Study of Low beta-y Straight Section in SPEAR 3

Abstract

The SPEAR 3 light source has two 7.6 m straight sections one of which is available for new insertion devices (ID). By reducing the vertical beta function at the center of the straight from 9.8 m to 1.5 m, the beam size can be decreased from 44 to 17 microns to reduce the ID gap, but the ID length may be limited by the increased beta-y variation in the ID. Alternatively, a ``double waist'' optics with two symmetric low beta-y locations and a chicane may be considered to implement two IDs. In this paper, we discuss the low beta-y optics, effects on the beam dynamic aperture, and the ID parameters needed to maximize photon flux density and brightness while maintaining electron beam lifetime.