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Патент USA US2412824

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Dec. 17, 1946.
E. D. MCARTHUR
2,412,824
MAGNETRON ‘
Filed June 22, 1942
2 Sheets-Sheet .1
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Inventor‘:
Elmer’ D. McArthun
by iVa/wy 63W
His Attorney.
Dec. 17, 1946.
E. D. MGARTHUR
2,412,824 '
MAGNETRON
Filed June 22, 1942
2 Sheets-Sheet 2
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Patented Dec. 17, 1946
. 2,412,824 "
UNITED STATES PATENT OFFICE
Elmer D. McArthur, Schenectady,- N. Y., assignor
to General Electric Company. a corporation of
New York
‘ Application June 22, 1942, Serial No. 447,903
9~ Claims.
The present invention relates to improvements
in high frequency electronic devices of the‘ mag
netron type.
a
‘
‘
As is well-known, the functioning of a
( Cl. 250-275)
tion of the cathode of the device of Fig. 1;
Fig. 4 is a detail view of one of the structural ele
ments of the device of Fig. 1; Fig. 5 is a longi
tudinal section of a modi?cation of the inven
magnetron as a generator of high frequency
waves depends upon the combined action of ap 5 tion; Fig. 6 is a longitudinal section illustrating
a further modi?cation, and Fig. 7 is a perspective
propriately directed electric and magnetic ?elds
of one element of the device of Fig. 6.
‘upon electrons which move in an interelectrode
Referring particularly to Fig. 1 there is shown
space. In general, the frequency of the waves
which may be developed by such devices is a func 10 an elongated cylindrical container, the lateral
wall structure of which is provided by a single
tion of the strength of the magnetic ?eld em
metal tube IU consisting of ferromagnetic ma-_
ployed, the required ?eld strength being higher
terial such as cold rolled steel or the like. The
for the higher frequencies. Because of this rela
tlonship,
magnetrons which are operable in the ‘
ends of the container are closed by?anged mem
. ultra-high frequency band
bers H and I2 which are welded or otherwise
have heretofore been
required to be associated with massive magnetic 15 hermetically joined to the inner surface of the
structures, leading to a cumbersome construction
for the apparatus as a whole.
It is a primary object of the present invention
part III. The outer surface of the envelope is
provided with a series of circumferentially ex
tending ?ns I4 which are adapted to serve as heat
dissipating elements and a somewhat larger
to provide an improved type of ultra-high fre
quency magnetron in which the weight and size 20 circular element l5 provided near the upper end
of the container acts as a‘ mounting '?ange for
of the operative parts, including especially the
magnetic elements, are reduced to a minimum.
_ In general this object is realized by the use of a
the device as a whole. (Any numbervof addi
tional cooling ?ns may be used, as required.)
Within the container and approximately at its
construction in which the magnetic ?eld is pro
duced by permanently magnetized pole pieces 25 central region there is provided an anode struc
ture 20 shown in plan view in Fig. 2. This com
located‘within a container which consists wholly
prises a circular member which has a relatively
or in part of ferromagnetic components arranged
large central opening 22 and a series of smaller
to provide a return path for magnetic flux
openings 23 arranged symmetrically about the
traversing the pole pieces. In this Way, with the
electrodes of the device located Within the con 30 central opening. The central opening is joined
to the openings 23 by means of radially extending
tainer in appropriate proximity to the pole pieces, ‘
slots 25.
it proves possible to obtain intense magnetic ?elds
The structure 20, which preferably consists of
in the interelectrode space without the use of a
‘ copper, is supported by being brazed to the in
separately excited electromagnet or other external
appurtenances. The resultant structure is light.
terior Wall surface of the part l0. To facilitate
the brazing operation, small channels 28 are cut
in weight and has the further advantage that
in the outer periphery of the structure and these
its magnetic components may be adjusted in the
_ are used to receive rings of brazing material ap
factory for best operation with the assurance that
plied before the anode structure is inserted with
no further adjustment will be required in the
40 in the container. A relatively large circumferen
?eld.
>
A further important feature of the improved
construction consists in an arrangement by.
which the current supply
wires for the cathode
are introduced through the center of one of the
magnetic pole pieces in a manner which avoids
tially extending channel 29 serves to reduce the
overall weight of the structure.
Within the opening 22 of the anode structure
there is provided an indirectly heated cathode
comprising a‘sleeve 32 of nickel or other suitable
material having ?anges 32' spun up at its ex
coupling the cathode circuit to the high fre
vquency ?elds generated by the operation of the
tremities. This sleeve, which may be coated ex
magnetron.
ternally with a suitable activating material such
as barium oxide, contains a ?lamentary heater
The features of the invention desired to be
protected herein are pointed out in the appended 50 34 by which it may be maintained at an emissive
temperature. One end of the cathode sleeve is
claims. The invention itself, together with its
further objects and advantages may best be un- ' closed by a metal disk 36 while an apertured disk
derstood by reference to the following descrip
tion taken in connection with the drawings in
which Fig. 1 is a vertical section of a magnetron
device suitably embodying the invention; Fig. 2'
is a transverse sectional view serving to illustrate
the anode structure employed in the device of
Fig. 1; Fig. 3 is an enlarged view in partial sec
31 partially closes its other extremity.
In the operation of the device a space charge is
assumed to be developed in the‘space between the
structure by the application of a suitable poten
tial impressed between one of the cathode lead-in
wires 31’ and 31" and the container Ill to which
the 31.10518 structure is directly conductively con
2,412,824
3
Fig. 1, each of these rings is interposed between
charge are given a spiral or orbital motion by a
one surface of the anode structure and the sur
Vnected. The electrons which compose this space
face of an apertured disk 56, 51, each disk in
magnetic ?eld produced by means shortly to be
tumrbeing
in abutment with an appropriately
described, and their resultant gyrations about the
formed‘ shoulder provided on the adjacent pole
cathode produce excitation of the anode structure Cl piece
as indicated at 58 and 59. The spacing
at its resonant frequency. The functioning of
rings 54 and 55 may be welded in place before the anode structure in the latter connection may
the pole pieces are inserted within the container.
be explained from one point of view by consider
With the pole pieces 40 and 4| arranged inside
ing that it is made up of a plurality of mutually
container In it becomes convenient to use the
coupled resonant units in each of which_>in-. 10 the
pole pieces as a supporting means for the cathode
ductance is provided by the wall surface bounding
structure 32. This may be done, for example,
one of the circular openings 23 and capacitance
by the use of a pair of insulating beads 62 and
is provided by the opposing surface of one of the
63 which are respectively centered in axially ex
slots 25. Taking this viewpoint, it will be seen
tending. openings 65 and 66 cut in the pole pieces.
that the operating frequency is in a large measure
The lower bead 63 is provided with a central
determined by the dimensions of the openings 23.
For the purpose of providing a magnetic ?eld
of suflicient intensity to permit the apparatus to
» apertureadapted to receive a. centering stud 68
projecting downwardly ,from the cathode end
plate 36. The upper head 62 has two separate
function in its intended fashion, there are pro
vided within the container I0 tapered magnetic 20 openings 10 and ‘H through which the current
supply wires 31' and 31" extend. These wires,
pole pieces 4|] and 4| which are directed axially
which are held in spaced relation within the
of the container and which extend in close prox
channel 65 by means of additional insulators 16
imity to the upper and lower surfaces of the an
and 11, are joined at their extremities to rela
ode structure 20. For present purposes these
tively heavy lead-in wires 19 and 80. These in
pole pieces are assumed to be permanently mag
turn are sealed into the container through a
netized in such a sense that the north pole of
glass-to-metal seal which comprises a body of
one faces the'south pole of the other.
glass 8| fused to the extremity of a metal eyelet
In order to assure the existence of a magnetic
82. This arrangement of the cathode supply
?eld of the required intensity the pole pieces 40
leads
has the particular advantage that it avoids
and 4| should be constituted of a magnetizable
any substantial coupling between the cathode
substance having a high coercive force and a high
energy factor. One of the materials which may
be used in this connection is that known as
supply circuit and the high frequency ?elds gen
erated in the interelectrode space, thus being a
consequence of the fact that :both the supply leads
Alnico, meaning a particular class of alloys of
aluminum, nickel and cobalt. Alloys of this type 35 extend axially with respect to the‘ electrode
structures and are fully shielded by the body of
are described, for example, in Tokuschichi Mishi
the pole piece 40.
.
ma Patents 2,027,994 to 2,028,000 inclusive and
In fabricating the construction of Fig. 1 the
are further described in W. E. Ruder Patents
anode structure 20 is ?rst positioned within the
1,947,274 and 1,968,569. Other magnetic mate
rials which may be employed are alloys of iron, 40 container part l0 and secured in place. There
after, the spacing rings 54 and 55 are inserted
nickel and titanium as described, for example, in
and ?nally the pole pieces and their associated
Honda Patents 2,105,652 and 2,105,658.
basing structures are put in place. The cathode
32 may be preliminarily assembled with the pole
piece 40 before that part is lowered into the con
tainer. After the closure members II and |2
If the pole pieces 40 and 4| are constituted of
Alnico, which'is considered to be a preferred ma
terial, they are normallyprepared in cast form
and have their critical surfaces ?nished by grind
have been welded in, the container may be evacu- ,
ing. The ground surfaces may include, for exam
ated through an exhaust tabulation 85, which is
ple, the end surfaces of both pole pieces and the
then sealed off as indicated at 86.
peripheral surfaces indicated by the numerals 44
and 45 respectively. These latter surfaces, to 50 To permit the evacuation of all parts of the
container, it is necessary to provide suitable pas
gether with the end surfaces which adjoin them
sageways connecting the various sections of the
may advantageously be copper plated to reduce
enclosed space. To this end, the disk-like mem
losses attributable to high frequency circulating
bers 48 and” may be provided with radially ex
currents induced by the proximity of these sur
tending slots such as the slot 49' which is illus
faces to the interelectrode spaces in which high
trated
in Fig. 4 in connection with the part 49.
frequency waves are generated.
In order to provide a low reluctance connec
In this way the channel 66 is enabled to commu
nicate with the space outside the pole piece 4|
through the channel 49', and a similar connection
tainer, the pole pieces may be respectively seated 60 with reference to the channel 65 is provided by
the corresponding slot in the part 48. With the
upon relatively thick disk-like members 48 and
same object in view, openings’ 90 may be provided
49 consisting of ferro-magnetic material such as
in the positioning disks 56 and 51. An opening
steel. For the purpose of securing the pole pieces
tion between the base extremities of the respec
tive pole pieces and the lateral wall of the con
92 provided in one surface of the anode structure
?xedly to these basing members, use may be made
of clamping rings 5| and 52 slipped over the pole 65 20 makes the channel 29 accessible to the .evacu
atingsystem.
pieces and welded to the basing members. Each
, After the container is fully evacuated and sealed
basing member is of such diameter as to ?t snugly
off, the pole pieces 40 and 4| may be magnetized
within the tubular container part III so as to
in a known manner by being placed in a magnetic
provide a low reluctance connection with that
?eld of suitable intensity. It is an advantage of
part, and-is welded to one of the closure mem 70
the illustrated construction that for each partic-.
bers||,|2.
-
_
.
Accurate spacing of the pole pieces 40 and
with reference to the anode structure 20 may
obtained by the use of spacing rings 54 and
used in the manner indicated. As is 8.130“!!!
4|
be
55
in
ular device the degree of magnetization of the
pole pieces can be adjusted in the factory to a
value which assures the most satisfactory opera
' tion of the device as a whole. Since all the parts
2,412,824.
5
.
of the tube structure are ?xed and since no ex
ternal magnetic appurtenances have to be added
in the ?eld, installation and use of these tubes is
greatly simpli?ed.
‘
When a device such ‘as that‘illustrated in Fig.
6
structure by means of a coupling loop, which,
however, does not appear in the particular view
of the structure which is afforded by Fig. 5.
The cathode, which extends centrally through
1 is placed in operation, it is, of course, necessary ‘ 5 the anode structure I24, comprises an emissive
tubular part I3i9-which terminates in flanges I40
to provide some means for abstracting a portion
of the energy developed in the interelectrode
and I40’. A heater (not shown) is arranged with
in the part I39 and serves to maintain it at emis
sive temperature. The cathode ?ange I 40 is seated
rangement which includes a coupling loop I00
introduced through an opening I02 in the wall of 10 in an. appropriately formed recess provided in the
space.
This may be done in one way by an ar
lower extremity of the pole piece I20 so that the
the anode structure. The coupling loop in the
cathode is electrically grounded to the magnetic
arrangement shown has an extension in the form
structure. A lead-in wire I 4| which extends ax
of a wire I04 which constitutes the inner con
ially through the pole pieces I20 and through an
ductor of a coaxial transmission line having a
tubular part I05 as its outer conductor. The tube 15' insulating bead I42 at the upper end of the oath
ode make it possible to supply heating current to
I05 passes through the wall of the container cyl
the cathode ?lament, a return path for this cur- _
inder I 0 and may be exteriorly connected through
rent being provided through the grounded struc
a tapering enlargement I01 with a somewhat
larger tubualr part I08. In similar fashion, the 20 ture of the cathode proper.
It is not essential that a magnetron produced
wire I04 is merged into a larger conductor I09
in accordance with the invention be symmetrical
through a tapered transition region II 0 which
with respect to a central transverse plane, and
is of such con?guration as to avoid any substan
the alternative embodiment of Fig. 6 represents a
tial change in the characteristic impedance of
construction in which this condition is not ful
the line. (The ful?llment of this latter condi
tion requires the maintenance of a constant ratio 25 ?lled. In this case a permanently magnetized
between the diameters of‘ the outer and inner
conductors.) The conductors I08 and I09 may
pole piece I50 is enclosed within a ferromagnetic
container I5I which forms part of the magnetic
circuit. The pole piece I50 is based upon a ferro
connect with an antenna or other agency for uti
magnetic header I53 which closes the upper end
lizing the high frequency energy developed by the
apparatus, and their size is determined with this 30 of the container I5I andvis partially supported
within the container by means of a non-mag
end in'view. The vacuum tightness of the con
netic ring I54. A cathode structure I51 depends
tainer is preserved by means of a head of glass
centrally from the lower extremity of the pole
II2 which forms a seal between the conductor
piece I50, being insulated from the pole structure
I09 and the surrounding tubular member I08.
In an arrangment such as that of Fig. 1 in 35 by means of an interposed insulating element
indicated at I58. Potential and heating current
which the cathode is not at ground potential it
are supplied to the cathode through lead-in
is necessary to provide an insulating transformer
wires I59.
in connection with the supply of ?lament heating
Below the cathode I51 there is provided a
current. In order to avoid this requirement it is
preferable in some instances to employ a struc 40 multicavity anode I62 which is shown in perspec
tive detail in Fig. 7. This anode is formed of
ture in which the cathode is grounded to the
magnetic material (e. g., iron or steel) so that
structure of the enclosure and to adopt provisions
it serves not only as an anode but also as a oom_
for insulating the anode from ground. This pos
plementary pole piece for the magnetic pole I50.
sibility is illustrated; in Fig. 5.
In the ?gure last referred to the magnetic ~35 However, it is not necessarily permanently mag-'
structure is of the same general character as
that described in connection with Fig, 1 and com
netized.
The exposed surfaces of the anode are
'coated, by plating or otherwise, with copper or
other highly conductive material adapted to per
prises permanently magnetized pole pieces I 20
mit the free circulation of high frequency cur
and HI which are enclosed within a metallic cone
tainer I22 consisting of ferromagnetic material. 50 rents. The whole anode structure is based upon
the bottom closure I63 of the container so that a
The pole pieces have a low reluctance magnetic
complete magnetic circuit is provided through
connection with the structure of the enclosure so
the container walls.
‘
that a return path is provided for the magnetic
As appears most clearly in Fig. 7 the anode is
?ux.
The anode structure, which is indicated at I24, 55 provided with a number of radially extending
circular channels I65 which communicate ‘with
is functionally similar to the anode 20 of Fig. 1,
the space'above the anode through slots I 66. The
being provided internally with a plurality of res
channels and the slots connect at their inner
onant cavities (not shown) which have a reso
ends with an opening I61 formed centrally in the
nant frequency corresponding to the desired fre
quency of operation of the apparatus. The struc (so anode structure. By virtue of this arrangement
the anode is enabled to function as a multi-cavity
‘ture is insulated from the metallic enclosure I22
resonator adapted to be excited by the rotating
and from the other parts of the device by means
space charge developed in proximity to its upper
of glass insulators I26 and I21 which serve also
surface by the electrons emitted from the cathode
as seal-in means for anode terminals I 28 and I29.
These terminals are associated with ‘cup-like 0.; I51. The high frequency energy thus developed
in the resonant cavities may be utilized externally
members I30 and I3I which are sealed into the
by the use of a coupling loop (not shown) extend
glass rings I26 and I21 respectively, the rings in
ing into one of the cavities in the manner indi
turn ‘being supported from metal eyelets I33 and
cated in Fig. l.
I34 secured to the outer surface of the enclosure. To
The arrangement of Fig. 6 has the particular
Heavy conductive rods I36 and I31 extending be
advantage that no signi?cant magnetic gap ex
tween the anode structure I24 and the cap mem
ists between the anode I62, viewed as a magnetic
bers I 30 and I 3I afford a rigid support for the
pole piece, andv thesource of the electrons de
anode structure.
Power is assumed to be taken out of the anode 75 sired to be a?ected by the magnetic ?eld. Be
cause of this circumstance the effective reluc
9,419,884.‘
7'
''
tance of-the total magnetic path is reduced. This
effect can-“be still further enhanced by fore
shorteninglthe cathode structure to bring the
pole pieces ISO-and I62 into closer proximity to
piece, and an anode and a cathode in proximity
to said pole piece and within the in?uence of said
magnetic ?eld, said cathode comprising an equi
potential emitting part, a ?lamentary heater for,
- discharge devices having transversely extending
said part and a pair of current supply wires for
said heater extending axially through one of said
pole pieces and sealed through a wall of said con
anode cavity constructions such as those illus-’
trated by ‘Figures 6 and '1 since the invention
tainer.
5. An electronic discharge device including an
parting from the invention. I therefore aim in
erating electrodes within said container and in ‘
scope of the foregoing disclosure.
-What I claim as new and desire to secure by
providing the envelope of said device and includ
one another.
'
'
In.this patent I do not claim magnetron type
illustrated thereby is covered broadly by certain 10 elongated cylindrical container forming the en
velope of said device and having its‘ lateral walls
claims in my pending application Ser. No. 674,194,
constituted principally of ferromagnetic material,
?led June 4, 1946, and constituting a continua
ferromagnetic members closing the ends of the
tion in part of the application for this patent.
container, a pair of magnetic pole pieces'respec
While the invention has been described by ref
tively supported from said members in mutually
erence to particular embodiments thereof, it will
spaced relation within said container and in
be understood that numerous modi?cations may
magnetic contact with said members, and coop
be made by those skilled in the art without de
the space between said ‘pole pieces.
the appended claims to cover all such equivalent
6. A magnetron device comprising a container
variations as come within the. true spirit and 20
‘ Letters Patent of the United States is:
1. An electronic device comprising a container
forming the envelope of said device and having a
part of its wall structure constituted of ferromag
netic material, means including a permanently
ing a hollow cylinder of ferromagnetic material,
a self-resonant anode structure supported within
said cylinder intermediate its ends, a cathode
structure concentric with said anode structure,
and magnetic pole pieces within said container
adjacent the ends thereof and on opposite sides
of said anode structure, each of said pole pieces
having a direct ferromagnetic connection with
‘producing a magnetic ?eld in a particular region
of the enclosed space; and cooperating electrode 30 said cylinder whereby the combination of said
magnetized pole piece ‘within said container for
- elements located in the said magnetic ?eld, said
pole piece having a direct magnetic connection
cylinder and said connections provides a low re
luctance return path for magnetic flux traversing
the pole pieces.
"with the ferromagneticpart of said wall struc
'7. An electronic device comprising an elon
ture and forming therewith a low reluctance path
which is-closed except for region of said elec 35 gated container forming the envelope of said detrodes.
'
vice and having a part of its wall structure con
stituted of ferromagnetic material, a self-reso
nant anode structure within said container and
ated'container having its walls constituted main
intermediate the ends thereof, a‘ cathode in coop
ly of ferromagnetic material, means including
a permanently magnetized pole piece within the 40 eratively spaced relation with respect to said
anode structure, magnetic pole pieces within said
container for producing a localized magnetic ?eld,
2. An electronic device comprising an evacu-v
' a ferromagnetic member supporting said pole
piece and providing a direct magnetic connection
between the pole piece and a ferromagnetic'por
tion of the wall of the container, whereby a low
reluctance return path‘is provided for magnetic ‘
container'on opposite sides of said anode struc
ture and having a low reluctance connection with
said container, and spacing means interposed be
tween said anode structure and said pole pieces
maintaining them in a predetermined structural
relationship.
flux traversing the pole piece, and mutually co
8. A magnetron comprising an evacuated c011
operating discharge electrodes in proximity to
tainer constituted principally of ferromagnetic
said pole piece and within the in?uence of the
50 metal, electrodes cooperatively spaced within said
said magnetic ?eld.
container, one of said electrodes being connected
‘ 3. A magnetron device comprising a container
directly to the container, another of said elec
forming an envelope of the device and having its
trodes being supported in insulating relationship
lateral walls constituted principally of ferromag
to said container, and means including a perma
netic material, ferromagnetic members extending
transversely of said container and presenting sur 55 nently magnetized element within said container
for producing a magnetic ?eld in the space be
faces within the container, a pair of magnetic
tween said electrodes, said container having a
pole pieces in mutually spaced relation within said
direct ferromagnetic connection with said ele
container, said pole pieces being respectively sup
‘ported by said ferromagnetic members, whereby
a low reluctance ?ux path between the remote ex
tremities of said pole pieces is provided through
said members and. through. the lateral walls of
the container, and cooperating electrode ele
ments positioned in the space between said pole
pieces.
4. Electronic apparatus comprising a container
having a substantial part of its wall structure
constituted of ferromagnetic material, means in
cluding a permanently magnetized pole piece
within said container for producing a magnetic
?eld therein, said pole piece having a low reluc
tance connection with the wall structure of said
container whereby said wall structure provides a
return path for magnetic ?ux traversing the pole
ment to provide a low reluctance return path for
60 magnetic ?ux traversing said element.
9. A magnetron device comprising a container
providing the envelope of said device and includ
ing a hollow cylinder of ferromagnetic material,
a self-resonant anode structure supported within
65 said cylinder intermediate its ends, a cathode
structure concentric with said anode structure,
and pole pieces of permanently magnetized mate
rial within said containeron opposite sides of said
anode structure, said pole pieces each having a
direct and continuous ferromagnetic connection
with said cylinder whereby the cylinder provides
a low reluctance return path for magnetic ?ux
traversing the pole pieces.
ELMER D. MCARTHUR.
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