Lattice Effects Due to High Currents in PEP-II

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The very high beam currents in the PEP-II B-Factory have caused many expected and unexpected effects: Synchrotron light fans move the beam pipe and cause dispersion; higher order modes cause excessive heating, e-clouds around the positron beam blow up its beam size. Here we describe an effect where the measured dispersion of the beam in the Low Energy Ring (LER) is different at high and at low beam currents. The dispersion was iteratively lowered by making anti-symmetric orbit bumps in many sextupole duplets, checking each time with a dispersion measurement where a dispersive kick is generated. This can be done ... continued below

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Decker, F.-J.; Smith, H.; Turner, J.L. & /SLAC May 9, 2005.

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The very high beam currents in the PEP-II B-Factory have caused many expected and unexpected effects: Synchrotron light fans move the beam pipe and cause dispersion; higher order modes cause excessive heating, e-clouds around the positron beam blow up its beam size. Here we describe an effect where the measured dispersion of the beam in the Low Energy Ring (LER) is different at high and at low beam currents. The dispersion was iteratively lowered by making anti-symmetric orbit bumps in many sextupole duplets, checking each time with a dispersion measurement where a dispersive kick is generated. This can be done parasitically during collisions. It was a surprise when checking the low current characterization data that there is a change. Subsequent high and low current measurements confirmed the effect. One source was believed to be located far away from any synchrotron radiation in the middle of a straight (PR12), away from sextupoles and skew quadrupoles and created a dispersion wave of about 70 mm at high current while at low current it is negligible.

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3 pages

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  • Presented at the 9th European Particle Accelerator Conference (EPAC 2004), Lucerne, Switzerland, 5-9 Jul 2004

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  • Report No.: SLAC-PUB-11166
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 890842
  • Archival Resource Key: ark:/67531/metadc883154

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  • May 9, 2005

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  • Sept. 21, 2016, 2:29 a.m.

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  • Nov. 29, 2016, 6:14 p.m.

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Decker, F.-J.; Smith, H.; Turner, J.L. & /SLAC. Lattice Effects Due to High Currents in PEP-II, article, May 9, 2005; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc883154/: accessed December 11, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.