EPAC 2004 - List of Authors

A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Seeman, J.

Paper	Title	Page
MOPLT051	Experimental Characterization of PEP-II Luminosity and Beam-beam Performance	665
	W. Kozanecki CEA/DSM/DAPNIA, Gif-sur-Yvette M.A. Baak NIKHEF, Amsterdam J. Seeman, M.K. Sullivan, U. Wienands SLAC, Menlo Park, California
	The beam-beam performance of the PEP-II B-Factory has been studied by simultaneously measuring the instantaneous luminosity, the horizontal and vertical e⁺ and e^- beam sizes in the two rings, and the spatial extent of the luminous region as extracted from BaBar dilepton data. These quantities, as well as ring tunes, beam lifetimes and other collider parameters are recorded regularly as a function of the two beam currents, both parasitically during routine physics running and in a few dedicated accelerator physics experiments. They are used to quantify, project, and ultimately improve the PEP-II performance in terms of achieved beam-beam parameters, dynamic-beta enhancement, and current-dependence of the specific luminosity.
MOPLT135	Damping the High Order Modes in the Pumping Chamber of the PEP-II Low Energy Ring	854
	A. Novokhatski, S. Debarger, F.-J. Decker, A. Kulikov, J. Langton, M. Petree, J. Seeman, M.K. Sullivan SLAC, Menlo Park, California
	The Low Energy Ring of the PEP-II B-factory operates with extremely high currents and short positron bunches. Any discontinuity in the vacuum chamber can excite a broad-band spectrum of the High Order Modes. A temperature rise has been found in the vacuum chamber elements in one transition from straight section to arc. The power in the wake fields was high enough to char beyond use the feed-through for the Titanium Sublimation Pump. This pumping section consists of the beam chamber and an ante-chamber. Fields, excited in the beam chamber penetrate to the ante-chamber and then through the heater wires of the TSP come out. A small ceramic tile was placed near the TSP feed-through to absorb these fields. A short wire antenna was also placed there. HOM measurements show a wide spectrum with a maximum in the 2-3 GHz region. A special water cooled HOM absorber was designed and put inside the ante-chamber part of the section. As a result, the HOM power in the section decreased and the temperature rise went down. The power loss is 750 W for a beam current of 2 A. Measurements of the HOM impedance for different bunch patterns, bunch length and transverse beam position will be presented.
MOPLT141	IR Upgrade Plans for the PEP-II B-Factory	869
	M.K. Sullivan, S. Ecklund, N. Kurita, A. Ringwall, J. Seeman, U. Wienands SLAC, Menlo Park, California M.E. Biagini INFN/LNF, Frascati (Roma)
	PEP-II, the SLAC, LBNL, LLNL B-factory has achieved a peak luminosity of over 7e33, more than twice the design luminosity, and plans to obtain a luminosity of over 1·10³⁴ in the next year. In order to push the luminosity performance of PEP-II to even higher levels an upgrade to the interaction region is being designed. In the present design, the interaction point is a head-on collision with two strong horizontal dipole magnets (B1) located between 20-70 cm from the IP that bring the beams together and separate the beams after the collision. The first parasitic crossing (PC) is at 63 cm from the IP in the present by2 bunch spacing. The B1 magnets supply all of the beam separation under the present design. Future improvements to PEP-II performance include lowering the beta y * values of both rings. This will increase the beta y value at the PCs which increases the beam-beam effect at these non-colliding crossings. Introducing a horizontal crossing angle at the IP quickly increases the beam separation at the PCs but recent beam-beam studies indicate a significant luminosity reduction occurs when a crossing angle is introduced at the IP. We will discuss these issues and describe the present interaction region upgrade design.
MOPLT143	Results and Plans of the PEP-II B-Factory	875
	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
	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.
MOPLT144	Design for a 10³⁶ Super-B-factory at PEP-II	878
	J. Seeman, Y. Cai, F.-J. Decker, S. Ecklund, A.S. Fisher, J.D. Fox, S.A. Heifets, A. Novokhatski, M.K. Sullivan, D. Teytelman, U. Wienands SLAC, Menlo Park, California
	Design studies are underway to arrive at a complete parameter set for a very high luminosity e⁺e^- Super B-Factory (SBF) in the luminosity range approaching 10³⁶/cm²/s. The design is based on a collider in the PEP-II tunnel but with an upgraded RF system (higher frequency), magnets, vacuum system, and interaction region. The accelerator physics issues associated with this design are reviewed as well as the site and power constraints. Near term future studies will be discussed.
MOPLT146	Trickle-charge: a New Operational Mode for PEP-II	881
	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
	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.
MOPLT155	Study of Beam-beam Effects at PEP-II	896
	I.V. Narsky, F.C. Porter CALTECH, Pasadena, California Y. Cai, J. Seeman SLAC, Menlo Park, California W. Kozanecki CEA/DSM/DAPNIA, Gif-sur-Yvette
	Using a self-consistent, three-dimensional simulation program running on parallel supercomputers, we have simulated the beam-beam interaction at the PEP II asymmetric e⁺e^- collider. In order to provide guidance to luminosity improvement in PEP-II, we have scanned the tunes and other machine parameters in both rings, and computed their impact on the luminosity and particle loss. Whenever possible, the code has been benchmarked against experimental measurements, at various beam currents, of luminosity and luminous-region size using the BaBar detector. These studies suggest that three-dimensional effects such as bunch lengthening may be important to understand a steep drop of luminosity near the peak currents.
THPLT154	Design of an X-ray Imaging System for the Low-Energy Ring of PEP-II	2816
	A.S. Fisher, D. Arnett, H. De Staebler, S. Debarger, R.K. Jobe, D. Kharakh, D.J. McCormick, M. Petree, M.C. Ross, J. Seeman, B. Smith SLAC, Menlo Park, California J. Albert, D. Hitlin CALTECH, Pasadena, California J. Button-Shafer, J.A. Kadyk LBNL, Berkeley, California
	An x-ray beam-size monitor for positrons in the low-energy ring (LER) of the PEP-II B Factory at SLAC is being designed to accommodate the present 2-A, 3.1-GeV beam and anticipated currents of up to 4.7 A. The final photon stop of an arc will be rebuilt to pass dipole radiation through cooled apertures to optics 17 m from the source. Zone-plate imaging there can achieve a resolution of 6 microns, compared to 35 for a pinhole camera. Two multilayer x-ray mirrors precede the zone plate, limiting the bandwidth to 1%, in order to avoid chromatic blurring and protect the zone plate. Despite the narrow bandwidth, the zone plate?s larger diameter compared to a pinhole camera allows for a comparable photon flux. We will image all 1700 LER bunches and also measure them individually, searching for variations along the train due to electron-cloud and beam-beam effects, using a scanning detector conceptually derived from a wire scanner. A mask with three narrow slots at different orientations will scan the image to obtain three projections. In one passage, signals from a fast scintillator and photomultiplier will be rapidly digitized and sorted to profile each bunch.