Theoretical and experimental investigations of the autoaccelerator

Theoretical and experimental work on the coaxial autoaccelerator is presented. The theoretical investigation of instabilities in the autoaccelerator is divided into two areas: resonant and nonresonant interactions. The coaxial autoaccelerator is found to be stable against resonant instabilities such as the longitudinal bunching mode and transverse beam breakup mode because it does not behave as an efficient slow wave structure. From the large class of nonresonant instabilities, the klystron instability has been examined in detail. A stability criterion has been obtained which indicates stability for the projected operating parameters in the experiment. A long pulse (800 ns risetime) beam generator is described capable of producing a ramp charging beam pulse of 1.5 MV peak voltage and 50 KA peak current. The beam generator is equipped with a self break oil switch capable of reducing the peak beam current by a factor of four in less than 5 ns. Experiments on the generation and propagation of beams with peak voltages and currents of 1.1 MV and 35 KA are discussed. Initial experimental results on one-cavity beam autoacceleration, in agreement with theoretical predictions, will be presented. Operation of a six cavity system is anticipated in the near future.