RADIOFREQUENCY SYSTEM FOR EXTRACTING PARTICLES FROM A CYCLOTRON

The impressive rate of particle loss by vertical beatfrequency (VBF) blowup in the low electrical field of a synchrocyclotron suggests the application of a radiofrequency perturbation to induce growth of radial oscillation amplitude for beam extraction. The use of an electrical field with a linear gradient on the outward side of a reference orbit and extending 60 in azimuth has been studied. The radiofrequency is chosen to make radial oscillations, described by an equation of the Hill type, unstable. Orbit calculations for a cyclotron with 50-Mev deuterons in a 17,000-gauss field have been made on a digital computer. Two essential features were observed: (a) a reasonable separation between successive turns influenced by the perturbation, and (b) a phasing of orbits so that the maxima following an increase in amplitude occur near one azimuth. An electrical gradient of 4.3 kw/cm/sup 2/ was used in the computations. The application of this system to variable-energy constant-frequency cyclotrons and very-high-energy accelerators is under study. The possibility of changing the electrical frequency and gradient to match operating conditions eliminates difficulties arising in magnetic extraction systems for variable-energy machines. (auth