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Патент USA US3076921

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Feb. 5, 1963
J. |_. TURNER ET AL
3,076,911
METHOD OF AND APPARATUS FOR THE REDUCTION OF THERMIONIC
EMISSION IN DISCHARGE DEVICES
Filed May 18, 1960 '
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27'
I
lNV NTORS
Zi?'lh? it
Eye.
Patented Feb. 5, 1%
2
3,076,911
METHQD ?ll‘ AND APPARATUS FUR THE REZJUQ
TEEN (BF THERll/ilQIsllC EMESSHQN 1N Did
CHARGE DEVli'JEE‘a
.lohn L. Turner, Needhnin, and Seymour Goldberg, Lex
ington, Mass, asslgnors to Edgerton, Germeshausen &
Grier, Inca, Boston, Mass, a corporation or‘ Massa
chusetts
Filed May 18, H59, Ser. No. 2994s
14- Ciaims. (6i. Slit-1&7)
emission suppressant materials are not applied to the
particular electrode from which it is desired to prevent
spurious emission but rather are appropriately disposed
with respect to this electrode, the desired result may be
achieved Without any of the disadvantageous features
before discussed. An object of the invention, therefore,
is to provide a new and improved method of and appara
tus for reducing electron emission from other elements or
electrodes in the tube than the cathode, and that shall not
10 be subject to the disadvantageous features of the prior
The present invention relates to electric-discharge de
art.
vices and, more particularly, to discharge tubes and the
A further object is to provide a new and improved
the involving electron or similar emissive electrodes and
electron-emission suppressing structure.
other surfaces.
Other and further objects will be explained hereinafter
Emission in thermionic tubes from elements other than 15 and will be more particularly pointed out in connection
the cathode is a serious problem. It can, for example,
with the appended claims.
it the emission is from the control grid, cause a leakage
current in the controlwrid circuit, thereby detrimentally
lowering the grid input impedance. This problem of
spurious emission from the grid electrode becomes even
more serious in the case of Witching tubes that require
high anode hold-off voltage, such as hydrogen thyratrons
of the type disclosed in United States Letters Patent No.
2,842,699, issued July 8, 1958, to Kenneth J. Germeshau
sen and the applicant herein, Seymour Goldberg, be
The invention will now be described in connection with
the accompanying drawing the single
of which is
a longitudinal section of a gaseous discharge tube con
strncted in accordance with a preierred embodiment of
the invention.
While the invention is shown applied to a particular type
of gaseous-discharge device, it will be evident that the
invention is equally adaptable to other types of discharge
devices and it is, accordingly, not to be construed as limit:
to the illustrated device. The tube shown in the draw
ing is of the type disclosed in the said Letters Patent, em
is multiplied by the high anode voltage, it represents a
bodying a cup-shaped anode 9 having an active substan
source of considerable anode dissipation. Typical switch
tially planar surface 17 and a similar backing-plate sur
ing tube applications include a radar modulator, a pulse 30 face 19 disposed on opposite surfaces of ti e planar bottom
generator, 21 stroboscope or a ?ash-photography system
wall of the anode cup 9. The anode serves as an upper
or the like. In gas~iilled tubes, moreover, the ionization
Wall
of the ceramic or similar envelope 3, thereby ‘to dis
caused by the how of the grid-emission current to the
sipate heat. The anode cup 9 may be of copper and the
anode can often readily cause the grid to lose control
active planar electrode surface 17 may be of molybdenum
of the tube and c?ect premature anode ?ring.
or the like, with the backing late ill of Kovar material
Such undesirable spurious emission in thermionic tubes
or the like. Flanges 13 are shown extending outward of
is caused by evaporation or sputtering of active emitting
the envelope 3 between a ceramic backing ring 3’ and the
materials from the cathode upon the various elements
main
ceramic cylindrical Wall 3 of the tube, being sealed
or electrodes, such as the control grid. When such an
thcrebetween as taught, for example, in the said Letters
element or electrode becomes heated, either by radiation 40 Patent.
The external portions or" the ?anges 13 may be
from the cathode or by some other power dissipated in
cause a substantial amount of the grid~emission leak
ave current ?ows to the anode and When this current
the tube, the electrons will be spuriously thermionically
emitted from that element or electrode and will ?ow to
the anode.
curved into a rim l3’ and may serve not only to dissipate
heat, but to reduce potential gradients in the region of
the seal and to establish electrical connection to the
anode 9.
Various attempts have been made throughout the years 45
An inverted heat-dissipating cup-shaped control elec
to solve this problem of undesirable emission in thermionic
trode or grid 37, as of copper and the like, is disposed with
tubes. One proposal has involved coating the element
its upper substantially planar surfaces
apertured at
or electrode, from which it is desired to prevent emission,
41,
in
close
proximity
to
and
substantially
parallel
to the
with an electron-emission suppressing material, or fabri
active
surface
17
of
the
anode
9.
Depending
from
the
cating the element or electrode from such a material. 50
central region of the planar surface 3%‘ of the grid 37,
This type of solution, however, has often presented many
is a reinforcing mem er 2t) having grooves 22 intermedi~
new problems as a result of the characteristic differences
ate the apertures ?ll in the planar region 35? and so posi
between the suppressant material and the tube elements
tioned
to provide an electron path through the reinforcing
or electrodes. Gold, for example, has been a popular
electron emission suppressant; but gold has the disadvan 55 member 26' and the grid 39 to the anode surface 17'.
The control electrode or grid 37 is provided with ex
tages that it has a high vapor pressure, that there is loss
ternally
extending feet or ?ange {l3 sealed between the
of diffusion into the base metal, and that the cathode
bottom of the cylindrical envelope wall 3 and a lower
often becomes accordingly poisoned. Other disadvan
extension 3” thereof, as in the manner discussed in the
‘cages in the prior use of emission-suppressing materials
said Letters Patent.
upon the electrode from which spurious emission is to be 60
The cathode structure, indicated generally by 2.1, is dis
posed within the grid cup 37—-39. Electrical heater and
voltage connection to, and support for, the cathode struc
ture Zll may be effected by plugs 27, sealed through the
ceramic base 5 of the envelope. A gas intubulation
pressant, moreover, the grid becomes covered with a 65
chamber 27’ may similarly be sealed into the base 5. The
suiliciently thick layer of active cathode materials and/ or
cathode 21 is shown comprising a set of substantially
other materials sputtered from other members of the
parallel planar vanes 21a extending from a common
tube, to render the emission suppressant on the base metal
base 215, which may be heated as described in copending
ineffective.
application Serial No, 589,551, ?led April 25, 1956, by
70
In accordance with the present invention, on the other
the said Kenneth J. Germeshauscn and Seymour Gold
hand, it has been discovered that if appropriate electron
berg for Electric-Discharge Device and Cathode, now
suppressed, include the fact that thin suppressant layers
are often sputtered oil by ion bombardment. After long
periods operation of tubes having, for example, a grid
electrode containing thereupon an electron-emission sup
aorscn
4
it has been found to work in practice, providing very
Us. Letters Patent No. 2,937,301, issued May 17, 1960,
large improvement in results, it is believed that one of
or heated through the passage of current therethrough, as
the following theories may provide a possible explanation.
Under discharge conditions, the cathode baf?e elements
21g and Zlli are bombarded with high-energy gas ions,
causing sputtering and continuous relocation of the emis
disclosed in application Serial No. 660,592, ?led May
21, 1957, by the said Seymour Goldberg, for Electric
Discharge Device and Cathode, now US. Letters Patent
No. 2,937,302, issued May 17, 1960. As disclosed in
said applications, the vane surfaces 21a are coated with
electron-emissive material, as is well known, in order to
sion-suppressant on the grid 39. This, then, prevents a
thick layer being formed that would render the emission
suppressant ineffective, as occurs when the suppressant
enable the emission of substantial quantities of electrons
upward through the apertures 22 of the reinforcing mem 10 is applied directly to the grid or other electrode or ele
ent from which emission is to be suppressed. An
ber 20, and 41 of the control grid electrode 39-37 to the
other possible explanation may reside in the fact that a
active surface 17 of the anode 9.
large part of the emissive material from the cathode
The cathode Z1 is shown contained within a cup-like
vanes 21a which is eventually deposited on the grid sur
structure 210 which, in turn, is supported in a larger
face 39, is first deposited on the battle elements Zlg-Zli
cylindrical structure 21d terminating in outwardly ex
interposed therebetween and is therefore rendered inoccu
tending heat~conducting and electrical-connection~provid
ous through a process of mixing with the suppressant at
ing ?ange 21c, sealed, as before described, between the
A, B, C and D.
envelope portion 3” and the base 5. Gaseous reservoir
Further modi?cations will occur to those skilled in the
21,‘ may be employed, such as that described in United
art
and all such are considered to fall within the spirit
States Letters Patent No. 2,919,368, issued December 29,
and scope of the invention, as de?ned in the appended
1959, to the said Seymour Goldberg and Edward I. Goon,
claims.
for Gaseous Reservoir and Method, having within the
What is claimed is:
container 21f, for example, a rare earth or the like, car
1. An electric-discharge device having, in combina“
rying absorbed gas so as to diffuse the gas into the tube
tion, an electron-emissive cathode electrode and at least
an additional electrode and the like displaced from the
to replace gas that has been used up during operation.
interposed in the space between the electron~emissive
cathode vanes 21a and the control-grid electrode surface
cathode wihin the ‘discharge device, and toward which
electrons may be emitted from the cathode, the addition‘
39 is an open~sided cover 21g for the cathode cup 210.
The cover 21g is provided with an aperture 21h above
a1 electrode being adapted to produce spurious electron
emission upon the sputtering thereupon of electron
which is suspended a baffle piece Zli.
In accordance with the present invention, it has been
discovered that if the elements 21g and iii, interposed
between the electron-cmissive surfaces 21a of the cathode
and the grid surface 39 from which it is desired to pre
vent electron emission, is coated with the electron-emission
suppressing material, rather than coating that electron
emission suppressing material on the surface 39 itself
from which it is desired to suppress electron emission,
the desired result can be obtained without any of the
disadvantages of the prior art, before stated.
emitting material from the cathode, and means for interposing a surface that inherently suppresses electron endssion in the region of the electron path between the elec-‘
tron-emissive cathode and the said additional electrode to
inhibit the said spurious emission from the additional
electrode.
2. An electric-discharge device having, in combination,
an electron-emissive cathode electrode and at least an ad
ditional electrode and the like displaced from the cathode
40 within the discharge device, and toward which electrons
As an illustration, a thin foil or layer of platinum
was applied to the upper and lower surfaces of the ele
may be emitted from the cathode, the additional elec
trode being adapted to produce spurious electron emis~
sion upon the sputtering thereupon of electron-emitting
ments 21g and 151i indicated in the drawings by the letters
material from the cathode, a surface of an electron
A, B, C and D, interposed between the region of electron
emission from the active portions 21a of the cathode 45 emission-suppressing material, said surface being disposed
in the region of the electron path between the electron
and the surface 39 of the electrode 37 from which it is
emissive cathode and the said additional electrode to
desired to prevent electron emission, This was found to
inhibit ‘the said spurious emission from the additional
reduce electron emission from the grid 37-39 in the
electrode.
tube by a factor of one hundred, and without the disad
3. An electric-discharge device having, in combination,
vantageous features before referred to that occur when 50
on electron-emissive cathode electrode and at least an
the suppressing material is directly coated upon the grid
additional electrode and the like displaced from the cath
itself.
ode within the discharge device, and toward which elec-'
The invention, however, is not limited to platinum foil,
trons may be emitted from the cathode, the additional
but may be practiced with similar results by using other
similar suppressants such as, for example, titanium, niobi 55 electrode being adapted to produce spurious electron
emission upon the sputtering thereupon of electron-emit
um, gold, and the like. The suppressants, moreover, need
ting material from the cathode, and a further element dis
not be applied as foil coverings, but may be provided by
posed in the region between the electron-emissive cathode
other techniques including electro-plating, sintering, and
and the said additional electrode in the path of the emitted
the like. In fact, the element itself may be constructed
of the electron~emission suppressing material and thereby 60 electrons, said further element being composed of an
electron-emission-suppressing material to inhibit the said
preclude the use of a coating.
spurious emission from the additional electrode.
By describing the invention in terms of the preferred
embodiment, it is by no means limited to this particular
embodiment.
e invention has utility whenever the
electron~ernission suppressing material is so positioned
within the discharge device that a substantial portion of
the electron emission from the cathode during discharge
comes in contact with or in close proximity to the sup
pressant before the discharge reaches the region of the
element from which it is desired to prevent spurious
emission.
While it is not fully understood how ‘the reduction in
the ‘grid emission is obtained by placing the platinum or
4. An electric-discharge device as claimed in claim 3
and in which the said electron-emission-suppressing ma
terial is selected from the group comprising platinum, ti
tanium, niobium, and gold.
5. An electric-discharge device having, in combination,
an electron-emissive cathode electrode and at least an ad
ditional electrode and the like displaced from the cathode
within the discharge device, and toward which electrons
may be emitted from the cathode, the additional electrode
being adapted to produce spurious electron emission upon
the sputtering thereupon of electron-emitting material
from the cathode, a further element disposed in the region
other foil or covering on the cathode baffle structure 21g
and 211', it‘being sufficient to describe the invention as 7-5 between the electron-'emis'sive cathode and the‘ said addi
5
3,076,911
tional electrode in the path of the emitted electrons, and
an electron-emission-suppressing material disposed upon
the further element to inhibit the said spurious emission
from the additional electrode.
6. Apparatus as claimed in claim 5 and in which the
further element comprises an apertured cover having
vba?le means.
7. Apparatus as claimed in claim 6 and in which the
said cover and ba?ie means is coated with the e1ectron~
6
emitted electrons, and an electron-emission-suppressing
material disposed as a coating upon portions of the con
ductive element to inhibit the said spurious emission from
the additional electrode.
11. An electric-discharge device as claimed in claim
10 and in which the said electron-emission-suppressing
material is selected from the group comprising platinum,
titanium, niobium and gold.
12. An electric-discharge device having, in combina
emission-suppressing material and is electrically connected 10 tion, an electron-emissive cathode electrode and at least
[to the electron‘emitting cathode.
an additional electrode and the like displaced from the
8. An electric-discharge device as claimed in claim 7
cathode within the discharge device, and toward which
and in which the said electron-emission-suppressing ma—
electrons may be emitted from the cathode, the addi
\terial is selected from the group comprising platinum, ti
tional electrode being adapted to produce spurious elec
tanium, niobium and gold.
15 tron emission upon the sputtering thereupon of electron
9. An electric-discharge device having, in combination,
emitting material from the cathode, a conductive element
an electron-emissive cathode electrode and at least an ad
disposed in the region between the electron-emissive cath
ditional electrode and the like displaced from the cathode
ode ‘and the said additional electrode in the path of the
within the discharge device, and toward which electrons
emitted
electrons, and an electron-emission-suppressing
may be emitted from the cathode, the additional electrode
material disposed upon the conductive element to inhibit
being adapted to produce spurious electron emission upon
the said spurious emission from the additional electrode.
the sputtering thereupon of electron-emitting material
13. An electric-discharge device as claimed in claim 12
from the cathode, a further element disposed in the region
and in which the conductive element is connected elec
between the electron-emissive cathode and the said addi
trically with the cathode.
tional electrode in the path of the emitted electrons, and 25
14. An electric-discharge device as claimed in claim 13
an electron-emission-suppressing material disposed as a
‘and in which the said electron-emission'suppressing ma~
coating upon portions of the further element to inhibit the
terial is selected from the group comprising platinum,
said spurious emission from the additional electrode.
titanium, niobium and gold.
10. An electric-discharge device having, in combina
tion, an electron~emissive cathode electrode and at least
References Cited in the ?le of this patent
an additional electrode and the like displaced from the
UNITED STATES PATENTS
cathode within the discharge device, and toward which
electrons may be emitted from the cathode, the addi
2,399,003
Crapuchettes _________ __ Apr. 23, 1946
ti'on-al electrode being adapted to produce spurious elec
tron emission upon the sputtering thereupon of electron
emitting material from the cathode, a conductive element
disposed in the region between the electron-emissive cath
ode and the said additional electrode in ‘the path of the
2,417,460
2,516,841
2,518,879
2,831,999
2,919,368
Eitel et al. __________ __ Mar. 18,
Arditis et al. _________ __ Aug. 1,
Germeshausen ________ __ Aug. 15,
Doolittle _____________ __ Apr. 22,
Goldberg et al. _______ __ Dec. 29,
1947
1950
1950
1958
1959
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