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Патент USA US2404343

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vJuly 16, 1946.A
Filed Oct. 14, 1945
4, .
2,404,343 "
Patented July 16, 1946
Joseph E. Henderson, Seattle, Wash., and Robert
B. Janes, Verona, N. J.; saifd Henderson as
signor to the United States of America, as
represented by the Secretary of Navy and said
.lanes assigner to Radio Corporation of
America, a corporation of Delaware
Application October 14, 1943, Serial No. 506,274
10 Claims.
(Cl. Z50-_465)
2 ,
Figure 4 is a longitudinal sectional View of
apparatus suitable for performing one of the
Our invention relates to photo-electric tubes
and their-’method of manufacture, and particu
larly to tubes incorporating dual cathodes having
principal operations involved in the manufacture
of the phototube hereinafter described.
coatings of elements such as antimony, arsenic
and~ bismuth sensitized with an alkali metal.
In co-applicant Janes’ copending application,
Serial No. 434,681 filed March 14, 1942, there was
described a phototube of a very rugged type ca
pable of withdrawing high values of acceleration
both longitudinally of the tube and when the tube
' is subjected to an'angular acceleration, or cen
tripetal acceleration such' as exists when a whirl
In thel following description we will refer spe
ciñcally to antimony as a cathode> coating and it
will be appreciated that arsenic and bismuth are
the full equivalents of antimonyy and may be
substituted in whole >orin part for the antimony
without departing from the scope _ofour inven
-In accordance ‘ with our invention’ we have
found that a tube comprising a tubular section
or sections of insulating material and closed at
opposite ends by metal closure caps may be as
ing motion about‘its'longitudinal axis is'given to
the tube. In this prior tube it was substantially
impossible to obtain a very close spacing between
the anode and cathode While still retaining its
rugged character and'v high sensitivity. For ex
semb'led> with an additional -cathode' intermediate
the closure caps if certain precautions are taken
in the order of assembly and in the application
ample, co-applicant .Janes found that it was nec
essary to separate the anode and cathode by a
ofthe antimony coatings on the cathode founda
distance of at least three-quarters ofan inch. 20 tions, such as on one of the closure caps and the l
Certain applications require _closer spacing than
’intermediatecathode foundation. More particu
larly we -»have found that a tube of the type de
this and, furthermore, such lapplications require
scribedin co-applicant Janes’ above-mentioned
the use of a second cathode which preferably
application may be constructed with an addi- ,
serves as an anode to the ñrst cathode,
tional photo-cathode intermediate opposltely dis
It is an object of our invention to provide a
posed envelope closure caps serving as anode and
very rugged phototube of the dual cathode anti
mony, arsenic >or bismuth coated type; It is an
cathode respectively with the two cathodes ex
without distortion or mechanical failure of the
parts or variation in the operating characteris
tics of the tube while providing >a structure which
cordance with our invention, the tube comprises
two end closure caps _land 2, each of which is
ceedingly close together, provided the cathode
other object toprovide a dual cathode photo
tube of the alkali metal treated antimony, arsenic 30 foundations are provided with their antimony
coatings following the sealing of the foundations
or bismuth type, wherein the cathodes may be
>or foundation supports inthe tubular envelope.
placed very close together. It is a further object
Referring to Figure 1 whereinv we have shown
to provide .a phototube of the dual cathode type
ka phototube having dual cathodes made in ac
which will withstand high forces of acceleration
sealed to Vpre.determined lengths o_f glass tubing
3 and 3e. The minimum axial length of the tubing 3 is not critical andmay be considerably less
may be easily processed .and having high photo
sensitivity. It is a further object to provide an
improved method of manufacturing a very rugged
phototube o-f the dual cathode antimony, arsenic
and bismuth coated types; It is a still further
obj ect Ito provide a method of manufacture allow
ing the production of dual antimony coated cath
odes withoutdeterioration of the antimo-ny coat- t
ing or coatings during processing.'
yThe foregoing and'other objectsyfeatures and
advantages of our invention will 'be apparent
when considered in view’of the following descrip
tion and the accompanying drawing wherein, `
Figure 1 is a View in longitudinal section of ' a
than AVone-'half inch although the minimumlength
of .thevtubingggëa must not `be less than'one-half
inch Vand‘is _preferably not less than three-quar
tersï’of an inch. ‘Preferably one of the caps; such '
- as' "rl-he#A cap I, is apertured‘as shown at 4 and is
provided with aglass’ftubulation 5 sealed around
the'aperture `for evacuation and sothat »following
evacuation the tubulat'ion'> maybe closed Vsuchwa's
‘by a V»tippirig-off operation. ‘The opposite closure
cap 2 Aisnon-apertured- and suppórts‘asource 6
ofV 'alkali metal> such as a caesium compound re
v'ducible ‘toY _caesium upon vthe application> of >hea/t
phototube made in accordancewith our invention, ` - ' to the central outer area of the capl.
In addition 4and in ' accordance with our ï-inven
Figure 2 is a cross sectional view of the photo
tube shown in Figure 1 taken along the lines 2-2,‘ 'i 4tionwe provide intermediate the closure caps vI
and >2 `a secondcathode foundation] at a distance, i
Figure 3 is a sectional view of -a modified elec
55 :preferably desertores .Closure cap l 'than théhlö
trode for use in the tube of Figure Ñl., and "
3 ,
sureccap 2. The foundation 'I serves both as an
the tubing 3 and 3a. A chrome-iron which we
anode for the iirst cathode and, when further
have found satisfactory for such use with lime
processed, as a cathode with respect to the cap 2.
glass contains as the principal constituents-k
Further, inv accordancewith 'our invention the
closurecapl supports a closely adjacent coating
Chromium _________________________ _ _
of antimony oran equivalent >element facing in
the general direction of the cap 2 but shieldedA
_, Nickel
therefrom by the second cathode foundationl. '
As shown in Figure 1, the‘reasons for which ap-L '
pear more fully hereinafter, the secondcathode 10
Manganese ________________________ __
Silicon _____________________________ __
Iron __ _____________________________ __ Balance
Following formation of a closure cap I to a satis
factory form, onecap for each tube is apertured
foundation 'I is supportedat aV relatively'short
distance from the end cap'I land at a larger dis
tance from the end cap 2 -by vsupporting means t as shown at 4 andwhere a foundation member
other than the cap for the first cathode is desired,
such as a ring~shaped or annular support mem
ber 8. It has been found that the foundation'l 15 such as the disc IB shown in Figure 3, the disc vII?)
is attached to the cap I, such as by welding. The
cannot be photo-electrically sensitized with an
alkali metal treated antimony, arsenic or bis-` ‘ " material of the disc I0 as well as of the founda-f
tion 1 is preferably of high chromium content
alloy such as chrome-nickel, the content of chro
minimum, such as> less than one-half inch al 20 mium ranging from 5 to 30% by weight, the alloy
being oxidized to a greenish color as disclosed in
though this distance is preferably not less than
muth coating if the distance between the end cap
2 and the coating is less than a predetermined
Janes" copending application,- vSerial No. 481,246
three-_quarters of an inch. y However, in accord
filed March 31, 1943. Thetubulation 5 is then
sealed around the aperture '4 and the cap I oxi
very close spacings ,less'than the minimum dis
tance-,of one-_half inch by following oury improved 25 dized to provide'a film of oxide which forms a good
bond` between the'cap I and thev glass tubing 3
method- _of. manufacture. Since the cathode
ance with our invention/We are able to provide
during the next operation' of sealing these two
parts together. Such oxidation may occursimul
foundation 'I serves as a cathode with respect to
. thefcapßÍ-and'as ¿an anode withrespect to the
>taneo'usly with thesealing of ~the tubulation 5 to
end_‘capï I ,A andlthe end cap _I is made'photo-sen
sitive, the relatively close spacingV betweenthe .30
foundation'l~ and end cap I provides characteris
ticsïwhich were unobtainable in tubes of the types
described _using antimony coatings.l Conse- ,
_the cap I',f.although alternatively'the formed caps
may beuoxidizeîdV in moist vhydrogenV as described
byHull, vBurger and Navis _in an‘article entitled,
“_Gïlassfto-metal seals,” part 2, "J curnal of lApplied
quently, in_accordance with our invention wek pro
Physics, volume 12, No; 9,' September 1941', pages
toltheïuglasstubingf» land of the support ring 8
toboth the glass tubing sections 3 and 3a, a coat
ing-` ofna’ntimony 9on-l the inner surfaceY of the
with the surface of the capV land the disc I0, if
such vdisc isÍused as 'the cathode foundation. If
' vide,¿follo¿wing the assembly of the end capl 35 698-707. ' Such Íiiring produces a relatively> thick
coating of greenish'colored chromic oxide integral
the moist hydrogen' oxidation step is used we
end_,cap I as shown in Figure 1, or on a founda
tion», _I_û supported by the end cap I as shown in 40 prefer to bake the end‘ caps for a sufficient length
Figure-_5.A> AQnly then is the foundation ‘I sup
ported within the tube on the support ring 8, Vsuch
las by welding ¿metaltabs I I between the founda
tioni ,and the support ring 8 or other mechanical
>of- time," such as in a non-oxidizing atmosphere
» _coating I2 o_f an element such as antimony either
before‘ïor‘after its attachment to the support
î'ri'pgßiby the maar tabs, l l.
-More particularly we have found Ythat it is not
_of Vfires heating" the rim of the cap and the lower
end of the tubing 3. 'vWe use a similar sealing step
to attach the support ring 8 to the upper end of
.the glasstubing 3 and to the' lower en_d ofthe
glass tubing'Sa.' All 'of these steps are performed
at atemperatureof 500° C. forabout twelve hours
to removeany occludedhydrogen. 'l'he seal be
attachment. ’ The foundationA 1 is provided with a 45
lonlylydesirable but necessary to provide the an
timony coatings 9 ,and I2 at a definite time dur
ing'rtheï sequential manufacturing steps to pre
¿vent Vinjury to these coatings during subsequent
steps of theßmanufacturing processes. For eX
ample, .if thel coatings 9y and I2 _are subjected to
relatively high temperatures, >such as occur when
1n accordance with our invention before the ap
plicationof theantimonycoatings S and' I2, the
cap I'and the foundation ‘I only then being ready
for the application ofthe antimony coatings 9
and >Il which are applied in separate steps; f
Referring toFigure 4 and prior to’attachinent
of the foundation 'I toïthe ring member 8,' ‘we
insert the glass tubing 3"and ßa'ove'r a tubular or-
the closure cap I is sealed to the glass tubing 3
_orwhen the support rings is sealed between the
_tubularglass portions 3 _and 3d, permanent injury
_occurs‘mto the coatings.’ The sealing operations
tweenthe end capV ’IV and the glass tubing 3^may
be. made'byrotatin'g the parts 'in the presence
cylindricalopen endedlshieldV I5, _theÍshield ex
tending'ltowithin close proximity of the endcap
f musthecessarily Vbe performed in the presence
nI' or the disc I 0,' if such disc is "used, anden-which
_ofïnorrnal atmosphericïconditions *and- our se
the' antimonyf vis to loe-deposited. Í l The .shield AI5
4is preferably.supportedrwithin a'chamber or bell
jquence ogprocessingsteps avoids or substantially>>
tesV material oxidationof the antimony .
jar lßcapable'of being '.evacuated."y We"alsofsup"-
, _cpatir,lgsl on the foundations. g Furthermore, the 65 Vport, opposite theï'cap I> a? _source ofantimcny to
,closure _cap I and the support ring 8 must be sub- . be vapòrizle'd - and " condensed ~'thereonJ- ' Such a
source ofÍanti'inony may- comprisea refractory
¿je ,_ ed¿to¿ce_rtain»processing steps to provide good
glproperti'es at the time the seals are‘made
>`.hetwee,nr-_lthesemembers and the glass tubings 3
Vand 3d, such¿steps-fbeing_incompatible with pre
viouslyapplied antimony coatings.
Y ,- ,The `»closure _caps ;I- and 2, as well as the ring
metal; 9011y l1 supportingy a quantity 4Vof 'antimgny
¿I8 onotherelement such/asV arsenic or,` .bismuth
and whichvmay _belvaporizedrby passing> an elec
Ktric current through the. connecting leads i9.
4,lî’ollotv'ing ¿therinrsertion of théÍOpen >endeVdjvv'aiis
mberß, are-_preferablyof material such as
Lof- 'theV tubeshown in »Figurellß’ ~the bell` `J
„chrome-iron having a, cov-efficient _of- expansion:A is evacuatedftoîaghigh .Vacuums A.the .residuallair
A`substantially matched with that ofthe glass of 7 pressure preferablymbeiná less than 40.5 "microns »
and sufficient antimony is yvaporized froml the
source I8 and condensedon the inner surface of
the cap I to 'provide the'antimony coating 9.- The
~ thickness `of this antimony coating Amay Arange
fromva thickness'corresponding to 0.1 to 0‘.'16»mi1-
ligram per square centimeterywhichis sufficient
to provide good sensitivity when such a-- coating is
treated with alkali metal. The rate of vaporiza
minutes to one-half hour, we vapor-ize alquantitv
of alkali metal such as caesium from the- source 6
to sensitize both of the >coatings -9 and I-2-._ îTo
allow -access of the alkali metal to the antimony
coating 9 the foundation 1 is provided with 'an
aperture 4a although sufficient spacing `may be
` provided about the periphery of the foundation.
Following the vaporization of the alkali `metal the
tube is baked, preferably at a temperature `of 160°»
tion and condensation is preferably'low,_being less
than 0.2 milligram per'square centimeter of the 10 C., for thirty minutes and during this baking the
alkali :metal apparently combines with Athe anti
surface to be vcoated per second, since higher rates
to provide photocathode surfaces
of condensation may beA detrimental, forming a
sensitivity to light. Following
non-uniformcoating.- The entire :bell jar assem
the baking the tubulation 5 may be tipped-off and
bly With the exception of the coil I1 and the heated
antimony source I8 is preferably maintained at 15 the tube removed from thel pump and preferably
rebaked at a'temperature of 160°>C. fora period
room- temperature during the evaporationand
of twenty minutes, following which'the tubeis`
condensation steps, except for `such slight heating
aged to further stabilize the photoelectric emission
of the cap- I as may occur by radiation fromthe
from the cathode.
' "
In operation the cap I serves as a cathode con
The Yantimony coating I2 on the ,foundation 1 20
nection and is operated at a negative potentialV
may be applied to a similar thickness in a simi
with respect to the ring member 8 which sup
lar manner either in the bell jar- I6 following Aat
ports and is electrically connected to the cathode
tachment of the foundation 1 to the yring member
foundation 1, this member likewise being main
8 by the metal strips I I, in> which >event'the shield
I5 is made somewhat'shorte'r terminating 'adja 25 tained at a negative potential with respect to the
.anode cap 2. The'electrons liberated from the
cent the upper surface of the foundation 1,l `alcoating 9 are ldirectly proportional to theïlight
though the antimony coating I2 may be applied
incident thereon through the glass tubing 3 and
prior >to its attachment while separately sup
similarly electrons liberated from the coating I-2
ported in vacuum with-exposure to a heated an
timony source. If this latter method is used the '30 and collected by ‘the anode cap 2 are directly
proportional to the light incident on the coating
foundation 1 is affixed to the ring member 8 fol
lowing the application of the antimony coating I2.
“I_n accordance with our invention and following
theapplication'andiassembly steps referred to
above, the envelope formed by the tubular glass
‘sections 3 and 3a. is closed by sealingjthe vcap_2
to the upper end of the tubing Salat a sufficient
distance, such as three-quarters of an inchv from
I2 through theglass tubing 3a. Consequently the
disclosed structure isv ideally adapted to -inulti-V
directional use wherein either one or more light
sources. or a broad source such as the sky are
fusedv since the' cathode'smay be illuminated from
all azimuths' on» sides facing theA respective
the surface of the nearest adjacent antimony coati
-- While »we have `described AourA invention with
a'small apertured container,- whereupon'the cap
ode »phototubea’can -«be made both in the struc
ture fandgin the method of manufacturing with
ing, such as the coating I2. A source 6 of alkali 40 Äparticular reference to a dual-cathode phototube
Vand'. have set forth our,A preferred method of
metal such 'as a caesium bearing compound jis
manufacturing such a tube,- it will be appreciated
first valii-ized to the inner surface> of the end cap 2,
that various modiiications'such as multiple cath
such as by enclosing al compound of -caesium in
2, previously oxidized as ‘described above, is sealed
to the upper end of the glass tubing 3a.. To pre-k
vent'excessive heating of the antimony coatings
out :departing ‘from the spirit of our invention
orthe scope Vthereof as set forth in the appended
during this ñnal sealing step, we prefer toV cool
the ring member 8 as well as the yend cap I, such
1f. A phototube comprising a tubular >glass en
vas by a blast» of air directed thereon during the 50
velope, a metal closure at each end of and form
sealing -of the cap 2 to the upper »end of the glass
ingï the -end~ walls of said envelope, -al cathode
foundation extending transversely of said en
The'only other,u precaution which need be fol
velope intermediate said closures, a coating se
lowed in the assembly of `our'dual cathode photo
tube is the maintenance of the antimony coatings 55 lected from the group consisting of antimony,
arsenic, and bismuth on the surface of said foun
in the absence of high concentration of water va
dation facing one of said metal closures, a simi
por, especially during the time these coatings are
lar coating on the other of said closures and
subjected to temperatures above normal room tem
alkali metal within said envelope to sensitize said
perature. Consequently the relative humidity of
the atmosphere to which the coated cathode foun 60 coatings.
2. A phototube comprising a tubular glass en
dations are subjected should be low and prefer
velope, a metal cap sealed to each end of said
ably less than 80% relative humidity at 25° C.,
envelope, a coating selected from the group con
which corresponds to a water vapor-concentra
sisting of antimony, arsenic, and bismuth on one
tion equivalent to 8 grains of water vapor per
cubic footvof air. The satisfactory results ob 65 of said metal caps as a cathode foundation, a
second cathode foundation extending transverse
tained are believed to be due to the fact that
ly of said envelope between said caps, a coating
antimony does not oxidize when subjected to nor
selected from the group consisting of antimony,
mal atmospheric conditions in the presence of low
arsenic, and bismuth on the surface of said foun
We claim:
Following the assembly of the tube as shown in 70 dation facing the other of Said caps, and a quan
tity of caesium within said envelope to sensitize
Figure 1, the internal Volume thereof is exhausted
said coatings.
through the tubulation 5 and the tube is baked at
3. yA phototube as claimed in claim 2 wherein
a temperature of 275 to 310° C. to remove any
said coatings are of antimony.
occluded gases contained in the tube parts. Fol
4. A phototube comprising a tubular envelope
lowing this baking which may be from `iìfteen 75
of ~transparent material, `a metal cap. sealed -. .to
comprising sealing one or said caps toene end
and'closing'each ofthe opposite ends of saidven
velope, a cathode foundation extendingl >trans
of said’ member, sealingafsuppo'rt'fora photo
sensitive electrode intermediate the .ends of `said
versely of said -envelope between saidmetalïcaps
member, depositing an element selected _fromxthe
and being spaced more closely to one of said caps
’ group consisting of antimony,.arsenic» and bis
than the other cap, a coating selected fromrthe
group of elements consisting of` antimony;_arsenic_
math-on a-surface in'electrical contact with the
cap 'sealed to -oneend- of said'meníber, attaching
andgbismuth 0n said one of-said4 caps andga sec
an - electrode- foundation `'adapted to bel photoelec
ondi Coating selected `from Asaid group of >elements
tricallysensitized Vto said support and then seal
on,` tlfiezsurface Vof , said foundation facing the
ing theother cap to the other end of said mem
ber, evacuating the envelope formed by said mem
ber and said.A caps, land sensiti'zing said _deposited
other ofi-said caps.;` and anv alkali-metal> deposited
on- „each o_f- said- coatings' to render said coatings
element and said foundation with an alkali metal.
'~„ 5, 1A: phototube-.comprising a Vcylindricalv glass
envelope, af metal cap at each'end of said en
velope,._«;one' of said caps »being lapertured and
closed by an lexhaust tubuiation, la-'cathode foun
ing comprising sealing one of said closurefcaps
to [one end ofv one of> said sections of glass tubing,
dationafûxed-‘directly to oneY of; saidcaps 'and
facing in the direction of the other-of said caps,
,ak second cathode foundation Vextending _trans
versely across said envelope parallel to and be
sealing a support for a photosensitive electrode
20 tothe opposite-end of said one-section,seali_ng
one» end of ther-other section of glass ltubing to
tween said caps a-nd closer to said iirst cathode
foundation than to the other end cap, and a
coating of alkali metal treated antimony on each
of said, cathode foundations. Y
6. A phototube comprising a pair of coaxial,
separated transparent envelope portions sealed
9. vThey method of manufacturing a Vphototube
having an envelope of two metal closure caps
sealed to and separated by sections of glass .tub
said support coaxial with said one section, deposit- ,Y
ing .a coating of an element which when sensi
_tized with an alkali» metal is photo-sensitive on
a surface vadjacent said one closure cap, attach- '
ing a foundation which when sensitized ¿with an
alkali..metal Vis photo-sensitive -orí'said support,
at their adjacent ends to a metalsupport ring in
sealing' the other closure cap >to the other end of
a plane transverse to said envelope, a metal cap
said-other glass tubing section to form an en
sealed‘to each of the opposite ends of said envel 30 velope,fevacuating said envelope and sensitizing
ope portions, a coating of alkali metal treated- an
said coating and said foundation with an alkali
` timony _onrone of said metal caps and a photo
sensitive electrode extending transversely across
. 10`. The method Vof 1 manufacturing a photo
said envelope and supported by said metal supu
tube having two closure caps separated by tubular y
port ring between said coating and the other of 35 insulating material comprising sealing one of `"
said metal caps and having a photo-sensitive
surface facing said other metal caps. _
7. A phototube comprising a. pair of longitudi
said .closure Vcaps to» one end of said tubular in
sulating material, sealing an 'electrode support to
said insulating material intermediate the opposite
ends thereof, inserting an open-ended shield with-l
nally spaced coaxial transparent envelope por
tions sealed at their adjacent ends to an elec 40 in the Aopen end of said tubular insulating material
trode support member, one of said portions hav
beyondsaid electrode support and to within close
ing anaxial length less than three-quarters of an
proximity of said sealed'closure cap, evaporating
inch, the other having a minimum length of ap
and-condensingantimony on a surfaceadjacent
proximately one-half to three-quarters of an
inch, a Dhotocathode attached to and carried by
said electrode support, a metal end cap closing the
open end of each of said envelope portions and a
coating of caesiated antimony on the cap-sealed
to that envelope portion whose minimum length
is approximately one-half tov three-quarters, of
8. The method of manufacturing a phototube
having two closure caps separated by a tubular
insulating member and an intermediate electrode
saidclosure cap while the inner walls of said in
sulating material and said electrode support are
vprotected from condensation rthereon by said open
ended shield, removing said shield, attaching an
antimonycoated electrode to said-electrode sup
i port, sealingthe other closure cap to the open end
`of said tubularinsulating- material to'form an
envelope evacuating said envelopeand sensitiz
ing said antimony with an alkali metal.
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