Non-Linear Optics for the Final Focus of the Single-Pass-Collider

Abstract

The purpose of the final focus system (FFS) is to demagnify the beam envelope in the Collider arc lattice to a size suitable for beam collisions at the interaction region. The final spot size is determined by the beam emittance, the beta function ..beta..* at the IR, the momentum spread in the beam, and the quality of the FFS optics. In particular, if the focusing system is not chromatically corrected, the momentum dispersion in the beam can lead to a substantial degradation in the quality of the final focus. The objective is to design a FFS for 50 GeV/c within approx. 100 meters having an IR spot size sigma/sub xy/ of approximately 2 ..mu..m for a beam emittance of epsilon = 3 x 10/sup -10/ m-rad and a momentum spread of delta = +-0.5%. This requires a ..beta../sub x,y/ equal to or less than 1 cm. This report considers the problems encountered in the design of a final focus system that will reliably provide the desired beam size for collisions.