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Патент USA US2410055

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Oct. 29, 1946.
Filed June 2, 1942
Patented Oct. 29.1946
John Heaver Fremlin and Roger Norman Hall,
London W. C. 2, England, assignors to Standard
Telephones and Cables Limited, London, Eng
land, a British company ,
' ‘
Application June 2, 1942),‘ Serial No. 445,503
In Great Britain August 2, 1940
7 Claims.‘ (Cl. 250—27.5)
This invention relates to electron discharge
apparatusemploying ‘electron beams focussed or
and resonator structure to provide a focussing
?eld along the beam path,
directed in a straight path by means of a mag
Embodiments of the invention as applied to
velocity modulated tubes of the kind disclosed in
‘United States Patent No. 2,320,860 to J.
lin‘ will now be described with reference to Figs.
netic ?eld. The invention is primarily applicable
to apparatus operating at extremely high ire- .
gquencies, particularly apparatus of electron-ve
locity “modulated type.
‘In- certain electron tubes for use at very high
frequencies, ‘it is necessary to use a magnetic
?eld for directing the electron paths if it is de
sired to obtain the highest efficiency. This may
be done in the case of many sealed off tubes by
1 and 2) of the accompanying drawing.
‘ '
Fig. 1 is, a perspective view of ‘a tube cut away
‘to show a cross-section along the beam path.
The electrode structurecomprises a co-axial tube
resonator I With ?ns 2, 3 bounding apertures for
the beam path. A cathode 4 and a focussing
electrode 5 together forming an electron gun are
means of a permanent magnet. In order to do
located in line with the apertures in the reso
this with as light a magnet as possible the gaps
in the magnetic circuit must be made as small as 15 nator and are preferably carried on the resonator.
These elements are slid into a tubular metal en
possible. It is proposed, therefore as a ?rst
velope portion or sheath 6 A permanent mag
means of doing this that pieces of high perme
ability material should be incorporated in the
vacuum tube structure as pole-pieces or exten
net ‘I is provided outside the sheath 6 to provide
an intense ?eld along the beam path. In order
Such pole-pieces 20 to shorten the gap as much as possible and thus
obtain a strong ?eld, magnetic pole-pieces 8, 9
are also useful in obtaining a concentrated ?eld
are provided inside the sheath.‘
in the case where an electro-magnet is used.
Pole-piece 8 lies behind the cathode 4 and is
Developing further the same idea, it is pro
insulated by sheet material NJ from the sheath
posed that the vacuum envelope or a part there
so that a ?eld of the high potential of the res
of be made itself of a material capable of main 25 onator and the sheath is not set up in close prox
sions of external pole-pieces.
taining a high degree of permanent magnetisa
tion, if necessary plated inside with a metal of
high conductivity to avoid high frequency losses.
imity to the cathode. This pole-piece may if
desired be connected to the cathode;
Pole-piece 9 forms a part of the resonator
Alternatively, if it is desired to avoid the use 30 structure and serves also as a collecting elec
of magnetic materials for the external envelope,
trode. Its sides may be covered with a more high
the structure including the permanent magnet
ly conductive metallic layer if desired. Its col
may be contained in a glass envelope of any de
lecting face may be so shaped or coated as to
sired size, the need for minimum size of envelope
suppress secondary emission if this is required.
being eliminated by the fact that the magnet 35 It will be seen that a substantial shortening of
structure is internal.
the magnetic ?eld gap is accomplished by the
In further aspects, the invention resides in
‘provision of the internal pole-pieces, and that
electron discharge apparatus of the electron-ve
only a single gap is employed this gap thus short
locity-modulated type comprising within a vac
ened still includes the entire length of the beam.
uum-tight envelope an electron gun adapted to 40
Fig. 2 is a similar view of a modi?ed. tube in
project electrons in a beam through a resonator
which a tubular permanent magnet ll, formed
with inwardly-projecting pole-pieces 8' and 9’ in
structure, and, for collecting the electrons, a col
line with the apertures in the resonator ll, consti
lector electrode which may form part of the res
tutes a part of the evacuated envelope itself. The
onator structure, characterised by one of the fol
45 internal surface of the magnet may be plated with
lowing features:
a metal of high conductivity.
(a) Magnetic pole-pieces are provided within
If it is desired to avoid the use of magnetic ma
the envelope at the ends of the electron beam
terials for the external envelope, the structure
path, said pole-pieces being adapted to form part
including the permanent magnet ll may be con
of a magnetic circuit including a permanent
magnet or an electromagnet outside the envelope. 50 tained in a glass envelope as indicated in Fig. 2.
What is claimed is:
(b) The envelope itself comprises a permanent
1. Electron discharge apparatus of the electron
magnet having poles at the ends of the beam
velocity modulated type comprising a tubular me
path for focussing the beam.
tallic member forming part of a vacuum-tight en
(0) A permanent magnet is provided within
the envelope and embracing the electron gun 55 velope, a resonator comprising a short length of
' 2,410,054
coaxial line having diametric aligned apertures
and disposed within said tubular metallic mem
ber, means for generating and directing a beam of
electrons through said apertures also disposed
within said tubular metallic member, and a pair
of the beam path with a single magnetic gap
therebetween including the entire length of the
beam path, at least one pole-piece having a pole
face within the envelope.
4. An electron discharge apparatus according
of magnetic pole pieces disposed one at each end
to claim 3 wherein one magnetic pole-piece con
of the electron beam path having only a single
stitutes a collector electrode and is conductively
gap therebetween, one of said pole pieces being
connected to ‘the resonator.
mounted upon saidvtubular metallic member and
5. An electron discharge apparatus according
the other of said pole pieces being mounted upon 10 to claim 3 wherein there is means for completing
a magnetic circuit of the pole-pieces comprising
said resonator.
a permanent magnet located within the envelope.
2. Electron discharge apparatus of the electron
6. An electron ‘discharge apparatus according
velocity modulated" type comprising a resonator
to claim 3 in which the cavity resonator comprises
including a short length of coaxial line having
diametric aligned apertures, means adjacent 15 a short length of coaxial line having diametrical
thereto for generating a beam of electronsgiand
positioned for directing it through said apertures,
aligned apertures through which the electron
beam path passes.
7. An electron discharge apparatus of the elec
tron-velocity modulation type comprising elec
and a single tubular permanent magnet sur
rounding said resonator and provided with a pair
of inwardly directed pole pieces disposed one at 20 tron beam generating electrodes, a cavity reso
each end of the electron beam path and in line
nator constituted by a short length of coaxial line
with said apertures,
having diametrical aligned apertures through
3. An electron discharge apparatus of the elec
which the beam path passes, beam focusing
tron-velocity modulation type comprising beam
means having magnetic pole-pieces located re
generating electrodes within a vacuum-tight en 25 spectively at the ends of the beam path, at least
velope, a cavity resonator positioned adjacent to
one pole-piece having a pole-face with-in the
the path of the beam for cooperating with the
envelope and forming part of the resonator.
electron beam, beam focusing means having mag
netic pole-pieces located respectively at the ends
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