Travelling wave tube using a plasmafilled waveguide as a slow wave structure

Claim 1

A TRAVELLING WAVE TUBE FOR USE AS AN AMPLIFIER, INCLUDING A SEALED ENVELOPE FILLED WITH GAS, A LENGTH OF HOLLOW METAL WAVEGUIDE THE WHOLE OF THE INTERIOR OF WHICH FORMS PART OF THE INTERIOR OF THE ENVELOPE, A FIRST RADIO FREQUENCY CONNECTOR FOR FEEDING AN INPUT SIGNAL TO THE WAVEGUIDE, A SECOND RADIO FREQUENCY CONNECTOR FOR DERIVING AN OUTPUT SIGNAL FROM THE WAVEGUIDE, THE TWO CONNECTORS BEING SPACED APART ALONG THE LENGTH OF THE WAVEGUIDE, AND AN ELECTRON GUN FOR PROJECTING AN ELECTRON BEAM ALONG THE LENGTH OF THE INTERIOR OF THE WAVEGUIDE SO AS TO PASS THE FIRST AND SECOND CONNECTORS IN THAT ORDER, THE ELECTRON GUN BEING CAPABLE OF PROVIDING AN ELECTRON BEAM OF SUFFICIENT DENSITY TO GENERATE WITHIN THE WAVEGUIDE, BY IONISATION OF THE GAS THEREIN, A PLASMA OF DENSITY SUCH THAT, WITH THE WAVEGUIDE DISPOSED IN A MAGNETIC FIELD DIRECTED SUBSTANTIALLY PARALLEL TO ITS LONGITUDINAL AXIS, THE PLASMA FREQUENCY IS AT LEAST AS GREAT AS THE CYCLOTRON FREQUENCY CORRESPONDING TO SAID MAGNETIC FIELD, AND THE WAVEGUIDE IS CAPABLE OF PROGATING SPACE CHARGE WAVES IN A FORWARD WAVE MODE OVER A RANGE OF FREQUENCIES EXTENDING BELOW BOTH THE CYCLOTRON FREQUENCY CORRESPONDING TO SAID MAGNETIC FIELD AND THE NORMAL CUT-OFF FREQUENCY OF THE WAVEGUIDE IN THE ABSENCE OF THE PLASMA, AND THE PRESSURE OF THE GAS FILLING LYING WITHIN A RANGE SUCH THAT, WITH A GIVEN SET OF OPERATING CONDITIONS INVOLVING APPROPRIATE VALUES OF THE STRENGTH OF THE MAGNETIC FIELD, THE MEAN VELOCITY AND DENSITY OF THE ELECTRON BEAM, AND THE ELECTROSTATIC POTENTIAL DIFFERENCE BETWEEN THE WAVEGUIDE AND THE CATHODE OF THE ELECTRON GUN AND WITH AN INPUT SIGNAL HAVING AN APPROPRIATE FREQUENCY WITHIN SAID RANGE OF FREQUENCIES APPLIED TO THE FIRST CONNECTOR, THERE MAY BE OBTAINED AT THE SECOND CONNECTOR AN AMPLIFIED OUTPUT SIGNAL WHICH IS NOT MASKED BY OSCILLATIONS GENERATED IN THE TUBE.