SNS ring optics tuning

Detailed studies of the SNS ring lattice optics have been conducted. The horizontal and vertical tuning ranges for matched solutions with well-behaved lattice functions were determined and the power supply margin verified. Using stability criteria, potential working points have been identified and studied in detail. Studies, focused on behavior of the lattice functions under increasingly complex assumptions, included chromatic effects and sextupoles, and lattice perturbations due to the injection chicane and to dynamic bumps for painting. Results are being used in determining injection painting schemes, in dynamic aperture studies, and in validating collimator settings.

1 INTRODUCTION

The SNS accumulator ring will compress a 1 msec high intensity proton beam from a linac into a sec bunch for delivery to a mercury target. The compressed bunch will contain in excess of 10¹⁴ protons, and uncontrolled losses cannot exceed 10⁻⁴. These constraints of high intensity and low losses place stringent requirements on the ring design. The SNS ring contains four superperiods, each consisting of a 90° arc and a straight section. The four straight sections each perform a distinct function: injection, collimation, extraction and gap kicker, and RF. In order to provide sufficient room for this, each straight sections consists of two doublets separated by a 12.5 m drift, and two 6.85 m drifts between the doublets and the arcs. To guarantee zero dispersion in the straight sections, each arc is an achromat consisting of four fodo cells. The SNS ring lattice was designed for a 1 GeV proton beam and can accommodate a 1.3 GeV beam with minor changes [1]. The circumference of the ring is 248m.