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Nov. 27, 1962 D. B. LANGMUIR ETAL 3,065,640 CONTAINMENT DEVICE Filed Aug. 27, 1959 9 Sheets-Sheet 1 OSC\LATR 5 l /OSCoILAT‘R 2O PuMP OSClL ATOR 25 DAV/0 B. LANéMu/R ROBERT M zA/vamu/R HAywooD SHELTON RALPH /-T Wuze KER IN VEN TORS BY Nov. 27, 1962 D. B. LANGMUIR ETAL 3,065,640 CONTAINMENT DEVICE Filed Aug. 27, 1959 9 Sheets-Sheet 3 ix % M WN 0‘.0 (Q 0n. N.O DAV/0 B. LANG/Mull? RoggQT l/. LANG/Halli Amywoao 5H£LT0~ RALPH E WME/QKEQ INVENTORS BY QM} F a A wore/v15 )0’ m m NOV- 27, 1962 D. B. LANGMUIR ET AL 3,065,640 CONTAINMENT DEVICE Filed Aug. 27, 1959 9 Sheets-Shéet 4 BY //%m ATTORNEY: NOV- 27, 1962 D. B. LANGMUIR ETAL 3,065,640 CONTAINMENT DEVICE Filed Aug. 27, 1959 9 Sheets-Sheet 5 0Awo B. LANGMU/R ROBERT M LANC-vMu/R HAYWOOD SHELT'ON RALPH l-T WUER/(?/Z INVENTORS A 77-0 R/VE VJ Nov. 27, 1962 D. B. LANGMUlR ETAL 3,065,640 CONTAINMENT DEVICE Filed Aug. 2'7, 1959 9 Sheets-Sheet 6 DAV/0 B. LANéMU/R E: @055/87‘ l/ LANGMU/R HA ywooo SHEL TO/V x § RALPH /-‘. Wu?RKEQ INVENTORS A 77'ORNE Y! Nov. 27, 1962 D. B. LANGMUIR ETAL 3,065,640 ‘ CONTAINMENT DEVICE 9 Sheets-Sheet 7 Filed Aug. 27, 1959 LW #6 Br ,jwUOPIa<?r5>w 33 r2 QwRHRax / @MW% 3 a u, U.md 0 w OKR ,N ALfWm.A M Z@E/MTRW NWR ZNMSw /NAMWum/ Qr I Nov. 27, 1962 D. B_ LANGMUIR ET AL 3,065,640 CONTAINMENT DEVICE 9 Sheets-Sheet 8 Filed Aug. 27, 1959 w?7 2m, UTM w? CJ : 1Av 2 _ = Xv E v 5740MP». an“ 052w 3%9 R R wgwmWMQoAPLuMMFmKMmWwUvms?nl A./Am wm~ I NOV- 27, 1962 D. B. LANGMUIR ET AL 3,065,640 CONTAINMENT DEVICE Filed Aug. 27, 1959 9 Sheets-Sheet 9 CA MERA MICROSCOPE 0BSERVAT\ON CURRENT CHARGING POWDER \NJ'EQT\ON 50o VOLTS Put-$5 E Z2 . 11 — 5000 V Do DAV/0 B. LA/veMu/R ROBERT M LANG/MUIR HAYWOOD §H£4TON RALPH F. Mada/(Ea INVENTORS United States ,Patent O?ice 3,065,640 Patented Nov. 27, 1962, :15 2 3,065,640 CONTAINMENT DEVICE In order that the charged particle or particles within the cube may be studied, it is preferred that both unidirec tional and alternating voltages be selectively variable so that the types of particle motion may be controlled and David B. Langmuir, Santa Monica, Robert V. Langmuir, Altadena, Haywood §helton, Woodland Hills, and Ralph F. Wuerker, Palos Verdes Estates, Calif., as signors to Thompson Ramo Wooldridge Inc., Los An geles, Calif, a corporation of Ohio Filed Aug. 27, 1959, Ser. No. 836,486 22 Claims. (Cl. 73--517) so that the group of charged particles within a stable region of operation of the device may be compressed or expanded. The subject mater which is regarded as a portion of this invention is particularly pointed out and distinctly claimed 10 in the concluding portion of the speci?cation. The inven tion, however, as to its organization and method of opera The present invention relates to a particle containment tion, together with further objects and advantages thereof device and more particularly to a device providing for the will best be understood by reference to the following de electrodynamic containment of charged particles with an scription taken in connection with the accompanying draw arrangement for placing the charged particles within the con?nement space and observing such particles. 15 ings, in which: FIG. 1 is a schematic diagram of one embodiment ofv The containment device described herein offers a new approach to colloid physics, mass spectroscopy, ion source physics, and low density plasma physics. According to the present invention, charged particles can be dynamically contained by alternating electric ?elds which pass through the present invention; FIG. 2 is a graph of the stability diagram for the. Mathieu differential equation; 20 the con?nement volume in accordance with voltages ap plied to the surrounding metallic electrode walls. In a speci?c application, visually observable charged particles FIG. 3 is a curve illustrating regions of stable oscilla tion Within the device shown in FIG. 1; FIG. 4 is a nomogram for computing the parametric qz values of a chamber of characteristic dimension Z0=1A I of iron, aluminum, and/ or latex several microns in diam inch; eter were contained either singly or in groups. In such an application it is feasible to investigate as a function of single charged particle within the suspension device of the operating conditions the motions, the resonant fre quencies, and in the case of a plasma of many particles the ordered arrays. In another application, neutral gases of low atomic weight were used in studying, as a function 30 of theoperating conditions, the formation and generation of such exotic ions as He- (negative ion of helium), H FIG. 5 illustrates a typical oscillatory motion of a FIG. 1; FIG. 6 illustrates a typical crystal-like array of several particles within the suspension device of FIG. 1; FIG. 7 is a schematic diagram of another embodiment of the present invention; FIG. 8 is a schematic diagram of an accelerometer uti lizing the embodiment of the present invention shown in FIG. 7; The construction of an electro-dynamic containment de vice provided with means for inserting charged particles 35 FIG. 9 is a curve illustrating regions of stable oscillation ‘within the device shown in FIG. 7 when Vac)‘: Vdcy; therein and means for allowing observation of the mo FIG. 10 illustrates a typical crystal-like array of several tion of the particles has proved to be a challenging task. particles within the suspension device of FIG. 7; and Prior art illustrates methods for containing ions within FIG. 11 is an exploded perspective detailed view of the DC. and simple A.C. voltage ?elds emanating from hyper bolic electrodes. Many of the problems encountered in 40 chamber illustrated in FIG. 7 showing certain auxiliary (the negative hydrogen ion), and H3+. this type of device have prevented fabrication of a simple mechanism allowing studies of the particle motion. equipment. Referring now to the drawings, in which like numerals indicate identical parts, in FIG. 1 there is shown a hollow‘ container such as a cylindrical pill box 10 having a verti servation device wherein various surfaces thereof have 45 cal surface or ring electrode 11 between a top surface cap 12 and a bottom surface cap 13, thus de?ning a space applied thereto voltages of controllable frequency and suitable for particle containment. The top surface cap magnitude. 12 and the bottom surface cap 13 are connected by elec-v A further object of the present invention is to provide tric circuit means 14 including a beta oscillator 15 pro~' the combination of a particle containment chamber and Therefore, an object of the present invention is to pro vide a simple and reliable particle containment and ob means for injecting into this chamber charged particles. Another object of the present invention is to provide the combination of a charged particle containment device and means for observing particles within the device. Still another object of the present invention is to pro vide a means of ejecting as a group the charged particles which were formed and held within the con?nement space. A more speci?c object is the provision of an accelerom viding a voltage 2V, and a unidirectional power supply 16 providing a voltage V8. The vertical side surface 11 is electrically connected to the electric circuit means 14 by electric circuit means 17 including a driving oscillator 18 providing a voltage 2Vac, a unidirectional voltage source 19 providing a voltage 2V“, and a pump oscillator 20 providing a voltage 2Vp measured between the elec trodes 11 and 12 or 13. The electric ?elds near the center of this structure may be selected to support charged eter. particles inserted from an aperture 21 of a charged par Brie?y, in accordance with one embodiment of the present invention, the charged particle containment de 60 ticle source 23, such as a powder reservoir and injector, _ or an ion gun, or an electron gun, through one of the aper— vice comprises a cubical structure de?ned by three mutu tures 25. Also there are provided ?lters 22 and 24 in the‘ ally perpendicular pairs of surfaces energized by a fre electric circuit means 14 and 17 respectively to isolate the quency and magnitude controllable three-phase A.C. volt age as well as D.C. voltage selectively applied thereto. Charged particles injected into the center of the space de ?ned will oscillate in a predeterminable manner. At least one of the surfaces is provided with a central aperture through which the charged particles may be injected. alternating and unidirectional voltages. ’ As will become more apparent from the following . discussion, the contained charged particles can be de tected and studied by the following techniques or com binations of methods: (1) By observing directly with the aid of a microscope Also one of the surfaces has a central aperture through 70 through one of the apertures 25; which any particles within the cubical space may be illu (2) By observing and/ or measuring the loading on. minated and another surface has an observation aperture. 3,065,640 4 VJ the ,6 oscillator 15 when its frequency is tuned to any The differential equations of motion of a single charged particle of charge to mass ratio e/m within the potential one of the characteristic resonant frequencies which the contained particles can have in the z direction; (3) By noting the loading on the pump oscillator 20 when its frequency is adjusted to either twice or equal to the resonant frequency of the ions in either the ver tical or radial (z or r) directions; ?eld of the electrode structure 11, 12 and 13 When only the external sources 18 and 19 are present, are (4) By measuring the transfer of electrical energy between the pump oscillator 20 and the B circuit 14 when the frequency of the former is adjusted to twice the resonant frequency of the contained particles in the z direction and the frequency of the latter is adjusted to The equations of motion of a single particle in the two directions of space are seen to be identical except for equal the particle resonant frequency; the negative 2:1 ratio between the constants. Equation (5) By properly increasing the voltages V8 and 2Vdc so that particles are ejected out of the chamber through 15 4 is a function of 2 only, while (5) is a function of r only. The motions in z and r are therefore mutually the aperture 25 in the top surface cap 12 and collected independent. Each of the above equations is thus a on an external electrode or Faraday cup 26 to which is special case of the Mathieu differential equation which connected a sensitive galvanometer or ammeter 27. in its general form is usually written It is recognized that the elements 28 shown sche matically as transformers can consist of high frequency resonant elements or resonant cavities dependent upon the frequency of the system as determined by the charge in which 11 may represent either z or r. The dimension to mass ratio of the particles under observation. less constants in the above equation are related to those The relation between the electric ?elds and the particle mass and charge is mathematically de?nable. If the 25 of the present physical problem through the transforma tion equations surfaces of the device shown in FIG. 1 are curved in wardly the following mathematical discussion applies to a slightly larger volume than in the case of the cylindrical structure. The necessary condition for the proper operation of this type of electric ?eld containment system depends upon having an electrode structure which gives time varying forces at least near the center of the container whose strengths are proportional to the distance from Inspection of Equation 6 shows that it reduces to a the center (i.e., the origin). When these time varying 35 simple second order linear differential equation when the forces are sinusoidal the differential equations of particle driving term q becomes zero. For this limiting case, the motion in the three independent directions of space are differential equation has stable or unstable solutions of each special cases of the Mathieu differential equation. the forms A three-dimensional electrical ?eld distribution which satis?es this requirement is the axially symmetric poten 40 tial distribution _V T2 V(z,r,t) = Z02“ Z2~§] cos Qt (1) The quantity e=2.718 . . . depending on whether a is formed by the electrode surfaces 11, 12, and 13 as shown in FIG. 1. The quantities in Equation 1 have the fol respectively positive or negative. When a is positive and lowing meanings: Vac is one-half the peak value of the alternating voltage of angular frequency 9 applied be sinusoidially with simple harmonic motion of normalized q is zero the motion is bounded and the particle vibrates frequency 13 which can be related to the real angular tween the ring electrode 11 and the end surface caps 12 frequency of oscillation through the ‘transformation and 13; Z0, the characteristic dimension of the electrode Equation 7; namely, structure, is approximately equal to half the distance be 50 w,,=/sc/2 (12) tween electrode surface caps 12 and 13; z and r are re spectively the vertical and horizontal displacements of For example, in the case of the containment chamber the particle from the geometrical center of the chamber. shown in FIG. 1 when Vac=0 and Vdc is focusing in the Differentiation of Equation 1 shows that the electric ?elds vertical z direction (i.e., az positive and ar negative) the have the required spacial dependence and are respec 55 particle will execute the following motions in the two tively independent directions 60 (13) and The negative 2:1 ratio between Equations 2 and 3 shows that when the electric ?eld is focusing toward the origin 65 (tXZtl-We era» ( in the z direction in series the same direction then it must be defocusing in the r and vice versa. The addition of other sources where A, (p, L and M are constants of integration whose with the alternating drive adds more terms of 70 values are determined by the initial conditions. The spatial form as Equation 1 to the expression for above example is merely an expression of Earnshaw’s the electrical potential within the con?ning electrode theorem of electrostatics which states that with only a structure. For example, the insertion of the DC. source $.06 source a charged particle can never be stably con 19 in series with the AC. driving supply 18 merely adds a. time independent term of the same form to Equation 1. 75 ne . The constant a in Equation 6 therefore represents the 3,065,640 S contribution of either static focusing or defocusing forces different charge to mass ratios when the ?eld gradient depending on its sign. The constant :1 on the other hand carries the contribution of forces which vary sinusoidally is 2Vac/Z02=2.480 volts/cmE’a with a normalized period of 1r(1r=3.1416 . . J. The Mathieu Equation 6 is solvable in terms of an in?nite Fourier series and has solutions which are either stable or unstable depending upon the numerical values of a Atomic Mass Units Particle elm coulombs/kilogram 0. 000549 1.008 16.000 and q (see McLachlan, N.W., Theory and Applications of Mathieu Functions, Oxford, 1947). H6. 2 shows a Uranium (U+) region of the stability diagram for Equation 6 in terms .. __._ 238 Drive Fre quency/21 for q,=0.535 1. 76x1011 9. 6X107 6 04><10° 644 me 15 Inc. 3.8 1110. 4 05><105 980 kc. 1 micron diameter iron par ticle carrying 10,000 elemen of the normalized a-q values. The shaded areas repre sent the regions corresponding to values of a and q yield tary units of charge __________________ ._ 0.3 840 0.13.8. 0.005 109 c.p.s. 20 micron diameter aluminum particle carrying 0.35 million ing stable solutions. In this ?gure the curves labeled 13:0 and 18:1 bound the stability domain which is em— ployed in the present device. Within this region the solution of the Mathieu equation is of the form units at elementary charge" __________ __ Operation of the present system is speci?ed in the az—qz space by a straight line intercepting the origin having a slope u=A cos Bil-£32? az/qz=2Vdc/ Vac E (15) The stable motion according to this expression is seen to ‘consist of a harmonic oscillation at the normalized a frequency upon which is superimposed smaller vibrations at frequencies 2—/8, 2+5, 4—[3, 4+5, etc. The funda (17) That is to say, for given applied voltages Vdc and Vac this operational line determines the range of driving frequency Q/21r through Which a particle of given e/m will be stably bound. Conversely if the frequency is also held constant the a/q operational line speci?es the range of e/m values 25 which will be accepted (i.e., higher e/m particles corre spond to higher q values). Thus it can be seen that by properly adjusting the ratio of the two voltages so that the operational line just passes one of the edges of the 2 by the curves labeled 18:0, 18:02, 5:03, 5:04, etc. stability curve the e/m acceptance of the chamber can be That is to say, the iso-,B curves trace out the loci of a—q 30 made quite narrow. values which give the same normalized resultant fre According to the previous discussion, the selection of mental or resultant frequency of motion a is a function of the a and q parameters as shown graphically in FIG. quency of motion. In the region of small q, the func tional dependence of B on the operating parameters can be shown to be approximately the values of Vac, Vdc, and 9 so that the aZ and qz values are within the stability region of FIG. 3, therefore means that a single charged particle will execute stable vertical 35 and horizontal motions of the forms of Equation 15. (16) Because of the relations between the az, ar, qz, and qr co efficients, the motions along the two independent direc tions will not necessarily be the same. The resultant or when qgl/z. The line [i=0 has the physical signi?cance p frequencies in the two directions, will according to Equa that the effective binding due to the driving q term is 40 tions 12 and 16, be in the ratios exactly cancelled by the defocusing action of the static negative a term. For the containment device shown in FIG. 1, the ques (18) tion of a2, ar, qz and qr values giving stable motions simultaneously in all three dimensions of space is most simply presented by a single Cartesian graph plotted in terms of the az and qz values which correspond to the limiting curves pz=0, ?z=l, 5,:0, and ,Br=1. For this This can be written as a function of a2 and qz through Equations 8 and 9 namely; case, the limiting curves for the r motion are expressed in terms of aZ and qZ through the negative two to one 50 relationship between the parameters, i.e., a,=—aZ/2 and q,=qz/2 in accordance to Equations 8 and 9. FIG. 3 shows the resulting common stability plot for the axially F? Ti; a, %r_ " (19) 2 + 8 When az=0 the above equation shows that the two re-i symmetric potential distribution having the form of Equation 1. The circles represent experimental deter 55 sultant frequencies are in a 2:1 ratio. Thus the motion, when viewed in the vertical plane, will have the appear minations using single charged particles of dust of the stability boundaries. The experimental curves lying with in this “necktie” diagram show the visually determined ance of a 2:1 Lissajou pattern upon which is superimposed‘ and 1:2. FIG. 4 presents a nomogram for ?nding the qz values within a single phase containment chamber of characteristic dimension where Z0=0.25O inch. The use of this graph is shown by the solid line for the case of a tracing taken from a microphotograph of a characteristic the ripple due to the higher frequency terms in solution of Equation 15. loci of points for which the resultant frequencies in the z This is most clearly demonstrated by FIG. 5 showing and r directions are respectively in the ratios of 2: 1, 1:1, 60 2:1 Lissajou trajectory executed in the r_—z plane by a single charged particle of aluminum dust contained by a single-phase electrodynamic containment system. For singly ionized hydrogen ions when the drive frequency 65 this photograph Z0=0.250 inch, Vac=500 volts (r.m.s.); Vdc=0, SZ/21r=200 c.p.s.; and wz/21r==l6.3 c.p.s. From Q/211'=15 megacycles and 2Vac=1000 volts peak. For this case qz=0.535. Also the use of the graph is indi cated in a dashed line for uranium when the drive fre quency Q/21r=1 megacycle and 2Vac=2000 volts peak. In the case of uranium qZ=0.274. This graph enables 70 one to quickly explore the driving frequencies and volt these empirical data one can calculate: e/m=.0053 coulombs/kilogram, (12:0, qz=.232, and ?z=.163 The addition of the direct voltage source 19 in FIG. 1 in series with the drive voltage source 18 acts to strengthen ages required to contain any of the atomic or molecular the effective binding in one of the independent directions. ions within a container of given size. at the expense of the other with the result that the re The following table further illustrates the range of drive frequency encountered with particles of widely 75 sultant vibrational frequencies will be altered. For ex? speaeao ample, the application of a series voltage Vdc so that it is focusing along the r direction (i.e., az negative and 0,. the ratio of the resultant frequencies in the presence of space charge becomes positive) acts to make up for the inherent geometrical Weakness in this direction. The proper addition of D.C. voltage can cause the particle to vibrate with equal re sultant motions in both directions (i.e., wz/wr=1) and the trajectory will have the over-all appearance of a circular Lissajou pattern. Solution of Equation 19 shows that this showing that when P=O the resultant frequencies are in condition can occur whenever aZ=—qz2/4. Further in the expected 2:1 ratio. However, with increasing charge crease in the r focusing past this point will increase the 19 (density P the ratio of these frequencies diverges, becoming resultant frequency while decreasing still more frequency infinite when i’ reaches its limiting value in the z direction. One can also ?nd a condition for which a single particle will vibrate on the average twice as fast in the r direction as in the z direction. (P mew: The ap proximate theory shows that this condition occurs when ever az=¢—5qz2/ 12. Further increase in the r focusing will eventually cause the static ?eld to exactly cancel out the binding effect of the drive in the z direction (i.e., wz/wr=0). According to Equation 19 the ?rst term in the analytical expression for the boundary line [32:0 is given by the equation az=—qZ2/ 2. The other boundary curve in the stability diagram, FIG. 3, corresponding to 18,:0 (i.e., wz/w,=eo) is to ?rst approximation a2: 22/ 4. 20 (P maX),,Z=u=~_O.1l Vac qz micro-micro coulombs/cm.3 or equivalently in terms of the number of singly ionized particles; (n max)az=o= 6.9 Vac qz><105 ions/cm.3 The discussion has shown that the containment system of FIG. 1 will maintain a particle in dynamic equilibrium and that both the frequencies and the orbit of the particle can be controlled by the externally alternating and static voltage sources (18 and 19 in FIG. 1). (24) This expression enables the calculation of the maximum charge density which can be stored in the chamber when (171:0. For example if the chamber has a characteristic dimension Z0=0>.250 inch then (25) where n is number of ions or charged particles per cubic centimeter. The above theory has shown that the present electro~ dynamic containment system is able to compete against Another way of expressing the ability to con?ne is to say that a particle harmonic forces such as those due to externally ap can ?nd itself in an e?ective potential well of depth be— 30 plied D.C. ?elds (corresponding to negative a values), tween the outer wall and the center of the container of those due to space charge, or both. The case of uniform forces such as gravity, effective gravitational forces due to the acceleration of the apparatus, and/or constant (20) electric ?elds will now be considered. Such forces modify the original Mathieu differential equation of mo tron to Such an effective well is “a priori” a mechanism for the storage of many charged particles. This fact can be most dzu graphically observed and demonstrated when charged particles of dust are injected within the containment re gion. FIG. 6 has been included to show a tracing taken from a micro photograph of typical array viewed in the H9 plane through the aperture 25 of the cap electrode 12 d—€2+(a—2q cos 2£)u=-A where A, the normalized constant is related to the phys ical force F through the transformation equation of many positive charged particles (thirty two such parti cles being shown in FIG. 6) contained in device of type presented in FIG. 1. This containment was obtained at Vac=500 volts (r.m.s.), Vdc=0, Q/21r=135 c.p.s., and wz=43.6 c.p.s. (26) An’mtl2 (27) For example when the uniform force results from a volt age Vg applied across the two end caps (12 and 13 in FIG. 1), the expression for the force on a particle with The average charge to mass ratio of a in the chamber becomes single particle is e/m-=0.00765 coulombs/kilogram. The ordered array or “space crystal” results from the removal F _eVg of the initial energy of motion from the particles. In 50 (28) —2Z0 the case of the dust particles shown in this picture the The complete solution of Equation 26 is the sum of the initial energy was removed by having a background gas particular integral due to the constant term F and the pressure, such as air, of the order of several microns of complementary function, Equation 15. Mathematical mercury. analysis shows that within the ?rst region of stability the particular integral of Equation 26 in normalized form When many particles of the same sign are simultane ously contained, the space charge forces of repulsion will is closely serve to alter the resultant frequencies of motion of the individual particles. Assuming the charge to be uniform ly distributed throughout the volume of the chamber 10 one can write an expression for the variation in the result (29) ant z and r frequencies due to this space charge when qZEII/Z; namely demonstrating that a uniform force displaces the center of motion by an amount proportional to its magnitude and inversely proportional to the square of the resultant 65 frequency of motion. Thus for the present physical problem, the displacement ‘of the center of the motion when the force is in the z direction is approximately and ‘ ‘ 70 TrzZeZmTtsJm (30) Further Equation 29 shows that the particle will vibrate about its displaced equilibrium position in opposition to the oscillating drive ?eld. That is to say, the equilibri where P is the space charge density in coulombs/per cubic um oscillatory motion is 180° out of phase with the drive meter and 60 is the permitivity of space. For the speci?c cases in which az=0 the expression for 75 and of magnitude proportional to the normalized q pa 3,065,640 If) The differential equation of motion of a single particle rameter and the displacement. If the equilibrium dis placement A/B2 equals the dimension of the apparatus the particle is lost. For example, with a macroscopic in the presence of these three quadrupolar ?elds now becomes; particle such as a 1 micron diameter piece of iron the gravitational force can cause the particle to “fall out” when the resultant frequency is too small. For such par ticles gravity will slightly alter the appearance of the lower stability curve shown in FIGURE 2. The source V.g when used in conjunction with a proper variation of the DC quadrupolar source (19 in FIG. 1) 10 can act as a means of ejecting the mass of contained par ticles out of the electrode structure through either one (26) of the apertures (25 in FIG. 1) in the end caps (12 or 13 in FIG. 1). This method of emptying the cham One can handle either one of these two more complicated differential equations through suitable approximation. ber is achieved by offsetting the equilibrium position of 15 In this case the ?rst two terms in either equation are ap the plasma with the Vg source and varying Vdc towards high negative 11,, values. This action will squeeze the contained particles out of the chamber through the aper ture which lies in the direction of force ?eld due to VB. This operation can be achieved by a Vdc voltage pulse 20 of long enough duration to empty the chamber. The ejected mass of charged particles could then be collected proximated by the differential equation of simple har monic motion with the frequency of harmonic oscilla tion being equated to one of the harmonic components of the stable solution of the Mathieu equation. For ex ample for the case of the z motion one lets on an external electrode (such as 26 in FIG. 1). The ejected particles could on the other hand be directed to entrance aperture of an accelerating system with the con 25 tainment chamber functioning as a particle source for a device such as a particle space drive system for a space with wz=w,, or 9-40,, or 9+1”, etc. Mathematically the original complicated Hill equation has been approxi vehicle. mated by a Mathieu equation. Such an approximation Having reviewed the effects of the uniform source Vg is fair when VD<<Vac. According to Mathieu equation 30 and/ or other uniform force ?elds, the use of the 13 oscil theory the above approximate differential equation will lator (15 in FIG. 1) as a means of exciting the contained have stable or unstable solutions depending upon ratio particles or plasma will now be considered. When the of the harmonic frequency to the pump frequency. The alternating ?eld due to this source is present the differ analysis shows that an unstable solution will exist when ential equation for the motion in the z direction then ever 35 becomes: where N is an integer. Also in a like manner the mo tion in the r direction will be unstable whenever 40 or in normalized az, qz, and 5 form, 2 Z—£%+(a—2q cos 2£)z=(7i-> where wr=w,,, Q—m?, Q-l-w?, etc. The pump source can therefore serve as a second means for transferring energy sin %;3 to the contained particles or plasma. For this mode of excitation the particle motion will be in resonance with the pump oscillator whenever the pump frequency is re (32) The earlier discussion has shown that the stable solutions 45 lated according to Equations 38 or 39 to any one of the of the left hand side of the above Equation 32 contain Fourier frequencies in the stable solutions in z and r the frequencies wz (the resultant or )3 frequency), of the differential equations of motion in the absence of n-wz, Q+wz, 2Q—wz, 2'Q+wz, etc. When the frequency the pump. For example when the pump frequency is of the ,8 oscillator equals any one of these discreet fre twice the resultant or 5 frequency of motion in the z di quencies the particle motion will be in resonance with 50 rection (i.e., wD=2wZ=?zQ) the orbit of a single particle the applied ,8 ?eld and the orbit will elongate as energy in the z direction will grow exponentially in time as is fed into the particle or plasma. At resonance the mo energy is transferred from the pump circuit to the particle tion will grow according to the expression according to the equation 55 When the )8 oscillator is adjusted to any one of the Fou Like the 18 source, the pump source can also be employed rier components of the stable motion which result from to heat up the plasma of contained particles. the action of VM and Vdc energy will be transmitted from When the resonance condition between the frequency the ,3 source to the plasma. In this manner the plasma 60 of the pump oscillator and the frequencies of the stable can be “heated.” Similarly the presence of the contained particle motion due to the drive is not ful?lled, the pump particles can be detected by their loading on the )8 cir source can be gainfully employed to trap simultaneous cuit when it is in resonance. That is to say, the imped ly two particles of widely different charge to mass ratio. ance measured across electrode caps 12 and 13 will dip whenever the plasma is in resonance with the B circuit. 65 For example consider two particles of charge to mass ratios (e/m)1, (e/m)2 such as electrons and protons, Finally consider the e?ect of the third or pump oscil protons and charged dust particles, etc. For this case, lator (20 in FIG. 1) on a particle which is contained the motion of each particle will be speci?ed by the dif stably by the action of the drive and/or the static sources ferential equations cited in the previous paragraph (18 and 19 in FIG. 1). Since the pump source is in se~ ries with the drive sources, it acts to superimpose a sec 70 (Equations 35 and 36). If it is now assumed that own; the particle of lowest charge to mass ratio will be ond oscillating quadrupole ?eld within the electrode stably contained by the drive of lowest frequency (as structure of the same spacial form as the drive, namely suming of course that the magnitude of Vac is proper) and will be relatively unaffected by the higher frequency 75 9. The particle of highest charge to mass ratio will on 3,065,646 11 12 the other hand be contained by the action of 9 but its mo quency wp may be connected to the zero voltage terminals tion will be strongly in?uenced by the presence of the of the three phase A.C. drive voltage source 50. low frequency drive at frequency can. If wp does not ful ?ll the resonant condition on the lighter particle, the par ticle will still be stably maintained. In summary the above mathematical discussion has three phase A.C. pump voltage source 54 has across its three legs 55, 56 and 57 the voltages V" sin (wpt+41r/3), Vpy sin (wpt+21r/ 3), and Vpz sin (opt) respectively which outlined the theory by which alternating electric ?elds the particles contained as a result of the action of the can be employed to stably contain charged particles in three phase A.C. drive voltage source 50. Finally uni a manner known in the art of nuclear machines as alter directional sources 58 and 59 are connected in series to nating gradient focusing or hard focusing. The can act as a second means of exciting through resonance Further it 10 two of the zero voltage terminals of the AC. pump has been shown that by the use of other AG. sources placed either across the end caps, in series with the drive, voltage source 54. or both, the particles contained within the pillbox elec— sources 50 and 54) to the opposing electrode surfaces 31--33 and 32—34 respectively. The four quadrupolar voltage sources 50, 54, 58 and 59 act together to establish within the electrode structure trode structure 10 can be resonantly excited. Although the above mathematical discussion has dealt with sinus oidally time varying ?elds, it should be realized that other periodic wave shapes (such as rectangular, triangular, etc.) and phases can also be used to gainfully contain charged particles. The device shown in FIG. 1 can be The two D.C. sources 58 and 59 serve to apply voltages of Vdl,x and Vdcy (through the of the cube 30 near and about the geometrical center a. potential distribution of the form; mounted in an evacuated vessel or continuously pumped container, having suitable insulated and hermetically sealed electric leads, in order to eliminate or control col lisions between the electrodynamically contained charged particles and neutral or background gas molecules. De tails of a suitable vacuum system are known and need not be presented here. The electrode structure and the mode of excitation may also take a form other than the cylindrical shape shown in FIG. 1. Referring now to FIG. 7 there is shown an equilateral polygon such as a cube 30, having planar electrode surfaces 31, 32, 33, 34, 35 and 36 with each surface de?ning a central aperture 41, 42, 43, 44, 45 and 46 respectively. Each pair of opposing surfaces (speci?cally; 31—33, 32-34, and 35—36) are elec trically connected to separate balanced voltage sources (37, 38, and 39 respectively) which serve to apply both an alternating voltage V, and a unidirectional voltage Vg across the three orthogonal x, y, and z directions of the electrode structure. That is to say, source 37 sup where d is the width of the electrode structure (i.e., the distance between 31 and 33). Inspection shows that the above potential distribution satis?ed the Laplace equation (i.e., V2V(x,y,z,t)=0). The differential equations of motion of a charged particle in this electrical potential are found by solving for the ?elds in the three orthogonal directions of space and using Newton’s law of motion. The mathematical analysisshows that three equations of motion are of the form; plies voltages Vgx and VBX sin w?xt across the electrodes 31 and 33, source 38 supplies voltages Vgy and V,Y sin w?yt between electrodes 32 and 34 while source 39 sup plies across electrodes 35 and 36 voltages Vgz and Vi,Z sin w?zt. As explained above, the unidirectional components of the sources 37, 38 and 39 act near the Here u stands for either x, y, or z and 5:927 2. The values of a, q, and q’ for the three Cartesian directions are center of the cube 30 to add compensating uniform elec tric force ?elds for the purpose of steering or offsetting the equilibrium position of the particles or plasma which is contained within the electrode structure. The alter nating components of the three voltage sources 37, 33 and 39, can be employed to excite through resonance either separately or in unison the contained particles at their frequencies of oscillation along the orthogonal x, y, and 2 directions. The three sets of opposite electrode surfaces (31--33, 32-34 and 35——36) are next connected at the electrical centers or balance points of the sources 37, 33 and 39 to the high voltage terminals of a Y connected three phase A.C. drive voltage source 50 furnishing across each of its three legs 51, 52 and 53 voltages of the same fre 60 quency but phased 120° apart (i.e., V,,cx cos (Qt-l-41r/ 3), Vac), cos (Qt-i-21r/3), and Vacz cos Qt, respectively). This three phase A.C. drive voltage source 50 acts as the alternating drive at frequency 9 by which a charged When the pump voltage is removed (i.e., Vp=q’=O) particle or plasma can be stably con?ned within the cube 65 the differential equation of motion (Equation 42) reduces to the Mathieu differential equation (Equation 6). That 30. It is preferred that the three phase A.C. drive volt age source 50 be variable both in magnitude and fre is to say, the motion of a charged particle will be stable in x, y and 2 directions when the values of ax and qx, quency in order to provide controllable compression or expansion of a multi-particle “plasma mass” contained 70 ay and qy, a2 and qZ lie within their limiting stability curves within the cube 30 and to provide the correct operating (as in the case of FIG. 2). Further, if Vdcx=Vdcy then conditions for containing particles of a different charge Equation 49 gives a relation between a2 and ax or ay and to mass ratio. The three high voltage terminals of a second Y con nected three phase A.C. pump voltage source 54 of fre, 75 the x and y stability extremes can be plotted on the az—qz stability diagram. FIGURE 8 shows the stability diagram for the cubical . I3 electrode structure of FIG. 7 when Vdcx=Vdcw and electrode 11 in FIG. 1 could be split in quadrants with Vp=(). In this diagram the solid line passes through they unidirectional sources added to opposite sectors. According to the above discussion, the three-phase theoretical values presented in FIG. 2 while the circles locate the experimentally determined (9:400 cycles/sec containment system can be used as a three-dimensional ond) boundaries between stable and unstable single par accelerometer or as a gravity meter. ticle operation. The question of the range of driving frequency and drive voltage Vac necessary to contain a particle of charge tems to determine both the velocity of a craft and An accurate ac celerometer is particularly valuable in autopilot sys the instantaneous location. This device is particularly suited for such an application since the focusing due to to mass ratio e/ m is answered by calculating the q values given by Equation 43. The results of such a calculation 10 the A.C. drive voltage is isotropic. Thus when a single charged dust particle 60, FIG. 8, of several microns or can be presented either tabularly or in the nomogram more in size is placed within the electrode structure of the cube 30 with a background gas pressure of around several microns of mercury, the particle 60 (in the characteristic dimensions Z0=0.250 inch can also be ap plied to a three phase cube 30 of width d=0.567 inch. 15 absence of any gravitational or externally applied uni form forces) will settle as a function of the background When the particle is stable three dimensionally, it will gas pressure to the geometrical center of the cube 30. execute vibratory motions in x, y, and z of the form of The application of a gravitational force or an accelerating Equation 15, having resultant or B frequencies of oscil form. The results which have been cited in Table 1 or the nomogram of FIG. 4 for a single phase chamber of lation for small values of q given by Equation 16; i.e., force due to the acceleration of the electrode structure 20 will upset the equilibrium position of the particle 60 by amounts along the x, y and z directions, (according to Equation 29), proportional to the vector components of the applied force. Using Vgx, Vgy and Vgz, (FIG. 7), the displacement can be counteracted by opposing 25 electric ?elds, the magnitudes of which could serve as a measure of the applied gravitational force g. That is to say, the Vg electric force required to return the macroparticle 60 back to the center of the cube 30 where q<1/2. ‘ v would measure directly the applied gravitational force That is'to' say, the motion in each of the three independent 30 directions will consist of a large oscillation at the normal ized frequency ,8 upon which is superimposed the smaller more rapid oscillations at the higher normalized fre Thus the particle 60 is continuously maintained at the center of the electrode structure in a charging gravita quencies 2-5, 2-1-18, 4—/3, 4+5, etc. For example, when ?eld (which is being measured) by a balanced Vdcx= Vdcy=0=Vp the effective focusing is isotropic and 35 tional optical servo system which controls the magnitudes of a single particle will execute a 1:1 Lissajou pattern upon vgx’ Vgy’ Vgz' which is superimposed the ripple motion due to the higher Although details of such an optical feedback sys frequency components. tem are known and need not be presented fully here, ' FIG. 10 shows a tracing from a microphotograph of FIG. 8 illustrates a simpli?ed optical locating arrange an array of positively charged aluminum dust particles 40 ment of the type usable in an accelerometer utilizing contained with the cubical electrode structure of FIG. the cube 30 containing the single dust particle 60 which 7 by the action of the drive (source 50 in FIG. 7) and is illuminated by a light source such as a carbon are the static quadrupolar ?elds (sources 58 and 59 in 61 and a lens 61a. Light re?ected from the particle FIG. 7). For this photograph, d=1+5/32 inches, 45 60 passes through the aperture 42 in the surface 32., Q/21r=60 cycles/second, Vac=208 volts r.m.s., Vdcx= through a lens 62, and an optical wedge 63 to energize Vdcy=—44 volts, and Vgz=—27 volts. The unidirec a photocell 64. Motion of the particle 60 in the z tional component Vgz of source 39 was employed in direction will cause the image to pass through the vari this instance to counteract the gravitational forces act able density optical wedge 63 to provide a variable light ing upon the individual particles. The picture further illustrates that in the cubical electrode structure the particles (which are held away from the center of the intensity signal So from the circuit including the photo cell 64, a battery 65 and a tuning rheostat 66. This‘ signal So is compared to a reference signal Sr in a dif chamber by space charge forces of repulsion) execute ference ampli?er 67 to provide a control signal Sc. It individually elliptical orbits about their equilibrium posi is preferred that the reference signal Sr be a function tions as a result of the 120° phase difference between of the light intensity of the light source such as the 55 the three A.C. drive signals. carbon are 61, so that variations of the light source The other voltage sources shown in FIG. 7, (speci? will be compensated automatically. This may be ac cally 37, 3,8, 39 and 54) serve as a means of exciting or steering the contained charged particles or plasma about the interior of the electrode structure. The uni direction components Vgx, Vgy and Vg2 add a constant uniform electric force ?eld near the center of the elec trode structure of the form V Elayvzz gx,a y, 1 (53) 65 complished by providing another photocell 68 in line with the light beam from the are 61 With the signal from the photocell 68 passing through a reference net Work 69 to provide the desired signal Sr. The accel erometer may be rotatably mounted on a pendulum like structure (not shown) so that a single signal Sc is provided, but it is preferred that three such signals Sc be provided by photocell systems of the type illustrated by components 61-67 so that each of the signals (8,) may correspond to a displacement of the particle 60 in Such forces serve, as has been seen from the discussion each of the x, y and 2 directions. of Equations 26-30 to displace the center of motion Referring again to FIG. 7, the AC. components of by an amount proportional to the applied force and inversely proportional to the square of the resultant 70 the sources 37, 38 and/or 39 can be used to excite or resonate (according to the discussion 'of Equations frequency of motion. Unlike the single phase con 3l-—33) the contained particles whenever the frequen tainment system as it is shown in FIG. 1, the three ‘cies of these sources equals any one of the oscillatory phase device has the ability to offset the contained frequencies of the contained particles, Equation 15. particle mass along any one of the three orthogonal di rections of space. However, it is realized that. the ring 75 Thus a particle or plasma can be excited in the zdirec 3,065,640 15 16 tion by the A.C. component of the source 39 when the frequency of this source equals any one of the z vibrational frequencies of the particle (i.e. wz, Q—wz, surface 31-36 respectively are 3/16” in diameter. It is suggested that all inner surfaces of the cube 30 be painted with a non-re?ecting covering, such as aquadag, to reduce the problem of spurious light re?ections. It is also pre Q+wz . . . ). In a like manner the plasma can also be excited along the y direction by the source 38, ferred that the chamber be completely insulated from and/or in the direction by the source 37. surrounding devices by the use of some supporting device such as ceramic spacers 7 6 supportingly engaging the lower surface 35. Thus the system may be used to detect rapidly varying gravita tional forces in any one of the x, y or z directions. The quadrupolar source (54 in FIG. 7) serves in still another way of exciting or resonating the contained particles or plasma. The mathematics of this mode of resonance has been previously discussed in Equations 34~40. When applied to the three phase system it is found that the A.C. pump voltage source 54 will trans~ During one type of operation, aluminum macroparticles 60 having an average diameter of approximately 10 mi crons are initially stored in the powder reservoir 23 pro vided with an upwardly opening aperture 21 beneath the aperture 45 of the lower surface 35 of the suspension device. Particle injection into the suspension chamber of fer energy to the plasma and coherently excite it when 15 the cube 30 is effected by pulsing the powder reservoir 23 with a high voltage such as a 5,000‘ volt negative potential ever its frequency is related according to Equation 38 relative to an anode-like portion 78 of the particle gun to any one of vibrational frequencies in either x, y, or including the reservoir 23. This results in the entrance z, of the contained particles. For the three phase sys of a cloud 84 of the charged particles 60, through the aper tem quadrupole resonance will occur when, ture 45 where they come within the current stream of an electron or ion gun 86 positioned to cause substantial elec w» (54) tron ?ow through another aperture such as the aperture 43. The electron gun ‘86 is maintained at a negative 500 where n is an integer and wx, y, Z are the stable oscilla tory frequencies due to the several drive voltages re volts relative to the cube 30‘ so that the eleectrons impinge , upon the particles 60 at a relatively high velocity. Thus spectively. Equation 54 assumes that Vp<<Vw Fur ther it should be realized that although the A.C. pump electrons are accelerated into the suspension chamber of voltage source 54 has been shown as a Y connected the cube 30 to impinge upon and further charge at least to three phase generator in FIG. 7, such a requirement some of the aluminum dust particles 60 within the cloud is really not necessary. For example, a single phase 84. Even without use of the electron gun 86 a few of the A.C. generator could equally well have been shown 30 dust particles 60 are of sut?cient charge to be contained (i.e., the voltages in two legs 55 and 56 could have within the containment ?elds. Moreover, the electron gun been shorted out) without changing the resonance con 86 may be replaced by an ion gun. Only charged aluminum dition shown by Equation 54. particles 60 remain within the suspension chamber where they may be observed by a simple microscope 88 posi The above discussion has demonstrated the manner in which alternating three phase voltage can be used to 35 tioned adjacent to another aperture, such as the aperture stably contain charged particles within the cube 30 in a 44 or 42, with illumination of the ?eld of view of the mi croscope 83 being provided at 90° through the aperture 31 manner known in the art of nuclear machines as alternat ing gradient focusing. Moreover, means of resonantly by a carbon are light source 89. Also a camera 90 may be exciting the particles have been demonstrated. Also placed over an observation aperture such as the aperture means for steering or offsetting the equilibrium positions 40 46. On the other hand, resonance of the particles may be of the contained particles have been demonstrated. Al~ detected electronically. though the above mathematical discussion of the three Referring again to both FIGS. 7 and 11, one suitable phase system has dealt with sinusoidally time varying arrangement of the A.C. drive voltage source 50 utilized ?elds, it should be realized that other periodic wave shapes in supporting aluminum dust particles 60 provides as much (such as rectangular, triangular, etc.) could be used. 45 as 1200 volts at 400 cycles and the alternating voltage 5 Finally it should be realized that the phase condition on oscillator sources 37, 38 and 39 provide as much as 450 the A.C. drive voltage is not in the least strict and that volts at 60 cycles. Actually only one 13 oscillator source the system is capable of containing particles within the was used during certain of the testing work using the de vice of FIG. 11. The unidirectional voltage supplies 58 cube 30 for any phase (O—360°) between the adjacent legs of the A.C. drive voltage source 50. For example, if the two legs 51 and 52 were shorted out, then the ?elds due to the A.C. drive voltage source 50 would have the form of Equations 2 and 3 and the device would function like the single phase system shown in FIG. 1. In order to eliminate undesired collision between the contained 55 charged particles and uncharged particles such as air, the containment device shown in FIG. 7 can be mounted in an evacuated vessel or vacuum system 92 (FIG. 8), hav and 59 are variable up to a maximum of 500- volts and the unidirectional voltage supply 37 is on the order of 90 volts. By varying the voltage source 39, the electrostatic voltage Vg between the top and bottom surfaces 35 and 36 may be adjusted to cancel the effect of gravity, a great er or lesser amount, whereby the particles under suspension may be moved vertically up or down toward or away from the center of the electrode structure of the cube 30. With the provision of a three-phase alternating voltage source connected to mutually perpendicular pairs of plate sur for connecting to the controllable external voltage sources. 60 faces respectively (FIG. 7), the oscillatory motion of each of the particles 60 within a crystal-like structure is Details of a suitable vacuum system are known and need an elliptical-shaped particle trajectory as shown in FIG. not be presented herein. Referring now to FIG. 11 showing an exploded view of 10. This results from the effect that the drives exerted on each particle are in three perpendicular directions one particular chamber which chamber has been tested and operated in accordance with the above theory. The 65 which are 120° out of phase with each other, with the motions in these three directions being similarly 120° cube 30 has inner dimensions (d) of 1+5/32" with each of out of phase. If the voltages or frequencies are changed the six separate surfaces 31—36 being %6" thick alumi slightly or if the background vacuum is changed, the num members. In order to obtain a simple self-supporting ‘crystal-like structure (FIGS. 6 and 10) will “melt,” and structure, the edges of the aluminum members are pro vided with 45° ?anges 70 to facilitate insulating supports 70 although suspension may be maintained and the mean average of the particle “mass” may remain ?xed, the rela between each side of the cube 30. The ?anges 70 of adja tive location between each particle changes rapidly. A cent edges may be secured by insulating screws 72 of a material such as nylon or porcelain and spaced apart by melted particle mass will have a cloud-like appearance. With a plurality of particles under suspension, as shown insulating washers such as 1%5" thick Lucite spacers 74. The apertures »4_1—48 de?ned in the central region of each 75 in FIGS. 6 or 10, increasing the voltage of the unidirec ing insulated vacuum-tight electrical leads (not shown) ‘3,065,646 17 tional voltage source 39 may be utilized to cause a few of the uppermost particles 60 to become unstable and leave the region of the oscillating support. Thus the number of particles under suspension may be reduced. This proc 18 faces for providing electric ?elds in the containment space de?ned thereby; a source of chargeable dust particles of a size on the order of at least one micron positioned adjacent to one of the apertures; means for injecting ess may be continued until only one particle 60 remains, charged particles from said source into the containment whereupon the observation of this single particle is pos sible. Although the cube 36B of FIGS. 8 and 11 is placed to provide three-dimensional alternate gradient focusing space; means for controlling said electric circuit means in an evacuated container $2 (FIG. 8), means such as a containment of the charged particles; and means for vacuum pump (not shown) are provided for reducing the vacuum. Usually in a continuously pumped system there is provided a throttle (or leak) valve means 93 to detecting and observing the particles. raise the background pressure to a value on the order of around a micron or two so that the particles on will be damped to form a stable array in a matter of a few minutes. 15 de?ning a containment space, with a plurality of said While there have been shown and described several embodiments of the present invention, other modi?cations 4. A particle containment and observation device, comprising: conductive members having inner surfaces surfaces having apertures therethrough; electric circuit means selectively connected to said surfaces for providing electrodynamic ?elds in the containment space de?ned thereby; a source of particles positioned adjacent to one of the apertures; means for injecting particles from said source into the containment space; means adjacent to a may occur to those skilled in the art. For instance, it is second of the apertures and focusable therethrough for understood that for either one of these containment sys tems (see FIGS. 1 or 7), the drive voltage Vac and/ or the 20 charging the injected particles; means for controlling said electric circuit means to provide three'dimensional alter unidirectional voltage Vdc is actu-able by a step function. In this manner particles charged externally to the elec nate gradient focusing containment of the charged parti trode structure will be trapped as they pass into the con cles; means positioned adjacent to a third of said aper tures for illuminating the contained particles, said sur ?nement space. The A.C. drive (and/or the DC. series voltage) would in this case be turned on and controlled 25 faces being provided with a substantially non-re?ective coating facing the containment space; and means posi by an electronic network timed to turn the drive voltage tioned adjacent to a fourth of the apertures for allowing on at the instant that the charged particle mass reaches the observation of the illuminated particles. I the center of the con?nement space. Furthermore, in the earlier paragraphs it was explained that the contained 5. A particle containment and observation device, com particle mass can be ejected from one of the apertures, 30 prising: conductive surfaces de?ning a containment space, for example, 25 in FIG. 1, or 41—46 in FIG. 7, by prop erly varying the magnitude of the static voltage source with a plurality of said surfaces having apertures there through electric circuit means selectively connected to said surfaces for providing electro-dynamic ?elds in the Vdc (19 in ‘FIG. 1 or 58 and 59 in FIG. 7). It should containment space de?ned thereby; a source of particles be realized that the time rate of change of this voltage will determine the duration of the ejected current stream. 35 positioned adjacent to one of the apertures; means for injecting charged particles from said source into the Thus a step in the series voltage source will cause particles containment space; means adjacent a second of the aper to be ejected as a pulse. A linear variation of the mag nitude of Vdc will cause particles to issue out as a cur tures and focusable therethrough for further charging the injected particles; means for controlling said electric cir rent stream of length determined by the time rate of change of the series source. Also only a portion of the 40 cuit means to provide three-dimensional alternate gradi ent focusing containment of the charged particles; and particle mass may be ejected by such a pulse. There means for detecting and observing the contained particles. fore it is intended by the appended claims to cover all 6. A particle containment and observation device, such modi?cations as fall within the true spirit and scope comprising: metal surfaces de?ning a containment space, of this invention. with each of said surfaces having a central aperture; elec— We claim: tric circuit means selectively connected to said surfaces 1. A particle containment and observation device, for providing electro-dynamic ?elds in the containment comprising: conductive surfaces de?ning a containment space de?ned thereby; means for injecting charged ‘par space; electric circuit means selectively connected to said ticles through one of the apertures into the containment surfaces for providing electric ?elds in the containment space; an electron gun focused through a second of the space de?ned thereby; means for injecting charged dust particles of a size on the order of a micron or more into apertures for further charging the injected particles; the containment space; means for controlling said elec tric circuit means to control the electric ?elds to provide means for controlling said electric circuit means to pro three-dimensional alternate gradient focusing contain vide three-dimensional alternate gradient focusing con tainment of the charged particles; means positioned adja and observing the particles. tained particles; and optical magnifying means positioned ment of the charged particles; and means for detecting 55 cent to a third of the apertures for illuminating the con . 2. A particle containment and observation device, adjacent to a fourth of the apertures for allowing the observation of the illuminated particles. 7. A particle containment and observation device, com comprising: conductive surfaces de?ning a containment space with a plurality of said surfaces having apertures therethrough; electric circuit means selectively connected prising: pairs of mutually perpendicular metal surfaces three-dimensional alternate gradient focusing contain ment of the charged particles; means positioned adjacent gun focused through second of the apertures for further charging the injected particles; means for controlling said de?ning a cubical containment space, with each of said to said surfaces for providing electric ?elds in the con— surfaces having a central aperture; electric circuit means tainment space de?ned thereby; a source of dust particles selectively connected to said pairs for providing electro positioned adjacent to one of the apertures; means for dynamic ?elds in the containment space de?ned thereby; injecting charged particles from said source into the containment space; means for controlling said electric 65 means for injecting charged macroparticles through one of the apertures into the containment space; an electron circuit means to control the electric ?elds to provide electric circuit means to control the electro-dynamic ?elds to a second of the apertures for illuminating the con tained particles; and means positioned adjacent to another 70 resulting in three-dimensional alternate gradient focusing containment of the charged particles; means positioned of the apertures for allowing the observation of the il adjacent to a third of the apertures for illuminating the luminated particles. contained particles, and optical magnifying means po_si—; 3. A particle containment and observation device, com tioned adjacent to a fourth of the apertures for allowing prising: conductive surfaces de?ning a containment space; electric circuit means selectively connected to said sur 75 the observation of the illuminated particles. 3,085,640 19 8. A particle containment and observation device, comprising: metal members having inner surfaces de ?ning a containment space, within an evacuated con tainer, with each of said surfaces having a central aper ture; electric circuit means selectively connected to said surfaces for providing electro-dynamic ?elds in the con tainment space de?ned thereby; means for injecting visual ly observable charged particles through one of the aper tures into the containment space; a charged particle gun focused through a second of the apertures for further 10 charging the particles; means for controlling said electric circuit means to provide three dimensional alternate gradient focusing containment of the charged particles; means positioned adjacent to a third of the apertures for 2%) surfaces for providing electric ?elds in the containment space de?ned thereby; means for injecting charged par-v ticles of a ?rst type and of a second type of charge to mass ratio into the containment space; means for con trolling said electric circuit means to provide different frequency electro-dynamic ?elds resulting in three-dimen; sional alternate gradient focusing containment of both the ?rst and second types of charged particles; and means for detecting and observing the contained particles. 13. A particle containment and observation ‘device, comprising: pairs of mutually perpendicular metal inema bers having inner surfaces de?ning a containment space, within an evacuated container, with at least one of said members having a central aperture; electric circuit means illuminating the contained particles; means for regulating 15 selectively connected to said pairs for providing electro; the background pressure within the evacuated container; dynamic ?elds in the containment space de?ned thereby; and optical magnifying means positioned adjacent to a at least one charged dust particle within the containment fourth of the apertures for allowing the observation of space; means for controlling said electric circuit means to‘ the illuminated particles, said control means being vari provide three-dimensional alternate gradient focusing con= able to provide a stable containment wherein each illu 20 tainment of the charged particle; means positioned adja; minated particle has a ?xed mean average location rela cent to the containment space for illuminating the con; tive to other illuminated particles with the result that the tained particle; means for regulating the background pres sure within the evacuated container; and optical means 9. A particle containment and observation device, com positioned adjacent to at least the one aperture for detect prising: pairs of mutually perpendicular metal members 25 ing the presence and location of the illuminated particle, having inner surfaces de?ning a containment space, within said control means being variable to provide a stable con an evacuated container, with each of said members hav tainment wherein the illuminated particle has a ?xed mean ing a central aperture, and each of said surfaces having average location. non-re?ecting coating thereon; electric circuit means selec 14. A particle containment and observation device, tively connected to said pairs for providing electrodynam 30 comprising: pairs of mutually perpendicular metal mem ic ?elds in the containment space de?ned thereby; means bers having inner surfaces de?ning a containment space, particle array observed is crystal-like. for injecting visually observable charged particles through one of the apertures into the containment space; means for controlling said electric circuit means to provide three within an evacuated container, with at least one of said members having a central aperture; electric circuit means selectively connected to said pairs for providing electro‘ dimensional alternate gradient focusing containment of 35 dynamic ?elds in the containment space de?ned thereby; the charged particles; means positioned adjacent to a second of the apertures for illuminating the contained particles; means for regulating the background pressure within the evacuated container; and optical magnifying at least one charged ‘dust particle within the containment space; means for controlling said electric circuit means to provide three~dimensional alternate gradient focusing con‘ tainment or" the charged particle; means positioned adja= means positioned adjacent to a third of the apertures for 4,0 cent to the containment space for illuminating the con= allowing the observation of the illuminated particles, said tained particle; means for regulating the background pres control means being variable to provide a stable con sure within the evacuated container to damp the motion tainment wherein each illuminated particle has a ?xed of the particle, said control means being variable to pro vide a stable containment wherein the illuminated particle mean average location relative to other illuminated par ticles with the result that the particle array observed is crystal-like. 10. A particle containment and observation device, comprising: conductive metal members having inner sur faces de?ning a containment space with a plurality of said surfaces having apertures therethrough; electric circuit means selectively connected to said surfaces for providing electric ?elds in the containment space de?ned thereby, at least one charged dust particle in the containment ‘space; means for controlling said electric circuit means to provide three-dimensional alternate gradient focusing con tainment of the charged dust particle; and means for detecting and observing the charged dust particle. 11. A particle containment and observation device, comprising: pairs of mutually perpendicular metal sur comes to rest at the center of the containment space; and optical means including balanced photocell arrangement positioned adjacent to at least the one aperture for detect ing the presence and location of the illuminated particle and providing a signal indicative of the displacement of the particle from the center. 15. A particle containment and observation device usable as an accelerometer comprising: metal members having inner surfaces de?ning a containment space‘, within an evacuated container, with at least one of said members having a central aperture; electric circuit means selectively connected to said members for providing electro-dynamic‘ ?elds in the containment space de?ned thereby; one‘ charged dust particle within the containment space; means for controlling said electric circuit means to provide three faces de?ning a cubical containment space, with each 60 dimensional alternate gradient focusing containment of of said surfaces having a central aperture; electric circuit the charged particle; means positioned adjacent to the means selectively connected to said pairs for providing containment space for illuminating the contained particle; electro-dynamic ?elds in the containment space de?ned a background pressure within the evacuated container of thereby; a charged macroparticle within the containment a magnitude which will damp the motion of the particle, space; means for controlling said electric circuit means 65 said control means being variable to provide a stable con to provide three-dimensional alternate gradient focusing tainment wherein the illuminated particle comes to rest containment of the charged macroparticle; means posi tioned adjacent to the containment space and focused therein for illuminating the contained macroparticle; and optical magnifying means positioned adjacent to one of the apertures for allowing the observation of the illu tioned adjacent to at least the one aperture for detecting minated macroparticle. 12. A particle containment and observation device, indicative of the displacement of the particle from the near the center of the containment space; and optical means including balanced photocell arrangement posi the presence and location of the illuminated particle along one axis of the containment space and providing a signal center. comprising: conductive surfaces de?ning a containment 16. A particle containment and observation device, space; electric circuit means selectively connected to said 75 usable as an accelerometer, comprising: pairs of mutually 53,065,640 21 22 and means connected to said electric circuit means for varying the electric ?elds to selectively eject at least a perpendicular metal members having inner surfaces de?n ing a containment space, within an evacuated container, with at least one of said members of each pair having a central aperture; electric circuit means selectively con portion of the charged particles contained in a predeter mined direction. nected to said mutually perpendicular pairs for providing Cl electro-dynamic ?elds in the containment space de?ned thereby; one charged dust particle within the containment space; means for controlling said electric circuit means to provide three-dimensional alternate gradient focusing con tainment of the charged particle; means positioned adja 20. A particle containment and observation device, comprising: conductive surfaces de?ning a containment space; electric circuit means selectively connected to said surfaces for providing electric ?elds in the containment space de?ned thereby; and means for injecting charged dust particles of a size on the order of a micron or more into the containment space; said electric circuit means including a ?rst alternating frequency source for contain cent to the containment space for illuminating the con tained particle; a background pressure within the evacuated ment of said particles and a second alternating frequency container of a magnitude which will damp the motion of source for pumping said particles. the particle, said control means being variable to provide 21. A particle containment and observation device, a stable containment wherein the illuminated particle 15 comprising: conductive surfaces de?ning a containment comes to rest near the center of the containment space; space; electric circuit means selectively connected to said and optical means including balanced photocell arrange surfaces for providing electric ?elds in the containment ment positioned adjacent to one of the apertures in each space de?ned thereby; and means for injecting charged of said mutually perpendicular pairs for detecting the presence and location of the illuminated particle along 20 dust particles of a size on the order of a micron or more into the containment space; said electric circuit means including a ?rst alternating frequency source for contain each axis of the containment space and providing a signal indicative of the displacement of the particle from the ment of said particles and a second alternating frequency source for pumping said particles, said ?rst and second 17. A particle containment and observation device, comprising: metal surfaces de?ning a containment space, 25 alternating frequency sources being series connected. 22. A particle containment and observation device, with each of said surfaces having a central aperture; elec comprising: conductive surfaces de?ning a containment tric circuit means selectively connected to said surfaces space; electric circuit means selectively connected to said for providing electro-dynamic ?elds in the containment surfaces for providing electric ?elds in the containment space de?ned thereby; means for injecting charged parti space de?ned thereby; and means for injecting charged cles through one of the apertures into the containment center. space; voltage step producing means for controlling said electric circuit means to provide the electric ?elds result ing in three-dimensional alternate gradient focusing con tainment of the charged particles when the particles have entered the containment space. dust particles of a size on the order of a micron or more into the containment space; said electric circuit means including a ?rst alternating frequency source for contain ment of said particles and a second alternating frequency 35 source for pumping said particles, said second alternating 18. A particle containment device, comprising: conduc tive surfaces de?ning a containment space; charged par ticles within the containment space; ?rst electric circuit means selectively connected to said surfaces for providing three-dimensional alternate gradient focusing containment of the charged particles; and second electric circuit means connected to said surfaces for exciting through resonance the contained particles. 19. A particle containment and ejection device, com prising: members each having an inner conductive sur 45 face de?ning a containment space with at least one of said members having an aperture therethrough; charged particles within the con?nement space; electric circuit means selectively connected to said members for provid ing electric ?elds resulting in three-dimensional alternate gradient focusing containment of the charged particles; frequency source being connected to only a portion of said conductive surfaces. References Cited in the ?le of this patent UNITED STATES PATENTS 2,718,610 Krawinkel ___________ __ Sept. 20, 1955 2,837,693 2,868,991 Norton _______________ __ June 3, 1958 Josephson et al _________ __ Jan. 13, 1959 2,895,067 2,904,411 Deloffre ______________ __ July 14, 1959 Pfann _______________ __ Sept. 15, 1959 OTHER REFERENCES Foley’s College Physics, fourth edition, revised by J. L. Glathart, 1947, pages 348 and 349.