The aim of the beta-beams is to produce highly energetic beams of pure electron
neutrino and anti-neutrino, coming from beta-decays of the 18Ne10+ and 6He2+,
both at gamma=100, directed toward experimental halls situated in the Fréjus tunnel.
The high intensity ion beams are stored in a ring until the ions decay. The beta-decay
products have a magnetic rigidity different from the one of the parent ions and are
differently deflected in the 6 T superconducting dipoles. Consequently, all the injected
ions are lost anywhere in the ring, generating a high level of irradiation. So, the dipole
apertures need to be large enough to avoid the decay products hitting their walls, which
may worsen the field quality. A study on its tolerances has been carried out. Since the
decay ring has to accept the beam during a large number of turns, the chosen criteria is
the size of the dynamic aperture that the multipolar defects in the dipoles may shrink.
Tolerances on the systematic errors of these defects have been investigated. In order
to relax the tolerances, a routine was written which automatically enlarges the dynamic
aperture in presence of field errors. |
