Download Electron discharge device

July 10, 1945-
B. c. FLEMING-WILLIAMS’
2,380,225
ELECTRON DISCHARGE DEVICE
Filed Aug. 20, 1941
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INVENTOR
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ATTORNEY
Patented July 10, 1945
2,380,225‘
UNITED I STAT Es PATENT OFFICE
ELEGTRON‘DI‘SCHARGE DEVICE
Brian ‘CliffordFleming-Williams, London, Eng
land, assig-nor to A; C. Coss’o‘r Limited, London,v
England, a company oil-England
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Application August 20, 1941, Serial No. 407,688
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In Great ‘Britain June 26, 1940
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1201mm.
This invention relates to electronbeamde?ec
tion valves. ~A valve of this kind usually com-.
prises‘ an- electron‘beam generating and ‘fo
cussing system, a pairv of electrostatic de?ector
plates and a pair‘of target electrodes. Variation
of the potential difference between ‘the de?ector
plates produces variation of the proportion in ,
which the beam current is divided between the
target electrodes.
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tion, at least part of the focussing of the elec
tron beam is effected by the de?ector plates,
while these simultaneously perform their normal
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electron beam valve in which curved electrodes‘
are used for focussing the beam, and Figs. 2 and '
3 are similar views illustrating two: further em
bodiments of the invention.
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A divergent ribbon electron beam is generated
by the electrode system comprising cathode C,
shield electrode G, and anode A. Anode A is a
sheet electrode having a slot whose length lies
perpendicular to the plane of the ?gure. Shield
.,
. In the arrangement according to .the, inven
function.
‘(01. 250-27)
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If an‘ electron “beam is introduced between a
10 electrode G, and the active surface of cathode
C, are each of part-cylindrical form and may.
have their curvatures struck from the centre of
the slot in anode A. Shield electrode G may,
forexample, be maintained at the same .poten
15 tial as cathode C (indicated in Fig. 1 as zero),
and anode A may be maintained 400 volts posi
pair of coaxial part-‘cylindrical electrodes, the
tive to cathode C.
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inner one of which is maintained su?icientl'y
The ribbon beam diverges from a crossover
positive with respect to the outer to cause the
which is of substantially line form, perpendicu
electron beam to follow the .curved path be-.
tween them,v then the ?eld between the-electrodes 20 lar to‘the plane of the figure, and situated close
to the slot of anode A. It then enters between
will have a focussing effect upon the beam. If
de?ector plates P1, P2. These plates are part
the beam is divergent‘ from a point in the ?eld
cylindrical, and are co-axial about the axis 0,
between, the electrodes, 'it will be brought sub
which is perpendicular to the’ plane of ‘the ?gure.
electrodes through‘ an' angle of. 631/2' degrees. 25 The angle XOY subtended by the plates at the
Similarly,.if the beam is parallel at one position
axis 0 is somewhat less than 127°, say 110°. The
bias potentials of plates P1 and P2 should be
in the ?eld between the electrodes, it will be
brought approximately to ya focus after. travelling
balanced about the potential of anode A, and
must be such as to ‘give the beam the necessary
through an angle of 63% degrees. Slight vari
ations of the potential difference betweenthe 80 curvature to follow the arcuate, path between
plates P1 and P2. Potentials of about 480. and
electrodes will produce small changes in the po
320 volts positive to cathode may be found sat
sitionsof the foci, but will not ‘appreciably dis
stantially parallel after travelling between the
isfactory‘if the ratio of the radii of curvature
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of the plates is 4:5.
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An electron beam de?ection valve according
to the invention comprises a‘pair of de?ector 35 The effective length of the plates, owing to
plates in the form of co-axial particylinders be
fringing ?ux, is somewhat greater than the
actual length. Also, in the valve illustrated, the
tween which, superimposed on the varying de
beam diverges somewhat after leaving the cross
?ection voltages, a steady potential diiference is
over and‘before entering the ?eld between plates
' maintained whereby the beam is made to pass
along the arcuate ‘path between the plates.
.40 P1 and P2. It will, therefore, become substan
tially parallel after following through an angle
‘ By this arrangement the electron beam gen
of rather less than 631/22 say about 55°, the
erating and focussing system is made more sim
curved path between the plates. ‘It will then
ple and the ‘total size of the. valve may be re
be ‘caused to converge, but willvnot. yet have
duced. A high value of beam current can be
employed for a given spacing of the de?ector 45 reached a focus when it leaves the ?eld between
the plates P1 and P2. ' It will, however, be con
plates, and the degree of aberration 'which “oc
vergent, and it will reach a focus at ‘F1, not far
ours in the focussing is. remarkably low. It fol
from the emergent end of plates P1, P2. 1This
lows that a. high value ‘of mutual conductance
turb the focussing effect.
is obtainable.
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will be. a line focus perpendicular to the, plane ~
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A beam of ribbon form is preferably employed, 50 of the ?gure.
The precise values of the bias potentials are
so arranged that‘ its. thickness lie‘sin the radial
chosen to give. the beam the necessary curva
direction of the deflector plates. By this means
ture so ‘that the focus F1 is formed on-the edge
also a high mutual conductance is obtained.
In the accompanying-drawing Fig; ‘is a Idia
of the ?rst target T1. Axial adiustment‘of the
position of this focus maybe effectecl‘by. adjust
grammatic longitudinal sectional view of an
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ing the potential of a sheet electrode S having
a slot sufficiently wide for the beam to be able
to pass under all conditions of de?ection. The
~ the beam would diverge and again converge to a
focus. This process may also be repeated more
than once by still further extensions. The plates
thus extended may be subdivided to any desired
primary purpose of electrode S is to serve as a
degree.
suppressor to prevent secondary electrons gen
erated at the targets T1, T2 from travelling to
wards the plates P1, P2, and for this purpose
The beam need not necessarily enter between
the plates as a divergent beam. It may, for ex
ample, be generated and focussed as a. parallel
beam before entering between the plates. With
electrode S» may have any potential somewhat
below the lowest potential likely to be reached
by either of the targets T1, T2 during operation“ .10 plates of length subtending an angle of nearly
If the potential of plate P1 is raised or low
‘63%’, say 55°, the beam will then issuer in form
rapidly converging toward a focus. A similar
ered relatively to that of plate P2 by a few mi
result will be obtained if the plates are extended
crovolts, the position of focus F1 is moved radially
by another 127", so that they subtend an angle of
to a slight degree so that a greaterorless pro
portion of the beam current will impinge upon, 15 about 180°.
and be collected by, the ?rst target T1. The re
Also, the beam need not necessarily leave the
plates in convergent form. Post-de?ection fo
mainder of the beam current is collected by tar
cussing means may be provided to bring the
get T2 placed beyond T1. By way of example,-a
beam to a ?ne focus on the edge of a target, if
push-pull input circuit is shown connected be
.tween plates P1 and P2. This is indicated as an 20 required.
alternating source B and a pair of impedances
Z1 and Z2 connected in the leads from plates
If an electron beam de?ection valve has more
than one pair of plates arranged beside the beam
P1 and P2 respectively to their bias potential
like de?ector plates for the same direction of
sources. Any suitable output circuit may be
the de?ection, the output may be taken from one
connected with the targets; for example, the im 25 of these pairs of plates other than the ?rst
pair as shown in Fig. 3. The ?rst pair of
pedances Z3 and Z4 in the leads to the targets
provide a push-pull output between the termi
plates P1 and P2 are employed as de?ector plates,
the input de?ection voltage being applied by
nals D.
source B as in Fig. 2. As the electron beam
By the placing of one target behind the other,
provided the focus is ?ne on the edge of the ?rst 30 movesnearer to one plate and further from the
other plateof a pair, a positive charge will appear
target, the de?ection necessary to transfer the
on one of these plates and a negative charge on
beam from one target to the other is reduced to
a low value; in other words the mutual con
ductance is made high. The capacity between the
targets is also reduced to a low value by this
arrangement.
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the other. 'A voltage therefore appears between
the plates Pa and P4. The voltage is large when
the de?ection frequency is'high. The valve feeds
energy to an output circuit connected between
this pair of plates, here shown as an impedance
Z5 connected to the plate P4, and the voltage is
section, to discourage the emission of secondary I
proportional to the velocity of the sideways move
electrons. The side of target T1 adjacent to that
part of the beam which has passed F1 and which 40 ment of the beam. It follows that this method
of obtaining the output from a beam de?ection
is travelling towards target T2, is preferably in
valve is particularly effective at the higher fre
clined away from that part of the beam, so that
quencies. A single target may be employed to
it will not collect current from the beam.
collect the electron beam, which need not be
De?ector plates P1, P2 could be divided at OZ, as
shown in Figs. 2 and 3, and di?erent de?ection 45 brought to a focus. Alternatively,‘ a pair of tar
gets may be employed, the beam being focussed
voltages could then, if desired, be applied between
on the edge of one target in the ordinary manner,
the two successive pairs of de?ector plates 50
and between these targets there may be connect
formed, or the two pairs could be used for other
The targets are preferably of U-shape cross
purposes hereinafter described. In Fig. 2, for’ ‘ ed another output circuit, or a feedback or other
instance, an asymmetrical de?ection voltage be 50 desired circuit.
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tween plates P1 and P2 is indicated by the alter
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nating source B1 in series with the lead of plate
1. In ’ an electron beam de?ection valve, an
.P1 only. A second asymmetrical de?ection volt
electron gun to generate a beam of electrons, said
age is applied to plates P3 and P4 by means of
gun comprising a cathode and an electrode hav
the alternating source B2 in series with plate P4 55 ing only a single opening through which said
only. An asymmetrical output between the tar
beam passes, whereby said beam is focused to pass
gets is indicated by impedance Z3 in the lead to
through a crossover and diverge therefrom, a fo
cusing system including a pair of co-axial part
the target T1 only. '
cylindrical electrodes of different radii so ar
If desired, one pair could be spaced consider
ably apart from the other, and the beam would 60 ranged that they bound an arcuate space through
then travel in a straight path between the pairs.
which the beam passes and means to maintain
a steady component of potential difference be
If angle XOZ were about 60°, the beam in pass
tween said part-cylindrical electrodes to focus
ing between the pairs would be approximately
into a parallel beam the electrons issuing from
parallel. If angle XOZ were smaller or larger,
the beam would be divergent or convergent while 65 said crossover, means to ‘superimpose on said
steady component a relatively small alternating
passing between the pairs. The curvatures of
component of potential difference to de?ect said
the two pairs of plates need not be the same in
degree or in sense ‘provided that each pair has a
electrons, and means responsive to the de?ection
of said electrons to excite an output circuit in ac
- bias voltage appropriate to its curvature. Fur
cordance therewith.
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ther subdivision of the plates could be effected if
desired. Any tendency of the beam to diverge
2. In an electron beam de?ection valve, a plu
rality of electrodes including a ?nal anode to
when travelling between one pair of plates and
generate a beam of electrons divergent from a
another could be overcome by the provision of a
converging electronv lens.
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concentrated source, at least one target electrode
If the plates were extended by another 127°, 75 to collect said electrons, a pair vof co-axial part
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cylindrical de?ector electrodes of different radii
so arranged thatthey boundi‘an arcuate space
through which‘ the beam passes, means to main
tain substantially equal‘ and opposite steady com:
ponents of potential difference between» each of
said de?ector electrodes and said ?nal anode to
causesaid electrons to follow the arcuate path
between them, a pair'of output electrodes ‘dis
posed on opposite sides of said beam beyond said
de?ector electrodes; and means to superimpose
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remainder of said electrons, a focussing system
including a pair‘of co-axial part-cylindrical elec
trodes having vradii in the approximate ratio»
of 41:5 and so’ arranged‘ that they bound an ar
cuate space through which the beam passes be
fore reaching said ?rst target electrode, means
to maintain a steady component of potential dif
ference between said electrodes to cause said
electrons .to converge to a ?ne focus on the edge
of said ?rst target electrode, means to superim
on at least one of said steady components a rela-"
pose on said steady component a relatively small
tively small alternating ‘component of potential
alternating component of potential difference to
difference to vary the position of the beam rel
ative to said output electrodes to- induce an out
de?ect said electrons, and an output circuit con
nected between said ?rst and second target elec
‘ put voltage between them.
15 trodes to respond to variations of the distribu
tion of electrons between said target electrodes.
‘ 3. In an electron‘beam de?ection. valve, means
to generateand focus a beam of electrons to pass
'7. In an electron beam de?ection valve, means
to generate a beam of electrons divergent from
through a crossover and diverge therefrom, a fo
cussing‘ system including a pair of coaxial part
a concentrated source, a, focussing system includ
cylindrical electrodes of different radii so ar 20 ing a‘ plurality of co-axial part-cylindrical elec
ranged that they‘ bound an arcuate spacethrough ‘ trodes of different radii paired on ‘opposite sides
of said beam so that each pair of said electrodes
which the beam passes and means to maintain
a steady component of potential difference be-‘ _
bounds an arcuate space, means to maintain a
steady component of potential difference between
tween said electrodes to focus the» electrons issu
ing from said crossover into a parallel beam, 25 each pair of said electrodes to cause said beam
means for superimposing on» said steady compo
to follow the curvature of each said space, means
nent an alternating component of‘ potential dif
ference to de?ect said beam, a pair of output elec
trodes disposed on opposite sides of said beam
for superimposing a relatively small alternating
component of potential difference between at
least one ‘pair of said electrodes to de?ect said
beyond said ?rst electrodes and an output circuit 30 beam, and'means responsive to. the deflection of
connected with said output electrodes and ex
said beam for exciting an output circuit in ac-.
cited by the output voltage developed between
cor-dance therewith.
them according to the position of said beam.
. 8. In an electron beam deflection valve, means
to generate a beam of electrons divergent from a
4. In an electron beam de?ection valve, a plu
rality of electrodes including a ?nal anode to gen 35 concentrated source, a focussing system includ
erate and focus a beam of electrons to pass
ing a plurality of co-vaxial part-cylindrical elec
trodes of different radii paired on opposite sides
through a crossover and diverge therefrom, a ?rst
target electrode disposed in the path of said elec
of said beam so that each pair of said electrodes
bounds an arcuate space, means to maintain a
trons to collect a part thereof, a second target
electrode disposed in the path of said electrons .40 steady component of potential difference between
beyond said ?rst target to collect the remainder
each pair of said electrodes to cause said beam
to follow the curvature of each said space, means
of said electrons, means comprising a pair of co
for superimposing one relatively small alternat
axial part-cylindrical de?ector electrodes of dif
ing component of potential difference between
ferent radii so arranged that they bound an ar
cuate space through which ‘the beam passes, 45 one pair of said electrodes, means for superim
posing a di?erent relatively small alternating
. means to maintain substantially equal and oppo
site steady components of potential difference
component of potential difference between ‘an
between each of said de?ector electrodes and said
other pair of said electrodes, and means respon
sive to the resultant de?ection of said beam for
?nal anode to cause said electrons to follow the
- arcuate path between them and to focus said 50 exciting an output circuit in accordance there
with.
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electrons ?nely on the edge of said ?rst target
electrode, and means to superimpose on at least
9. In an electron beam de?ection valve, means
to generate a beam of electrons divergent from a
one of said steady components a relatively small
alternating component of potential difference to
concentrated source, a focussing system includ
vary the proportionate distribution of said elec 55 ing a plurality of co-axial part-cylindrical elec
trodes of different radii paired on opposite sides
trons between said target electrodes.
of said beain so that each pair of said electrodes
5. In an electron beam de?ection valve, means
to generate a substantially parallel beam of elec
bounds an arcuate space, means to maintain a
steady component of potential di?erence be
trons, a focussing system including a pair of co
axial part-cylindrical electrodes of di?erent 60 tween each pair of said electrodes to cause said
radii so arranged that they bound an arcuate
beam to follow the curvature of each said space,
means to de?ect said beam, and an output cir
space through which the beam passes, means to
maintain a steady component of potential dif
cuit connected between at least one pair of said
electrodes and excited by the output voltage in
ference between said electrodes to cause said
electrons to converge to a focus, means to de?ect 65 duced between them by de?ection of said beam.
said beam of electrons, and an output circuit
10. In an electron beam de?ection valve, means
for generating a beam of electrons divergent from
connected between said electrodes and excited
a concentrated source, a focusing system includ
by the output voltage induced between them by
ing a pair of coaxial part~cylindrical electrodes
de?ection of said beam.
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6. In an electron beam de?ection valve, means 70 of different radii so arranged that they bound an
to generate a substantially parallel beam of elec
arcuate space through which the beam passes
and means to maintain a steady component of
trons, a ?rst target electrode disposed in the path
potentialdi?erence between said electrodes‘to
of said electrons to collect a part thereof, a sec
ond target electrode disposed in the path of said
focus the electrons from said source into a par
electrons beyond said first target to collect the 75 allel beam, means for superimposing on said
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steady component'an alternating component of
potential difference to de?ect said beam, a pair
of co-axial part-cylindrical output electrodes dis
rality of electrodes including a ?nal anode to
posed on opposite sides of said beam beyond said
focusing electrodes, and an output circuit con
nected with said output electrodes and excited
anode, a focusing system comprising a pair of
co-axial part-cylindrical electrodes of different
'“12. In an electron beam de?ection valve; a plu
generate and focus a beam of electrons to pass
through a‘crossover situated close to said ?nal
by the output voltage developed between them
radii so arranged that they bound an arcuate
space through which said beam passes after pass
ing through said crossover, a ?rst target elec
11. In an electron beam de?ection valve, an
electron gun to generate a beam of electrons, said 10 trode disposed in the path of said beam to col
lect part of the electrons thereof and so situated
gun comprising a cathode and an electrode hav
ing only a single opening through which said
that the edge of said target and said ?nal anode
subtend an angle of approximately 127° at the
beampasses, whereby said beam is focused to
common axis of said part-cylindrical electrodes,
pass through a crossover and diverge therefrom,
a focusing system including a pair of co-axial 15 a second target electrode disposed in the path of
said beam beyond said ?rst target to collect the
part-cylindrical electrodes of different radii so
arranged that they bound an arcuate space
remainder of the electrons thereof, means to
maintain a steady component of potential dif
through which the beam passes'and means to
ference between said part-cylindrical electrodes
maintain a steady component of potential differ
ence between said part-cylindrical electrodes to 20 to focus said beam ?nely on said edge of said ?rst
target electrode, means to 'superimpose on said
focus the electrons from said source into a par
steady component a relatively small alternating
allel beam, means for superimposing on said
according to the position of said .beam.
steady component an alternating component of
component of potential difference to de?ect said
beam and to vary the proportionate distribution
potential di?erence to deflect said beam, a pair
of output electrodes comprising targets disposed 25 of the electrons of said beam between said target
one beyond the other in the path of said beam
electrodes, and an output circuit connected be
tween said target electrode.
beyond said part-cylindrical electrodes, and an
output circuit connected with said output elec
trodes and excited by the output voltage devel
BRIAN CLIFFORD FLEMING-WILLIAMS.
oped between them according to the position of 30
said beam.
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