Nonlinear Dynamics in the Spear3 Double-waist Chicane*

One of the two 7.6 m long straight sections in SPEAR3 has been divided into two short straights to provide places for two new small-gap insertion devices (IDs) [1,2]. A chicane generates an angular separation of 10 mrad between the two straights. A quadrupole triplet has been added in the center of the 7.6 m long chicane to create a ‘double-waist chicane’ optics with βy=1.6 m at the center of each of two future IDs. The new optics also reduces βy to 2.5 m in the four 4.8 m straight sections. In this paper, we discuss nonlinear dynamic studies associated with design and implementation of the new optics. We present tracking results generated during the design stage and compare them to nonlinear dynamics measurements made with the quadrupole triplet installed in SPEAR3. INTRODUCTION The double-waist chicane optics were designed over the course of four years, culminating in final optics design reviews in 2004 [1]. Details of the linear optics design can be found in these proceedings [2]. The new optics has reduced βy at six locations, with stronger focusing, higher vertical tune and chromaticity, and stronger sextupole strengths. The new quadrupole triplet was installed in SPEAR3 in summer, 2005, to enable testing of the new optics during the 2005-2006 run. Measurements over the past several months have shown that the optics perform as expected, with good injection and lifetime. Delivery of user beam in the new optics will start this fall. This paper will present the nonlinear dynamics tracking studies that were done for the 2004 optics design reviews, and will compare the tracking to subsequent beam measurements.