Superconducting accelerating structures for the acceleration and deceleration in the harmonic region. Final report

Existing superconducting accelerating structures for heavy ions are restricted to ion velocities of at least 0.03 c, requiring the ions to be preaccelerated by an electrostatic accelerator. There has been a growing interest recently in resonators capable of accelerating extremely low-velocity ions (less than 0.01 c); these would allow the elimination of the electrostatic injector. It was found that a combination of two resonators operating at 50 MHz and optimized for velocities of 0.01 and 0.016 could accelerate ions from 0.007 c to 0.03 c in the harmonic region, and to much higher velocity in their fundamental region. An analytical study of the acceleration process inside the resonator found the energy gain to be very different from that given by the usual first order approximation where the velocity is assumed to be constant. Of great importance to these very-low-velocity, harmonic resonators is the fact that substantial energy gain can still be obtained at the zeroes of the transit-time factor. An electromagnetic design of a 50 MHz, beta-0.01 resonator was performed