Closed orbit analysis for RHIC

The authors examine the effects of four types of errors in the RHIC (Relativistic Heavy Ion Collider) dipoles and quadrupoles on the on-momentum closed orbit in the machine. They use the PATRIS tracking/analysis code both to handle statistically the effects of kick-modeled errors and to check the performance of the Fermilab correcting scheme in a framework of a more realistic modeling. On the basis of the accepted RMS (root-mean-square) values of the lattice errors, it is concluded that in about 40% of all studied cases the lattice must be to some extent precorrected in the framework of the so-called first turn around strategy, in order to get a closed orbit within the aperture limitations at all. For approximately two thirds of the remaining cases it is found that a single-pass algorithm of the Fermilab scheme is not sufficient to bring closed-orbit distortions down to acceptable levels. The authors have modified the scheme and have allowed repeated applications of the otherwise unchanged three-bump method, and in doing so they have been able to correct the orbit in a satisfactory manner