Analysis of orbit perturbations of the SLC Arcs

The Stanford Linear Collider (SLC) is the first linear collider to be built. The repetition rate of a linear collider is much lower than that of a circular collider. To recover the luminosity, the emittance and beam size at collision point have to be one or two orders of magnitude smaller than a conventional collider. Therefore, for the SLC, the small beam emittance created from the damping ring has to be kept small by all possible means to preserve the luminosity potential for the physics experiment. To minimize emittance growth of electron and positron beams in the SLC Arcs, bending magnets with very strong quadrupole components have to be used. In addition, a sextupole component is included to eliminate the second order chromatic and geometric aberrations. Consequently, in the presence of magnet misalignments, both orbit error and optical distortion can be generated. This report concentrates on the generation and correction or orbit errors. The authors' analysis is applicable to any periodic lattice structure with periodic arrangement of beam monitors and correctors. The unique feature of SLC Arcs is that the orbit errors are corrected by moving magnets. The authors establish a general stability criterion for the orbit correction in Sec. 2. In Sec. 3, the rms orbit errors and corrector strengths are calculated. Finally, in Sec. 4, the formulation is applied to the design of SLC to obtain estimates for residual orbit distortion after correction