AN EFFICIENT HIGHER ORDER MULTI-MODE HIGH POWER MICROWAVE AMPLIFIER

RECENTLY PUBLISHED RESULTS OF THE SIX-YEAR ONGOING DEVELOPMENT OF HIGH PEAK POWER RELATIVISTIC KLYSTRONS FOR 11.4 AND 14 GHZ LINEAR COLLIDERS SHOW THAT NONE OF THE TUBES HAVE DEMONSTRATED EFFICIENCIES OF GREATER THAN 45%, AND THE MAJORITY HAVE OPE2RATED AT LESS THAN 35%. IN RECOGNITION OF THE POTENTIAL LIMITATION OF THESE VELOCITY MODULATION TUBES, AND BECAUSE OF THE BENEFICIAL IMPACT A MUCH HIGHER EFFICIENCY RADIO FREQUENCY (RF) SOURCE WOULD HAVE ON LINEAR COLLIDER TECHNOLOGY, THERE IS CONSIDERABLE INCENTIVE TO EXPLORE NEW APPROACHES FOR THE HIGH EFFICIENCY TRANSFER OF POWER FROM AN ELECTRON BEAM TO A COHERENT FLUX OF ACCESSIBLE HIGH FREQUENCY ELECTROMAGNETIC ENERGY. THIS PHASE I EFFORT INVESTIGATES A NEW APPROACH FOR GENERATING MICROWAVE POWER USING SPATIAL MODULATION OF A HIGH POWER ELECTRON BEAM AND A NOVEL HIGHER ORDER MODE OUTPUT CAVITY. THE EFFORT IS DIRECTED AT AVOIDING SOME OF THE LIMITATIONS AND DIFFICULTIES ASSOCIATED WITH MAGNICONS AND HIGHER HARMONIC (FAST WAVE) DEVICES BY ATTEMPTING TO DESENSITIZE THE DEPENDENCE OF TUBE EFFICIENCY ON BEAM CROSS SECTION, BY OPERATING AT MODERATE VALUES OF TRANSVERSE MOMENTUM, BY AGGRESSIVE SUPPRESSION OF MULTIPACTOR, AND BY USING A RELATIVELY LARGE, HIGHER ORDER MULTI-MODE OUTPUT CIRCUIT TO MINIMIZE DISSIPATION AND ELECTRIC FIELD INTENSITIES. THE TECHNIQUE IS DEPENDENT ON ESTABLISHING SETS OF HIGHER ORDER MODE FIELD PATTERNS THAT COEXIST WITHIN A COMMON BOUNDARY YET EXHIBIT EXTREMELY HIGH ISOLATION (E.G., 50 TO 60 DB) BETWEEN CONTIGUOUS AND/OR ORTHOGONAL MODES. A FURTHER OBJECTIVE OF THE PHASE I EFFORT IS TO ESTABLISH SPECIFIC DESIGN PARAMETERS FOR A PROTOTYPE TUBE, BASED ON A SUITABLE EXISTING HIGH POWER TEST FACILITY (HAVING AN RF DRIVE SOURCE IN THE RANGE OF 3 TO 11.4 GHZ), SO THAT IN PHASE II AN ECONOMICAL MEANS WILL BE AVAILABLE FOR TESTING THE NEW CONCEPT.