MULTIMEGAWATT CYCLOTRON AUTORESONANCE ACCELERATOR

Means are discussed for generation of high-quality multimegawatt gyrat ing electron beams using rf gyroresonant acceleration. TE(111)-mode cy lindrical cavities in a uniform axial magnetic field have been employe d for beam acceleration since 1968; such beams have more recently been employed for generation of radiation at harmonics of the gyration fre quency. Use of a TE(11)-mode waveguide for acceleration, rather than a cavity, is discussed. It is shown that the applied magnetic field and group velocity axial tapers allow resonance to be maintained along a waveguide, but that this is impractical in a cavity. In consequence, a waveguide cyclotron autoresonance accelerator (CARA) can operate with near-100% efficiency in power transfer from rf source to beam, while cavity accelerators will, in practice, have efficiency values limited to about 40%. CARA experiments are described in which an injected beam of up to 25 A, 95 kV has had up to 7.2 MW of rf power added, with eff iciencies of up to 96%. Such levels of efficiency are higher than obse rved previously in any fast-wave interaction, and are competitive with efficiency values in industrial linear accelerators. Scaling argument s suggest that good quality gyrating megavolt beams with peak and aver age powers of 100 MW and 100 kW can be produced using an advanced CARA , with applications in the generation of high-power microwaves and for possible remediation of flue gas pollutants. (C) 1996 American Instit ute of Physics.