Initial Performance of the 184-Inch Cyclotron of the University of California

Abstract

The successful application of the principle of phase stability 12 to a cyclotron has been reported from this Laboratory3. The satisfactory results of these experiments, performed on the 37-inch cyclotron, led to the decision to complete the 184-inch cyclotron then under construction as a frequency modulated machine. It ia the purpose of this note to describe briefly the equipment and experiments by which deuteron and alpha-particle beams of approximately 200 and 400 Mev, respectively, have been produced. The angular velocity of such ions in a magnetic field decreases by 11 percent because of the relativistic increase in mass during acceleration. In addition, a radial decrease of magnetic field, essentially linear from the center of a value of 95.4 percent of the central field at a radius of 80 inches, is provided to focus the ion beam properly. This field shape is produced by shims inside the vacuum chamber with contours empirically determined through measurements on a scale model. Thus a total minimum frequency variation of 16 percent is required; in practice it is desirable to provide a substantially greater frequency variation to insure that a satisfactory shape of the frequency vs. time curve is obtainable and to make adjustments less critical. E.M. McMillan, Phys. Rev. 68, 143 (1945). V. Veksler, J. Phys. U.S.S.R. 9, 153 (1945). J.R. Richardson, K.R. MacKenzie, E.J. Lofgren, and B.T. Wright, Phys. Rev. 69, 669 (1946).