Thermionic wave generator (TWG)

An energy converter comprising:

• a first electrode for emitting electrons;
• a second electrode for focusing the electrons emitted from the first electrode into an electron beam;
• a third electrode, wherein the second electrode is positioned between the first electrode and the second electrode;
• a fourth electrode for collecting electrons emitted from the first electrode, wherein the third electrode is positioned between the second electrode and the fourth electrode, wherein the fourth electrode is a multi-stage depressed collector, wherein the multi-stage depressed collector comprises a plurality of non-planar stages, and wherein the plurality of non-planar stages have progressively lower negative operating voltages;
• an inductive element positioned to electromagnetically interact with the electron beam between the second electrode and the fourth electrode, wherein the inductive element comprises a toroidal core inductor arranged to pass the electron beam through a central opening of the inductive element;
• and
• a housing defining an enclosed volume, wherein at least the first electrode, the second electrode, the third electrode and the fourth electrode are positioned within the enclosed volume.