CEA, Gif-sur-Yvette
With the local chromaticity correction scheme, the luminosity optimisation of the beam delivery systems of the e+ e- International Linear Collider (ILC) project is challenging. A manual optimization is a long and complex process and its automation becomes a necessity. Recent works have shown that it was possible to employ a simplex minimization method, applied to the beam size calculation at the Interaction Point (IP), to reach this objective automatically *. To achieve this goal in the ILC case, we have developed a minimization code which uses analytical computations of the IP beam sizes based on external code results, TRANSPORT** or MADX (with PTC extension)***. Two minimization algorithms can be employed. The maximum luminosity reached and the convergence time of the two codes and algorithms are compared. We also used the code TRACEWIN which tracks a particle cloud and minimise the rms beam spot sizes at IP to optimise the luminosity, and we compare with the previous results.
* Non-linear optimization of beam lines, R. Tomas, CLIC Note 659** Third-Order TRANSPORT with MAD Input, D. C. Carey, K. L. Brown and F. Rothacker, FERMILAB-Pub-98/310*** MADX User's Guide CERN
CEA, Gif-sur-Yvette
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 γ=100, directed towards experimental halls situated in the Frejus 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 6T 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 and random errors of these defects have been investigated. In order to relax the tolerances, a routine was written which enlarges automatically the dynamic aperture in presence of field errors.