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NOV» 12, w46»
Filed Jan. 3, 1942
2 Sheets-Sheet 1
Nav. 12, 1945.
Filed Jan. 3, 1942
2 Sheets-Sheet 2
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? ¿ma,ßATÍ'ORNEY.
Patented Nov. 12, 1946
David E. Kenyon, Smithtown, N. Y., assigner to
Sperry Gyroscope Company, Inc., a corporation
of New York
Application January 3, 1942, Serial No. 425,491
13 Claims. (Cl. Z50-27.5)
This invention relates, generally, to vacuum
tube structures and the invention has reference,
more particularly, to a cathode structure designed
for the production of high current density elec
used in starting emission does so in only a lim
ited area of the emitter surface, the emission
being spread from the original hot spot after
the current through said heater element is turned
tron beams. In prior art cathodes for such pur
poses, great difficulty has been experienced in
Other objects and advantages will become ap
producing heater coils having very low magnetic
parent from the speciñcation, taken in connec
fields, Said magnetic fields having an undesirable
tion with the accompanying drawings wherein
tendency to modulate the electron beam unless
the invention is embodied in concrete form.
special shielding precautions are resorted to. It 10
In the drawings:
has also generally been necessary to use oxide
Fig. 1 is a fragmentary perspective longitudi
coated emitting surfaces in order to produce
nal cross-sectional view and wiring diagram of
usa-ble emission currents, the temperature of the
a form of the invention.
emitting surface being usually limited by the
Fig. 2 is a longitudinal cross-sectional view,
maximum temperature at which the cathode
partly in elevation, showing an application of the
heater element can be operated and still give the
cathode disclosed in Fig. 1.
device a reasonable life of operation. The pres
Fig. 3 is a cross-sectional view of a modified
ent invention discloses a cathode structure rela
form of a portion of Fig. 1.
tively free of magnetic fields and whose emitting
Fig. 4 is a fragmentary longitudinal cross-sec
surface may be operated at elevated temperatures. 20 tional view of another modiñed form of the pres
The principal object of the present invention is
ent invention.
to provide a cathode having an emitting surface p
Fig. 5 is a plan view on a reduced scale of the
portion that is heated by electron bombardment,
structure shown in Fig. 4, taken along the line
the electrons for effecting such bombardment
5_5 of Fig. 4.
being supplied from a second surface.
Fig. 6 is a fragmentary longitudinal cross-sec
Another object is to provide means for heating
tional view of a further modification of the pres
said second surface to a predetermined initial
' ent invention.
temperature, and switching mechanism for then
Similar characters of reference are used in all
stopping said heater means and causing the ñrst
of the above figures to indicate corresponding
and second emitter surfaces to heat each other 30 parts.
by means of a high voltage alternating current
Referring now to Fig. 1, there is shown a pre
acting from electrons emitted on the adjacent
form of the present invention. lSpiral
surfaces of the two emitters.
heater element I, supported by leads 2 and 3
An object is to provide a cathode emission sur
which may pass through the conventional type
face’relatively free of warping due to thermal 35 ' glass
press (not shown) usually used in vacuum
to provide current lead and sup
Yet another object is to provide such a cathode
port means, is positioned preferably centrally
structure for the production of cylindrical elec
within a heat shield inner wall 4, leads 2 and 3
tron beams.
Still another object is the provision of such a 40 passing through holes 5 and 6 in end wall 1 of
the heat shield.~ 'I‘his heat shield has a folded
cathode structure for the production of radially
back portion in the form of a cylindrical Wall 8
projected electron beams.
spaced outwardly from and concentric to wall 4,
Yet another object is to provide such a cathode
to provide more effective heat shielding by the
in which all elements in use in other than start
ing operations are heated by means of high volt 45 well vknown double-wall eiïect. Wall 8 extends
below end wall 7 of said heat shield, and pressed
age, low current electron beams, thus minimiz
into the inner diameter of wall 8 is a second end
ing undesirable effects due to magnetic ñelds.
wall 9 for the heat shield, leads 2 and 3 passing
An object is to provide a cathode structure in
through holes I 0 and II in wall II.
which heating ñlaments are operated only in
centrally above spiral heater element
starting emission, thus allowing said emitting sur 50 I Positioned
is disk I2 which may be somewhat dished, in
faces to be operated at very elevated tempera
which case the convex side of disk I2 faces heater
I. Somewhat spaced from disk I2 on the side
A further object of the invention is the provi
sion 0f a cylindrical, radial or other beam pro
thereof away from heater I is a second disk I3 .
which may also be dished similarly to disk I2.
ducing cathode in which the heating filament 55 Heater _I may be of tungsten and disks I2 and I3
of tantalum, columbium, nickel, or other metal 0f
low electron work function; or heater I and disks
causes electrons emitted from heater I to strike
disk I2 with high velocity, thus heating disk I2
` vI2 and ,I3may be oxide-coated with any of the
to a temperature such that its upper side also
begins to emit electrons. At this time, time ac
well' known barium, strontium, etc., emission ma
terials. On the side of disk |3 away from disk
I2 is a focussing element with a central aperture
nearly as large in diameter as the diameter of
disk I3 and consisting of an inclined annular
portion I4, a flat annular surface I5 `substan- "
tially perpendicular to the axis of symmetry of
the structure, l and aV cylindrical y-wall surface“ |6
extending- fromsurface I5 vconcentric to heat
shield wall 8 and of somewhat greater diameter.
tuated relay 43 has been set to open its associated »
circuits, and time delay relay 4I closes, thus plac
ing a moderately high alternating current volt
age between disks I2 and I3. By energizing the
disks I2 and I3 through symmetrically disposed
leads 26 and 24 respectively, the magnetic fields
i produced by the flow of alternating current into
ther disks neutralize one another- and inhibit a1
ternating current modulation of the electron
Focussing shield I4, I5, I6 may be supported by( ' stream. Electrons being emitted from disk I2
three leads I1, I8, -I'S spaced 120°„apartand exf
.are accelerated toward disk I3 during alternate
tending into the glass press of the vacuum kenve
half cycles and impinge upon said disk I3 with
lope surrounding the cathode. Focussing shield
I4, I5, I6, supports, in turn, disk I3 by means of
high velocity, thus heating it to incandescence.
LAt the time disk I3 is raised to a sufilcient tem
angularly spaced wires 20, preferably-symmetri- '
perature, it begins to emit electrons from -both
cally disposed about the axis of the disk, e. g., 20 surfaces.` Those emitted from its under surface
at 120° intervals in the manner shown in Fig. 3
are accelerated toward disk I 2 striking the latter.
spot welded to the inner surfaces of shield por
The alternating current voltage between disks I2
tion I4 and disk I3. Heat shield 4, 8 may be`
and I3 thus maintains both at a proper tempera
supported by three angularly spaced leads 2|,
also extending into the aforementioned glass
Time delay relay 42 is set to close `its asso
ciated circuit at the time when the upper surface
Disk I2 may be supported by three angularly
of disk I3 has reached a sufficient temperature to
spaced leads 24 projecting radially'through holes
emit electrons. Relay 42 then applies a high di
29 and 30 in Walls 4 and 8 of the heat shield.
rect accelerating voltage between emission sur
Leads 24 ,are supported by and are equally spaced
face I3 and electrode 3|.
_about a current distributor >such as a ring 25
Electrode 3| and its contained aperture 33 and
concentric toY wall I6, which ring in turn is sup
grids 32, and focussing shield I4, I5, I6 are so
ported from theglass press by three leads 26, 21,
designed that there is projected an electron beam
28, which may be mutually spaced at 120°. ~ The
cathode structure may be positioned at a proper
distance froman accelerating electrode 3 I, which
may contain a central aperture 33 concentric to
the axis of symmetry vof the cathode, containing
therein grid bars 32, whose function is to further
improve the shape of the electron beamto'be
vprojected through aperture 33.
In use, there is preferably applied to spiral
heater I aI relatively low alternating voltage by
means of leads 2, 3 from the connected second
ary 34 of transformer 35. A moderate alternat
ing voltage isv also applied between lead 2 and
>diskr|2 from the secondary 36 of transformer 35
via lead 26, ring 25 and lead 24. Preferably a
relatively high alternating voltage is applied be
of uniform round cross-section into the space on
the side of electrode 3| away from emitter I3.
Thus, it is seen that when the cathode is in its
final state of operation the heating and acceler
ating currents involved are high voltage, low cur
40 rent ones, and that the only alternating heating
voltage involved is well shielded inside of mem
bers 4, 8, I2, I3, I4, I5, I6. Further, the final
temperatures of emission sources I2 and I3 are
not determined by a resistance heater unit -such
as the spiral heater I, and since this spiral heater
lI is in use only in starting the cathode, its life
time is greatly increased. In fact, disks I2 and
I3 may even be operated at temperatures much
higher than those at which oxide-coated emitters
tween disks I2 and I3 from a transformer 31 by 50 are usable, so that pure metal emitters of tan
talum, columbium and similar metals may be
way of lead I1, focussing shield I6, I5, I4, and
used. It is evident to one skilled in the art that
wires 20 on theone side and lead 26,' ring 25 and
a variety of starting devices are usable to give
lead 24` on` the other. ' A moderately high direct
the desired starting cycle, so that the system of
current voltage is applied between emitter I3 and
electrode 3| from power supply 39 via lead I1,
focussing shield |6,'»|5, I4, and wires 20 on the
shown is intended to lbe purely illustrative.
55 .relays
A cathode producing such an electron beam has»
many uses, such as in beam power tubes, cathode
v 44 is closed, time delay relays IIIA` and 42 being
open so that no current flows to transformer 31
or power supply 39. Time actuated relay 43 is of
In Fig. 2“, a cathode of the type described in
Fig. 1 is shown mounted in a reflex-type electron
one si'de and wire 38 on the other.
ray tubes, in electron beam velocity modulating
35l is shownsupplied through a time actuated
tubes such as those disclosed in patents, No.
relay43, »transformer 31 through a time delay
relay 4I, and powervsupply39 through a time 60 2,242,275 ventitled “Electrical translating system
and method,” issued May 20, 1941, to Russell H.
delay relay 42, all fromany; suitable alternating
Varian and No. 2,259,690 entitled “High frequency
current supply to which connection is made by
radio apparatus," issued October 21, 1941, to John
leads 40, 4t’.y
~ '
R. Woodyard, William W. Hansen, and Russell H.
W'hen it is desired to put the cathode into oper
ation, the following procedure is used. >Switch 65 Varian and in other types of electron tubes.
the well known commercial type which closes its
beam velocity modulating device of the type dis
closedin Patent No. 2,250,511 of Russell H. Varian
circuit immediately „when switch 44. is closed, 70 and William W. Hansen. As therein described,
being, set toppenl such circuit after any desired
predetermined time> interval.
With .-switchf44
an electron beam is projected through aperture
33 offth'eaccelerating grid electrode 3|, passes on
closed, currentëfromtransform'er secondary 34
through field-free-space tufbe 45, and is velocity
heats ñlament- I, and! the alternating 'current
modulated by an ultra high frequency alternating
voltagevappearing between heater I‘and ’disk'I2 76 electric ñeld appearing ‘between grids 46 and 41,
trons from spiral I is to heat an approximately
circular area of emitter I2' just below and con
centric to spiral I. Emission from s, correspond
ing circular area on the lower surface of emitter
I2.' then startaand if a moderately high alter
nating current voltage is imposed between an
nular emitters I2' and I3', a corresponding cir
cular area on emitter I3' becomes heated. As
quency characteristic of resonator 43. The ve
locity modulated electron beam passes on through
grid 41 and is reflected in the region near reflec
tor plate 43, said plate `43 being at or near the
potential o1' emitter surface I3. During the time
required for the electrons to nrst pass through
grid 43, becomerefiected by plate 43, and return
emitter I 2'. The bombarding action or the elec#
said alternating ileid being generated by a high
frequency electromagnetic field of natural fre
through grid 46, the velocity modulation has re 10 time passes, the two heated areas on I2' and I3'
spread around _these annular members, and the
sulted in density modulation, the electron groups
thus produced returning energy to the electric
entire surfaces of ‘emitters I2' and'l3' 4become
neld between grids 46 and 41, thus maintaining
hot enough to emit, the voltages betweenl leads
the electromagnetic ñeid in resonator 43. Ultra
2 and 3 and between leads 3 and 23’ having been
high frequency energy may then be removed from
removed at the proper time as in the above pre
viously described sequence ofevents. At approx
resonator 48 by means of well known types of
coupling devices (not shown). It is evident to
imately 'the time when the entire lower surface
‘ one skilled in the art that beams of various de
of cathode emitter I3' has become hot enough
grees- of convergence or ,divergence may be ob
. to emit electrons, a high direct voltage is placed
tained from such a cathode structure, depending 20 between cathode I3' and electrode 3l", thus pro
chiefiyupon the design of _the focussing element
jecting a cylindrical electron beam through an
I4, I5, I6, or upon the use of cooperating mag
‘nuiar aperture 33' and into the space below ac
celerating electrode 3 I '.
Fig. 6 illustrates a cathode producing an out
are slightly concave. The degree of concavity 25 wardly radially projected electron beam. Emitter
is such that the percentage distortion of the disk , I2", concentric to spiral filament 54, is illus
netic focussing means.
\ '
As shown in Fig. l, emitter elements I2 and I3
is very much less for a given temperature change
than that obtaining in the case of a flat emitter
surface. The structure shown in Fig. 3 may ibe
used in place of the disks I2 and I3 in Fig. 1. 30
trated as the figure of revolution of an arc of a
circle about the axis of the heater 54. Emitter
I3”, is also similar in shape and concentric to
emitter I2". Above and below emitters I2", I3"
are positioned two short cylindrical boxes 51 and
58, whose walls 4" and 8" act as heat shields.
In Fig. ,3, the convex disks :50, 53 have cylindrical
walls o‘rskirts 5I, 52 of equal diameter attached
to their respective peripherles, extending inward
l Concentric toand attached to emitter I3” is a
ly so that said walls areseparated lby a small gap.
focussing element consisting of annular inclined
Such a construction _improves freedom from warp- ' 35
portions I t", cylindrical wall I5", and apertured
ing due to- temperature changes, and forms a
morecompletely closed chamber so that electrons
accelerated back and forth between disks 50 and
53 have less chance to migrate »out of the space
wall I6". Heater 54 is positioned and has its
power-supplied by leads 55 and 58, lead 56 may
also support heat shield 53; Heat shield 51' may
be supported by lead 2i". Emitter I3" and`
defined between said disks.
40 focussing shield I4", I5",` I6" may be supported ~
Electron beams of annular, radialv or other
character may be produced by the rotation ofthe
cross-section surface of the device shown in Fig.
from leads I1", I3", in the conventional manner.
The method of operation of the cathode of Fig.
= -` 1 about an axis external thereto, in any'desired
projected electron beam resulting. It is obvious
manner. Two ofthe possible resultant configura
tions are disclosed in Figs. 4, 5 and 6.
Referring to Figs. 4 and 5, there is shown a
6 is exactly similar to .that of Fig. 1, a radially ' -to one skilled in the art that beams of ring
shaped cross-section, diverging or converging, can
b_e made by placing the axis about which the
cathode for the production of an annular beam,
~of a. type which may be used in an electron ve
cross-section of Fig.'1 is rotated at various angles
between the two used to produce the structures
locity modulating device such as the high power 50A of Figs.«4 and 6, such cathodes being useful in
oscillator shown in Fig. 'I of the aforementioned
producing beams ofthe type shown in Figs. 13
Patent No; 2,259,690. Enclosed in an annular
and 15 of the aforementioned prior Patent No.
heat shield composed of annular walls 4', 1', 8'
and 9" are two coopera-ting annular emitters I2',
As many changes could be made in the above
. I3’. The electron beam -from emitter I3'.is im 55
and many apparently widely dif
proved in form by annular focussing member I 4',
ferent embodiments of this invention could be
I5', I5",and projected toward electrode 3 I ', which
may contain annular grid structure 32' in aper- ‘ made without departing from the scope thereof,
it is intended that all matter contained _in the
ture 33', if desired. Focussing ring I4', I5', I6'
and emitter I3' are supported by leads I1', I8', 60 above description or shown in the accompanying
drawings shall be interpreted as illustrative and .
I3', heat shield 4', 8', 1', 9', by leads 2l', and
emitter I2' by ring 25' and leads 25', 21', 28' all
not in a limiting sense.
of said leads being supported in turn from the
glass press Vof the vacuum tube envelope or by
other suitable well known methods.
Starting filament I and cooperating leads 2
and 3 may be exactly similar to the starting nia
ment shown in Fig. 1, as is seen in Figs. 4 and 5,
or may actually be a ngure of revo tion as a
What is claimed is:
1. Electron discharge apparatus comprising a
substantially planar iliamentary element adapted
to serve as a source of electrons when heated, ay
ßrst emitter presenting a, relatively large surface
area. to said element, means connected to said eie
ment and said emitter for providing a difference
ribbonîa wire, or any other suitable form. In 70 of potential between said element and said
emitter whereby electrons leaving said element
are caused to bombard said emitter with high
is similar to that of Fig. 1. A proper current is
velocity, a second emitter adlacently spaced from
vallowed to ñow through lead 2, spiral I, and out
said ñrst emitter, and means connected to said
lead 3, heating the illament, and a proper alter
operation, the simple spiral cathode I of Fig. 4
nating voltage is imposed between niament I and 76 emitters for providing an alternating voltage be
. tween said emitters whereby said emitters heat
emitters for rendering said heating means in
operable after a predetermined period of- opera
each other by mutual electron bombardment.
2. The apparatus defined in claim 1, including
time actuated relay means connected to said ele
ment for automatically rendering .said element
inoperable to bombard said ñrst emitter after a
predetermined initial heating period.
tion and for applying said alternating voltage be
tweensaidy emitters, an electron beam-control
3. Electron discharge apparatus comprising two
substantially parallel electron emitter elements, ,
electrode mounted in spaced alignment with the
non-bombarded electron emission surface of the
other of said emitters. and time controlled means
for applying a substantially unidirectional elec
tron accelerating voltage between said other
means in said apparatus supporting said ele 10 emitter and said electrode.
ments in adjacent relation, said supporting means
7. Electron discharge apparatus comprising a
including. leads symmetrically», disposed with re
heater element, a substantially cup-shaped heat
spect to and extending from said elements,
shield partially enclosing said heater element, and
- means connected to said leads for applying an
substantially parallel spaced emitter elements
alternating voltage between said emitter elements 15 supported substantially across the-open end of
so that they heat each other by mutual electron
said shield, said emitter elements being non-con
bombardment, said symmetrical disposition of
ductively connected with said shield.
leads tending to neutralize the magnetic effects
8. 'I'he apparatus deñned in claim 7, including
produced by the flow of current through said /
means conductively interconnecting said heater
leads to said elements, an electron permeable 20 element and said shield.
conductive member mounted in alignment with
9. The apparatus deiined in claim '1, compris
' said elements and adjacent the non-bombarded
surface of one of said emitter elements, means
connected to said one emitter element and said
member for applying a substantially unidirec
tional voltage between said one emitter element
and said _member for accelerating electrons
emitted by said non-bombarded surface, and an
electron beam focusing means mounted inter
mediate said one emitter element and said mem
ing fixed support means electrically separated
from said shield, and means on said support
means mounting said emitter elements in said
25 spaced relation.
10. Electron discharge apparatus comprising
two spaced electron emitter elements, means con
necting said elements for producing an oscillating
potential between said elements such that they
30 heat each other by mutual elec-tron bombard
` ment, an electron focusing electrode disposed ad
4. The apparatus deñned in claims, including
jacent a non-bombarded surface of one of said
a iìlamentary heater member adjacent the other
emitter elements, and means supporting said one
of said emitter elements for initially heating said
emitter element from said focusing electrode.
other emitter element, and time controlled means 35
11. Electron discharge apparatus comprising a
connected to said heater rendering said heater
pair of electron emitter members adapted to be
inoperable when the non-bombarded surface of
energized by a stream of electrons and mounted
said one emitter element becomes electron emis-`
in closely spaced adjacent relation to be capable
of mutual electron bombardment of adjacent
’ 5. Electron discharge apparatus comprising two 40 surfaces, and skirt-like peripheral walls on each
spaced emitter elements, electrical ‘means con
nected to said elements in a predetermined sym
~metrical arrangement for applying a relatively
high alternating voltage between said elements
of said members extending toward each other
providing a shield about the electron discharge
between said surfaces.
12. Electron discharge apparatus comprising a
so that they heat each other by mutual electron 4. cathode assembly comprising spaced emitters
bombardment of adjacent surfaces, and beam~
adapted to heat each other by mutual electron
forming electrode means mounted in alignment
Ibombardment,'means connected to said emitters
With‘said elements for forming the electrons leav
for energizing said emitters, and means aligned
ing the non-bombarded surface of one of said
with said assembly and operable only after said
emitter elements into an electron beam of sub
energization has proceeded to a predetermined
stantially uniform cross-section, said emitter ele
condition for accelerating electrons from a non
ment electrical arrangement shielding said beam v
bombarded surface of one of said emitters.
against undesired magnetic disturbances from
13. Electron discharge apparatus comprising a
heating currents in said emitter elements.
heater element, a substantially cup-shaped heat
6. Electron discharge apparatus comprising two
spaced electron emitters, means in said appara
tus adjacent one of said emitters for heating said
one of said emitters by electron bombardment,
electrical means connected to said emitters for
providing an alternating voltage between said
emitters such that they heat each other by
mutual electron bombardment, time controlled
»means connected to said heating means and said
shield partially enclosing said heater element, an
emitter element supported substantially across
the open end of said shield and non-conductively
connected therewith, and electrical means con
necting said heater element and said emitter ele
ment for supplying a difference of potential be
tween said elements.
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