Spiral Design and Beam Dynamics for a Variable Energy Cyclotron

Beam-orbit studies were performed for the conversion of the SREL synchrocyclotron magnet for use as a room temperature, multiparticle, isochronous cyclotron. Based on model magnet measurements of field profiles for 8 to 23 K gauss hill fields, a four sector spiral pole tip design has been realized which allows all isotope species of heavy ion beams to be accelerated to required final energies. The total spiral angle of 38° allows injection of the beams from the MP tandem into the cyclotron through a valley. The two valley RF system of 140 kV peak accelerates beams on harmonic numbers 2, 3, 4, 6 and 10 at 14 to 21 MHz. Computer calculations indicated acceptable vz, Vr and phase space beam characteristics and passing of resonances for typical beams considered: 16O at 8 and 150 MeV/amu, 60Ni at 100 MeV/amu and 238U at 2.5 and 16 MeV/amu. Single turn extraction is achieved with electrostatic deflection.