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Патент USA US3065650

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Nov. 27, 1962
D. B. LANGMUIR ETAL
3,065,640
CONTAINMENT DEVICE
Filed Aug. 27, 1959
9 Sheets-Sheet 1
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BY
Nov. 27, 1962
D. B. LANGMUIR ETAL
3,065,640
CONTAINMENT DEVICE
Filed Aug. 27, 1959
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INVENTORS
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NOV- 27, 1962
D. B. LANGMUIR ET AL
3,065,640
CONTAINMENT DEVICE
Filed Aug. 27, 1959
9 Sheets-Shéet 4
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ATTORNEY:
NOV- 27, 1962
D. B. LANGMUIR ETAL
3,065,640
CONTAINMENT DEVICE
Filed Aug. 27, 1959
9 Sheets-Sheet 5
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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
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INVENTORS
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Nov. 27, 1962
D. B. LANGMUIR ETAL
3,065,640 ‘
CONTAINMENT DEVICE
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D. B. LANGMUIR ET AL
3,065,640
CONTAINMENT DEVICE
Filed Aug. 27, 1959
9 Sheets-Sheet 9
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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.
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