Vacuum Requirements for Heavy Ion Synchrotrons

Experimental charge-changing cross sections for uranium ions incident on H2 and N2 at 1.4 MeV/u are presented and extrapolation to higher energies is discussed briefly. The beam losses caused by charge-changing collisions between heaviest ions and residual gas molecules in a synchrotron have been calculated for different injection energies and ionic charge states. For example, if a beam of U+10-ions is accelerated from 1.4 MeV/u to 100 MeV/u by an average electric field BR=112 V/m an average working pressure of about 1×10-11 mbar is necessary to limit beam losses to several percent.