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Патент USA US2410863

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NW” 12, W46.
1.. F. BROADWAY ET AL
2,419,853
ELECTRON DIS CHARGE DEVICE
.Filed Dec. 29, 1942 ‘
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23
24’
Jay; .6:
TTO/TMEY
2,410,853
Patented Nov. 12, 1946
UNITED STATES‘: PATENT oFFicE
2,410,863
,
ELECTRON DISCHARGE DEVICE
Leonard Francis Broadway, Ickenham, and Cabot
Seaton Bull, Hillingdon, England, assignors to
Electric & Musical Industries Limited, Hayes,
England, a company of Great Britain
Application December 29, 1942, Serial No. 470,506
In Great Britain March 5, 1940
2 Claims.
1
(Cl. 250-275)
.
This invention relates to electron discharge
devices of the “velocity modulation” type. De
vices of this type ?nd special application as ultra
high frequency oscillators, ampli?ers and detec
2
greater than the other. The ribbon may be an
elongated rectangle, or may be elliptical, the ma
jor axis of which is long compared with the
minor axis. The electron beam need not be in
the form of a ribbon throughout its length pro
viding it is of ribbon shape in the vicinity of said
electrodes or resonator orresonators. The term
with the magnitude of the beam current, and
“longer sides of the beam” means the longer
the magnitude of the beam current will, depend
sides of the beam when‘viewed in transverse sec
.ing on the focussing action employed, determine
the area of the transverse section of the beam. 10 tion.
The electrodes of the input or output system
In order to increase the beam current a larger
may be of any suitable construction. For exam
cross-section beam must be employed and if, as is
ple, the ‘electrodes of the input or output sys
usually the case, a beam of circular section is
tem may consist of three rods adjacent one of
used it is found that the efficiency-of the tube
‘ the longer sides of the beam or three pairs of
is seriously diminished as the circular sectioned
rods embracing both the longer sides of the beam
beam is enlarged since large diameter apertures
or they may consist of three ?at strips disposed
in the tube electrodes are required which cause
along one of the longer sides of the beam, or
an unwanted radiation of energy together with
three pairs of ?at strips embracing both of the
an unwanted dissemination of electrostatic ?eld
which latter gives rise to increased transit time 20 longer sides of the beam, said strips having ap
preciable extension in the direction of travel of
of the electrons necessitating the use of abnor
the beam. Any other group of three electrodes
mally high voltages if the transit time is to be
may be employed which are capable of disposi
reduced to the required value. This di?iculty
tion near the beam without substantially ob
is not overcome by providing grids in the aper
tures since at ultra-high frequencies the lengths 25 structing the passage thereof. The ?rst and third
electrode of each group may have extensions,
of the wires of the grids present a high imped
such as of solid or perforated sheet metal or
ance. It is desirable in order to increase the
metal gauze, extending to the wall of the en
e?i'ciency of tubes of the type referred to, to
velope and preferably at right angles to the pathv
maintainlthe ratio of the capacity between the
electrodes or between said edges to the cross-sec 30 or the beam. The longitudinal spacing of the
three electrodes of each group is so related to
tional area of the beam as small as possible. It
the steady operating potentials that in the case
' is found that, for equal values of the beam cur
where these electrodes have negligible extension
rent, the above-mentioned di?iculties can be re
in the direction of beam travel the time of ?ight
duced or overcome or the required conditions can
be more conveniently satis?ed by using a beam 35 of the electrons between the ?rst and second
electrodes, and between the second and third
in the form of a ribbon.
electrodes, is equal to half the time period of
According to one feature of the'invention there
the high frequency potential, while in the case
is provided an electron discharge device of the
tors.
The usefulness of devices of this type increases
velocity modulation type provided with, means
where these electrodes have appreciable exten
for generating an’ electron beam in the form of 40 sion in the direction of beam travel, the time of
?ight from the gap between ?rst and second elec
a ribbon.
‘
trodes to the gap between second and third elec
According to another feature of the inventon,
trodes is equal to half the time period of the
there is provided an electron discharge device
high-frequency potential. In some cases it may
of the velocity modulation type provided with
means for generating an electron beam in the 45 be desirable to employ a longitudinal magnetic
?eld.
form of a ribbon and either the input or output
It may in some cases be desirable to inter
system, or both, comprises an apertured hollow
resonator arranged transversely of the path of
connect the rods of the pairs of electrodes with
transverse grid wires and since the rods can be
said beam, the apertures in said resonator or res
onators through which the beam passes being 50 arranged relatively close together due to the
ribbon shaped beam employed the lengths of the
_ shapedto conform generally to the transverse
wires will not present the dif?culties hereinbefore
section-of said ribbon beam.
referred to.
- .. The term “ribbon”_is intended in this speci?
Where either the input or output system, or,
cation to include any beam the transverse sec
tion of‘ which has one dimension substantially .55 both comprises a hollow resonator the latter may
3
52,410,863
4
generally comprise a hollow body surrounding the
beam and instead of having circular apertures
It is found advantageous to operate the cone
trol electrode 2 at a low positive potential and
through which the beam passes, as in known
forms of hollow resonators, the apertures are
shaped to conform to the transverse section of
the beam. If the beam is of elongated rectan
gular shape in transverse section, then the shape
of the aperture in the resonator through which
the beam passes will also generally be of an elon
gated rectangular shape, the resonator being suit
the accelerator 6 at a somewhat more positive
potential, since the preliminary focussing of the
electrons achieved in this manner tends to equal
ise the times of ?ight in the axial direction of
all the electrons of the beam, and hence to pro
duce more complete velocity modulation and
higher output.
10
ably , shaped accordingly.
In Figure 2 the various electrodes have the
same reference numerals as in Figure 1. [4 rep
resents the envelope of the device and I5 a seal
In order that the invention may be more clear
ly understood and readily carried into effect it
of a particularly suitable type for introducing
the high-frequency conductors into the tube.
to the accompanying drawing, in which:
15 The capacity per centimeter in W-farads of the
Figure 1 shows diagrammatically a plan View
electrodes 8 to electrodes 1 and 9 together and
of the electrodes of a tube according to one form
of electrodes 8a to electrodes la and 9a is ar
will now be more fully described with reference
of the invention,
Figure 2 is a side elevation of a complete tube
according to the invention,
Figure 3 is a transverse section of the tube
shown in Figure 2, but with a modi?ed con—
struction of electrode,
Figure 4 illustrates diagrammatically in cross
section a tube employing a hollow resonator con
structed in accordance with the invention, and
ranged to be the same as that of the transmission
line or resonant circuit to be connected to them,
20 and is given by the relation:
C: 33.3JK
Z0
where Z0 is the impedance of the transmission
25 line measured in ohms, and K is the dielectric
constant of the medium in which the electrodes
Figure 5 illustrates a front elevation of the
hollow resonator shown in Figure 4.
Referring now to Figure 1, l represents a
thermionic cathode having a plane rectangular _‘
emitting surface with its lesser dimension paral
lel to the plane of the drawing and its greater
dimension perpendicular thereto the cathode
are situated measured in electrostatic units.
If
the electrodes '1, 8, 9 and ‘la, 8a, 9a, consist of
pairs of rods with transverse wires, the capacity
is approximately equal to:
JWLE
47K‘ d __ Z0
serving to emit a beam in the form of a ribbon
neglecting edge eilects where W is the lateral
2 represents a control electrode comprising the 35 separation of the rods and d is their longitudinal
rods 3, 41 disposed symmetrically to the sides of
the cathode at a short distance in front thereof
and supporting a number of wires 5 parallel to
the plane of the drawing. 6 is an accelerator
electrode of the same construction as the con- ‘
trol electrode 2, and disposed at a short distance
in front thereof. The input and output systems
in the, example shown each comprise three elec
trodes consisting of pairs of strips ‘.7, 8, 9 and ‘la,
8a, 9a respectively, spaced apart along the length
‘of and disposed symmetrically with respect to
the beam l0, and closely adjacent thereto. The
electrodes lie along the whole length of both of
~ the longer sides of the beam.
separation. The correct relations for other elec
trode constructions may be found either experi
mentally or by calculation.
Although in the examples described with ref
erence to the drawing, the input and output sys
tems are both inductively coupled with the elec
tron stream, it is to be understood that the inven
tion is not limited to such a construction. For
example, in some cases the output from the tube
may be taken from an anode on which the elec
tron stream impinges.
Furthermore, the invention is not limited to the
types of input and output systems shown in Fig
For most e?lcient
ures l to 3 of the drawing since the invention
operation it is found that the extension of those
?nds a ready application to the type of velocity
strips in the direction of beam travel should
modulation device in which the input or output
be approximately equal to their transverse sepa
system, or both, comprises a hollow resonator
ration, and is thus dependent on the width of the
through which the beam passes. In this type of
beam. II is the collecting anode which may be
velocity modulation tube the hollow resonator is
provided with cooling ?ns l2, as shown, and I3 is " tuned to a desired frequency and the potentials
an electrode for suppressing secondary electrons
which impart the velocity modulation to the beam
emitted by the anode. The suppressor it may,
can be applied to one hollow resonator and the
for example, be of similar construction to the
output energy abstracted from another resonator
control electrode 2.
suitably spaced from the ?rst resonator. In ve
In operation it is desirable that the electrodes 60 locity modulation devices employed as oscillators
7 and ‘la shall be at a lower steady potential than
one resonator may be suitably coupled to an
the electrodes 8 and 8a respectively. This will
. other resonator or a. single resonator may be em
have the effect of focussing electrons through the
ployed and the velocity modulated beam may be
electrodes 8 and 8a thus reducing the D. C. cur
reflected back into the single resonator. The in
rent to these electrodes and maintaining a high 5 vention can be applied to any of these or other
value of D. C. impedance. The electrodes 9 and
types of velocity modulation devices employing
9a may be at any suitable steady potential con
hollow resonators. Figure 4 of the drawing il
sistent with the consideration that the time of
lustrates diagrammatically in cross-section with
flight of the electrons from the gap between elec
the envelope omitted, a device employing a single
trodes ‘I and 8 or la and 8a to the gap between 70 hollow resonator constructed in accordance with
electrodes 8 and 9 or Ba and 9a is equal to a half
the invention. In this device the cathode l is of
period of the high-frequency potential. 'Elec~
elongated form and may be associated with other
electrodes so as to cause it to generate a ribbon
trodes 7 and 9 and l'a and 9a are earthed as
regards high-frequency and the ?uctuating po
shaped beam. The ribbon-shaped beam is ar
" 7.5 ranged to pass through an aperture 20 in a hol
tentials are borne by electrodes 8 and 8a.
2,410,863
5
6
to the longer axis of the beam path, the ele
ments of each pair of electrodes being equal in
width and spaced apart transversely of the beam
path a distance equal to the width of said ele
ture being disposed as close to the beam as pos
ments parallel to the direction of movement of
sible. The beam after passing through the res
the electrons along the beam path.
onator is re?ected by a re?ecting electrode 22
2. An electron discharge device having a cath
back through the resonator. The resonator as
ode for supplying a single beam of electrons along
shown in Figure 5 generally comprises a pair of
a beam path, said beam of electrons having an
straight cylindrical portions 25, 24 lying along
the longer sides of the beam, the ends of said 10 elongated rectangular transverse cross-section, a
collector for receiving said beam of electrons, and
portions being interconnected by hollow semi
electrode means positioned between the cathode
circular portions 25, 25. The resonator is ar
and the collector and including a plurality of
ranged generally in a plane at right angles to
pairs of successively positioned ribbon-like elon
the axis of the beam and surrounds the beam, the
resonator as will be observed being similar to 15 gated narrow electrode elements of conducting
material, said conducting elements lying parallel
known forms of resonator with the exception that
to
the longer axis of the beam path, the elements
the aperture is shaped to enable the ribbon beam
of each pair of electrodes being of equal width
to pass therethrough and the general con?gura
and spaced apart transversely of the beam path
tion of the resonator shaped accordingly.
low resonator 2| the aperture being shaped to
conform generally to the transverse section of
the ribbon beam employed, the edges of the aper
20 a distance equal to the width of said elements
parallel to the direction of movement of the elec
1. An electron discharge device having a cath
trons along the beam path, the distance between
ode for supplying a single beam of electrons along
successive gaps'between adjacent pairs of ele
a beam path, said beam of electrons having an
ments along the beam path being equal to the
elongated rectangular transverse cross-section, a
collector for receiving said beam of electrons, 25 distance that an electron travels during a half
period of the high frequency at which said elec
and electrode means positioned between the oath
tron discharge device operates.
ode and the collector and including a plurality of
What we claim is:
pairs of successively positioned ribbon-like elon
gated narrow electrode elements of conducting
material, said conducting elements lying parallel
LEONARD FRANCIS BROADWAY.
30
CABOT SEATON BULL.
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