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Патент USA US3019404

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Jan. 30, 1962
w. H. BENNETT
3,019,394
CHARGED PARTICLE ACCELERATOR
Original Filed Nov. 21, 1955
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INVENTOR
WILLARD
H- BENNETT
ATTORNEY
Jan. 30, 1962
w. H. BENNETT
3,019,394
CHARGED PARTICLE ACCELERATOR
Original Filed Nov. 21; 1955
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WILLARD
INVENTOR'
H. BENNETT
BY
ATTORNEY
Jan. 30, 1962
w. H. BENNETT
3,019,394
CHARGED PARTICLE ACCELERATOR
Original Filed Nov. 21, 1955
3 Sheets-Sheet 3
INVENTOR
WILLARD
H. BENNETT
BYMJW
ATTORNEY
United States Patent O?fice
3,019,394
Patented Jan. 30, 1962
1
2
characters designate like or corresponding parts through
3,019,394
CHARGED PARTICLE ACCELERATOR
Willard H. Bennett, 174 Chesapeake St. SW.,
Washington, DC.
Original application Nov. 21, 1955, Ser. No. 548,283, now
Patent No. 2,942,106, dated June 21, 1960. Divided
and this application Apr. 27, 1960, Ser. No. 25,176
7 Claims. (Cl. 328—235)
(Granted under Title 35, US. Code (1952), sec. 266)
out the several views, there is shown in FIG. 1 which il
lustrates a typical embodiment of an accelerator 10 com
prising a disk-shaped evacuated chamber 11 which may
be coated on the inside with a conducting ?lm, and
positioned in coaxial relationship with the chamber are
adjacent D.-C. coils 12 or other means for producing a
steady magnetic ?eld across the evacuated chamber. The
means for evacuating the chamber is not shown for sim
Located on each side of the
10 pli?cation of the drawing.
The invention described herein may be manufactured
evacuated chamber are four wire loops 13, 14, 15 and
and used by or for the Government of the United States
16 on opposite sides of the chamber. The wires are
of America for governmental purposes without the pay
shaped to resemble the outer form of a four bladed pro~
ment of any royalties thereon or therefor.
peller, but the form of a propeller with any number
The present invention is a division of application Serial 15 of blades may be used. The wire loops are placed di
No. 548,283, ?led November 21, 1955, now Patent No.
rectly opposite each other on opposite sides of the cham
2,942,106, and relates to a device for accelerating high
ber so that more intense magnetic ?elds will be set up
energy particles and more particularly to a device for
within the loops and less intense magnetic ?elds set up
producing intense ion streams within a tube.
in the area between successive loops. The two propeller
The present invention may be used for producing sus
shaped wires have common connections to a line carry
tained streams of high-velocity ions mixed with electrons
ing frequency-modulated radio-frequency currents so that
comparatively at rest and to accelerate the ions around
the current through the wire loops will set up an azimuth
in a magnetic ?eld whose intensity is azimuthally modu
ally periodic radio-frequency ?eld and accelerate the ions
lated so that the ions follow paths which approximate
between the wire loops. The ions are accelerated by
a circle. Superimposed on the steady magnetic ?eld is 25 the electromagnetic forces set up within the chamber
a radio-frequency sinusoidal magnetic ?eld which induces
wherein the electromagnetic forces are produced by mag
an electromotive force on the cycling ions. These forces
netic ?ux lines around the wire loops on each side of
can produce a net gain of energy of ions, if at the fre
the chamber.
quency of the radio-frequency ?eld used, the time of
In the modi?cation shown in ‘FIG. 2 the evacuated
flight of the ions in an orbit is just the period of the
chamber 11 and the propeller shaped loops of wire on
radio frequency ?eld. The average magnetic ?eld is
opposite sides of the chamber are positioned within a
made to vary slightly with radius, and the radio-frequency
conductive box 17 which maybe copper. The box 17
is positioned within the magnetic ?eld between the D.-C.>
tooth manner, to move ions initially in low-energy orbits
magnetic coils 12 and con?nes the magnetic ?ux lines
nearer the axis toward the high-energy orbits lying far 35 produced by the wire loops to the area within the box.
from the axis and leaving them circulating there while
The Wire loops are energized with high frequency cur
?eld is frequency-modulated, which can be in a saw
additional ions are picked up and moved out by succeed
ing modulation cycles. The ions are accelerated to be
useful in producing nuclear reactions.
. It is accordingly an object of the present invention to
rent, usually at radio frequency as will later appear. Ad
ditionally, the frequency is preferably modulated. The
frequency modulation employed recurrently sweeps from
a lower limit to an upper limit, the transition from the
upper limit back to the lower limit taking place as ra-.
produce intense directed ion streams.
Another object of this invention is to produce intense
pidly as possible.
ion streams in a highly concentrated form.
type are well known and for this reason is shown in block
Radio frequency generators of this
‘A further object of this invention is to produce intense
form 20 in FIG. 1. The present invention may employ
ion streams of the magnetic self-focusing type.
a saw~tooth control wave derived from a multivibrator
A still further object of this invention is to produce
or blocking oscillator having amplitude and frequency con
essentially direct currents of ions.
trol adjustment and setting devices, and applying the con
Still another object of this invention is to produce
trol wave to a reactance tube coupled as a frequency con
intense ion streams utilizing sinusoidal alternating forces. 50 trol element of an electron tube oscillator. The frequency.
modulated output signal is preferably fed to the wire
A ?nal object of the present invention is to produce
loops through a power ampli?er and impedance match~
ion streams consisting of one or more species of parti
ing circuit.
cles.
The radio frequency current is to be saw-tooth fre
Other objects and advantages of the invention will
quency-modulated in such a manner that the lower fre
hereinafter become more fully apparent from the follow
quency limit of the current is such that ‘the period of
ing description of the annexed drawings, which illustrates
the radio frequency current corresponds to the time of
the preferred embodiments, and wherein:
?ight of the species of ions to be accelerated while the
FIG. 1 illustrates a diagrammatic view of the com
ions travel from loop to loop near the axis. The fre
ponents of the device of the invention,
quency of the higher frequency limit of ‘the saw-tooth
FIG. 2 illustrates a modi?cation of the device illustrated
corresponds to the time of ?ight of the ion from loop to
FIG. 1,
FIG. 3 is a diagrammatic sectional view of the device
of FIG. 1 taken along line 1-1 of FIG. 1 showing wire
loops on opposite sides of an evacuated chamber within
a magnetic ?eld, an ion gun, and means for collecting
the ions,
FIG. 4 is a modi?cation of the invention showing per
manent magnetic pole pieces on opposite sides of an
evacuated chamber, and
FIG. 5 is a diagrammatic view illustrating an ion gun
which ?res particles into the evacuated chamber.
Referring now to the drawings, wherein like reference
loop when the ion is traveling in an orbit near the outer
periphery of the evacuated chamber. The action on an
ion traveling in an orbit produced by the radio-frequency
current in the loops is such that the induced force on
the ion varies with the radial distance of the ion from
the axis and the phase of the radio frequency current
in the coil relative to the position of the ion in the
orbit is such that the accelerating force occurs while the
ion is in a loop and the decelerating force occurs while
the ion is in the areas between loops. The resultant effect
is to increase the speed of the ion.
3,019,394
FIG. 3 is a view along lines 3—-3 of FIG. 1 which illus
trates the propeller shapes of the wire loops on each side
nuclear reaction with the target material. An electron
of the chamber.
a metallic collector to generate X-radiation.
Further the view illustrates means
through which the charged particles can be injected into
the chamber and removed therefrom.
FIG. 4 is a modi?cation of the device shown in FIG.
beam established by the system may be directed on to
The de?ecting signal applied to the de?ection device
is preferably of short duration where continuous utiliza
tion of the system is desired. Upon cessation of the con
trol in?uence, therefore, the stable outer orbit is reestab
lished and further particles accelerated thereinto may then
chamber is positioned. The permanent magnet replaces
be de?ected for utilization.
the D.-C. coils and the device operates the same in all
The de?ection signal, when of a duration approaching
10
other respects as the device shown in FIG, 1.
or exceeding the outer orbital period, need not be repeated
Ion sources can be formed in many ways, one of
I and includes a permanent magnet 18 within which the
which is illustrated in FIG. 3 as an ion gun which can
be any type well known in the art. The ion gun 21 is
positioned near the outer edge of the evacuated chamber
until a succeeding cycle of frequency modulation acceler
ates more particles into the outer orbit. It is therefore
convenient to derive the de?ection control signal from a
and at an angle so that it will project a beam of negative 15 recurrent pulse generator having control devices. The
pulse frequency control device may operate under con
ions toward the middle of the chamber from the edge and
trol of the frequency modulator providing the saw-tooth
about midway between sectors, the beam is directed to
control wave to supply de?ection pulses at a desired phase
make the ions strike the wall of the chamber at grazing
and in a desired frequency relation thereto. Thus the
incidence adjacent to a wire loop. Some of the ions
de?ection signal generator may be a normally quiescent
will rebound from the wall as positive ions, moving in
blocking oscillator triggered by a signal derived from the
approximately the correct direction to be picked up and
accelerated by the radio-frequency and magnetic ?elds.
Another ion source is shown in FIG. 5 wherein the
end of a palladium tube 22 is bombarded ‘with electrons
saw-tooth oscillator through phase control circuitry, and
if desired, count-down frequency dividing circuits, to op
erate once each saw-tooth cycle or at a lower pulse fre
from a ?lament 23 nearby, while the palladium tube is 25 quency during spaced successive cycles of the saw—tooth
?lled with hydrogen.
generator. It is clear, however, that the de?ection sig
A screen 24 is interposed between the electrodes and
the principal portion of the evacuated chamber to- act as
a shield in preventing the potential on the electrodes from
nal generator need not be so synchronized because high
velocity particles are continually being made available
in the outer stable orbit.
For other purposes it may be desirable to intercept
interfering with the operation of the accelerator. ‘If suf 30
the beam when desired by a target probe 28 in FIGS.
?cient electron current is passed at suf?cient voltage, the
3 and 5, which may be movably mounted on the tube
palladium tube will be heated and will transmit hydro
envelope by a removable bellows type seal.
gen. The hydrogen upon emerging from the tube will be
It is to be noted that in this invention the orbits of
atomic and will be ionized *by the dense electron current.
The atomic hydrogen upon emerging from the palladium
tube and being ionized by the electron bombardment is
accelerated toward the ?lament but misses it due to the
atcion of the magnetic ?eld and is de?ected along the
path shown by the broken line 26 in FIG. 5. The axial
focusing action of the system makes the ions approach
a centered orbit and the next saw~tooth cycle of RF.
picks up the ions and moves them toward the outer orbit
as disclosed in reference to FIG. 1.
Instead of the palladium tube as shown in FIG. 5 an
electron injector could be used to inject electrons into
the evacuated chamber. The electrons would be injected
perpendicular to the outer orbit and would follow a path
toward the axis until it is picked up by radio-frequency
those electrons which are liberated in ionizations will ‘be
very small and for this reason the electrons are con
?ned to the immediate vicinity of magnetic lines of force
passing through their respective points of origin. It is
the ions which are the rapidly moving electnical charges
and consequently it is the ions which are magnetically
self-focusing and in excess. The electrons produced in
the ionizations will be driven out of the mid-plane of the
chamber until there are just enough left to neutralize
the space charge of the average positive ion density at
each position in the mid-plane of the chamber.
It should also be noted that this device can be an
electron accelerator by applying radio-frequency ?elds
with the appropriately much higher frequency. It is
feasible to apply both an R.-F. ?eld to accelerate ions,
alternating current and accelerated to the outer orbit.
Another source of ion arises from the presence of elec 50 and, simultaneously, by appropriate means an R.-F. ?eld of
another frequency for electrons. The ratio of the fre
trons everywhere in the tube. These can ‘be accelerated
quencies can be obtained approximately by using the
formula w=e/m-H., where w is the angular velocity,
e—the charge of the electron, m—mass of theion, and
the tube. This method will supply some ions to the ac
celerating system. The process may be directly initiated 65 H~—the guiding average magnetic ?eld.
A typical example for the operation of the device dur
by applying the radio-frequency ?eld with the D.-C. mag
and decelerated by the radio-frequency ?eld, spending part
of their time with energies su?icient to ionize the gas in
ing acceleration of protons is carried forth by the use of
netic ?eld off in order to ?ll the chamber with an elec
an evacuated accelerating chamber comprising a resilient
trodeless discharge. After the chamber has been ?lled
gas pressure of 10"6 mm. of Hg, and the mean free path
with ions and electrons, the D.-C. magnetic ?eld is ap
plied to accelerate the higher velocity ions which pro 60 of the ions is of the order of 104 cm. If the average mag
netic ?eld applied in the chamber is 1080 gauss, the en
duce secondary effects in sufficient density to sustain the
ergy of protons in the outer orbit will be 2,000‘ volts, the
ionization needed to serve as an ion source.
velocity will be 6x107 cm./ sec. and the mean-freeetime
The circulating beam of charged particles generated
of an ion is 1.7><l0~4 sec. If the saw-tooth repetition
by the present invention may be employed as desired.
frequency is 25,000 per sec., the current in the outer orbit
For instance, the particles may be collected by de?ect
will decrease 22% during ‘each saw-tooth cycle and the
ing them from their reentran-t stable path by applying
maximum current in the outer orbit will be approximately
a control potential to an electrode 27 shown in FIGS. 3
and 5. An attracting potential of a polarity determined
4.5 times the average current fed into the chamber from
by the particle charge will direct the beam outwardly
the inner orbits. This is only one typical example of
device may therefore receive particles of particular types
accelerating ions and the invention is not limited to ac
celeration of pro-tons but may be used for other ions and
accelerated by the system from among a variety of dif
ferent charged particles present therein. The target or
other valves.
It will be obvious to those skilled in the art that the
from the stable orbit to a target or collector device. This
steady magnetic ?eld can be radially increasing toward
collector may, if desired further or alternately receive the
particle at a velocity and energy to effect a physical or 75 the axis and the radio-frequency current can be such that
3,019,394.
5
the low frequency limit is at the outer orbit and the high
frequency limit near the center of the chamber. In this
system the ions would be accelerated from the axis toward
the outer orbits of the chamber, but in this case the
saw-tooth is from higher to lower frequency instead of
the reverse as previously described.
6
of said evacuated chamber between said D.-C. coils and
said evacuated chamber, and a radio-frequency alternating
current connected to said propeller shaped loops of wire,
said radio-frequency alternating current forming a mag
netic ?eld of azimuthal modulation in said evacuated
chamber.
5. An accelerator as claimed in claim 4, wherein said
evacuated chamber and said propeller shaped loops on
‘Obviously many modi?cations and variations of the
present invention are possible in the light of the above
teachings. It is therefore to be understood that within
opposite sides thereof are enclosed in a metal container,
the scope of the appended claims the invention may be 10 said metal container lying between said D.-C. coils and
practiced otherwise than as speci?cally described.
said propeller shaped loops of wire.
What is claimed is:
6. An accelerator for charged particles comprising a
1. An accelerator for charged particles comprising an
permanent magnet with a spacing between the pole
evacuated chamber means, means for producing a mag
pieces thereof to provide an axially symmetric magnetic
netic ?eld in which the magnetic lines of force are sym 15 ?eld, an evacuated chamber positioned in between the
metric with the axis of said chamber means, oppositely
magnetic pole pieces symmetrically with the magnetic
disposed propeller-shaped loops of Wire on each side of
?eld, oppositely disposed propeller-shaped loops of wire
said chamber means, and a frequency modulated radio
positioned on opposite sides of said evacuated chamber
frequency current connected to said loops of wire for
between said evacuated chamber and said pole pieces,
producing a sinusoidal magnetic ?eld coaxially superim
and a radio-frequency alternating current connected to
posed on said steady magnetic ?eld.
said propeller shaped loops of Wire, said radio-frequency
2. An accelerator as claimed in claim 1, wherein said
alternating current forming a magnetic ?eld of azimuthal
means for producing a magnetic ?eld across said chamber
modulation in said evacuated chamber.
means is produced by DC. coils on each side of said
7. An accelerator as claimed in claim 6, wherein said
chamber means.
25 evacuated chamber and said propeller-shaped loops on
3. An accelerator as claimed in claim 1, wherein said
opposite sides thereof are enclosed in a metal container,
means for producing a steady magnetic ?eld across said
said metal container lying between said pole pieces and
chamber means is produced by a permanent magnet.
said propeller-shaped loops of wire.
4. An accelertor for charged particles comprising
oppositely disposed D.-C. coils adapted to produce a mag 30
References Cited in the ?le of this patent
netic ?eld therebetween, an evacuated chamber positioned
UNITED STATES PATENTS
between said D.-C. coils within said magnetic ?eld axially
symmetric with said D.-C. coils, oppositely disposed pro
2,565,410
Tiley _______________ __ Aug. 21, 1951
peller shaped loops of wire positioned on opposite sides
2,598,301
Rajchman ___________ __ May 27, 1952
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