Author: Sen, A.
Paper Title Page
WE3PB04 Transmission of Heavy Ion Beams in the AGOR Cyclotron 420
  • A. Sen, S. Brandenburg, M.A. Hofstee
    KVI, Groningen, The Netherlands
  • M.J. van Goethem
    UMCG, Groningen, The Netherlands
  During the acceleration of intense low energy heavy ion beams in the AGOR cyclotron feedback between beam intensity and pressure, driven by beam loss induced desorption, is observed. This feedback limits the attainable beam intensity. Calculations and measurements of the pressure dependent transmission for various beam agree reasonably well. Calculation of the trajectories of ions after a charge change shows that the desorption is mainly due to ions with near extraction energies, hitting the outer wall at a shallow angle of incidence. For heavy ions like 206Pb27+ several charge exchanges are needed before the orbit becomes unstable. Our calculations indicate that these ions make thousands of turns before finally hitting the wall. They therefore are a large fraction of the circulating ions and may contribute to vacuum degradation through restgas ionization. Ion induced desorption for relevant ions and materials has been measured; it explains the observations in the cyclotron semi-quantitatively.
This work has been financially supported by the Foundation FOM, the Dutch funding agency NWO and the EU-FP7, Grant Agreement n° 262010 - ENSAR.
slides icon Slides WE3PB04 [5.272 MB]