Plasma-assisted tube with helical slow-wave structure

A plasma-assisted, microwave source configured to generate a microwave signal with the aid of an ionizable gas and without the aid of magnetic beam-focusing structures and to be cooled by a cooling liquid, said source comprising:

• a source waveguide configured with a wall and having first and second ends;
• a plasma-cathode, electron gun coupled to said source waveguide first end;
• a collector coupled to said source waveguide second end;
• first and second apertures defined by said source waveguide wall;
• input and output waveguides which are joined to said source waveguide wall and arranged to physically communicate respectively through said first and second apertures with said source waveguide, each of said input and output waveguides having a respective wall;
• a microwave load coupled to said input waveguide;
• a helix configured with a hollow interior and first and second ends, said helix positioned within said source waveguide;
• first and second waveguide antennas comprising extensions of said first and second helix ends away from said helix, said extensions passing respectively through said first and second apertures and joining said first and second helix ends in an orthogonal relationship respectively with the walls of said input and output waveguides;
• first and second liquid coupling ports comprising further extensions of said first and second helix ends through the walls of said input and output waveguides respectively, said first and second liquid coupling ports coupled to said hollow interior for communication of said cooling liquid into and out of said hollow interior;
• and
• first and second pressure windows positioned respectively across said input and output waveguides, with said first and second helix ends between said source waveguide and said first and second pressure windows respectively;
• wherein:
• said source waveguide and said first and second pressure windows are configured to receive and contain said ionizable gas about said helix and said first and second waveguide antennas;
• said electron gun is configured to inject an electron beam through said helix and through said ionizable gas to said collector, said electron beam thereby generating a plasma channel in said ionizable gas which assists in the confinement and transport of said electron beam to said collector
• said microwave load, said input waveguide and said first waveguide antenna permitting said microwave signal to be generated along said helix through interaction with said electron beam;
• and
• said second waveguide antenna and said output waveguide coupling said microwave signal from said helix.