Improvements in MAD in view of LHC design
Conference Record of the 1991 IEEE Particle Accelerator Conference
For the design of the LIIC (CERN Large Hadron Collider) it is important to perform extensive checks on long-time stability. Comparison of MAD (Methodical Accelerator Design program) with specialized tracking programs showed that, tracking speed of MAD was insufficient. Therefore time-critical routines have been tuned so as to take advantage of vectorizat,ion on both Cray and IBM vector computers. The superconducting magnets used in LHC contain various high-order multipole errors. Definition of
... ors. Definition of field error components has been made easier with a new command. Among other effects the multipole errors introduce strong coupling. In LHC it is removed by a few families of skewed quadrupoles. This design requires matching over the whole ring, and forces MAD to recompute a large nunlber of transfer maps over and over again. This process has been speeded up by orders of magnitude since MAD now precolnputes transfer maps for single elements and for large pieces of the ring ("lumps"), and recalculates them only when really needed. It detects maps which depend on variable parameters and updates them automatically. The effects of octupoles and decapoles have been included in the second-and third-order chromaticity calculation of IIARMON, and it is possible to match secondand third-order chromaticity by adjusting those elements.