Modifications to the University of Michigan 83‐Inch Cyclotron to Improve Beam Quality

Abstract

Recent studies of the internal and extracted beams at the higher energies (up to 40‐MeV deuterons and 80‐MeV α‐particles) led us to convert the dee system of the 83‐inch cyclotron from two 150° dees to one 180° dee. The primary purpose was to remove from the deflector channel the rf dee voltage, which because of its phase opposes the dc deflector voltage and in addition introduces an energy spread in the extracted beam. The one‐dee system offers further advantages. The equivalent first harmonic due to a gap‐crossing driving force which is a function of the dee geometry and dee voltage balance in the two‐dee system, is essentially eliminated, and control of the central orbits, in particular the selection of phase width, is facilitated. The measured values of the beam quality and energy spread are in good agreement with calculations. These results, together with the diagnostic instrumentation used in obtaining them, are described.