AN 11.4 GIGAHERTZ 800 MEGAWATT PHASE STABLE RADIO FREQUENCY GENERATOR

THIS APPLICATION, IN SUPPORT OF ONGOING RESEARCH AND DEVELOPMENT PROGRAMS AT LAWRENCE BERKELEY LABORATORY AND THE LAWRENCE LIVERMORE NATIONAL LABORATORY (LLNL), INVESTIGATES THE MEANS OF PROVIDING AN EFFICIENT (>50%), PHASE-STABLE SOURCE OF HIGH RADIO FREQUENCY (RF) POWER (800 MW) SUITABLE FOR HIGH GRADIENT, 11.4 GHZ LINEAR ACCELERATOR APPLICATIONS. IN PHASE I, EFFORTS ARE DIRECTED AT (1) ANALYTICALLY INVESTIGATING HIGH EFFICIENCY TECHNIQUES FOR RF MODULATING A RELATIVISTIC HIGH POWER BEAM DERIVED FROM A LINEAR INDUCTION ACCELERATOR (LIA); AND (2) ANALYTICALLY EVALUATING THE POSSIBILITY OF GENERATING 800 MW OF PHASE-STABLE RF POWER AT 11.4 GHZ, USING A NEW STYLE OF LOW IMPEDANCE TRAVELING WAVE (TW) STRUCTURE ESPECIALLY CONFIGURED TO PREVENT PULSE SHORTENING. SUCH AN RF POWER SOURCE, DESIGNED FOR OPERATION WITHIN A SMALL DIAMETER SOLENOID ASSEMBLY, COULD HAVE MULTIPLE OUTPUT ARMS ARRANGED FOR DIRECT CONNECTION TO THE CENTERLINE WAVEGUIDES OF A HIGH GRADIENT ACCELERATOR, THEREBY AVOIDING THE COST AND COMPLEXITY OF A PULSE COMPRESSION SYSTEM. RF EXPERIMENTS USING LIA BEAMS (AT LLNL AND THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY) AND DIFFERENT DESIGN, 11.4 GHZ RELATIVISTIC KLYSTRONS FITTED WITH HIGH GROUP VELOCITY TW OUTPUT STRUCTURES HAVE SUCCESSFULLY DEMONSTRATED OUTPUT POWER LEVELS OF 100 TO 300 MW. OPERATIONAL EXPERIENCE SUGGESTS THAT THESE HIGH POWER TW DESIGN CONCEPTS COULD BE EXTENDED TO REALIZE POWER LEVELS GREATER THAN 500 MW PER STRUCTURE, BUT THE SERIES OPERATION OF TWO OR MORE SUCH STRUCTURES WOULD RISK ENCOUNTERING SEVERE PULSE SHORTENING FROM A COMBINATION OF REGENERATIVE AND CUMULATIVE BEAM BREAKUP. PRELIMINARY ANALYSIS INDICATES THAT UNDER THESE CONDITIONS, HEAVY DAMPING OF THE HIGHER ORDER MODES (HOM) WOULD BE INSUFFICIENT TO PREVENT PULSE SHORTENING; THE INVESTIGATION OF A FAR MORE AGGRESSIVE TECHNIQUE FOR HOM SUPPRESSION IS PLANNED DURING PHASE I. IN PHASE II, A PROTOTYPE VERSION OF THIS HIGH EFFICIENCY, 800 MW, 11.4 GHZ RF GENERATOR WILL BE ENGINEERED, FABRICATED, AND PREPARED FOR INSTALLATION IN AN LLNL LIA TEST FACILITY FOR EVALUATION OF HIGH POWER PERFORMANCE.