General description and operating characteristics of the Berkeley 88-inch cyclotron

Abstract

The Berkeley 88-inch cyclotron is a variable-energy spiral-ridge machine with an electrostatic deflector for beam extraction. This accelerator was designed to satisfy the needs of the nuclear chemistry and low-energy physics groups, for variable-energy beams of a variety of ions. It will accelerate protons up to 50 MeV, douterons up to 65 MeV, and heavier ions up to corresponding energies. The machine is expected to produce an external beam of 100 to 200 μA. The r.f. has a frequency range of 5.5 to 16.5 Mc/s and a working voltage of 70 kV, dee to ground. The single-dee construction permits operation on the third harmonic mode, which in effect gives another factor of 3 in frequency range. The magnet has three flat hills on each pole, which produce a maximum magnetic-field spiral angle of approximately 55 deg. The iron gap between hills is 7.5 in., between valleys, 11.8 in. The maximum average field is 17 kG, with an effective flutter of ± 3 kG. Pole-face windings are provided for trimming the magnetic field. The first internal beam was obtained in December 1961. Subsequent internal-beam studies with alphas at 12 kG (65 MeV) show a well-behaved beam out to full radius. The beam has not yet been extracted with the electrostatic deflector.