SURVEY OF TRANSIT-TIME AMPLIFIERS FOR APPLICATIONS TO HIGH ENERGY PHYSICS ACCELERATORS

HIGH POWER TRANSIT-TIME AMPLIFIERS ARE A NEW CLASS OF RF SOURCE THAT CONVERTS THE KINETIC ENERGY OF AN ELECTRON BEAM INTO RF RADIATION IN A VERY EFFICIENT WAY. WHEN THE BEAM CROSSES THE CAVITY OF PROPER DIMENSIONS, IT WILL INTERACT WITH A SINGLE CAVITY MODE THEREBY RADIATING COHERENTLY AT THE MODE'S FREQUENCY. MODE GROWTH CONTINUES UNABATED UNTIL THE RF FIELDS ARE LARGE ENOUGH TO MODIFY THE BEAM OPTIMIZED DISPERSION CHARACTERISTICS AND SATURATION IS REACHED. THE SATURATED RF POTENTIAL CAN BE SEVERAL TIMES THE ORIGINAL BEAM VOLTAGE. THIS POWERFUL MECHANISM MAY BE USED FOR PRODUCING HIGH POWER RF RADIATION,BUNCHING THE BEAM, OR AMPLIFYING AN EXISTING RF SIGNAL BY SEVERAL ORDERS OF MAGNITUDE. IN THIS PROPOSED EFFORT, THIS MECHANISM WILL BE INVESTIGATED AS AN EFFICIENT MEANS FOR RF AMPLIFICATION. FIRST, THE BEST MODE WILL BE IDENTIFIED BASED ON THE CHARACTERISTICS OF THE DESIRED ACCELERATING FIELD AND FREQUENCY. NEXT, THE BEAM PARAMETERS AND THE CAVITY CONFIGURATION WILL BE IDENTIFIED AND OPTIMIZED AND FINALLY, A PROOF-OF-PRINCIPLE EXPERIMENT WILL BE DESIGNED. TRANSIT-TIME AMPLIFIERS DO NOT NEED AN EXTERNAL MAGNETIC FIELD AND, AS SUCH, ARE VERY COMPACT AND ECONOMICAL. FURTHERMORE, BASED ON OUR PRELIMINARY STUDIES, POSSIBILITY FOR FOIL-LESS DIODE DESIGN EXISTS THEREBY ALLOWING PULSE REPETITION RATES OF SEVERAL HUNDRED TIMES PER SECOND. IN TRANSIT-TIME AMPLIFIERS THE INPUT RF SIGNAL WILL TRIGGER THE GROWTH. AS SUCH, THE OUTPUT WILL BE PHASE-LOCKED TO THE INPUT. THE PHASE STABILITY OF THE AMPLIFIER WILL BE VERIFIED.