Plasma-assisted high-power microwave generator

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.

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.sup.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.

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.sup.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.

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.