplary separation of isotopes of uranium, U235 atoms are selectively excited by, for example, monochromatic light such as dye laser radiation:
3 h~ + U235 + U233_~U235~ + U238 (14) 45,832 The excited atoms U235 are then ionized by res-onance charge transfer wlth ions A , A+ + U235* + U238-~A + U235+ + U 3 . (15) As a more specific example, ~ 29 3A~ ~ U235 + U238~ U235 (2.328 eV) + U , ~16) and Cs (3.87 e~) + U235 (2.328 eV)~ Cs + U235+ (17) It is believed that the ionization potential of uranium is 6.22 + 0.5 eV ~see D. W. Steinhaus et al., Present Status of the Analyses of the First and Second Spectra of Uranium (UI
and UII~ as Derived from Measurements of Optical Spectra, Los Alamos Scientific Report LA-4501, October 1971) and the 5329.3 A radiation and the Cs ions in reactions (16) and (17) are chosen for illustration only, many other wave-lengths and ions being equally applicable. Other wave-lengths for selective excitation of U235 are well known.
The objective for a workable atomic charge transfer reaction for uranium is that the sum of the excitation energy of U235 and the ionization energy of A is substantially equal to, but no less than, the ionization energy of uranium 235. It is to be understood that while the exemplary reactions relate to atomic isotopic mixtures, the teaching is appli-cable to molecular isotopic mixtures.
One embodiment of apparatus for carrying out the disclosed process is shown in Figure 3, and another in Figure 4. While the exemplary cesium-uranium reaction is discussed, the process and apparatus are not to be construed as so limited.
In Fig. 3, cesium and uranium vapor are caused to 3 flow into a discharge tube 20 through an inlet 22. A few 7~ ~
45,832 Torr of a noble gas can advantageously be added to act as a bufrer and maintain a stable glow discharge. Cesiurn atoms are readily ionized due to their low ionization potential.
At the same time the discharge tube is irradiated with radiation of a predetermined frequency, such as monochrom-atic light so that U235 is produced and reacts with Cs to form U235 according to reaction (15). The U235 ions drift toward the walls of the discharge tube under the influence of an ambipolar diffusion field which is formed by the discharge reaction. The enriched fraction can then be collected downstream as shown.
Figure 4 shows apparatus particularly useful for high flow rates. The atomic uranium mixture is injected through ports 26 which supply the mixture downstream of a discharge zone 28 into a flowing cesium afterglow. Mono-chromatic radiation h~ is also introduced into the flowing medium in the area where uranium is injected. The U 35 ions created by charge transfer are separated from the mixture by an electrostatic-magnetohydrodynamic enhanced nozzle technique as shown. This includes flow of the reac-tion products at a velocity v through a curved centrifuge passage or zone 30 in the presence of magnetic field B32 acting in the direction perpendicular to the velocity shown.
The various products, under the influence of the curved passage and the magnetic field, are deflected along differ-ent flow paths and collected in different segmented areas 34, 36, 38.
As illustrated above, most photon-assisted physi-cal or chemical processes for isotope separation require, in addition to the isotopic mixture, electrons, ions or neutrals ~.Z3~84 ~5,~32 in some preferred state. For exam~le, the photon-enhanced dissociative electron attachment process h~ + lX~ + 2xy ~ (lxy~* ~ 2XY (2) and e~ + (1XY)* ~ lX- + Y, (1~), (6) requires a well defined range of electron (e ) energies.
Similarly, the dissociative charge transfer process h~ + lxy + 2xy ~ (lxy)* ~ 2xy (23 and A~ + (lxy)* + 2xy ~ lX~ + Y + A 1 2XY (3) requires an ion (A+) with appropriate ionization energy.
And, the photo-chemical process h~ + 1X ~ 2X ~ 1X* + 2X(19), (14) and AB + 1X* ~ 2X ~ 1XB ~ A + 2X (20) or B + lX* + 2X ~ 1XB + 2X (2~) requires neutrals AB or B which may be chemical radicals produced in a discharge.
The arrangement disclosed and illustrated in Figure 5 not only provides the capability to perform all of these processes, but also provides distinct operational, cost and efficiency advantages as compared to prior art arrangements. The present system for isotope separation combines the principle of aerodynamic mass separation and v x B drift of a moving charged particle (velocity v) in a 45,832 magnetic field, B. In addition, the teaching of the present invention utilizes flowing afterglow for positive ion pro-duction for a selective-dissociative charge transfer process for isotope separation. The electrons produced in the discharge can be used for space charge neutralization or negative ion production for further improvement of effi-ciency of isotope separation. An optical cavity can also be created in the discharge zone for further improvements in overall efficiency.
As shown in Figure 5, flowing gas A (or AB~, enters the passage 40 from an inlet area 42. A glow dis-- charge is struck in a discharge zone 44, for example, by discharge means such as a pair of electrodes 46. The elec-trons for reaction ~18) or A ions for reaction (3) are carried by the flow downstream where the mixture of isotopes lXY and 2XY or lX and 2X is injected into the stream. At the same time, these constituents are irradiated with a narrow line radiation (h~), such as from a tunable dye laser~ The selectively created isotopic species X from reaction (18), or lX+ from reaction (3) then enters an aerodynamic mass separation or curved centrifuge section 48 of the system with a flowing velocity v.
The aerodynamic mass separator 48 employs the centrifugal force upon particles traversing a curved path and takes advantage of the enhanced mass difference between isotopic species as a result of the effected reaction pro-cess. The heavier isotopic species 2XY traverses a flow path to the outer channel 38, formed by fingers 50, while the lighter species lX , or X , prefers an inner channel 36 3 for exit and collection, resulting in separation.
;: -18-378~
45,832 The mass separation can be enhanced further by magnetohydrodynamic means since lX , or X , is a charged particle for some period of time subsequent to formation.
A dc magnetic field, B, is applied transverse to the con-stituent flow v such that a Hall field v X B is developed across the flow passage 40. Thus the charged isotopic species under the influence of this field are caused to deflect toward the inner wall 52 of the passage 48, thereby enhancing the mass separation.
In the limiting case of no collisions, the ion drift velocity vl across the magnetic field and the drift distance dl due to the Hall effect at the end of the cen-trifugal section of length 1 are vl = MBl in cm/sec (22) and d = eBl_ in cm, (23) respectively. Here Mi is the mass of the ion formed from, for example, selective dissociative charge transfer, e is the charge of the ion in esu; 1 is the length of the centri-fugal section, v is the flowing gas velocity in cm/sec; andB is the transverse magnetic field in gauss. In the event collision of the ionic species with the buffer gas occurs, the drift velocity and distance can also be predetermined.
The curvature and length of the centrifugal section together with other parameters of the arrangement such as exit channel widths can be tailored to achieve optimum isotope separation.
A practical example of utilization of the present arrangement is an application to uranium or sulfur isotope separation using, for example, SF6 (or UF6) gas. Argon gas 3 is introduced into the device at inlet 42. The gas is ~ A
~-~ ~J ~ 45,832 ionized while passing through the pair of electrodes 46 where an adequate field, either ac or dc, is maintained.
Downstream of the discharge zone about 100 ~sec in the afterglow region, an isotopic mixture of SF6 gas is injected into the ionized gas stream. Simultaneously a cw C02 laser operated on the P(20~ to P(30~ and preferably the P(26) to P(30) transitions of the C02 (001-100) band is beamed at the injection zone so that the 32SF6 isotope is selectively excited. The intensity of the laser beam is such that a high concentration of 32SF6 is excited to the upper vibra-tional states where dissociative charge transfer with Ar ions is effective. The mixture of reaction products then CUt-";tl ~ear B flows into the _ region where both centrifugal force and v X B force act upon the charged particles.
Spatial separation of molecules and other species of dif-ferent mass is achieved and enrichment of the particular isotopic species 32S is obtained by proper location of the exit channel.
It will be apparent to those skilled in the art that the disclosed arrangement provides a convenient and practical means, such as electrical discharge, for provision of atomic or molecular species or chemical radicals not otherwise readily available for photochemical or other isotopic separation processes. Additionally, as a result of the discharge afterglow, the mean electron energy can be provided over a broad range, compatible with a large number of species, by varying the point of injection of the iso-topic mixture downstream in the afterflow. The energy can range from, for example, 1 eV to 0.03 eV. Further, the energy spread of the electrons in the afterflow at a selected ~ 4 45,~32 downstream distance is smaller- than that typically obtained with an electron beam. Also, the electron density obtain-able is in the range of 10~ to 1011 cm 3, which is substan-tially higher than the density obtainable with an ordinary electron beam in the same energy range. Complex electron beam formation apparatus is therefor eliminated.
Additional arrangements can also be advantageously utilized to further benefit the disclosed system and provide increased system efficiency. Figures 6 and 7 illustrate arrangements where the energy input to the discharge, typi-cally electrical energy, can be partially extracted as laser energy and used, respectively, directly or indirectly for the separation process. In both of the figures the discharge area is modified, such as by the addition of mirrors 52, to form an optical cavity 54. As shown in Figure 6, the result-ing laser beam can then be directed, through additional mirrors 56, to perform the irradiating function where proper photon wavelengths are obtained from the discharge. As shown in Figure 7, the resulting laser beam can also be utilized to pump another laser, such as a dye or solid state unit, which performs the irradiating function.
Further modifications and additions are possible in view of the above teachings. It therefore is to be understood that within the scope of the claims, the invent-ive embodirnents can be practiced other than as specifically described.
45,~32 ~AC~GROUND OF THE INYENTIOM
Field of the Invention:
.
This invention relates to isotope separation processes and more particularly to separation processes based upon selective isotopic excitation.
Descriptîon of the Prior Art:
Selected isotopic species are useful ~or many purposes including medical apparatus and treatment, tracer studies of chemical and biological processes, and as target materials and fuels for nuclear reactor application. Per-haps the largest present utilization is for nuclear reactors, which typically require, for example, fuel enriched in uranium-235.
The system most widely used today for isotopic separation is gaseous diffusion through a porous barrier, which requires a large, complex, and costly cascading net-work. More recently systems are being considered based upon technologies such as distillation and photo-ionization in the presence of magnetic and electric fields. Exemplary of the latter are U.S. Patent No. 3,772,519 in the name of R.
H. Levy et al. and U.S. Patent No. 3,443,o87 in the name of J. Robieux et al.
While such processes offer much promise for increas-ing the efficiency of isotopic separation processes, it is desirable to provide further alternatives, particularly with a view toward practical application.
SUMMARY OF THE INVENTION
This invention provides additional alternatives to existing and proposed isotope separation techniques. In 3 each of the preferred embodiments, an atomic or molecular ~k r~
45,~32 isotopic mixture is selectively irradiated so as to select-ively excite an isotopic species, preferably through photo-excitation by a laser.
In one embodiment a molecular isotopic species is selectively excited to a preselected internal energy and exposed to positive ions of a predetermined ionization energy. The sum of the internal and ionization energies is sufficiently high to cause a dissociative charge transfer process to occur, releasing as a fragment a positive ion form of the desired isotope. The positive ion is then separated from the balance of the mixture. Preferably, the sum of the ionization energy and the internal energy of the unexcited molecular species in the mixture is below the threshold energy for a dissociative charge transfer process between these constituents so as to decrease the probability for competing processes. This method is particularly appli-cable to the separation of uranium-235 in a mixture of U 35F6 and U233F6.
In another embodiment the positive ion form of the desired isotope, as summarized in the above paragraph, is ~,~ reacted with a negative ion form of the desired isotope to form a neutral species which is separated from the balance of the mixture. The negative ions are formed by addition-ally exposing the selectively excited molecular species to free electrons, thereby causing a dissociative electron attachment process.
Another embodiment exposes the selectively excited molecular isotopic species to another excited species such that the sum of the excitation energies is sufficient to cause a dissociative ionization process to occur, resulting 3~
45,832 in release of a positive ion of the selected isotope. The positive ion form is then separated from the balance of the constituents subsequent to the excitation transfer process by conventional magnetic, electrostatic, electromagnetic or chemical means, in addition to other separation means disclosed.
In other embodiments a near resonance charge transfer process is utilized to separate isotopes in an isotopic, preferably atomic mixture by exposing selectively excited isotopes to positive ions. The sum of the isotope excitation energy and the ionization energy is substantially e~ual to the ionization energy of the selected isotope, and the resulting resonance charge transfer process releases the selected isotopes as positive ions. The process is advan-tageously carried out in a discharge tube which creates an ambipolar diffusion field transverse to the tube axis.
Under the influence of the field, the desired positive isotope ions drift toward the tube periphery and can there-fore be separated from other constituents within the dis-charge tube. Separation can also be accomplished by flowing the products of the process through a curved passage and a magnetic field, thereby deflecting the desired ions to a collection area separate from the collection area for the balance of constituents.
Separation apparatus is also disclosed which can advantageously be used for such isotope separation processes and includes components positioned to enhance the reactions and efficiency of the processes. A discharge device, such as a pair of electrodes, acts upon a flowing gaseous species to form the initial ions and electrons. The isotopic molecu-lar or atomic species are injected into the flowing afterglow 45,832 region downstream of the discharge, mixing with the flowinggas, and are then selectively lrradiated by a ]aser. The i flowing products are directed along a curved centrifuge path, thereby being de~lected to dirfererlt degrees, and are then collected by segmented areas. In those instances where the desired isotope is in an ionic form, a magnetic field directed perpendicular to the flow velocity assists in the deflection, and hence enhances isotopic separation.
The advantages of the inventive embodiments are substantial and include alleviation of the need for an atomic beam as typical in other isotopic separation pro-cesses and apparatus. The invention further provides a convenient and practical means~ such as electrical dis-charge, for provision of atomic or molecular ion species, n e~a - ~bles meta stable3 or chemical radicals not otherwise readily ~, available for photochemical or other types of isotopic separation. Additionally, as a result of the discharge afterglow, the mean electron energy can be provided over a broad range, compatible with a large number of reaction processes, by varying the point of injection of the isotopic mixture downstream in the afterflow. Further, the energy spread of the electrons in the discharge afterflow at a selected downstream distance is smaller than that typically obtained with an electron beam. Also, the electron density obtainable is substantially higher than the density obtain-able with an ordinary electron beam in the same energy range. Complex electron beam formation apparatus is there-for alleviated. Additionally, where the discharge may provide photons of proper energy, a portion of the energy 3 required for the discharge can be extracted as a laser beam 3 ~ ~
~15,832 to be used for the selective excitation leading to enhance-ment in the charge and/or mass difference in the selected isotopic species, thereby increasing the overall system efficiency for isotopic separation.
It will be apparent to those skilled in the art that the various processes disclosed herein are not com-pletely efficient. Accordingly, it is to be understood that reference to the terms "separating", "collecting" and the like refer to increasing the concentration or enrichment of the selected isotopic species relative to the feed concen-tration. Similarly, reference to phrases such as "the balance of constituents" and the like refer to the various fragments, species and reaction products decreased in con-centration of the selected isotopic species. And, while the examples provided relate to actions directed primarily toward the desired isotopic species, it will also be appar-ent that actions can similarly be directed toward an unde-sired species and also provide isotopic separation.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages, nature and additional ~eatures of the invention will become more apparent from the following description taken in connection with the accompanying draw-ings in which:
Figure l is a block diagram of an isotope separa-tion process;
Figures 2 and 3 are schematic illustrations of apparatus in accordance with embodiments of this invention;
Figures 4 and 5 are perspective schematics of further apparatus in accordance with this invention; and 3 Figures 6 and 7 are schematic illustrations of 7o'~
45,832 additional embodiments of the apparatus of Figures 4 and 5.
DESCRIPTION OF TIIE PREFERRED EMBODIMENTS
According to the quasiequilibrium theory of uni-molecular decomposition of polyatomic ions, (see, ~or ex-ample, H. M. Rosenstock, M. B. Wallens~ein, A. L. Wahshaftig, and H. Eyring, Proc. Natl. Acad. Sci. USA 38, 667 (1952); H.
M. Rosenstock, Adv. Mass Spectrom. 4, 523 (1968); M. L.
Vestal, in "Fundamental Process in Radiation Chemistry", edited by P. Ansloos (Wiley, New York, 1968), pp. 59-118;
and A. L. Washshaftig, in "Mass Spectrometry", MTP Intnl.
, Review of Science, edited by A. Maccoll (Butterworths, London, 1972), Physical Chemistry Series One, Vol. 5, pp. 1-24), the fragmentation of such an ion is a function of its total internal energy and is independent o~ the means by which the ion state is arrived at prior to fragmentation.
For example, the dissociative charge transfer process can be written as ~ollows A + XY~ A + tXY ) ~ A + X + Y (1) where A denotes a positive ion, XY is a molecular compound, and the asterisk (*) denotes an excited state. The positive ion can also be that of a molecular compound, AB .
The total internal energy of the parent polyatomic ion (XY ) prior to decomposition consists of two parts: the thermal or internal energy of the neutral molecule XY and the ionization energy of A through transfer. The thermal e-nergy and the transferred energy are equivalent in promot-ing dissociation, since randomization of internal energy is assumed to be extremely fast, on the order of a few hundred vibrational periods, i.e., 10 12 sec., prior to dissociation.
Experimental evidence (W. A. Chupka, J. Chem.
3t7~4 l~5,832 Phys. 54, 1936, 1971; and C. Lifshitz and T. 0. Tiernan, J.
Chem. Phys. 59, 6143, 1~73) showed that the theory is essen-tially correct. In particular, Lifshitz and Tiernan have - found that fragmentation patterns of neopentane, 2-methyl-pentane, 2,3-dimethyl butane and n-octane all exhibit a - strong temperature dependence upon charge exchange with mercury ions ~Ig+. They observed a factor of two or more increase in the fractional abundance of the dissociated ions by increasing the temperature of the neutral molecules (XY) from 28C to 142C. The increase in the degree of fragmen-tation of XY to form X is believed to be the result of vibrational excitation of the molecule XY.
Accordingly, isotope separation can be accom-plished by employing a dissociative charge transfer process as exemplified in reaction (1) and modifying it so that positive ions of the desired isotopic species can be created selectively. This is performed by selective photo-excita-tion of the desired isotopic species followed by dissocia-tive charge transfer. Assuming for clarity that there are only two isotopic species in the target gas, then by virtue of the isotope shift in the absorption spectrum it is pos-sible to selectively excite one isotopic species over the other, hz~ + lxy + 2xy~ (lxy) + 2XY, (2) where h~ denotes the selectively exciting narrow band photo-irradiation of chosen wavelength for isotopic species lXY
and X and X denote different isotopes of an element, and so on throughout the specification.
Since the dissociative charge transfer process depends strongly on the internal excitation of the target ,t$~
4 5 , 8 3 2 molecule, the isotopic ionlc species lX can be created selectively via the following process A+ + (lXY)* + 2Xy_~A + (lXY ) + XY
~ ~ + lx+ + y + 2~y (3) Reaction (3) will occur if the following condition is met:
the sum of the ionization energy of A and the internal energy of ~lXY) is above the threshold energy needed for reaction ~1), while the sum of the energies of A and 2XY is below the threshold.
An example of photon enhancement of reaction (1) can be found in uranium hexafluoride (UF6) or sulfur hexa-fluoride (SF6). It is known that the threshold energy for SF5 from SF6 by electron impact is 15.7 + 3.8 eV, (see V.
H. Dibler and F. L. Mohler, J. Research Natl. Bureau Stand-ards, 40, 25, 1948) and that the ionization potential for argon is 15.68 eV, (R. C. Weast edited, "Handbook of Chem-istry and Physics", The Chemical Rubber Co., Cleveland, Ohio, 1968 p. E-59). It has also been found that at room temperature, the ~3 (943 cm 1) mode of vibration of SF6 is in resonance with the P(20) to P(30) lines, (and preferably the P(26) to P(30) lines) (~10.6~ m) of the carbon dioxide laser. It is therefore expected that the following reactions will occur:
h Y(0.117 eV) + SF6 ~(SF6) (4) where the SF6 is a gas at room temperature and Ar (15.68 eV) + (SF6) ~ SF5 (15.7 eV) + F (5) It will be recognized that reaction (5) is a resonance process. Since there is an isotope shift in the absorption spectrum of 32SF6 and 34SF6, then isotope separation of 32S
from 3 S is possible by selective excitation of the desired _g_ 3'~4 1~5, 832 isotopic species. SF5 is a stable ion and can be .separated and collected by conventional magnetic, electrostatic, electromagnetic, or chemical means, as well as by apparatus discussed hereinafter.
A block diagram of the exemplary dissociative charge transfer process for isotope separation is shown in Figure 1. Pure argon gas is introduced into the ionization zone 1 where the argon gas is ionized by either dc or ac discharge or by other means known in the art. The ionized argon gas flows into a reaction zone 2 where the isotopic molecu~Lar mixture of SF6 gas is injected from a gas source 3 at a controlled rate based upon the argon ion concentration, the gas flow rate and the intensity of a continuous wave (cw) C02 laser 4. For room temperature SF6 gas, the C02 laser 4 is operated on the P(20) to P(30), and preferably the P(26) to P(30) transitions of the C02 (001-100) band, - whereby 32SF6 will be selectively excited. The arrangement is preferably chosen such that the density ratio of Ar to 34SF6 in the reaction zone 2 is larger than the ratio of the cross section of excitation transfer (reaction (9)) to that of dissociative charge transfer (reaction (3)), as shown in (12). The dissociated ionic species 32SF5 from the reac-tion zone is then directed through an ion separator 5 where the positive ions are drawn in a direction different than the balance of constituents by electrostatic force resulting in isotope separation. In another mode of separation the desired isotopic species 32SF5 is neutralized through volume recombination with either electrons or negative ions.
The neutralized 32SF5 is then condensed out on the walls of a condenser 6. The temperature of the condenser wall is so ~3.,~3 ~l~3a~
45,832 adjusted such that 32S~5 is the selectlve condensate.
A relatively si}nple embodiment for utilizing a selective dissociative-charge-transfer process for isotope separation is illustrated in ~ig. 2. Neutral gas A is fed into a flowing afterglow tube 10 fro-rn one end. The tube 10 includes three basic regions. Gaseous discharge is estab-lished in region "a" where electrons and ions A are pro-duced. The discharge can be accomplished through any of a number of means such as by plates 12 which set up an elec-tric field in region "a". Electromagnetic wave, directcurrent, alternating current and microwave fields, among others, can also be utilized. The electrons and ions pro-duced are carried downstream by the flowing gas. At an appropriate point downstream, region "b", gaseous mixkure lxy + 2x~ is introduced into the flowing plasma through an inlet 14 and simultaneously radiation of proper frequency, for example, P(20) to P(30) lines of the CO2 laser, is used to selectively irradiate the mixture of S~6. The radiation is here shown as coming from a laser 16. The stable posi-tive product ions lX , produced in accordance with reaction(3), can be collected further downstream in region "c", through mechanical, chemical or the electrical process shown. The system illustrated has many degrees of freedom through adjustment of such parameters as the gas pressure and temperature, flow velocity, discharge intensity, iso-topic mixture feed density and laser intensity.
Electrons produced in the discharge also appear in the flowing afterglow. By proper location of the injection point of the isotopic mixture and hence selecting the proper energy of the electrons in the flowing afterglow, a selective 45,832 dissociative electr-on attachment process can also be accom-plished:
e + (lxy~ + 2xy-~lxy~~* + 2xy _~lX_ + y + 2xy (6) The negative product ions lX produced in accordance with reaction (6) and the positive product ions lX produced in accordance with reaction (3) will recombine readily. For example, in the case of sulfur hexafluoride SF5 + SF5 ~2SF4 + 2F (7) Accordingly, a simplified separation process can be utilized in region "c", such as cooling the reaction products to condense the enriched SF4 onto a removal surface.
For isotope separation of a uranium mixture, such as U235F6 and U238F6, similar dissociative charge transfer and dissociative electron attachment processes can be used. The threshold energy at which UF5 is formed from UF6 is 15.5 _ 0.7 eV (J. R. White and A. E. Cameron, Phys.
Rev. 71, 907, 1947). The argon ion is a preferred candidate for the process, although other ions can be utilized. As potential candidates for the primary positive ions A for any dissociative charge transfer process for isotope separa-tion, a whole spectrum of atoms and molecules with ioniza-tion potential ranging from as low as 3.87 eV (for cesium) to as high as 24.46 eV ~for helium) exist.
The processes taught can be Eurther extended to include a selective dissociative excitation transfer process for isotope separation. In reaction (3? a long-lived meta-stable excited species A is substituted for the positive ion A :
A + ( XY) + XY~ A + X + Y + e + XY (8) l~ere, the sum of the excitation energies of the species A
~ 3~8~ ~5,832 and (lXY) must be sufficient to cause reaction ~) to occur.
In any selective photon excitation process for isotope separation, a competing process to reduce the effect-iveness and overall efficiency of separation is the unde-sired excitation transfer, such as (lxy)~ + 2xy~ lxy + (2XY) (9) The cross section of this process has been found to be inthe range of 10 14 to 10 15 cm2. However, the dissociative charge transfer process, reaction (3), is also expected to be large where near energy resonance occurs, as illustrated in the example of Ar + (SF6) . In order to achieve a high separation factor in a practical device such as illustrated in ~ig. 2, the selective dissociative charge exchange rate of reaction (3) must be higher than the excitation transfer rate of reaction (9). This criteria is satisfied if [A ] ~ XY ] QDCT Vr1~[ XY ] [ XY] QXT Vr2, (10) where the brackets represent the particle density of the indicated species within a given reaction volume; QDCT and QXT are respectively the cross sections of the dissociative charge transfer process reaction (3), and the excitation transfer process reaction (9); and vr1 and vr2 are the relative velocities of the colliding partners in reactions (3) and (9), respectively.
The velocities are substantially equal, Vrl ~ Vr2, ( 11 ) and accordingly, a large separation factor can be achieved if [A ] > QXT (12) [ 2XY ] QDCT
45,832 Accordingly, once the cross sectlons QDCrll and QXT are accur-ately known, one can control the gas A flow rate, the dis-charge condition and the neutral lxy + 2XY injection rate so that reaction (12) is satisfied. Apparatus disclosed here-inafter, particularly with respect to Fig. 5, can be util-ized for carrying out the discussed reactions.
It has been found that atoms in an atomic isotopic mixture, such as U 35 atoms in a mixture including atoms of U 38, can be selectively ionized by a resonance charge transfer process following selecti~e excitation. The physi-cal separation of the ions from the balance of constituents of the process is preferably achieved by apparatus utilizing radial ambipolar diffusion techniques (P. C. Stangeby and J.
E. Allen, Nature 233, 472, 1971) or a combination of elec-trostatic and magnetohydrodynamic effects. This process advantageously eliminates the need for provision of an atomic beam of atoms, such as uranium atoms, as typically required.
It is known (J. B. Hasted, Advances in Atomic and Molecular Physics, Edited by D. R. Bates and I. Estermann (Academic Press, New York, 1968), p. 237) that the charge transfer cross section of A + B~ A + B +~E, whereQ E is the energy released (13) is very large ( 10 13 cm ) if QE~O. The neutral species B
in reaction (13) can be either in the ground state or in the excited states. For the exemplary separation of isotopes of uranium, U235 atoms are selectively excited by, for example, monochromatic light such as dye laser radiation:
3 h~ + U235 + U233_~U235~ + U238 (14) 45,832 The excited atoms U235 are then ionized by res-onance charge transfer wlth ions A , A+ + U235* + U238-~A + U235+ + U 3 . (15) As a more specific example, ~ 29 3A~ ~ U235 + U238~ U235 (2.328 eV) + U , ~16) and Cs (3.87 e~) + U235 (2.328 eV)~ Cs + U235+ (17) It is believed that the ionization potential of uranium is 6.22 + 0.5 eV ~see D. W. Steinhaus et al., Present Status of the Analyses of the First and Second Spectra of Uranium (UI
and UII~ as Derived from Measurements of Optical Spectra, Los Alamos Scientific Report LA-4501, October 1971) and the 5329.3 A radiation and the Cs ions in reactions (16) and (17) are chosen for illustration only, many other wave-lengths and ions being equally applicable. Other wave-lengths for selective excitation of U235 are well known.
The objective for a workable atomic charge transfer reaction for uranium is that the sum of the excitation energy of U235 and the ionization energy of A is substantially equal to, but no less than, the ionization energy of uranium 235. It is to be understood that while the exemplary reactions relate to atomic isotopic mixtures, the teaching is appli-cable to molecular isotopic mixtures.
One embodiment of apparatus for carrying out the disclosed process is shown in Figure 3, and another in Figure 4. While the exemplary cesium-uranium reaction is discussed, the process and apparatus are not to be construed as so limited.
In Fig. 3, cesium and uranium vapor are caused to 3 flow into a discharge tube 20 through an inlet 22. A few 7~ ~
45,832 Torr of a noble gas can advantageously be added to act as a bufrer and maintain a stable glow discharge. Cesiurn atoms are readily ionized due to their low ionization potential.
At the same time the discharge tube is irradiated with radiation of a predetermined frequency, such as monochrom-atic light so that U235 is produced and reacts with Cs to form U235 according to reaction (15). The U235 ions drift toward the walls of the discharge tube under the influence of an ambipolar diffusion field which is formed by the discharge reaction. The enriched fraction can then be collected downstream as shown.
Figure 4 shows apparatus particularly useful for high flow rates. The atomic uranium mixture is injected through ports 26 which supply the mixture downstream of a discharge zone 28 into a flowing cesium afterglow. Mono-chromatic radiation h~ is also introduced into the flowing medium in the area where uranium is injected. The U 35 ions created by charge transfer are separated from the mixture by an electrostatic-magnetohydrodynamic enhanced nozzle technique as shown. This includes flow of the reac-tion products at a velocity v through a curved centrifuge passage or zone 30 in the presence of magnetic field B32 acting in the direction perpendicular to the velocity shown.
The various products, under the influence of the curved passage and the magnetic field, are deflected along differ-ent flow paths and collected in different segmented areas 34, 36, 38.
As illustrated above, most photon-assisted physi-cal or chemical processes for isotope separation require, in addition to the isotopic mixture, electrons, ions or neutrals ~.Z3~84 ~5,~32 in some preferred state. For exam~le, the photon-enhanced dissociative electron attachment process h~ + lX~ + 2xy ~ (lxy~* ~ 2XY (2) and e~ + (1XY)* ~ lX- + Y, (1~), (6) requires a well defined range of electron (e ) energies.
Similarly, the dissociative charge transfer process h~ + lxy + 2xy ~ (lxy)* ~ 2xy (23 and A~ + (lxy)* + 2xy ~ lX~ + Y + A 1 2XY (3) requires an ion (A+) with appropriate ionization energy.
And, the photo-chemical process h~ + 1X ~ 2X ~ 1X* + 2X(19), (14) and AB + 1X* ~ 2X ~ 1XB ~ A + 2X (20) or B + lX* + 2X ~ 1XB + 2X (2~) requires neutrals AB or B which may be chemical radicals produced in a discharge.
The arrangement disclosed and illustrated in Figure 5 not only provides the capability to perform all of these processes, but also provides distinct operational, cost and efficiency advantages as compared to prior art arrangements. The present system for isotope separation combines the principle of aerodynamic mass separation and v x B drift of a moving charged particle (velocity v) in a 45,832 magnetic field, B. In addition, the teaching of the present invention utilizes flowing afterglow for positive ion pro-duction for a selective-dissociative charge transfer process for isotope separation. The electrons produced in the discharge can be used for space charge neutralization or negative ion production for further improvement of effi-ciency of isotope separation. An optical cavity can also be created in the discharge zone for further improvements in overall efficiency.
As shown in Figure 5, flowing gas A (or AB~, enters the passage 40 from an inlet area 42. A glow dis-- charge is struck in a discharge zone 44, for example, by discharge means such as a pair of electrodes 46. The elec-trons for reaction ~18) or A ions for reaction (3) are carried by the flow downstream where the mixture of isotopes lXY and 2XY or lX and 2X is injected into the stream. At the same time, these constituents are irradiated with a narrow line radiation (h~), such as from a tunable dye laser~ The selectively created isotopic species X from reaction (18), or lX+ from reaction (3) then enters an aerodynamic mass separation or curved centrifuge section 48 of the system with a flowing velocity v.
The aerodynamic mass separator 48 employs the centrifugal force upon particles traversing a curved path and takes advantage of the enhanced mass difference between isotopic species as a result of the effected reaction pro-cess. The heavier isotopic species 2XY traverses a flow path to the outer channel 38, formed by fingers 50, while the lighter species lX , or X , prefers an inner channel 36 3 for exit and collection, resulting in separation.
;: -18-378~
45,832 The mass separation can be enhanced further by magnetohydrodynamic means since lX , or X , is a charged particle for some period of time subsequent to formation.
A dc magnetic field, B, is applied transverse to the con-stituent flow v such that a Hall field v X B is developed across the flow passage 40. Thus the charged isotopic species under the influence of this field are caused to deflect toward the inner wall 52 of the passage 48, thereby enhancing the mass separation.
In the limiting case of no collisions, the ion drift velocity vl across the magnetic field and the drift distance dl due to the Hall effect at the end of the cen-trifugal section of length 1 are vl = MBl in cm/sec (22) and d = eBl_ in cm, (23) respectively. Here Mi is the mass of the ion formed from, for example, selective dissociative charge transfer, e is the charge of the ion in esu; 1 is the length of the centri-fugal section, v is the flowing gas velocity in cm/sec; andB is the transverse magnetic field in gauss. In the event collision of the ionic species with the buffer gas occurs, the drift velocity and distance can also be predetermined.
The curvature and length of the centrifugal section together with other parameters of the arrangement such as exit channel widths can be tailored to achieve optimum isotope separation.
A practical example of utilization of the present arrangement is an application to uranium or sulfur isotope separation using, for example, SF6 (or UF6) gas. Argon gas 3 is introduced into the device at inlet 42. The gas is ~ A
~-~ ~J ~ 45,832 ionized while passing through the pair of electrodes 46 where an adequate field, either ac or dc, is maintained.
Downstream of the discharge zone about 100 ~sec in the afterglow region, an isotopic mixture of SF6 gas is injected into the ionized gas stream. Simultaneously a cw C02 laser operated on the P(20~ to P(30~ and preferably the P(26) to P(30) transitions of the C02 (001-100) band is beamed at the injection zone so that the 32SF6 isotope is selectively excited. The intensity of the laser beam is such that a high concentration of 32SF6 is excited to the upper vibra-tional states where dissociative charge transfer with Ar ions is effective. The mixture of reaction products then CUt-";tl ~ear B flows into the _ region where both centrifugal force and v X B force act upon the charged particles.
Spatial separation of molecules and other species of dif-ferent mass is achieved and enrichment of the particular isotopic species 32S is obtained by proper location of the exit channel.
It will be apparent to those skilled in the art that the disclosed arrangement provides a convenient and practical means, such as electrical discharge, for provision of atomic or molecular species or chemical radicals not otherwise readily available for photochemical or other isotopic separation processes. Additionally, as a result of the discharge afterglow, the mean electron energy can be provided over a broad range, compatible with a large number of species, by varying the point of injection of the iso-topic mixture downstream in the afterflow. The energy can range from, for example, 1 eV to 0.03 eV. Further, the energy spread of the electrons in the afterflow at a selected ~ 4 45,~32 downstream distance is smaller- than that typically obtained with an electron beam. Also, the electron density obtain-able is in the range of 10~ to 1011 cm 3, which is substan-tially higher than the density obtainable with an ordinary electron beam in the same energy range. Complex electron beam formation apparatus is therefor eliminated.
Additional arrangements can also be advantageously utilized to further benefit the disclosed system and provide increased system efficiency. Figures 6 and 7 illustrate arrangements where the energy input to the discharge, typi-cally electrical energy, can be partially extracted as laser energy and used, respectively, directly or indirectly for the separation process. In both of the figures the discharge area is modified, such as by the addition of mirrors 52, to form an optical cavity 54. As shown in Figure 6, the result-ing laser beam can then be directed, through additional mirrors 56, to perform the irradiating function where proper photon wavelengths are obtained from the discharge. As shown in Figure 7, the resulting laser beam can also be utilized to pump another laser, such as a dye or solid state unit, which performs the irradiating function.
Further modifications and additions are possible in view of the above teachings. It therefore is to be understood that within the scope of the claims, the invent-ive embodirnents can be practiced other than as specifically described.
Claims (27)
1. A method for separating isotopes of a par-ticular element in a molecular mixture having first molecu-lar species including a first isotope of said element and second molecular species including a second isotope of said element, said method comprising:
a. selectively exciting said first species in preference to said second species such that said excited first species has a preselected internal energy;
b. exposing said excited first species to posi-tive ions each of predetermined ionization energy such that the sum of said preselected internal energy and said pre-determined ionization energy is sufficiently high to cause a dissociative charge transfer process to occur between said positive ion and said excited first species resulting in a release of fragments, one of which fragments is a positive molecular ion including said first isotope; and c. separating said ions of said first isotope from the balance of said mixture.
a. selectively exciting said first species in preference to said second species such that said excited first species has a preselected internal energy;
b. exposing said excited first species to posi-tive ions each of predetermined ionization energy such that the sum of said preselected internal energy and said pre-determined ionization energy is sufficiently high to cause a dissociative charge transfer process to occur between said positive ion and said excited first species resulting in a release of fragments, one of which fragments is a positive molecular ion including said first isotope; and c. separating said ions of said first isotope from the balance of said mixture.
2. me method of claim 1 wherein the sum of said predetermined ionization energy of said positive ions and the internal energy of said second molecular species is below the threshold energy to cause a dissociative charge transfer process to occur between said positive ion and said second molecular species.
3. The method of claim 1 wherein said exposing step is performed within a given volume and wherein:
[A+] [1XY*] QDCT vr1> [1XY*] [2XY] QXT vr2, and [A+]denotes the particle density of said positive ions within said volume;
[2XY] denotes the particle density of said second 45,832 molecular species within said volume;
QXT denotes the cross section of said dissociative charge transfer process between said positive ions and said second molecular species; and QDCT denotes the cross section of said dissocia-tive charge transfer process between said positive ions and said excited first species, and wherein .
[A+] [1XY*] QDCT vr1> [1XY*] [2XY] QXT vr2, and [A+]denotes the particle density of said positive ions within said volume;
[2XY] denotes the particle density of said second 45,832 molecular species within said volume;
QXT denotes the cross section of said dissociative charge transfer process between said positive ions and said second molecular species; and QDCT denotes the cross section of said dissocia-tive charge transfer process between said positive ions and said excited first species, and wherein .
4. The method of claim 1 wherein said molecular species are selected from the group consisting of uranium hexafluoride and sulfur hexafluoride.
5. The method of claim 1 wherein said positive ions are argon+.
6. The method of claim 1 wherein said molecular species is sulfur hexafluoride and wherein said selective excitation is performed by exposing said mixture to photon irradiation from the P(20) to P(30) lines of a carbon di-oxide laser.
7. A method for separating isotopes of a par-ticular element in a molecular mixture having a first molecular species including a first isotope of said element and a second molecular species including a second isotope of said element, said method comprising:
a. selectively exciting said first species in preference to said second species such that said excited first species has a preselected internal energy;
b. exposing some of said excited first species to positive ions each of predetermined ionization energy such that the sum of said preselected internal energy and said 45,832 predetermined ionization energy is sufficiently high to cause a dissociative charge transfer process to occur between said positive ion and said excited first species resulting in a release of fragments, one of which fragments is a positive ion of said first isotope;
c. simultaneous to said exposing, exposing some other of said excited first species to free electrons of predetermined energy such that the sum of said preselected internal energy and said electron energy is sufficiently high to cause a dissociative electron attachment process to occur between said electrons and said excited first species resulting in a release of fragments, one of which fragments is a negative ion of said first isotope;
d. combining said positive ion of said first isotope and said negative ion of said first isotope to form a neutral species; and e. separating said neutral species from the balance of said mixture.
a. selectively exciting said first species in preference to said second species such that said excited first species has a preselected internal energy;
b. exposing some of said excited first species to positive ions each of predetermined ionization energy such that the sum of said preselected internal energy and said 45,832 predetermined ionization energy is sufficiently high to cause a dissociative charge transfer process to occur between said positive ion and said excited first species resulting in a release of fragments, one of which fragments is a positive ion of said first isotope;
c. simultaneous to said exposing, exposing some other of said excited first species to free electrons of predetermined energy such that the sum of said preselected internal energy and said electron energy is sufficiently high to cause a dissociative electron attachment process to occur between said electrons and said excited first species resulting in a release of fragments, one of which fragments is a negative ion of said first isotope;
d. combining said positive ion of said first isotope and said negative ion of said first isotope to form a neutral species; and e. separating said neutral species from the balance of said mixture.
8. A method for separating isotopes of a par-ticular element in a molecular mixture having a first mole-cular species including a first isotope of said element and a second molecular species including a second isotope of said element, said method comprising:
a. selectively exciting said first species in preference to said second species such that said excited first species has a first preselected internal energy;
b. exposing said excited first species to another excited species having a second preselected internal energy such that the sum of said first and second internal energies is sufficiently high to cause a dissociative ionization 45,832 process to occur between said excited first species and said another excited species resulting in a release of fragments, one of which fragments is a positive ion of said first isotope; and c. separating said positive ion of said first isotope from the balance of said mixture.
a. selectively exciting said first species in preference to said second species such that said excited first species has a first preselected internal energy;
b. exposing said excited first species to another excited species having a second preselected internal energy such that the sum of said first and second internal energies is sufficiently high to cause a dissociative ionization 45,832 process to occur between said excited first species and said another excited species resulting in a release of fragments, one of which fragments is a positive ion of said first isotope; and c. separating said positive ion of said first isotope from the balance of said mixture.
9. A method for separating isotopes of a par-ticular element in an isotopic atomic mixture having first isotopes of said element and second isotopes of said ele-ment, said method comprising:
a. selectively exciting said first isotopes in preference to said second isotopes such that said excited first isotopes each have a preselected excitation energy;
b. exposing said excited first isotopes to selected positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substantially equal to the ionization energy of said first isotope so as to cause a resonance charge transfer process to occur between said excited first isotopes and said positive ions resulting in said first isotopes becoming positive ions of said first isotope; and c. separating said positive ions of said first isotope from the balance of said mixture.
a. selectively exciting said first isotopes in preference to said second isotopes such that said excited first isotopes each have a preselected excitation energy;
b. exposing said excited first isotopes to selected positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substantially equal to the ionization energy of said first isotope so as to cause a resonance charge transfer process to occur between said excited first isotopes and said positive ions resulting in said first isotopes becoming positive ions of said first isotope; and c. separating said positive ions of said first isotope from the balance of said mixture.
10. The method of claim 9 wherein said selective excitation and said exposing comprise flowing said mixture and said positive ions through a discharge tube exposed to narrow band radiation of a preselected frequency.
11. The method of claim 10 wherein said separa-tion comprises allowing an ambipolar diffusion field to be formed along the walls of said discharge tube such that said 45,832 positive ions of said first isotope drift toward said walls, and collecting said drifting ions.
12. The method of claim 9 wherein said separation comprises flowing said mixture through a curved passage exposed to a magnetic field.
13. A method for separating isotopes of a par-ticular element in an isotopic mixture having first isotopes of said element and second isotopes of said element, said method comprising:
a. flowing said mixture and a selected neutral species into a discharge tube;
b. selectively exciting said flowing first iso-topes in said discharge tube in preference to said flowing second isotopes and said flowing neutral species within said tube such that said excited first isotopes each have a preselected excitation energy;
c. effecting a discharge within said tube so as to ionize said neutral species to positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substan-tially equal to the ionization energy of said first isotope so as to cause a resonance charge transfer process to occur between said excited first isotopes and said positive ions resulting in said first isotopes becoming flowing positive ions of said first isotope and further causing formation of an ambipolar diffusion field along the walls of said tube so that said flowing positive ions of said first isotopes drift toward said walls;
d. collecting said drifting ions at a position toward said walls; and 45,832 e. collecting the balance of constituents of said resonance charge transfer process at a position toward the center of said tube.
a. flowing said mixture and a selected neutral species into a discharge tube;
b. selectively exciting said flowing first iso-topes in said discharge tube in preference to said flowing second isotopes and said flowing neutral species within said tube such that said excited first isotopes each have a preselected excitation energy;
c. effecting a discharge within said tube so as to ionize said neutral species to positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substan-tially equal to the ionization energy of said first isotope so as to cause a resonance charge transfer process to occur between said excited first isotopes and said positive ions resulting in said first isotopes becoming flowing positive ions of said first isotope and further causing formation of an ambipolar diffusion field along the walls of said tube so that said flowing positive ions of said first isotopes drift toward said walls;
d. collecting said drifting ions at a position toward said walls; and 45,832 e. collecting the balance of constituents of said resonance charge transfer process at a position toward the center of said tube.
14. A method for separating isotopes of a par-ticular element in an isotopic mixture having first isotopes of said element and second isotopes of said element, said method comprising:
a. flowing a selected neutral species through a discharge zone so as to form flowing positive ions of said species each having a predetermined ionization energy;
b. injecting said isotopic mixture into said flowing positive ions such that said isotopic mixture flows with said positive ions;
c. selectively exciting said flowing first iso-topes in preference to said second isotopes such that said excited first isotopes each have a preselected excitation energy and such that the sum of said excitation energy of said first isotopes and said ionization energy of said flowing positive ions is substantially equal to the ioni-zation energy of said first isotope so as to cause a res-onance charge transfer process to occur between said excited first isotopes and said positive ions resulting in said flowing first isotopes becoming flowing positive ions of said first isotope;
d. exposing said flowing positive ions of said first isotope and the balance of the flowing constituents to a magnetic field and a segmented curved passage such that said positive ions of said first isotope are deflected along a flow path through a selected segment and said balance of flowing constituents are deflected along a flow path through 45,832 other segments; and e. collecting said positive ions of said first isotope flowing through said selected segment.
a. flowing a selected neutral species through a discharge zone so as to form flowing positive ions of said species each having a predetermined ionization energy;
b. injecting said isotopic mixture into said flowing positive ions such that said isotopic mixture flows with said positive ions;
c. selectively exciting said flowing first iso-topes in preference to said second isotopes such that said excited first isotopes each have a preselected excitation energy and such that the sum of said excitation energy of said first isotopes and said ionization energy of said flowing positive ions is substantially equal to the ioni-zation energy of said first isotope so as to cause a res-onance charge transfer process to occur between said excited first isotopes and said positive ions resulting in said flowing first isotopes becoming flowing positive ions of said first isotope;
d. exposing said flowing positive ions of said first isotope and the balance of the flowing constituents to a magnetic field and a segmented curved passage such that said positive ions of said first isotope are deflected along a flow path through a selected segment and said balance of flowing constituents are deflected along a flow path through 45,832 other segments; and e. collecting said positive ions of said first isotope flowing through said selected segment.
15. Apparatus for separating isotopes in an isotopic mixture having a first species including a first isotope of a particular element and a second species in-cluding a second isotope of said element, said apparatus comprising:
a. structure defining a flow passage, said passage serially including means for inletting a flowing gas, means for passing said inletted flowing gas through a curved centrifuge section having an inner radius of curva-ture and an outer radius of curvature, and means for seg-menting said passage into a plurality of outlets including an inner segment disposed toward said inner radius and an outer segment disposed toward said outer radius;
b. means for creating a discharge zone between said gas inlet means and said centrifuge section;
c. means for injecting said mixture in a gaseous phase into said flow passage downstream of said discharge means; and d. means for irradiating said injected mixture between said injecting means and at least a portion of said centrifuge section so as to selectively excite said first species.
a. structure defining a flow passage, said passage serially including means for inletting a flowing gas, means for passing said inletted flowing gas through a curved centrifuge section having an inner radius of curva-ture and an outer radius of curvature, and means for seg-menting said passage into a plurality of outlets including an inner segment disposed toward said inner radius and an outer segment disposed toward said outer radius;
b. means for creating a discharge zone between said gas inlet means and said centrifuge section;
c. means for injecting said mixture in a gaseous phase into said flow passage downstream of said discharge means; and d. means for irradiating said injected mixture between said injecting means and at least a portion of said centrifuge section so as to selectively excite said first species.
16. Apparatus of claim 15 further comprising means for creating a magnetic field within said centrifuge section.
17. Apparatus of claim 15 wherein photons are formed within said discharge zone and further comprising 45,832 means for forming an optical cavity within said discharge zone and for directing said photons to said irradiating means.
18. Apparatus of claim 17 wherein said photons form a gas laser beam and further comprising a laser and means for directing said gas laser beam to pump said laser.
19. Apparatus for separating isotopes in an isotopic mixture having a first species including a first isotope of a particular element and a second species in-cluding a second isotope of said element, said apparatus comprising:
a. means for creating an electrical discharge zone;
b. means for flowing a selected gas through said zone;
c. means for injecting said mixture into said flowing gas a preselected distance downstream of said dis-charge zone such that said mixture flows in a direction substantially similar to the flow of said gas;
d. means for irradiating said mixture subsequent to said injection so as to selectively excite said first species and cause a predetermined release of reaction products, some of said products being of differing mass and including a species of said first isotope in a form differ-ent than its initial form prior to said irradiation;
e. curved means for deflecting said products of differing mass along differing flow paths; and f. means for collecting said deflected products including a segment for collecting said species of said first isotope in a different form.
a. means for creating an electrical discharge zone;
b. means for flowing a selected gas through said zone;
c. means for injecting said mixture into said flowing gas a preselected distance downstream of said dis-charge zone such that said mixture flows in a direction substantially similar to the flow of said gas;
d. means for irradiating said mixture subsequent to said injection so as to selectively excite said first species and cause a predetermined release of reaction products, some of said products being of differing mass and including a species of said first isotope in a form differ-ent than its initial form prior to said irradiation;
e. curved means for deflecting said products of differing mass along differing flow paths; and f. means for collecting said deflected products including a segment for collecting said species of said first isotope in a different form.
20. Apparatus of claim 19 further comprising means for creating a magnetic field in the region of said curved deflecting means.
21. Apparatus of claim 19 wherein said irradiating means comprise a laser for providing narrow band photon irradiation of a predetermined wavelength.
22. Apparatus of claim 19 wherein photons are formed in said discharge zone and further comprising means for forming an optical cavity in said discharge zone and for directing said photons to said irradiating means.
23. A method for separating isotopes of sulfur (S) in a mixture of sulfur hexafluoride (SF6) having 32SF6 and 34SF6, said method comprising:
a. selectively exciting said 32SF6 in preference to said 34SF6 such that said excited 32SF6 has a preselected internal energy;
b. exposing said excited 32SF6 to positive ions each of predetermined ionization energy such that the sum of said preselected internal energy and said predetermined ionization energy is sufficiently high to cause a dissociative charge transfer process to occur between said positive ions and said 32SF6 resulting in a release of fragments, one of which fragments is the molecular ion 32SF5+; and c. separating said 32SF5 molecule from the balance of said mixture.
a. selectively exciting said 32SF6 in preference to said 34SF6 such that said excited 32SF6 has a preselected internal energy;
b. exposing said excited 32SF6 to positive ions each of predetermined ionization energy such that the sum of said preselected internal energy and said predetermined ionization energy is sufficiently high to cause a dissociative charge transfer process to occur between said positive ions and said 32SF6 resulting in a release of fragments, one of which fragments is the molecular ion 32SF5+; and c. separating said 32SF5 molecule from the balance of said mixture.
24. A method for separating isotopes of sulfur (S) in an isotopic atomic mixture having 32S isotopes and 34S
isotopes, said method comprising:
a. selectively exciting said 32S isotopes in prefer-ence to said 34S isotopes such that said excited 32S isotopes each have a preselected excitation energy;
b. exposing said excited 32S isotopes to selected positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substantially equal to the ionization energy of said 32S
isotopes so as to cause a resonance charge transfer process to occur between said 32S isotopes and said positive ions resulting in said 32S isotopes becoming 32S+ ions; and c. separating said 32S+ ions from the balance of said mixture.
isotopes, said method comprising:
a. selectively exciting said 32S isotopes in prefer-ence to said 34S isotopes such that said excited 32S isotopes each have a preselected excitation energy;
b. exposing said excited 32S isotopes to selected positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substantially equal to the ionization energy of said 32S
isotopes so as to cause a resonance charge transfer process to occur between said 32S isotopes and said positive ions resulting in said 32S isotopes becoming 32S+ ions; and c. separating said 32S+ ions from the balance of said mixture.
25. A method for separating isotopes of sulfur (S) in an isotopic mixture having 32S isotopes and 34S isotopes, said method comprising:
a. flowing said mixture and a selected neutral species into a discharge tube;
b. selectively exciting said flowing 32S isotopes in said discharge tube in preference to said flowing 34S isotopes excited 32S isotopes each have a preselected excitation energy;
c. effecting a discharge within said tube so as to ionize said neutral species to positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substantially equal to the ionization energy of said 32S isotope so as to cause a resonance charge transfer process to occur between said excited 32S
isotopes and said positive ions resulting in said 32S isotopes becoming flowing 32S+ ions and further causing formation of an ambipolar diffusion field along the walls of said tube so that said flowing 32S+ ions drift toward said walls;
d. collecting said drifting 32S+ ions at a position toward said walls; and e. collecting the balance of constituents of said resonance charge transfer process at a position toward the center of said tube.
a. flowing said mixture and a selected neutral species into a discharge tube;
b. selectively exciting said flowing 32S isotopes in said discharge tube in preference to said flowing 34S isotopes excited 32S isotopes each have a preselected excitation energy;
c. effecting a discharge within said tube so as to ionize said neutral species to positive ions each of predetermined ionization energy such that the sum of said excitation energy and said ionization energy is substantially equal to the ionization energy of said 32S isotope so as to cause a resonance charge transfer process to occur between said excited 32S
isotopes and said positive ions resulting in said 32S isotopes becoming flowing 32S+ ions and further causing formation of an ambipolar diffusion field along the walls of said tube so that said flowing 32S+ ions drift toward said walls;
d. collecting said drifting 32S+ ions at a position toward said walls; and e. collecting the balance of constituents of said resonance charge transfer process at a position toward the center of said tube.
26. A method for separating isotopes of sulfur (S) in an isotopic mixture having 32S isotopes and 34S isotopes, said method comprising:
a. flowing a selected neutral species through a discharge zone so as to form flowing positive ions of said species each having a predetermined ionization energy;
b. injecting said isotopic mixture of 32S and 34S
into said flowing positive ions such that said isotopic mixture flows with said positive ions;
c. selectively exciting said flowing 32S isotopes in preference to said 34S isotopes such that said excited 32S
isotopes each have a preselected excitation energy and such that the sum of said excitation energy of said 32S isotopes and said ionization energy of said flowing positive ions is substantially equal to the ionization energy of said 32S isotopes so as to cause a resonance charge transfer process to occur between said excited 32S isotopes and said positive ions resulting in said flowing 32S isotopes becoming flowing 32S+ ions;
d. exposing said flowing 32S+ ions and the balance of the flowing constituents to a magnetic field and a segmented curved passage such that said 32S+ ions are deflected along a flow path through a selected segment and said balance of flowing constituents are deflected along a flow path through other segments; and 45,832 e. collecting said 32S+ ions flowing through said selected segment.
a. flowing a selected neutral species through a discharge zone so as to form flowing positive ions of said species each having a predetermined ionization energy;
b. injecting said isotopic mixture of 32S and 34S
into said flowing positive ions such that said isotopic mixture flows with said positive ions;
c. selectively exciting said flowing 32S isotopes in preference to said 34S isotopes such that said excited 32S
isotopes each have a preselected excitation energy and such that the sum of said excitation energy of said 32S isotopes and said ionization energy of said flowing positive ions is substantially equal to the ionization energy of said 32S isotopes so as to cause a resonance charge transfer process to occur between said excited 32S isotopes and said positive ions resulting in said flowing 32S isotopes becoming flowing 32S+ ions;
d. exposing said flowing 32S+ ions and the balance of the flowing constituents to a magnetic field and a segmented curved passage such that said 32S+ ions are deflected along a flow path through a selected segment and said balance of flowing constituents are deflected along a flow path through other segments; and 45,832 e. collecting said 32S+ ions flowing through said selected segment.
27. A method for separating isotopes of a par-ticular element in a molecular mixture having first molecular species including a first isotope of said element and second molecular species including a second isotope of said element comprising:
a. selectively exciting said first species in preference to said second species such that said excited first species has a preselected internal energy;
b. exposing said excited first species to positive ions each of a predetermined ionization energy whereby positive ions of said first isotope are produced; and c. separating said positive ions of said first isotope from the balance of said mixture by virtue of their positive charge.
a. selectively exciting said first species in preference to said second species such that said excited first species has a preselected internal energy;
b. exposing said excited first species to positive ions each of a predetermined ionization energy whereby positive ions of said first isotope are produced; and c. separating said positive ions of said first isotope from the balance of said mixture by virtue of their positive charge.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US86434477A | 1977-12-27 | 1977-12-27 | |
| US864,344 | 1977-12-27 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1123784A true CA1123784A (en) | 1982-05-18 |
Family
ID=25343064
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA315,163A Expired CA1123784A (en) | 1977-12-27 | 1978-10-31 | Isotopic separation |
Country Status (6)
| Country | Link |
|---|---|
| JP (1) | JPS5496697A (en) |
| AU (1) | AU4167278A (en) |
| CA (1) | CA1123784A (en) |
| DE (1) | DE2856378A1 (en) |
| FR (1) | FR2413121A1 (en) |
| GB (1) | GB2015241B (en) |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN108303457B (en) * | 2018-02-11 | 2023-12-29 | 中国科学院地质与地球物理研究所 | Instrument and method for ionosphere H, he isotope measurement |
| JP2022534379A (en) * | 2019-05-29 | 2022-07-29 | アクセリス テクノロジーズ， インコーポレイテッド | Improved charge stripping for ion implantation systems |
Family Cites Families (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4000051A (en) * | 1975-04-23 | 1976-12-28 | Andrew Kaldor | Laser isotope separation process |
| US4024217A (en) * | 1975-05-23 | 1977-05-17 | The United States Of America As Represented By The United States Energy Research And Development Administration | Method of isotope separation by chemi-ionization |
| US4090856A (en) * | 1975-07-25 | 1978-05-23 | Westinghouse Electric Corp. | Process for isotope separation employing cataphoresis |
| US4110182A (en) * | 1976-06-17 | 1978-08-29 | The United States Of America As Represented By The United States Department Of Energy | Isotope separation by photoselective dissociative electron capture |
-
1978
- 1978-10-31 CA CA315,163A patent/CA1123784A/en not_active Expired
- 1978-11-16 GB GB7844705A patent/GB2015241B/en not_active Expired
- 1978-11-17 AU AU41672/78A patent/AU4167278A/en active Pending
- 1978-12-22 FR FR7836187A patent/FR2413121A1/en not_active Withdrawn
- 1978-12-27 DE DE19782856378 patent/DE2856378A1/en not_active Withdrawn
- 1978-12-27 JP JP16029478A patent/JPS5496697A/en active Pending
Also Published As
| Publication number | Publication date |
|---|---|
| GB2015241B (en) | 1982-04-21 |
| AU4167278A (en) | 1979-07-05 |
| JPS5496697A (en) | 1979-07-31 |
| DE2856378A1 (en) | 1979-07-05 |
| FR2413121A1 (en) | 1979-07-27 |
| GB2015241A (en) | 1979-09-05 |
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