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Патент USA US2123024

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Í July 5, 193s. -
E. R. PloRE Er AL
Filed May 29,
193s .
t Louis Malter
M Gttorneg
\ 2,123,024 Í
nieuwe .my s, yuns `
` anaest
. Pa.. and Louis
Emanuel lt. Piore, Philadelp
)Kalten Oaklyn, N. J., asaignors to Radio Cor-.
poration of America. a corporation of Delaware
Application May zo, massaal No. n.452 _
. schaun.-
This invention relates to electric discharge de
vices, particularly to electrodes therefor, and has
- for its» principal object the provision of an elec
» trode having improved photo-sensitive and sec
with which it is treated. Thus, whereas the
prior art dictates the treatment of silver (whose
oxide has a>~heat of 4formation of the order of
5000 calories per mol.) with a single application of
caesium (whose oxide hasla heat of formation l,
g ondary-electron emissive characteristics.
Other objects will be apparent and the inven ~ of substantially 88,000 calories per mol.) , the pres
tion itself will be best understood by reference to ent invention involves a double application of
caesii'im,y or the like ‘(with the- introduction of
the'foliowing specification andto lthe accom
oxygen between these applications), to a metal
Fig. 1 is a diagrammatic view of an electron> whose oxide has a heat of formation of the same 10»
order- o_f magnitude as that 0f caesium.
multlplierf system wherein an electrode con
Among the metals whoseì emissive character
structed in accordance with -the invention may
istics .may be enhanced by the improved method
be utilized,
Fig. 2 is a partly diagrammatic cross-sectional of my invention are beryllium, zirconium, molyb
1s view'greatly‘ enlarged of a multiplying electrode denum. columbium and zinc. The heat of for- l5
mation of the oxides, per oxygen bond, of these
constructed in accordance with the principle .of ` metals
is of the order of 80,000 to 90,000 calories
the invention.
per mol. The alkali metals preferably employed
In order to increase the photo and secondary
electron emissive characteristics of certain metals, in treating the `above mentioned metals- are cae-v
zo such for instance as silver, it has previously been sium, rubidium, and zpotassium. The heat of '20
proposed to oxidize the metal and to treat the l formation of the oxides of these metals are, re
panying drawing, wherein:
oxidized surface with caesium, rubidium, sodium,
spectively, 88,000, 88,500, and 86,800. Sodium>
whose oxide has a heat of formation of substan
electron emissive constant of 'l to 9 is obtainable f" tially~100,000 may be included in this group.
yI_n carrying the _invention intoeil'ect the elec- 25
25 with caesium on oxidized-silver: rubidium on oxi
trode to be treated is first pre-oxidized, either '
or other electro-positive metal. A secondary
> dized silver will provide an emissive ratio of sub
before it is mounted in the dis
stantially 6.5 to 8.5 secondary electrons to each ‘ electrolytlcally
charge tube, or by- an oxygen glow discharge
impinging electron. ,
within the tube itself, or it may be oxidized within _
In constructing electrodes of the type described, or
without the tube in any known manner. Pref- '3o
30 the preferred practice is to mount the clean erably
this oxide coating is of a thickness of they
metal electrode structure in the tube and. after order of, say. three hundred atomic layers. 'With
evacuation, to introduce oxygen into the.y tube. ` the oxidized electrode surface or surfaces mount
The oxygen is activated orionized, as by the ap
plication of an externally applied high frequency ed within the tube, the tube is highly evacuated
a substantiaiamount of caes'ium, or like al- 35
35 neld and, thus activated. combines readily with ‘and
kali metal, is distilled into it. preferably in the
the electrode metal. When oxidization has been manner
previously described. The excess `caecompleted the tube is re-,evacuated- Caesium, slum or other
vapor is removed as by baking at
which may be contained Lin the form of pellets
within an auxiliary container connecting with 'a temperature of 200° P. for about ten minutes
40 the tube contai
the electrodes. is-vaporized as with the tube o'n the pump.
by the applicationo heat and the resulting’vapor admitted and allowed to remain in the tube for.
enters'into the main tube and combineswith the say three minutes, until it has reacted with- the
A oxidized metal to render it emissive. ExcessiveJ caesium to form a layer of a _mixture constituted
caesium is- removed or "taken-up," within the
ß tube. The tube is baked, on the pump; and the
of an oxide of caesium 'and the oxide o! the metal ‘
_of which the base is formed.. The tubeis then re- 45
'I'he4 present invention contemplates and its
exhausted, after- which the electrode is again
bathed in the alkali metal vapor. This' second
only been oxidized'and treated (as with caesium)
the- alkali metal on the siirface of the "mixed
_. sealing-in operation completed.
' practice provides a metal electrode which has not ` bath o! metal vapor forms a molecular layer of
` I. but also re-oxidised and retreated witlr the same
nalkali metal. The metal whose surface is to be
rendered emissive is selected from the group of
oxide layer". The excess metal vapor isremoved i0
by baking and pumping, as before, and thetube '
is then sealed oil.
_ f Referring now to Fig. l of the drawing in
metals whose oxides have a `heat of formation',1
per oxygen bond, of .the 'same'or substantially which electrodes'formed in accordance with the
Il the same order as that of the metallic element invention are utilised in an _electron multiplier ß
device of a' known type. The device comprises , Referring to Fig. 2, the base lupon which the
a Y-shape evacuated container I, within which, mixed oxide layer and the alkali metal coating
adjacent the closed ends of one of its arms, is is applied may be it mere sheetvof beryllium inti
mounted a photosensitive cathode 3 and adjacent mately -iointed, as by evaporation, to a base of
the‘closed end of the other of its arms is an out
another and cheaper metal, such for instance as
put ' electrode 5. A third electrode 1 is mounted nickel. Such construction is recommendedl where
between `the input and output electrodes 3 and the metal to which the mixed oxide layer and al
5 in the angle or stem of the Y-shape container kali metal `coating is applied is not available in‘
l. Both electrodes 3 and ‘I are constituted in ac
cordance with the invention of a metal base hav
ing a mixed oxide coating and a layer of alkali
metal superimposed on this coating. The out
put electrode 5 may be of nickel or other suitable
A_variable or a constant lightsource may be
so disposed with respect to the container that
light therefrom falls upon the photosensitive
cathode. In the drawing, such light source is ex
empliiled by a lamp 8 connected'in circuit with
2 O a battery 9 and a variable rheostat II, and a
lens I3.
Under the influence of light from the source,
electrons leave the surface of the photosensitive
`cathode in random directions.
Since it isde
25 sirable to focus all suchelectrons upon the multl-,
plying electrode an electromagnetic coil I5 may
be disposed around one arm of the container be
tween the photo-,sensitive cathode and the multi
A similar coil I 'I i»may be dis
‘ plying electrode.
posed around the other ,arm of the container for
the purpose of focusing secondary electrons upon
' the output electrode.
The several focusing coils may beprovided with
unidirectional potential from a battery I9 or the
like. In the drawing these coils are exemplified
sheet form.
As indicated in both Figs. 1 and 2, when the
electrons constituting the primary beam from
the cathode strike the composite electrode surface
with sufficient energy, secondary-electrons are
emitted. The electrons, so released are drawn
to the collector electrode, or if desired to another
similar surface for further multiplication by rea
son of the electric field applied between the
-emitter and the target electrode.
While the invention has been described in con
nection with a photo-actuated electron-multiplier
tube, it is to be understood that its application
is not to be limited tothe particular type of tube
here described, as the disclosure, in this respect,
is merely illustrative for purposes of explaining
the inventive concept.
What is claimed is:
1: An electrode comprising a metal base hav
ing thereon a layer of a mixture of an oxide of
said metal and an oxide of an alkali metal whose
oxide has a heat of formation, per oxygen bond,
of substantially the same order as that of the
oxide of the metal constituting said base, and a
coating of said alkali metal superimposed on said .
2. An electrode comprising a base of a metal 35
as being connected in parallel to the battery,\ whose oxide has a heat of formation, per oxygen
a potential divider 2| and a plurality of contact'
devices 23 and 25 being'utilized for the purpose
of individually controlling the magnitude of the
several focusing field currents. - It is our under
standing that the polarity of the coils is imma
A1ternative1y,`.` electrostatic focusing o'f
the electrons may be resorted to, or a combination
>of electrostatic and magnetic focusing.
In the operation of an electron multiplier of
thetype under discussion the output electrode 5
may be connected to any suitable utilization cir
cuit, such as a relay21. When utilizing a multi
plier of the type shown, the photosensitive~cathode
60 may be connected tothe negative terminal of a
potential divider 29 that
connected across a
bond, of the order of substantially 80,000 to 90,000
calories per mol., a layer on said base constituted - .
-of an' oxide of said metal and an oxide of an
alkali metal Whose oxide has a heat of formation, 40
per oxygen bond, of the order of substantially
80,000 to_100,000 calories per mol., and a surface
coating of said alkali metal on said layer.
3. An electrode comprising a base of beryllium,
a layer on said base constituted of beryllium and
casesium oxides and a surface coating of caesium
on said layer.
4. An electrode _comprising a base of beryllium,
a layer on said base constituted of beryllium and
rubidium oxides and a surface coating of rubidium
on said layer.
source of unidirectional potential 3l, the- output
5. An electrode comprising a base of beryllium,
electrode 5 connected to the positive terminal of a layer on said base constituted of beryllium `and f
the potential divider and thev multiplying electrode potassium oxides and asurface coating of potas
55 'I connected to an intermediate point thereon. f siumvon said layer.
The relative .potentials shown in rthe drawing
are to be construed solely as illustrative.
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