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| MOOCH01 |
Beam Based Alignment at the KEK-ATF Damping Ring
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36 |
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- M. Woodley, J. Nelson, M.C. Ross, J.L. Turner
SLAC, Menlo Park, California
- K. Kubo
KEK, Ibaraki
- A. Wolski
LBNL/AFR, Berkeley, California
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The damping rings for a future linear collider will have demanding alignment and stability requirements in order to achieve the low vertical emittance necessary for high luminosity. The Accelerator Test Facility (ATF) at KEK has successfully demonstrated the <5 pm vertical emittance specified for the GLC/NLC Main Damping Rings [*]. One contribution to this accomplishment has been the use of Beam Based Alignment (BBA) techniques. The mode of operation of the ATF presents particular challenges for BBA, and we describe here how we have deduced the offsets of the BPMs with respect to the quadrupoles. We also discuss a technique that allows for direct measurements of the beam-to-quad offsets.
* "Extremely Low Vertical-Emittance Beam in the Accelerator Test Facility at KEK", K. Kubo, et al., Phys.Rev.Lett.88:194801,2002
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Video of talk
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Transparencies
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| MOPLT128 |
Lattice Effects due to High Currents in PEP-II
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836 |
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- F.-J. Decker, H. Smith, J.L. Turner
SLAC, Menlo Park, California
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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 were 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. It is located far away from any synchrotron radiation in the middle of a straight (PR12), away from sextupoles and skew quadrupoles and creates a dispersion wave of about 70 mm at high current while at low current it is negligible.
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| MOPLT139 |
Beam-based Alignment and Beta Function Measurements in PEP-II
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866 |
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- G. Yocky, J. Nelson, M.C. Ross, T.J. Smith, J.L. Turner, M. Woodley
SLAC, Menlo Park, California
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Careful optics studies and stringent lattice control have been identified as two key components to increasing PEP-II luminosity. An accurate, trusted BPM system is required for both of these strategies. To validate the existing BPM system and to better understand some optical anomalies in the PEP-II rings, an aggressive program of beam-based alignment (BBA) has been initiated. Using a quad-shunt BBA procedure in which a quadrupole?s field strength is varied over a range of beam positions, relative offsets are determined by the BPM readings at which quadrupole field changes no longer induce a closed orbit shift. This procedure was verified in the HER and is well underway in the LER IR. We have found many surprisingly large BPM offsets, some over one centimeter, as well as a number of locations where the current nominal orbit is several millimeters from the quadrupole center. Tune versus quadrupole field data were taken during the BBA process in the LER IR, and the non-linear response in each case is compared to simulation to infer local beta functions.
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| MOPLT146 |
Trickle-charge: a New Operational Mode for PEP-II
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881 |
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- J.L. Turner, S. Colocho, F.-J. Decker, S. Ecklund, A.S. Fisher, R.H. Iverson, C. O'Grady, J. Seeman, M.K. Sullivan, M. Weaver, U. Wienands
SLAC, Menlo Park, California
- W. Kozanecki
CEA/DSM/DAPNIA, Gif-sur-Yvette
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In regular top-up-and-coast operation, PEP-II average luminosity is about 70…75% of the peak luminosity due to detector ramp-down and ramp-up times plus the time it takes to top-up both beams. We recently commissioned a new operational mode where the Low Energy Ring is injected continuously without ramping down the detector. The benefits?increased luminosity lifetime and roughly half the number of top-ups per shift?were expected to give an increase in delivered luminosity of about 15% at the same peak luminosity; this was confirmed in test runs. In routine trickle operation, however, it appears that the increase in delivered luminosity is more than twice that due to an increase in availability credited to the more stable operating conditions during trickle operation. In this paper we will present our operational experience as well as some of the diagnostics we use to monitor and maintain tuning of the machine in order to control injection background and protect the detector. Test runs are planned to extend trickle-charge operation to the High Energy Ring as well.
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| TUPLT153 |
Orbit Response Matrix Analysis Applied at PEP-II
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1488 |
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- C. Steier, A. Wolski
LBNL/AFR, Berkeley, California
- S. Ecklund, J.A. Safranek, P. Tenenbaum, A. Terebilo, J.L. Turner, G. Yocky
SLAC, Menlo Park, California
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Beam-based techniques to study lattice properties have proven to be a very powerful tool to optimize the performance of storage rings. The analysis of orbit response matrices has been used very successfully to measure and correct the gradient and skew gradient distribution in many accelerators. The first applications were mostly in synchrotron light sources, but the technique is also used increasingly at colliders. It allows determination of an accurately calibrated model of the coupled machine lattice, which then can be used to calculate the corrections necessary to improve coupling, dynamic aperture and ultimately luminosity. At PEP-II, the Matlab version of LOCO has been used to analyze coupled response matrices for both the LER and the HER. The large number of elements in PEP-II and the very complicated interaction region present unique challenges to the data analysis. The orbit response matrix analysis will be presented in detail, as well as results of lattice corrections based on the calibrated machine model.
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| MOPLT143 |
Results and Plans of the PEP-II B-Factory
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875 |
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- J. Seeman, J. Browne, Y. Cai, S. Colocho, F.-J. Decker, M.H. Donald, S. Ecklund, R.A. Erickson, A.S. Fisher, J.D. Fox, S.A. Heifets, R.H. Iverson, A. Kulikov, A. Novokhatski, M.T.F. Pivi, M.C. Ross, P. Schuh, T.J. Smith, K. Sonnad, M. Stanek, M.K. Sullivan, P. Tenenbaum, D. Teytelman, J.L. Turner, D. Van Winkle, U. Wienands, M. Woodley, Y.T. Yan, G. Yocky
SLAC, Menlo Park, California
- M.E. Biagini
INFN/LNF, Frascati (Roma)
- J.N. Corlett, C. Steier, A. Wolski, M.S. Zisman
LBNL, Berkeley, California
- W. Kozanecki
CEA/DSM/DAPNIA, Gif-sur-Yvette
- G. Wormser
IPN, Orsay
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PEP-II is an e+e- B-Factory Collider located at SLAC operating at the Upsilon 4S resonance. PEP-II has delivered, over the past four years, an integrated luminosity to the BaBar detector of over 175 fb-1 and has reached a luminosity over 7.4x1033/cm2/s. Steady progress is being made in reaching higher luminosity. The goal over the next few years is to reach a luminosity of at least 2x1034/cm2/s. The accelerator physics issues being addressed in PEP-II to reach this goal include the electron cloud instability, beam-beam effects, parasitic beam-beam effects, trickle injection, high RF beam loading, lower beta y*, interaction region operation, and coupling control.
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