Sectored Cyclotrons

Conventional fixed frequency cyclotrons evolved from the pioneering work of E. O. Lawrence and M. S. Livingston1; typical performance characteristics include fixed output energy, fixed e/m of the accelerated ions, energy less than 10 MeV/nucleon2, poor beam quality and poor duty cycle. In recent years a series of new concepts have revolutionized the fixed frequency cyclotron. These new concepts include (a) sector focusing, (b) variable frequency rf systems, (c) resonant extraction, (d) programmed orbits, and (e) acceleration of negative ions. The resulting machines, referred to herein as "sectored" cyclotrons3, have essentially ideal properties as compared with the classical cyclotron, i.e., variable energy, variable e/m, arbitrary final energy, good beam quality, and greatly improved duty cycle. The initial section of this paper reviews fundamentals of modern sectored cyclotrons with illustrative examples drawn from the present generation of such machines; the final section considers possible features and design problems of future machines of this type.