Abstract
We have studied the beam dynamics in a high field separated-sector cyclotron to establish conditions required to achieve single-turn extraction. Extraction efficiency above 99% is aimed to avoid beam-induced damages. A sufficient last-turn separation and a preservation of beam quality throughout the acceleration are the prerequisites. The last-turn separation can be enhanced with the orbital precession induced by an off-centering injection as in existent lower field separated-sector cyclotrons. The beam qualities, on the other hand, are affected by the resonances traversed or approached during the acceleration. Acceleration of light nuclei to the energies of 300--400 MeV/u was especially disturbing because of the broadening of radial beamwidth upon crossing the ${\ensuremath{\nu}}_{r}=3/2$ resonance. Tolerance to the third harmonic gradient field, which causes the resonance in lowest order, is set to be 0.1 G/cm. The integer resonance ${\ensuremath{\nu}}_{z}=1$ can be avoided with a proper design of the yoke. The longitudinal space charge forces were also investigated to estimate the intensity limits determined by the energy spreads of beam assuming simplified charge distributions. Moreover, beam preparations for injection matching are described in view of reducing the beam losses into the extraction elements.
Highlights
A superconducting ring cyclotron (SRC) which is under construction at RIKEN will accelerate high-current heavy ion beams to produce radioisotope (RI) beams through a projectile fragmentation process [1]
Once the field strength and geometry of the SRC are outlined, the energy gain determined by the number of arranged cavities and by the peak gap voltage is a prime parameter on the turn separation
The intensity limit imposed by longitudinal space charge forces was investigated, and preparations for the injection matching of beams were discussed
Summary
A superconducting ring cyclotron (SRC) which is under construction at RIKEN will accelerate high-current heavy ion beams to produce radioisotope (RI) beams through a projectile fragmentation process [1]. The total number of turns is larger for the light nuclei being accelerated from 126 to 400 MeVu because the total energy gain of the light nuclei is larger than that of the heavy nuclei Those light nuclei are the main design particles in the beam extraction study. Independent excitations of the main and some trim coils on each sector can be utilized for compensation of the harmonic field originating from nonuniformity among sector magnets and from the fringe fields of the injection and extraction elements. The drifting, mismatching, beams should be removed prior to injection to the SRC to reduce beam losses into the extraction elements
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call