Compensation of magnetic imperfections in the SCC

The compensation of nonlinear multipole errors in the magnets of the SSC (Superconducting Supercollider) is discussed. The results described have mainly been obtained using TEAPOT. An SSC modeling program was used for some cases, to investigate the operational feasibility correction of the schemes. Because the cost of the SSC is dominated by the main arcs and because the optical defects of those arcs are dominated by field errors in the superconducting dipoles, this study focuses on compensating for those field errors. Degradation due to nonlinear field errors can be quantified by tune shifts and by smear. In analyzing the SSC the following principles have usually been found to be approximately valid: (i) systematic multipole errors cause tune shifts and not smear, and (ii) random multipole errors cause smear not tune shifts. The present studies have eroded this separation a bit, since random orbit errors, in combination with systematic multipole errors, are found to contribute significantly to smear. For that reason one cannot neglect closed-orbit errors, which combine with these errors to cause coupling and smear. >