RADIO-FREQUENCY LINEAR ACCELERATORS FOR COMMERCIAL ION IMPLANTERS.

There is now a demand for production-type ion implanters capable of delivering high beam currents at energies in the Mev range. Hitherto, this application has been fulfilled only with dc machines of somewhat limited beam current. A recently developed radio-frequency linear accelerator has produced much higher beam currents yet is just as flexible as a dc machine in the sense that within seconds it can be programmed to accelerate any particle in the range of boron to antimony, to any selected final energy. Included in this review is a discussion of the general principle of rf acceleration including factors which determine the accelerating voltage gradient, energy spread, space charge limits, radial focusing, and the flexibility derived from independent rf phase control of individual rf accelerating cells. Various structures such as the ″two gap″ resonator and the rf quadrupole are considered in relation to ion implantation applications.