Significant Lifetime and Background Improvements in PEP-II by Reducing the 3rd Order Chromaticity in LER with Orbit Bumps

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Orbit bumps in sextupoles are routinely used for tuning the luminosity in the PEP-II B-Factory. Anti-symmetric bumps at a pair of identical sextupoles separated by -I section generate the net dispersion, while symmetric horizontal bumps induce a tune shift and beta beat. By combining two of these symmetric bumps with opposite signs, where the second pair is 90{sup o} away, the tune shift cancels and the beta beat doubles. In the low energy ring (LER), there are four -I sextupole pairs per arc, located one after another 90{sup o} apart, where pairs 1 and 3 are at the same phase ... continued below

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3 pages

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Decker, F.J.; Nosochkov, Y.; Sullivan, M.; Yocky, G. & /SLAC December 18, 2007.

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Orbit bumps in sextupoles are routinely used for tuning the luminosity in the PEP-II B-Factory. Anti-symmetric bumps at a pair of identical sextupoles separated by -I section generate the net dispersion, while symmetric horizontal bumps induce a tune shift and beta beat. By combining two of these symmetric bumps with opposite signs, where the second pair is 90{sup o} away, the tune shift cancels and the beta beat doubles. In the low energy ring (LER), there are four -I sextupole pairs per arc, located one after another 90{sup o} apart, where pairs 1 and 3 are at the same phase and pairs 2 and 4 are 90{sup o} away. By making two symmetric bumps with opposite sign in pairs 1 and 3, the tune shift and beta beat outside this region cancel, but there is a local change of phase and beta in the 2nd sextupole pair located in the middle. By using this bump knob, the LER lifetime improved by a factor of 3, losses by a factor of 5, and the beam-beam background in the drift chamber of the BaBar detector by 20%. Optics analysis showed that the local phase change at the 2nd sextupole pair can compensate the 3rd order chromaticity.

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3 pages

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  • Contributed to Particle Accelerator Conference (PAC 07), Albuquerque, New Mexico, 25-29 Jun 2007

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  • Report No.: SLAC-PUB-12719
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 921293
  • Archival Resource Key: ark:/67531/metadc892964

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  • December 18, 2007

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  • Sept. 27, 2016, 1:39 a.m.

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  • Dec. 9, 2016, 7:10 p.m.

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Decker, F.J.; Nosochkov, Y.; Sullivan, M.; Yocky, G. & /SLAC. Significant Lifetime and Background Improvements in PEP-II by Reducing the 3rd Order Chromaticity in LER with Orbit Bumps, article, December 18, 2007; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc892964/: accessed October 23, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.