A 17 GIGAHERTZ HIGH-GRADIENT ACCELERATOR STRUCTURE FOR A COMPACT 30 MEV PICOSECOND BUNCH ELECTRON SOURCE

ONGOING STUDIES OF ELECTRON ACCELERATOR LINEAR COLLIDERS AND RESULTS PRESENTED AT RECENT INTERNATIONAL WORKSHOPS CONTINUE TO SUPPORT EARLIER CONTENTIONS THAT THE MOST FAVORABLE CHOICE OF LINAC FREQUENCY IS IN THE RANGE OF 10 TO 20 GHZ WITH GROWING INTEREST IN THE UPPER END OF THIS BAND, AND IN INCREASING THE NUMBER OF BUNCHES PER PULSE. ALTHOUGH CONSIDERABLE INTEREST EXISTS IN 17 GHZ LINEAR COLLIDER CONCEPTS, AND 17 GHZ HIGH PEAK POWER RADIO FREQUENCY (RF) GENERATOR RESEARCH AND DEVELOPMENT ACTIVITIES ARE ALREADY IN PROGRESS AT THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY (MIT) AND IN INDUSTRY, THERE ARE NO ACCELERATOR WAVEGUIDE STRUCTURES PRESENTLY AVAILABLE TO SUPPORT 17 GHZ HIGH GRADIENT ACCELERATOR RESEARCH. (MICROWAVE ACCELERATOR STRUCTURE DEVELOPMENT FOR LINEAR COLLIDERS IS AT 14 GHZ IN RUSSIA, AND AT 11.4 GHZ IN THE USA AND JAPAN). PHASE I STUDIES THE MICROWAVE AND BEAM OPTICS PARAMETERS OF A 17 GHZ TRAVELING WAVE (TW) ACCELERATOR STRUCTURE DESIGNED FOR 30 MEV, 5 DEGREE BUNCH (0.8 PS) OPERATION, USING A HIGH VOLTAGE ELECTRON INJECTOR AND AN INPUT PEAK RF POWER OF 20 MW. THE ACCELERATOR WAVEGUIDE IS BEING DESIGNED AS A HIGH GRADIENT (50 MEV/M),NONUNIFORM IMPEDANCE STRUCTURE CAPABLE OF OPERATING IN BOTH THE STEADY STATE AND STORED ENERGY REGIMES, AND HAVING AN RF FILLING TIME OF APPROXIMATELY 70 NS. IT IS A FURTHER OBJECTIVE OF THE PHASE I EFFORT TO PREPARE AN OVERALL FACILITY LAYOUT DRAWING INDICATING THE INTENDED METHOD OF INTEGRATING THE PROPOSED 17 GHZ ACCELERATOR CENTERLINE WITH AN EXISTING HIGH POWER 1 MUS PULSED MODULATOR AT THE MIT PLASMA FUSION CENTER. IN PHASE II, THE 17 GHZ TW ACCELERATOR STRUCTURE AND ITS DIAGNOSTIC EQUIPMENT SHALL BE FABRICATED AND INSTALLED IN AN EXISTING RADIATION SHIELDED FACILITY, AND HIGH POWER TESTS SHALL BE CONDUCTED TO EVALUATE THE PERFORMANCE OF THE STRUCTURE.