• Y.-N. Rao, R.A. Baartman, G. Dutto, L.W. Root
  TRIUMF, Vancouver

Funding: TRIUMF receives funding via a contribution agreement through the National Research Council of Canada.

The TRIUMF cyclotron is 6-fold symmetric, but has a 3rd harmonic magnetic field gradient error. As well, there is a 3rd harmonic component generated from the beating of the primary harmonics with the 9th harmonic. Both can contribute and drive the nu_r=3/2 resonance. As a consequence, the radial phase space ellipses become stretched and mismatched; this introduces a radial modulation of beam density and thereby causes a sensitivity of the extracted current to, for example, small changes in rf voltage. The cyclotron has "harmonic" correction coils, but these were designed to generate a first harmonic, not a third harmonic. Their 6-fold symmetric layout can only generate a 3rd harmonic at one particular phase and so can only partially compensate for this resonance. For a complete compensation, the 6 pairs of this harmonic coil would have to shift in azimuth by ~30degr. This paper describes the simulations performed with COMA to study the effect of this resonance. Initial measurement results are also presented.

• T.J. Zhang, Y.J. Bi, F.P. Guan, X.L. Jia, S.M. Wei, J.Q. Zhong
  CIAE, Beijing
• G. Dutto, G.H. Mackenzie, L.W. Root
  TRIUMF, Vancouver
• J.Z. Wang
  Department of Physics, Central China Normal University, Wuhan

There is increasing interest in high current compact H^- cyclotrons for RIB, isotope production or as injectors for sub-critical reactor testing facilities. For compact cyclotrons, a practical limit on the output energy, to prevent significant Lorentz stripping and resulting activation, is ~100 MeV. Vacuum dissociation is another critical problem, because a compact structure and small parts inside the tank make high vacuum challenging. This paper describes how Lorentz stripping and vacuum dissociation were calculated for our “CYCIAE-100” under construction. In order to take into account non uniform magnetic fields and vacuum, losses were calculated by numerically integrating loss equations along tracked orbits, as these were being calculated by the beam dynamics code. To verify the code, losses derived with field and vacuum data from the TRIUMF 500 MeV cyclotron were compared with measurements. For the CYCIAE-100 cyclotron we predict that electromagnetic losses will account for less then 0.3% of total beam, vacuum losses for less than 0.58%, with peak magnetic fields up to 1.35T and average vacuum up to 5·10^-8 Torr.