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Dec. 17, 1946.
c_ w_ HANSELL
2,412,772 7
ELECTRON DISCHARGE DEVICE GENERATOR
Filéd Feb. 6, 1945
1
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INVENTOP.
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Dec. 17, 1946.
c. w. HANSELL
2,412,772
ELECTRON DISCHARGE DEVICE GENERATOR
Filed Feb. 6, 1943
0.63 some:
2 Sheets-Sheet 2
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70
328
F/EL D COIL
JOUPOE OF a/vooE'
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387
582
dlanelwe W?ans’ell/
2,412,172
Patented Dec. 17, 1946
UNITED STATES PATENT OFFICE
2,412,772
ELECTRON DISCHARGE DEVICE
GENERATOR
Clarence W. Hansell, Port Jefferson, N. Y., assign
or to Radio Corporation of America, a corpora
tion of Delaware
Application February 6, 1943, Serial No. 474,943
24 Claims. (Cl. 250——36)
1
This invention relates to electron discharge de
vice oscillators, and more particularly to such
oscillators which require the use of a magnetic
?eld. One such oscillator is known in the art
as a magnetron.
An object of the present invention is to enable
a high frequency oscillation generator to oper
ate on the magnetic induction acceleration prin
2
as the electrons speed up. However, if the field‘
is increasing, this tends to increase the cene
tripetal force and decrease the diameter of the
spirals.
As an overall. result, during a con
siderable portion of each half cycle of the mag
netic ?eld variation, the increase in electron
velocity and the increase in magnetic ?eld
strength may have a combined effect which causes
the electrons to move around a circular path
Another object of the present invention is to 10 of nearly constant diameter while the electrons
provide an electron discharge device oscillator
accelerate continuously and eventually reach very
employing a changing magnetic ?eld to accelerate
great velocities corresponding to very high po-»
the electrons to a high velocity ‘and to curve them
tentials. In these known induction accelerators,
to follow an orbital path.
as shown by Steenbeck and. Kerst and Serber,
A further object is to provide a magnetron 15 the average magnetic ?ux density within the
ciple.
oscillator employing an alternating magnetic
?eld to produce high velocity electrons, which in
turn produce current pulses of very high radio
approximate circle described by the electron path
discharge device oscillator of the magnetron type
which requires only moderate anode-to-cathode
potentials, and employs a changing magnetic
enclosed by the circular path should correspond
to a ?eld intensity having an average magnitude,‘
must be twice the flux density on the electron
path in order that the diameter of the orbit may
frequency energy.
,
remain independent of the time and strength of
A still further object is to provide an electron 20 the ?eld; or putting it in other words, the flux
twice as great as the guiding ?eld.
?eld to accelerate the electrons to velocities cor
In accordance with the preferred embodiment
responding to much larger potentials.
25 of the present invention, oscillations are pro-‘
The principles underlying the acceleration of
duced in an electron discharge device of the
electrons by means of magnetic induction for
multi-anode segment type, in which the electrons’
the purpose of obtaining X-rays and nuclear
are accelerated to a high velocity by means of
disintegration are known and have been de
an alternating magnetic ?eld whose frequency is
scribed in such articles as “The acceleration of
very low compared to the frequency of the radio
frequency oscillations. Preferably, the mean
magnetic ?eld intensity within the area bounded
by approximately circular electron paths at some
distance inside the anodes should be somewhat
35 more than twice the magnetic ?eld intensity
twenty million electron volt betatron or induction
along the electron path, so that electrons accele
accelerator,” by D'. W. Kerst, published in “The
rated by- the ?eld tend to be thrown out into
Review of Scienti?c Instruments,” September,
the paths of increasing diameter, as the veloc
1942, pages 387 to 394; and United States Patent
ity increases, but for electron paths at and close
No, 2,103,303, granted to M. Steenbeck, Decem
to the anodes the ?eld intensity inside the paths
ber 28, 1937, to which reference is made for an
should be somewhat less than twice the magnetic
understanding of electron phenomena and theory
?eld intensity along the paths so that electrons
forming the basis of the present invention.
tend to be thrown inward toward paths some-7
Generally speaking, it is known that in an
what less in diameter than the anode diameter.
induction accelerator for producing X-rays and 45 Thus, electrons tend to move toward a common
nuclear disintegration, an alternating magnetic
orbit having a diameter somewhat less than the"
?eld is made to traverse an evacuated chamber
inside diameter of the anode, while they‘ are ‘be;
containing free electrons. As a consequence of
ing accelerated by the changing magnetic ?eld.‘
the presence of the changing magnetic ?eld, the
Thus, the system is so designed that the electrons
electrons are givenan acceleration by a force
as they are acceleratedmay be made to accumu
proportional to the rate of change of magnetic
late in a more or less cylindrical sheet rotating
?eld intensity. At the same time, the presence
rapidly inside the anode structure, and by nega-j ,
of the ?eld causes the electrons to be bent into
tive resistance effect this accumulation produces,
electrons by magnetic induction” by D. W. Kerst,
published in “Physical Review,” July 1, 1941, pages
47-53; “Electronic orbits in the induction acceler-_
ator,” by D. W. Kerst and R. Serber, published in
“Physical Review,” July 1, 1941, pages 53—58; “A
curved paths which, due to centrifugal force,
momentarily, extremely powerful oscillations at
tend to become spirals of increasing diameter 5,5 extremely high frequencies. During oscillation,"
2,412,772
3
:1
4
netic induction accelerator oscillation generator
the energy which is extracted from the electrons
by the high frequency oscillations tends to re
duce the diameters of the electron paths. The
frequency of the alternating magnetic ?eld may,
for example, be of the order of 500 cycles per
second. The accelerated electrons then produce
short duration pulses of radio frequency energy.
Each pulse of radio frequency energy may have a
of the invention;
Fig. 2 shows, partly schematically and partly
in cross-section, another embodiment of a mag
netic induction accelerator of the invention toe
gether with the associated circuits for suitably
energizing the elements of the'oscillator; and
Fig. 3 shows, in cross-section, the construc
tional details of another embodiment of the in
duration of one microsecond more or less. The
repetition rate of the pulses under an assumed 10 vention.
Referring to Figs. 1 and la, there are shown in
condition of a 500 cycle alternating magnetic
these two ?gures the essential constructional de
?eld will be 1000 per second. By superimposing
tails of a magnetron electron discharge device
a direct current magnetic ?eld upon the alter
oscillator designed to function on the magnetic
hating magnetic ?eld, the repetition rate of the
induction accelerator principle, in accordance
pulses may be made to be 500 per second. The
with one embodiment of this invention. Fig. la is
frequency of the oscillations produced by the
a cross-section of Fig. 1, along the lines Y—~Y.
oscillator of the invention may range anywhere
The anode and cathode elements of the mag
from 100 megacycles to 10,000 magacycles and
netron are mounted in an evacuated envelope lo
higher, depending upon the design of the oscil
cated in a gap in the central leg of a three-legged
lator and the values and adjustments of the
magnetic core .353 made of laminated iron suit
associated circuit elements. The pulse rate can,
ably machined, or of ‘powdered iron moulded into
if desired, be changed by changing the frequency
shape with a‘v suitable binder. The cathode is
of the alternating magnetic ?eld, and the phase
not shown in Fig. 1 but is identi?ed by reference
of the pulses can be changed (i. e., advanced
or retarded) by changing the phase of’ the al
25 numeral 2% in Fig. la.
The core 350 is excited
with a relatively low frequency magnetizing cur
rent ?owing through a pair of coils 35H, 35!.
These coils are mounted on opposite sides of the
anode and cathode structures and encircle the
ternating magnetic ?eld with respect to a‘source
of reference current of the same frequency as
the. alternating ?eld.
According to one embodiment of the invention, 30 magnetic pole pieces am, In use, they are pref
' and in order to assist in forcing electrons out
erably tuned by means of a condenser so that only
the power current must be supplied from an al
from the surface of the cathode, there is em
ternating current generator. The relatively low
ployed an induction accelerator magnetron device
for producing pulses of ultra high frequency os
frequency source for magnetizing the coils and
cillations, wherein the pole faces are so con
structed and arranged that the alternating mag
r' the condenser is not shown in Figs. 1 and 111 but
is illustrated and described in more detail later.
in connection With Fig. 2. The magnetic ?eld
netic ?eld which drives the electrons decreases
lines are illustrated in Fig. 1 by the dotted endless
in strength, at ?rst, with the distance from the
lines 220. The central leg of the magnetic core is
axis of the device and then increases in strength.
This is done by so shaping the magnetic pole 40 so designed that the pole faces m, 3H] on oppo~
site sides of the magnetron anode structure are.
faces that they are more closely spaced near the
shaped to provide a tapered magnetic ?eld.
axis of the magnetron along which the cathode
‘In Fig, 1 the curved lines 3“! illustrate genlies, and not soclosely spaced as the distance
erally and qualitatively a preferred type of mag
from the axis increases. Preferably, the distance
between the pole faces again decreases in the 45 netic pole face in cross-section, although other
vicinity of the anodes. Putting it in other words,
simpler types may be used.
»
The magnetron anode structure indicated by
the strength of the instantaneous magnetic ?eld
the reference numeral 210 is preferably generally
varies or tapers from a maximum in the vicinity
of the cathode to a minimum at a certain dis
of the type described in my United States Patent
tance from the cathode, and then increases again
2,217,745, or in my U. S. application Serial No.
in thevicinity of the anodes.
470,433, "?led December v29, 1942, in that it con
Further, over most of the range in which the
magnetic ?eld intensity decreases with increas
ing distance from the axis, the rate of decrease
is preferably such that the average intensity of r
the ?eld inside any given radius is greater than
twice the intensity at the radius. For radii ap
proaching'the radius of the inner surfaces of the
anode, the ?eld then stops decreasing and pref
erably increases with increasing radius.
60
One feature of the invention relates to the
means for making the electron current substan
. tially independent of cathode temperature, so
tains an even number of anode target portions
which together form a cylindrical anode struc
ture. These target portions, which may be any
desired even number (preferably six .or eight, al-»
though a lesser or greater number may be em
ployed) are shown in Fig. la insulated from one
another by insulating spacers .205, to prevent short
circuiting for the potentials induced by the chang
ing magnetic ?eld. The insulation spacers 205
are of high-resistance material to permit a small
amount of direct current to ?ow over them for
enabling positive polarizing potentials to be ap
plied to the anode segments. Alternatively, they
long as the temperature remains higher than the
temperature which would cause saturation of 65 may be of good insulating material and may be
shunted with resistances for passing the relatively
electron current. Such means may comprise a
smalldirect current anodecurrents.
grid or control electrode surrounding the oath
ode and positively charged relative thereto, and
a resistance in the cathode electrode current con
nection.
.
The anode structure as a whole surrounds a
cathode .290 which is a ring affair. The annular
70 ring cathode .200 may be heated by a ?lament in
.Other objects and features will appear from a
reading of the following description, which is ac
the interior thereof,- in the manner of an indi
rectly heated cylindrical cathode, or, if desired,
companiedby drawings wherein:
may be of a type which can ‘be heated by induc
Figs. -1 and la show, in cross-section, the con
tion from the alternating current driving mag
structional details of one embodiment of the mag 75 netic .?eld. By virtue of the shaping ofjthe pole
2,412,772
5
Ia'ceszin the manner illustrated in Fig. 1 (and
als'oinfFig. 2 to‘ be described later), there are
obtained variations in the magnetic ?eld in
tensity ‘with variation in distancefrom the axis
of the tube. The magnetic ?eld intensity is made
to ‘be highest near the cathode and the intensity
physics .text books. ,\See, for exampla'the tables
in the .bookl‘r‘Electron and Nuclear Physics,” by.
J. BartonaHoag, published by D. Van Nostrand
Company.
>
.
,
~
.The magnetic assembly, as described above,
should be ‘made of laminated or molded powdered
iron and should be so shaped as to bring about.
?rst diminishes at a certain minimum rate of
diminution until the distance approaches the
an accumulation of electrons emitted for a rela-‘
anode radius, then increases again more or less
tively long period of time into a ring of space
abruptlynear the radius of the inner surface of 10 charge circulating inside the anode segments in
the anodes.
.
a stabilized location, which, when the electrons
The output ‘coupling loop 352 serves to abstract
reach sufficiently high densities and velocities,
will cause oscillations to start. The starting of
the high frequency energy from the oscillation
generator.
‘
l
‘ It is’preferred that the anodes be given a mod
erate positive potential'relative to the cathode
oscillation, by slowing the electrons, will: render
15 the electron orbits unstable so that the diameter
of the orbits will decrease and stop the oscillation
again, after which the space charge will be dis;
sipated as the magnetic ?eld decreases again
and extracts the remaining energy from the elecl
tial will usually be far less than would be re 20 trons; Theoretically, at least, it is possible to ac-‘
quired to give electrons the ?nal velocities re
cumulate electrons bver a period which is,‘ say,
quired for oscillation at the desired frequencies.
1000
times longer than the duration of the pulse
‘ The shaping of the magnetic pole faces as ‘
of high frequency oscillation. For example, we
illustrated in Figs. 1A and 2 enables the alter
may be able to obtain pulses of high frequency
nating current magnetic driving ?eld to be most
l power which are less than one microsecond in
intense at the cathode surface, and then to de
length but which result from accumulation of‘
crease in strength rather rapidly with distance
electrons for, ‘say, 1000 microseconds. There
from the axis and then increase again. The de
fore, the instantaneous electron current taking
sired taper in magnetic ?eld intensity toward
part in producing‘ the oscillations may ‘corre-,
lower values with increasing distance from the 30 spondingly
be 1000 times the cathode emission‘.
cathode is obtained in ‘the arrangements illus
current. In practice, even if much lower ratios
trated, by shaping the pole pieces of the lami
of peak circulating current to cathode electron
nated electromagnet more or less as shown in
emission‘current
are obtained, still there will be
cross-section, instead of using flat'pole pieces.
great bene?t derived from the electron current
This pole shape has the additional advantage of 35 accumulation
effect.
'
tending to concentrate the electrons leaving the
‘ Although the “induction accelerator magnetron
cathode longitudinally of the axis toward a plane
pulser devices of Figs. 1 and la have been shown
midway between the pole pieces and at right
and described as having many anode segments, it
as an aid to drawing a larger number of elec
trons from ‘the cathode than is possible without
this positive potential on the anode. This poten
angles to the axis. Preferably, the mean mag
netic ?eld intensity within the area bounded by a
circular electron path near the anodes should
be somewhat more than twice the magnetic ?eld
intensity along the electron path, so that elec
trons accelerated by the ?eld tend to be thrown
out into paths of increasing diameter as the ve-,
locity increases, up to a diameter somewhat less
should be distinctly understood that for the lower _
radio frequencies of oscillation, and for lower
power outputs, it maybe advisable to use only
one pair of anode segments in the magnetron.
For considerably higher frequencies, and for
higher power outputs, a greater number of anode.
segments is preferable.
Fig. 2 illustrates one form of magnetron, to
than the anode diameter, after which, if they
gether with associated circuit elements, which
reach larger path diameters, they tend to be
can be employed in producing a complete induc
thrown inward toward the preferred path diam
tion accelerator magnetron pulser system.‘ The’
eter. By this means, as the electrons are ac 50 constructional details of the magnetron per se
celerated they may be made to accumulate in
are substantially like those shown in Figs. 1 and
more or less cylindrical sheet rotating rapidly
1a.. However, in Fig. 2 an anode structure hav
past the anode, and, by negative resistance ef
ing only two segments has been illustrated. In
fect, this accumulation can momentarily pro
Fig. 2, the magnetron is shown as having a coiled
duce extremely powerful oscillations at extremely 55 ?lament 360 in the center thereof along the‘axis.
high frequencies.
all
‘ The anode structure and the cathode are con
With the arrangement of Figs. 1 and 1a, when
tained ‘within an evacuated glass envelope 35L
the ?eld eoils 35!, 35f are energized with an al
The output coupling loops 352 are also shown
ternating current of, let us say, 500 cycles per , within the evacuated structure. The envelope 36I second, then maximum electron velocities are 60 is shown mounted in the gap of the central leg of
reached in one direction or the other around the
a three-legged magnetic core made of laminated
or powdered iron molded into shape with a suit
able binder. The pole faces are'shaped in the .g
through the velocities required to produce high
manner ‘illustrated in Fig. l to accumulate and
frequency oscillations of the magnetron. It is (55 concentrate electrons into a whirling'ring. The:
axis twice per cycle. If these maxim-um veloci
ties are high enough, they will reach or pass
possible to predict, in any particular case, what
the approximate maximum attainable electron
velocity potentials will be, up to a point where
two driving coils 35l, 35! providing the alternat
ing current magnetic ?eld are shown on oppoe
site sides of the evacuated envelope in a manner‘
oscillations start, by knowing the maximum ob
similar to that illustrated in Fig. 1. ‘A protective.‘
tainable magneticv ?eld intensity along a circular 70 metallic can 365 surrounds the foregoing assemjé:
path taken by the electrons just inside the anodes.
blage, though this is not essential in the prac- .
The electron potentials andvelocities ‘for elec-'
tice of the invention. ‘ ' ‘
trons moving in an orbit of any given radius in
The cathode is heated by means of any suit
any value of magnetic ?eld, over a large range,
‘able,
power source, illustrated ‘by ‘battery‘3_2ll,'v
are listed in tables which appear in certain 75 Whose leads extend through suitable apertures
2,412,772.
7
mounted in a re?ector for obtaining directive:
as shown. ‘The two anodes obtain. their. positive
polarizing potentials from an anode biasing. pow
er source illustrated by battery 32| overvpaths
which include the folded radiators 310, 310. The
two coils 351,. 35] are energized in series from
an audio frequency generator 315 which-by way
of example, may be of the order of 500 cycles, per
second. A condenser 316, in shunt, serves to
transmission.
tion energy conveyed to a radiator, or to radi
ators', by means of. a wave guide or a transmis
sion line. This feature is shown in more detail
in connection with Fig. 3.
.
'
The arrangement of Fig. 2 has one very great
advantage in that there should be no spurious os
cillation frequencies anywhere near thedesired
output frequency, since all other resonances in
the anode system are at frequencies too high-to‘
that ‘the tuning condenser 315 be adjustable. It
has a capacitance which is large compared. to the
tuned circuit or folded radiators 310, .310.
make oscillation at these frequencies possible.
This freedom from. spurious modes'of oscillation
is made‘- possible by the very high electron fveloc
ities which permit extremely high frequency 0s
cillation with only two anodes. The-foregoing
statement does not mean that magnetron-s with.
‘ In. order to have the electrons thrown. out from.
the cathode, the rate of diminution of ?eld in
tensity with distance from the axis along which
the cathode lies mustv be such that the intensity
along. any chosen circle‘ concentric with’ the axis
should: be somewhat less than one-half the mean
small distances. from the-cathode but this is not
important because the electric ?eld due to direct
Alternativelyrthe conductors of
the output circuit may be shielded, and oscilla
‘ tune the. generator and the coils. It is preferred
?eld intensity in the area enclosed by the circle.
In practice, this conditionca‘nnot be ful?lled for
8.
tion, the whole' oscillator assemblage may. be
both sides of the central legiof the magnetic: ‘core,
more than two anode segments may not be used.
when frequencies :higher than obtainable with
only .two anode segments are desired. The state
' ment merely means that the inductively driven
current potential between.v the Y anode segments
magnetron with two anode segments can reach
the same frequency band as that now obtained
with conventional magnetrons having a.v greater ,
and. cathodeserves to pull electrons away from
the cathode su?iciently to get them into orbits
number of anode segments. '
which tend to expand out toward the limiting
In the operation of .magnetic" induction elec
orbit diameter inside the anode. Likewise, to
tron acceleration magnetron oscillators, I have
have electrons which. reach orbits too large in di
ameterv thrown. back toward a chosen diameter . found that sometimes two or more pulses of os-.
cillation may take place while the magnetic ?eld
of orbit, the mean ?eld intensity inside any great—
is‘
increasing. This happens when the maximum
or diameter orbit than the preferred one must be
value of the alternating current magnetic field‘,
somewhat lessv than twice the average intensity
also taking into account‘ the direct current an.
of magnetic ?eld enclosed by the chosen orbit.
When the taper or variation in relative magnetic 35 ode-to-cathode potential, is too'great for: single
field: intensity is. correctly proportioned, electrons
accelerated inmost of the space inside the anodes
are simultaneously thrown out toward the an
I odes, but at a chosen» distance from the anodes
pulse operation of a particular magnetron oscil
lator assembly. For this condition of excess mag.
netic ?eld, it appears that, before the?eld has:
come near to its maximum value, a su?iciently
this tendency for the electrons to be thrown out 40 rapid and intense electron space charge maybe‘
accumulated to cause oscillations to start. There‘
is reversed and in the space near the anodes the
is
then a momentary pulse of oscillations which
radial force is toward the. cathode. As av result,
dispels
much of the space charge due to high
when the magnetic ?eld ‘is increasing, there is
frequency electric ?elds. Then, as the magnetic
an accumulation ofelectrons effective for a rel
atively long time into a whirling space charge 45 ?eld continues to increase, another ring of circu
lating space charge accumulates with increasing
ring at a little distance inside the anodes. As the
density'and velocity which may reach the pointof
density of the electrons in the whirling ring in
oscillation before the magnetic ?eld" has passed.
creases,'while the magnetic ?eld is increasing
through its maximum and begun to‘ decrease
from zero to its maximum, the velocity of the
again.
7
electrons is also increasing rapidly. This veloc
Thus, it appears that if sufficiently intense
ity may reach extremely high values for practical
magnetic ?elds are used, there may be a series of
values of magnetic ?eld intensity, (a few thou
pulses produced whilethe magnetic ?eld is in
sand g-aussese or less). By means. of suitable ad
creasing.v For. some‘purposes this may not be ob
justments of ?eld and potential, the velocities
jectionable but may even be desirable. For most
maybe made to reach such a value as to cause 55
purposes, it is undesirable and may be
negative resistance oscillations to start between ' signaling
a source of ‘operating, dif?culty which requires
the anode segments and the frequency of these
rather close design and adjustment
oscillations may be extremely high. By so de
To overcome this diiiiculty, by making it pos
signing. and adjusting the device that the velocity
sible
to obtain only one pulse of oscillation-each
60
of electrons reaches close to that for starting'os
time the magnetic field increases, I may make use
cillations, at the lowest frequency for which the
of the arrangement of Fig. 3.
.
anodes. tune, at just about the top of the cycle of
Fig. 3 shows in cross-section‘ theconstructional
magnetic: ?eld intensity, the magnetron maybe
caused to develop two pulses of very high radio,
frequency oscillation per cycle of low‘ frequency 65
drive‘ current. The beginning of oscillation is ac
companied by abstraction of energy’ from the
details of amulti-anode segmentmagnetron hav
whirling. electrons. in a manner to slow them down .
ing associated therewith several desirable features
not shown or described in connection with: the
other ?gures. In Fig. 3 the output energy derived
from. loop 352 is passed. through. a glass seal.» to.
ously. form. folded radiators.v With this combina
probe 38! , recti?ed by the diode: recti?er 3823.? and:
a coaxial transmission. line 38!] from which the
and‘ decrease the diameter of their orbit. This
tends to destroy the velocity and electron pathv 70 energy is utilized by an antenna‘ or radiator (not
shown). In order to. improve: and control the
diameter required for oscillation and, therefore
automatically quenches the oscillations. The an.
quenching
desired multiple
of thepulses,
oscillations,
a small
andpartto prevent
of the high
rangement of Fig. 2 shows the anode segments
tuned with conductors 3'50, 310, which simultane- ' frequency energy is taken by a capacity Coupling;
2,412,772.
applied: (ampli?ed ‘if necessary) vas a cut-0E
biasing potential to a control electrode or grid 383
surrounding the cathode. This cut-off biasing
potential is appliedtothe control electrode‘383
fora su?icient time to prevent undesired mul
tiple pulses. This is accomplished by charging
a condenser withthe recti?ed current and by con
trolling the value of resistance through which the
charge leaks off to control the time. Fig. 3 also
shows an adjustable resistance 390 in the cathode
electron current connection, as a result of which
the electron current may be made to be substan
tially, independent of ?lament temperature, so
long as the temperature remains higher than the
temperature which would cause ‘saturation of elec
tron current. It should be noted that the control
electrode 383 may be at, either a negative or a posi
10
the cathode and in the production of pulses of
radio frequency energy.
i
i
i
2. An ultra high frequency electron discharge
device oscillator comprising a multi-legged iron
magnetic core having at least one leg divided into
two parts by a gap, an evacuated envelope in
said gap, said envelope containing therein a cath
ode surrounded by an anode structure, said cath
ode extending in a direction generally parallel to,
the lines of ?ux across said gap, and, means for
activating said magnetic core, with an‘ alternating
current, the pole faces of said one leg which are
adjacent said envelope being shaped to obtain
maximum magnetic ?eld intensity in the region
near said cathode and a diminution of ?eld in
tensity with transverse distance from said cathode
until said distance approaches the anode radius
at which particular. distance the ?eld intensity
tive potential relative to the cathode. The cir
cuit arrangement illustrated provides an automa
again increases.
tic bias for the grid 333 due to current flowing in 20
3. An electron discharge device having a» cath
the resistance 39!]. The current through the re
ode, an anode structure surrounding said cath
sistance 390 tends to hold more nearly constant
ode and comprising a plurality of anode seg
charging current between pulses, and thus makes
ments, and means for producing a changing mag- .
the system independent of Variations in cathode
netic ?eld varying at an audio frequency rate
emission, provided the emission is su?ciently high 25 and having flux lines extending generally par- ‘
to supply the required current. If desired, the
allel to said cathode, whereby the electrons are
control of electron current through the grid elec
accelerated to'high velocities by said changing
trode may, be utilized to cause only one pulse
of‘ oscillation for each‘ period of increasing mag
netic ?eld‘ by controlling the rate of accumula 39
tion of rotating electron space charge. By this
means, recti?er 382‘may be made unnecessary.
In certain embodiments successfully tried out
in practice, the alternating current magnetic
magnetic ?eld and caused tofollow substantially
circular paths near said anodes, the mean mag~
netic ?eld intensity within the area bounded by
some of said circular electron paths within saidv
anode structure and whichare smaller than the
stable orbit necessary to produce oscillations be-,
ing greater than twice‘th‘e magnetic ?eld inten
?eld ‘was created by an audio frequency generator
sity along the electron path of the, stable orbit.
4. A magnetic induction accelerator oscillator
of ,500 ‘cycles. This‘ audio frequency is merely
mentioned by way of example, because where the
system is utilized for airplanes, the audio fre
comprising an electrondischarge ,devicehaving
meansfor producing electrons, a resonant anode.
quency generator may be of a standard frequency
surrounding said means, and meansvfor.
of say 400 cycles, in‘ view of the fact that 400 40 structure
producing an alternating magnetic ?eld which
cycle, generators have been standardized for use
varies at a rate considerably lower than the fre
in‘ some‘ airplane installations.
By
the , same '
token, a generator of greater audio frequency cur
rents may also be utilized, let us say of 800 cycles
or‘ more.
.
quency of the generated oscillations, said alter
nating magnetic ?eld serving to accelerate the
electrons to high velocities and to cause very
high frequency oscillations to take place while
saidl?eld is changing and to cause them to fol
If desired, a steady magnetic ?eld of suitable
value may be superimposed on the alternating
low substantially circular paths.
current magnetic ?eld and this may be done by
5. A magnetic induction accelerator ‘oscillator ‘
the same or another ?eld winding with direct
of.
ultra high frequency oscillations comprising a
cu‘rrent‘?owing in it.‘ This additional steady ?eld 50 cathode, an anode structure surrounding said
can thus act as a ‘biasing ?eld,” so that only the
positivev peaks of the alternating current magnetic '
?eld‘are capable of reaching values which will al
low the tube to oscillate. This ‘feature is shown
cathode and composed of an even number of
anode segments located on a circle, means for
causing a whirling ring of electron space charge
surrounding said cathode, said means including
' in Fig. 2 wherein the D. C. source‘ I00 serves to 55 means for producing an alternating magnetic
provide‘the steady magnet ?eld superimposed on
the alternating magnetic- ?eld. The condenser
I (H is a bypass condenser for the alternating out
put from generator 315.
_“What is claimed is:
.
?eld having ?ux lines extending generally par
allel ‘to said cathode and which varies at an audio.
frequency rate, said alternating magnetic ?eld ‘
serving to accelerate the electrons emitted by
said cathode to ‘high velocities and to cause very.
‘1; An ultra high frequency electron discharge so. high
frequency oscillations to take place» while
deviceoscillator comprising am‘agnetic core made
said ?eld is changing and to cause them to fol-‘
of iron material, said core having a leg madeuof
low substantially circular paths. ,
‘ i
two parts separated by a ‘gap, an evacuated en
A magnetic induction acceleratoroscillator‘
velope in said gap, said envelope containing there 65 of 6.ultra
high frequency oscillations comprising
ina cathode surrounded by a plurality of anodes,
apair
of
poles
of magnetic material, an electrode
a circuit for. producing a changing magnetic ?eld
structure located between said poles and includ
including a coil surrounding each part of said leg,
ing a cathode surrounded by an anode, the flux
and means ‘for causing a whirling ring of electron
lines
between said poles being parallel to said
space‘ charge surrounding said cathode, said 70 cathode,
means in circuit with‘ said. poles for
means including means for exciting said coils with
producing an alternating magnetic ?eld which
audio frequency currents and over a range of
varies at an audio frequencyrate, whereby the
values which‘ results in the substantial transfer of
electrons
emitted by said cathode are accelerated. .
energy from the resulting changing magnetic‘ ?eld
to high velocities and caused; to follow substan-‘
tothe electron space charge circulating around
75 tially circular paths, the pole faces being shaped
2,412,772‘
to obtain variations in magnetic ?eld intensity in
the space between the cathode and the anode
with a maximum near the cathode, the rate of
diminution of ?eld intensity with distance from
the cathode being such that the intensity along Cl
any chosen circle near the anode and concen
trio with the cathode is greater than zero and
somewhat less than half the mean ?eld intensity
12
velocity primarily as -a result of the rate of"
change of; the magnetic ?eld.
.7
l 12. -A magnetic induction accelerator “oscilla
tor generating high frequencyenergyin ipulses. I
which are short in duration compared with the.
time space between them, comprising ‘a cathode,
and an anode surrounding said cathode, and
means for causing a whirlingi ring of electron
in the area enclosed by the circle, whereby elec
space charge surrounding said cathode, said
- and a surrounding anode, and means for produc
generating high frequency energy in pulses which
trons» as they are accelerated move into circles 10 means including means for producing a magnetic
?eld of desired intensity, and means for chang
of increasing diameter.
ing the strength of said magnetic ?eld at a ire"7. ‘A magnetron oscillator including a cathode "
quency which is half the frequency of repetition
and a surrounding anode, and means for produc
of the pulses, said electrons being periodically
ing a magnetic ?eld which varies from a maxi
accelerated to a high velocity ‘primarily ‘as a»
mum near the cathode to a minimum in the
result of the rate of change of the magnetic ?eld.
space between said cathode and anode.
‘
13. A ‘magnetic vinduction accelerator oscillator
8. A magnetron ‘oscillator including a cathode
are of short duration compared to the time space
' ing a magnetic ?eld which varies from a maxi
mumrlnear the cathode to a minimum in the space , 20 between them, comprising a cathode, an anode
surrounding said cathode, means for causing va
between said cathode and anode, and then in
posed of an even number or anode segments sur
rounding said cathode, a control electrode sur
whirling ring of electron space charge surround
ing said cathode, said means including means ‘for
producing a unidirectional magnetic ?eld, and
means for modulating the (unidirectional mag-Y‘
netic ?eld strength at the frequency of repetition
rounding" said cathode and located in the space
between said cathode and anode structure, means
for producing an alternating magnetic ?eld
accelerated to a high velocity primarily asa re
sult of the rate of change ofthe magnetic ?eld.
creases at the location of said anode.
" .9. A magnetic induction accelerator oscillator
comprising a cathode, an anode structure com
which varies at an'audio frequency rate and
which, has flux lines extending parallel to said
of the pulses, said electrons being periodically
14. In an electron discharge device oscillation
30
generator for producing pulseslof radio frequency
oscillation, comprising a cathode, an anode,
cathode, a circuit for maintaining said control
means to provide a unidirectional electric poten
electrode at a positive potential relative to said
tial between anode and cathode, means for pro
ducing a rapidly rotating cylinder of' electron‘
cathode, and'a connection between said cathode
and said» control electrode, a resistance in the
cathode circuit, said resistance having such value
that ‘the ‘electron current is substantially inde
space charge surrounding said cathode, ‘and
means comprising a ‘cyclically changing magnetic
pendent of cathode temperature, so long as the
?eld of such value as to accelerate the electrons
to high velocities corresponding to those ~obtain-'
ture'which would cause saturation of electron 40 able by the application of considerably larger‘
anode-to-cathode potentials, and as a result of
current.
this acceleration to produce pulses of radio fre
.10; An electron ‘discharge device oscillator
quency energy.
'
'
comprisingla cathode, an anode structure com
15. In a magnetron high frequency oscillator
posed of an even number of anode segments sur
including a cathode, an anode, and means "for
rounding said‘ cathode,v means for causing a
temperature remains higher than the tempera
whirling ring of electron space charge surround
‘ producing a magnetic ?eld, means to ‘accumulate.
ing said cathode, said ‘means including an elec
tromagnet for producing a magnetic ?eld having
space charge ring surrounding said cathode for
flux. lines extending ‘substantially parallel to said
cathode, "a- source of audio frequency current of
electrons into a whirling high velocity electron
a relatively long period of time followed by uti
50 lization of the space charge to produce high fre
constant ‘amplitude continuously" exciting the
coil of said. electromagnet for producing a chang
ing magnetic ?eld to thereby accelerate elec
trons, 'a' condenser in shunt to said source for
tuning said source and‘said coil, and a source of 65
unidirectional . current
for
maintaining
said
anode structure at a positive potential relative
to? said cathode, the values or» said magnetic ?eld
quency oscillations for a relatively short time,
said last means including a, source of unidirec
tional potential coupled between said anode and‘
cathode for producing an electric ?eld and a.
source of cyclically varying current for produc_-.
ing an increasing magnetic ?eld, said last sources?‘
being so related and having such values that said
oscillator produces radio frequency oscillations.
and saidsour-ce of unidirectional current being
such and so related that said oscillator produces
primarily as a result of the absorption of energy‘
radio, frequency oscillations in pulses primarily
increasing magnetic ?eld.
as a result or the absorption of energy by .the
by’ the whirling electron, space charge, from the
'
16;, An electron discharge device oscillation.
generation system comprisinga cathode, a. reso-l
nant' anode structure surrounding,‘ said cathode”
11. vA magnetic induction accelerator high fre 65 a magnetizable core structure formed, to provide;
an aperture adapted to accommodate saidanode.
quency oscillator having a cathode, a plurality
accelerating electronsfrom the changing mag
netic?eld.
-
'
-
of. anodes, a magnetic ?eld, and means for
structure and a ‘pair of, polar projections on 09-,
causing a whirling ring of electron space charge
posite sides of said aperture, said‘ polar p'rojed-i,
surrounding ‘said ‘cathode, said means including
tions de?ning a pair of pole faces, said pole faces.
means to. cyclically and continuously vary the 70 being non-planar and so‘ shaped to. provide]
strength of the magnetic ?eld at a frequency far
clearly de?nedareas of maximumand minimum;
magnetic ?eld strength within the diameter of;
less, than the frequency of oscillation and over
said; aperture which graduallyfmerge into one‘
> a. rangev of values which-causes the, oscillator to
produce pulses of radio frequency energy, said
eIect-rons'ibeing periodically accelerated to a high 75
another. ,
17. An oscillation ‘generator system’ com'pris-"rv
2,412,772
13
14
ing a magnetizing winding, and a laminated core
structure formed to provide an aperture for ac
commodating an evacuated envelope containing
an electrode structure therein, and a pair of
polar projections on opposite sides of said aper
ture, said electrode structure including a linear
21. in an electron discharge device oscillation
generator for producing pulses of radio frequency
oscillation, comprising a cathode, an anode,
means to provide a unidirectional electric poten
tial between anode and cathode, means for pro
ducing a rapidly rotating cylinder of electron
space charge surrounding said cathode, and
means comprising a cyclically changing magnetic
‘ cathode and a resonant anode, said projections
de?ning pole faces having curved surfaces to pro
vide a magnetic ?eld which changes from a maxi
?eld of such value as to accelerate the electrons
mum value to a minimum value in a direction 10 to high velocities corresponding to those obtain
perpendicular to said cathode and at points be
tween said cathode and anode, said cathode be
ing positioned at a point near where the maxi
able by the application of considerably larger
anode-to-cathode potentials, and to produce
pulses of radio frequency energy, there being
mum value occurs.
means in said generator which provide a distribu
18. An electron discharge device oscillation 15 tion of magnetic ?eld intensity which causes
generator for producing pulses of high frequency
electrons accelerated to seek a common orbit.
energy, comprising a cathode and a surrounding
22. An electron discharge device having a cath- ‘
coaxial resonant anode structure, a source of uni
ode, an anode structure surrounding said cathode
directional potential for maintaining said anode
and comprising a plurality ‘of anode segments,
structure at a positive potential relative to said 20 and means for producing a changing magnetic
cathode, and means for accelerating the elec
?eld varying at a audio frequency rate and hav
trons emitted by said cathode to cause them to
ing ?ux lines extending generally parallel to said
follow orbital paths of very high velocities cor
cathode, whereby the electrons are accelerated to
responding to those obtainable by the applica
tion of appreciably larger anode-to-cathode po
high velocities by said changing magnetic ?eld
of alternating current of audio frequency coupled
to said coil for producing a changing magnetic
?eld which changes at an audio'frequency rate,
the mean magnetic ?eld intensity within the area 30
sity within the area bounded by some of said cir
cular electron paths nearer to said anode than
to said cathode being greater than twice the mag
25 and caused to follow substantially circular paths
tentials, said means including a coil and a source
, near said anodes, the mean magnetic ?eld inten
bounded by approximately circular electron paths
at some distance inside the anodes being some
what greater than twice the average magnetic
netic ?eld intensity along the electron path of the
stable orbit.
23. A magnetron oscillator including a cathode
and a, surrounding anode, means for producing a
magnetic ?eld which varies from a maximum
?eld intensity along the electron path, whereby
electrons accelerated by the ?eld tend to follow 35 near the cathode to a minimum in the space be
paths of increasing diameter as the velocity in
tween said cathode and anode, and means for
creases, the magnetic‘?eld intensity, however,
superimposing a direct current magnetic ?eld
inside the electron paths at or close to the anodes
upon said varying magnetic ?eld.
being somewhat less than twice the magnetic
24. A magnetic induction accelerator oscillator
?eld intensity along said last paths, whereby
of ultra high frequency oscillations comprising
electrons tend to follow paths of less diameter
a cathode, an anode structure surrounding said
than the anode diameter.
cathode and composed of an even number of
19. A magnetron oscillator including a cath
anode segments located on a circle, means for
ode and a surrounding resonant anode, and
causing a whirling ring of electron space charge
means for producing a magnetic ?eld which
varies in a radial direction from said cathode
from a maximum value to a minimum value in
the space between said cathode and anode.
20. A magnetic induction accelerator oscilla
tion generator of high radio frequency Waves, in
cluding an electron emitting cathode and an
anode, means for cyclically producing a time
surrounding said cathode, said means including
means for producing an alternating magnetic
?eld having ?ux lines extending generally par
allel to said cathode and which varies at an audio
frequency rate, said alternating magnetic ?eld
50 serving to acceleratethe electrons emitted by said '
cathode to high velocities and to cause very high
frequency oscillations to take place while said
?eld is changing and to cause them to follow sub
varying magnetic ?eld of non-uniform space
distribution so proportioned as to tend to con?ne
electrons from said cathode to a desired closed
orbit which is inherently stable for said space
stantially circular paths, and means for superim
posing a direct current magnetic ?eld upon said '
alternating magnetic ?eld.
distribution while continuously accelerating them
along the orbit, and means for causing said gen
erator to produce oscillations only after the elec
trons have been accelerated to a high velocity.
CLARENCE W. HANSELL.
60
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