Large aperture narrow quadroupole for the sns accumulator ring.

摘要

The accumulator ring of the Spallation Neutron Source (SNS) is designed to accept high-intensity H(sup -) beam of 1 GeV kinetic energy from the injecting LINAC, and to accumulate, in a time interval of 1 msec, 2 x 10(sup 14) protons in a single bunch of 700 nsec. In order to optimize the effective straight-section spaces for beam-injection, extraction and collimation, we have minimized the width of the large aperture quadrupoles which are located in the same straight sections of the accumulator ring with the injection and extraction systems. By minimizing the width of the quadrupoles to (+-)40.4 cm, the beam-injection and extraction angles are lowered to 8.75(sup o) and 16.8(sup o) respectively. Further optimization of the narrow quadrupole, minimizes the strength of the dodecapole multipole component of the quadrupole, thus reducing the width of the 12pole structure resonance and allowing a larger tune space for stability of the circulating beam. In this paper we present results derived from magnetic field calculations of 2D and 3D modeling, and discuss the method of optimizing the size of the quadrupole and minimizing its dodecapole multipole component.