US4912367A — Plasma-assisted high-power microwave generator

Claim 1

Independent Claim 108 words

An oscillator for generating electromagnetic radiation within the microwave to millimeter-wave range, comprising: a waveguide housing, means for introducing an ionizable gas into said waveguide housing, an electron gun for injecting an electron beam into said waveguide housing, and means for maintaining the gas pressure within said waveguide housing at a level sufficiently low to avoid a voltage breakdown of the beam, and sufficiently high to provide enough ions to substantially neutralize space-charge expansion of the beam, said electron gun injecting said beam into the waveguide housing with a sufficient current density to at least partially ionize the gas therein and generate electromagnetic radiation at said gas pressure.

Claim 2

Dependent Claim 108 words

An oscillator for generating electromagnetic radiation within the microwave to millimeter-wave range, comprising: a waveguide housing, means for introducing an ionizable gas into said waveguide housing, an electron gun for injecting an electron beam into said waveguide housing, and means for maintaining the gas pressure within said waveguide housing at a level sufficiently low to avoid a voltage breakdown of the beam, and sufficiently high to provide enough ions to substantially neutralize space-charge expansion of the beam, said electron gun injecting said beam into the waveguide housing with a sufficient current density to at least partially ionize the gas therein and generate electromagnetic radiation at said gas pressure.

Claim 3

Dependent Claim 18 words

The oscillator of claim 1, wherein said gas pressure is maintained within the approximate range of 1-20 mTorr.

Claim 4

Dependent Claim 30 words

The oscillator of claim 2, implemented as a slow-wave tube, said waveguide housing having a rippled wall, wherein said gas pressure is maintained within the approximate range of 1-5 mTorr.

Claim 5

Dependent Claim 24 words

The oscillator of claim 2, implemented as a plasma wave tube, wherein said gas pressure is maintained within the approximate range of 10-20 mTorr.

Claim 6

Dependent Claim 24 words

The oscillator of claim 1, wherein said electron gun generates a beam with a current density of at least about 1 amp/cm 2 .

Claim 7

Dependent Claim 107 words

The oscillator of claim 5, said electron gun comprising a hollow cathode having an outlet, an apertured grid at said cathode outlet, means for introducing an ionizable gas into said hollow cathode, means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within said cathode, the grid having a generally high transparence but with apertures small enough to prevent the passage of plasma through it, a generally transparent anode on the opposite side of the grid from the cathode, and means for applying an electrical potential to said anode to extract an electron beam from the plasma behind said grid.

Claim 8

Dependent Claim 53 words

The oscillator of claim 6, wherein the inner cathode surface is formed from a chemically active metal, and said gas introducing means includes means for doping the gas with a trace amount of oxygen to react with said metal and form an oxide thereof, thereby enhancing the secondary electron yield from the cathode.

Claim 9

Dependent Claim 26 words

The oscillator of claim 6, wherein said hollow cathode and anode have respective sets of apertures which are mutually aligned to yield a high perveance beam.

Claim 10

Dependent Claim 25 words

The oscillator of claim 6, wherein the cathode surface, grid and anode are curved concave with respect to the beam to geometrically focus the beam.

Claim 11

Dependent Claim 20 words

The oscillator of claim 6, said hollow cathode being cylindrical to generate an electron beam with a substantially circular cross-section.

Claim 12

Dependent Claim 38 words

The oscillator of claim 1, wherein said means for introducing an ionizable gas into the waveguide housing also introduces said ionizable gas into the electron gun at a pressure approximately equal to the pressure within the waveguide housing.

Claim 13

Dependent Claim 37 words

The oscillator of claim 11, said electron gun including means for establishing an electrical glow discharge through the ionizable gas within said gun to establish a plasma therein, said plasma providing an electron source for said beam.

Claim 14

Dependent Claim 21 words

The oscillator of claim 12, said electron gun including means for producing said discharge in pulses of about 1-100 μsecond duration.

Claim 15

Dependent Claim 38 words

The oscillator of claim 1, said electron gun injecting an electron beam into one end of the waveguide housing, and further comprising a horn antenna at the opposite end of the waveguide housing for emitting output electromagnetic radiation.

Claim 16

Dependent Claim 206 words

An oscillator for generating electromagnetic radiation within the microwave to millimeter-wave range, comprising: (a) a waveguide housing, (b) an electron gun coupled to said waveguide housing for injecting an electron beam into said waveguide housing, (c) means for introducing an ionizable gas into the waveguide housing and electron gun at a pressure sufficiently low to avoid a voltage breakdown of the beam, and sufficiently high to provide enough ions within the waveguide housing to substantially neutralize space-charge expansion of the beam, and (d) said electron gun comprising: (i) a hollow cathode having multiple outlets to said waveguide housing, (ii) a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, (iii) means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, (iv) a perforated anode on the opposite side of the grid from t he cathode, and (v) means for applying an electrical potential to said anode to extract an electron beam from the plasma behind the grid into said waveguide housing, said electron gun generating said beam with a sufficient current density to at least partially ionize the gas therein and generate electromagnetic radiation.

Claim 17

Dependent Claim 206 words

An oscillator for generating electromagnetic radiation within the microwave to millimeter-wave range, comprising: (a) a waveguide housing, (b) an electron gun coupled to said waveguide housing for injecting an electron beam into said waveguide housing, (c) means for introducing an ionizable gas into the waveguide housing and electron gun at a pressure sufficiently low to avoid a voltage breakdown of the beam, and sufficiently high to provide enough ions within the waveguide housing to substantially neutralize space-charge expansion of the beam, and (d) said electron gun comprising: (i) a hollow cathode having multiple outlets to said waveguide housing, (ii) a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, (iii) means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, (iv) a perforated anode on the opposite side of the grid from t he cathode, and (v) means for applying an electrical potential to said anode to extract an electron beam from the plasma behind the grid into said waveguide housing, said electron gun generating said beam with a sufficient current density to at least partially ionize the gas therein and generate electromagnetic radiation.

Claim 18

Dependent Claim 18 words

The oscillator of claim 15, wherein said cathode has an inner cathode surface formed from a non-magnetic metal.

Claim 19

Dependent Claim 55 words

The oscillator of claim 15, wherein said cathode has an inner cathode surface formed from a chemically active metal, and said gas introducing means includes means for doping the gas with a trace amount of oxygen to react with said metal and form an oxide thereof, thereby enhancing the secondary electron yield from the cathode.

Claim 20

Dependent Claim 26 words

The oscillator of claim 15, wherein said cathode outlets and anode have respective sets of apertures which are mutually aligned to yield a high perveance beam.

Claim 21

Dependent Claim 24 words

The oscillator of claim 15, wherein said cathode, grid and anode are curved concave with respect to the beam to geometrically focus the beam.

Claim 22

Dependent Claim 20 words

The oscillator of claim 15, said hollow cathode being cylindrical to generate an electron beam with a substantially circular cross-section.

Claim 23

Dependent Claim 92 words

Apparatus for generating a generally non-spreading electron beam, comprising: an electron gun for generating an electron beam, a housing coupled to the electron gun for receiving the electron beam, and means for introducing an ionizable gas into said housing for ionization by the beam, said gas being introduced at a pressure at which sufficient ions are generated in the vicinity of the beam to substantially neutralize space-charge blowup of the beam, said gun generating said beam with a sufficient current density to generate electromagnetic radiation within the housing at said gas pressure.

Claim 24

Dependent Claim 92 words

Apparatus for generating a generally non-spreading electron beam, comprising: an electron gun for generating an electron beam, a housing coupled to the electron gun for receiving the electron beam, and means for introducing an ionizable gas into said housing for ionization by the beam, said gas being introduced at a pressure at which sufficient ions are generated in the vicinity of the beam to substantially neutralize space-charge blowup of the beam, said gun generating said beam with a sufficient current density to generate electromagnetic radiation within the housing at said gas pressure.

Claim 25

Dependent Claim 25 words

The beam generating apparatus of claim 21, wherein said gas is introduced into the housing at a pressure within the approximate range of 1-20 mTorr.

Claim 26

Dependent Claim 25 words

The beam generating apparatus of claim 21, wherein electron gun generates said beam with a current density of at least about 1 amp/cm 2 .

Claim 27

Dependent Claim 153 words

An improved slow-wave tube, comprising: a ripple-walled waveguide housing, means for introducing an ionizable gas into said housing at a pressure within the approximate range of 1-5 mTorr, and an electron gun for injecting an electron beam into said housing with a current density of at least about 1 amp/cm 2 , said electron gun comprising: (a) a hollow cathode having multiple outlets, (b) means for introducing an ionizable gas into the cathode, (c) a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, (d) means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, (e) a perforated anode on the opposite side of the grid from the cathode, and (f) means for applying an electrical potential to said anode to extract an electron beam from the plasma behind said grid.

Claim 28

Dependent Claim 153 words

An improved slow-wave tube, comprising: a ripple-walled waveguide housing, means for introducing an ionizable gas into said housing at a pressure within the approximate range of 1-5 mTorr, and an electron gun for injecting an electron beam into said housing with a current density of at least about 1 amp/cm 2 , said electron gun comprising: (a) a hollow cathode having multiple outlets, (b) means for introducing an ionizable gas into the cathode, (c) a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, (d) means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, (e) a perforated anode on the opposite side of the grid from the cathode, and (f) means for applying an electrical potential to said anode to extract an electron beam from the plasma behind said grid.

Claim 29

Dependent Claim 12 words

The improved slow-wave tube of claim 24, wherein said gas is helium.

Claim 30

Dependent Claim 154 words

An improved plasma wave tube, comprising: A waveguide housing, means for introducing an ionizable gas into said waveguide housing at a pressure within the approximate range of 10-20 mTorr, and an electron gun for injecting an electron beam into said housing with a current density of at least about 10 amp/cm 2 , said electron gun comprising: (a) a hollow cathode having multiple outlets, (b) means for introducing an ionizable gas into the cathode, (c) a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, (d) means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, (e) a perforated anode on the opposite side of the grid from the cathode, and (f) means for applying an electrical potential to said anode to extract an electron beam from the plasma behind said grid.

Claim 31

Dependent Claim 154 words

An improved plasma wave tube, comprising: A waveguide housing, means for introducing an ionizable gas into said waveguide housing at a pressure within the approximate range of 10-20 mTorr, and an electron gun for injecting an electron beam into said housing with a current density of at least about 10 amp/cm 2 , said electron gun comprising: (a) a hollow cathode having multiple outlets, (b) means for introducing an ionizable gas into the cathode, (c) a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, (d) means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, (e) a perforated anode on the opposite side of the grid from the cathode, and (f) means for applying an electrical potential to said anode to extract an electron beam from the plasma behind said grid.

Claim 32

Dependent Claim 13 words

The improved plasma wave tube of claim 25, wherein said gas is helium.

Claim 33

Dependent Claim 35 words

The improved plasma wave tube of claim 26 wherein said waveguide housing has a smooth cylindrical wall and a single electron beam is injected into said housing to produce a pair of counterstreaming plasma waves.

Claim 34

Dependent Claim 98 words

An improved high current electron gun, comprising: a hollow cathode having multiple outlets, means for introducing an ionizable gas into the cathode, a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, a perforated anode on the opposite side of the grid from the cathode, and means for applying an electrical potential to said anode to extract an electron beam from the plasma behind said grid.

Claim 35

Dependent Claim 98 words

An improved high current electron gun, comprising: a hollow cathode having multiple outlets, means for introducing an ionizable gas into the cathode, a perforated grid located adjacent to said multiple cathode outlets, said grid having apertures small enough to prevent the passage of plasma, means for establishing an electrical glow discharge between the cathode and the grid to generate a plasma within the cathode, a perforated anode on the opposite side of the grid from the cathode, and means for applying an electrical potential to said anode to extract an electron beam from the plasma behind said grid.

Claim 36

Dependent Claim 17 words

The electron gun of claim 29, wherein the inner cathode surface is formed from a non-magnetic metal.

Claim 37

Dependent Claim 54 words

The electron gun of claim 29, wherein the inner cathode surface is formed from a chemically active metal, and said gas introducing means includes means for doping the gas with a trace amount of oxygen to react with said metal and form an oxide thereof, thereby enhancing the secondary electron yield from the cathode.

Claim 38

Dependent Claim 27 words

The electron gun of claim 29, wherein said cathode outlets and anode have respective sets of apertures which are mutually aligned to yield a high perveance beam.

Claim 39

Dependent Claim 25 words

The electron gun of claim 29, wherein said cathode, grid and anode are curved concave with respect to the beam to geometrically focus the beam.

Claim 40

Dependent Claim 22 words

The electron gun of claim 29, wherein said hollow cathode is cylindrical for generating an electron beam with a substantially circular cross-section.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-03-26	1993-09-25	1994-03-27	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-03-26	1997-09-25	1998-03-27	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-03-26	2001-09-25	2002-03-27	$7700.00	Window Closed / Lapsed

Plasma-assisted high-power microwave generator

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