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CESR Lattice for Two Beam Operations with Narrow Gap Undulators at CHESS

Suntao Wang, David Rubin, James Shanks, Kim, Dong Eon (Ed.), Schaa, Volker RW (Ed.), Petit-Jean-Genaz, Christine (Ed.), Ko, In Soo (Ed.), Kim, Kyung Sook (Ed.)
CESR has operated as a dedicated light source since the conclusion of colliding beam program in 2008. Two undulators with a 6.5mm-vertical gap were installed in Fall 2014, replacing a wiggler in the sextant of CESR that is the home to all CHESS beam lines. In order to operate narrow gap undulators with two beams, CESR pretzel lattice was redesigned so that e⁻ and e⁺ orbits are coincident in one machine sextant but separated in return arcs. In particular both e⁻ and e⁺ orbits are on axis through
more » ... are on axis through undulators. This "arc-pretzel" lattice has been the basis for undulator operation. To better understand the beam dynamics and improve machine performance, we developed many simulation tools: undulator modeling, injection tracking, etc. With installation of an additional quadrupole near undulators, the CESR lattice will be further modified with a low beta waist in the insertion devices, allowing a more than two fold reduction of local beta functions. This reduction is anticipated to mitigate the effects of small aperture and undulator field errors and to enhance the xray brightness. The characterization of the lattice will be compared with measurements of injection efficiency, tune scans, etc.
doi:10.18429/jacow-ipac2016-wepow053 fatcat:dx6ny24dejgfpmnfswh2jsfxhm