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

Beam Losses in the Extraction Line of a TeV e+e−e^+ e^- Linear Collider with a 20 mrad Crossing Angle

In this paper, we perform a detailed study of the power losses along the post- collision extraction line of a TeV $e^+e^-$ collider with a crossing angle of 20 mrad between the beams at the interaction point. Five cases are considered here: four luminosity configurations for ILC and one for CLIC. For all of them, the strong beam-beam effects at the interaction point lead to an emittance growth for the outgoing beams, as well as to the production of beamstrahlung photons and $e^+e^-$ pairs. The power losses along the 20 mrad extraction line, which are due to energy deposition by a fraction of the disrupted beam, of the beamstrahlung photons and of the $e^+e^-$ coherent pairs, were estimated in the case of ideal collisions, as well as with a vertical position or angular offset at the interaction point

Tuning Knobs for the NLC Final Focus

Compensation of optics errors at the Interaction Point (IP) is essential for maintaining maximum luminosity at the NLC. Several correction systems (knobs) using the Final Focus sextupoles have been designed to provide orthogonal compensation of linear and the second order optics aberrations at IP. Tuning effects of these knobs on the 250 GeV beam were verified using tracking simulations.Comment: 4 pages, 3 figure