198 research outputs found
Tracking Simulations Near Half-Integer Resonance at PEP-II
Beam-beam simulations predict that PEP-II luminosity can be increased by
operating the horizontal betatron tune near and above a half-integer resonance.
However, effects of the resonance and its synchrotron sidebands significantly
enhance betatron and chromatic perturbations which tend to reduce dynamic
aperture. In the study, chromatic variation of horizontal tune near the
resonance was minimized by optimizing local sextupoles in the Interaction
Region. Dynamic aperture was calculated using tracking simulations in LEGO
code. Dependence of dynamic aperture on the residual orbit, dispersion and
distortion of beta function after correction was investigated.Comment: 4 page
Dynamic Aperture Studies for SPEAR 3
The Stanford Synchrotron Radiation Laboratory is investigating an accelerator
upgrade project that would replace the present 130 nm rad FODO lattice with an
18 nm rad double bend achromat (DBA) lattice: SPEAR 3. The low emittance design
yields a high brightness beam, but the stronger focusing in the DBA lattice
increases chromaticity and beam sensitivity to machine errors. To ensure
efficient injection and long Touschek lifetime, an optimization of the design
lattice and dynamic aperture has been performed. In this paper, we review the
methods used to maximize the SPEAR 3 dynamic aperture including necessary
optics modifications, choice of tune and phase advance, optimization of
sextupole and coupling correction, and modeling effects of machine errors,
wigglers and lattice periodicity.Comment: 23 page
Dynamical Effects Due to Fringe Field of the Magnet in Circular Accelerators
The leading Lie generators, including the chromatic effects, due to hard-edge
fringe field of single multipole and solenoid are derived from the vector
potentials within a Hamiltonian system. These nonlinear generators are applied
to the interaction region of PEP-II to analyze the linear errors due to the
feed-down from the off-centered quadrupoles and solenoid. The nonlinear effects
of tune shifts at large amplitude, the synchro-betatron sidebands near half
integer and their impacts on the dynamic aperture are studied in the paper.Comment: 3 pages, 2 figure
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