Study of Low β y Straight Section in SPEAR 3 1

The SPEAR 3 light source [1] has two 7.6 m straight sections one of which is available for new insertion devices (ID). By reducing the vertical β y function at the center of the straight from 9.8 m to 1.5 m, the beam size can be decreased from 44 µm to 17 µm to reduce the ID gap, but the ID length may be limited by the increased β y variation in the ID. Alternatively , a " double waist " optics with two symmetric low β y locations and a chicane may be considered to implement two IDs. In this paper, we discuss the low β 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. Abstract The SPEAR 3 light source [1] has two 7.6 m straight sections one of which is available for new insertion devices (ID). By reducing the vertical β y function at the center of the straight from 9.8 m to 1.5 m, the beam size can be decreased from 44 µm to 17 µm to reduce the ID gap, but the ID length may be limited by the increased β y variation in the ID. Alternatively, a " double waist " optics with two symmetric low β y locations and a chicane may be considered to implement two IDs. In this paper, we discuss the low β 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.