EPAC 2006 - Classification:01 Circular Colliders/A02 Lepton Colliders

01 Circular Colliders

A02 Lepton Colliders

Paper	Title	Page
MOYBPA02	Operation of High-luminosity Meson Factories and the Challenge to go to the Next Generation	19
	K. Akai KEK, Ibaraki
	This talk will present an overview of the operational status of B- and Phi-Factories, and address their present luminosity performance and limitations, such as electron cloud effects. It will also discuss upgrade plans, including motivation and beam dynamics challenges, new ideas, R&D and machine experiments in view of the next generation of meson factories with ~100 times more luminosity. In particular, it will address machine tests with strong RF focusing, crab cavity developments and first operational experience at KEKB.
	Transparencies
MOPLS026	Monitoring of Interaction-point Parameters using the 3-dimensional Luminosity Distribution Measured at PEP-II	598
	B.F. Viaud Montreal University, Montreal, Quebec W. Kozanecki CEA, Gif-sur-Yvette C. O'Grady, J.M. Thompson, M. Weaver SLAC, Menlo Park, California
	The 3-D luminosity distribution at the IP of the SLAC B-Factory is monitored using e⁺ e^- -> e⁺ e-, mu+ mu- events reconstructed online in the BaBar detector. The transverse centroid and spatial orientation of the luminosity ellipsoid provide a reliable monitor of IP orbit drifts. The longitudinal centroid is sensitive to small variations in the average relative RF phase of the beams and provides a detailed measurement of the phase transient along the bunch train. Relative variations in horizontal luminous size are detectable at the micron level. The longitudinal luminosity distribution depends on the e± overlap bunch length and the vertical IP beta-function betay. In addition to continuous online monitoring of all the IP parameters above, we performed detailed studies of their variation along the bunch train to investigate a temporary luminosity degradation. We also used controlled variations in RF voltage and beam current to extract separate measurements of the e⁺ and e^- bunch lengths. The time-history of the betay measurements, collected over a year of routine high-luminosity operation, are compared with HER & LER phase-advance data periodically recorded in single-bunch mode.
MOPLS027	Beam-beam Simulations for a Single Pass SuperB-factory	601
	M.E. Biagini INFN/LNF, Frascati (Roma) P. Raimondi, J. Seeman SLAC, Menlo Park, California D. Schulte CERN, Geneva
	A study of beam-beam collisions for an asymmetric single pass SuperB-Factory is presented. In this scheme an electron and a positron beam are first stored and damped in two damping rings, then extracted, compressed and focused to the IP. After collision the two beams are re-injected in the DR to be damped and extracted for collision again. The explored beam parameters are similar to those used in the design of the International Linear Collider, except for the beam energies. Very flat beams and round beams were compared in the simulations, with the GuineaPig code, in order to optimize both luminosity performances and beam blow-up after collision. With such approach, luminosities of the order of 10³⁶ /(cm² sec) can be achieved. http://arxiv.org/abs/physics/0512235.**D. Schulte. “Study of electromagnetic and hadronic background in the Interaction Region of the TESLA Collider”, PhD Thesis, Hamburg, 1996.
MOPLS028	DAFNE Status Report	604
	A. Gallo, D. Alesini, M.E. Biagini, C. Biscari, R. Boni, M. Boscolo, B. Buonomo, A. Clozza, G.O. Delle Monache, E. Di Pasquale, G. Di Pirro, A. Drago, A. Ghigo, S. Guiducci, M. Incurvati, P. Iorio, C. Ligi, F. Marcellini, C. Marchetti, G. Mazzitelli, C. Milardi, L. Pellegrino, M.A. Preger, L. Quintieri, R. Ricci, U. Rotundo, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, S. Tomassini, C. Vaccarezza, M. Vescovi, M. Zobov INFN/LNF, Frascati (Roma) G. Benedetti CELLS, Bellaterra (Cerdanyola del Vallès) L. Falbo INFN-Pisa, Pisa J.D. Fox, P. Raimondi, D. Teytelman SLAC, Menlo Park, California E. Levichev, S.A. Nikitin, P.A. Piminov, D.N. Shatilov BINP SB RAS, Novosibirsk
	The operation of DAFNE, the 1.02 GeV c.m. e⁺e^- collider of the Frascati National Laboratory with the KLOE detector, started in April 2004 has been concluded at the end of March 2006 with a total delivered luminosity of 2 fb-1 on the peak of the Phi resonance, 0.2 fb-1 off peak and a high statistics scan of the resonance. The best performances of the collider during this run have been a peak luminosity of 1.5 1032 cm-2s-1 and a daily delivered luminosity of 10 pb-1. The KLOE detector has been removed from one of the two interaction regions and its low beta section substituted with a standard magnetic structure, allowing for an easy vertical separation of the beams, while the FINUDA detector has been moved onto the second interaction point. Several improvements on the rings have also been implemented and are described together with the results of machine studies aimed at improving the collider efficiency and testing new operating conditions.
MOPLS029	Preliminary Study of a Crab Crossing System for DAFNE	607
	A. Gallo, D. Alesini, F. Marcellini, P. Raimondi, M. Zobov INFN/LNF, Frascati (Roma)
	The implementation of a crab crossing scheme at the Frascati Phi-factory DAFNE is under consideration, together with several other ideas and upgrades to increase the collider luminosity. The crab crossing is beneficial to the luminosity because it is expected to optimize the geometrical superposition of the colliding bunches and to weaken the synchro-betatron beam-beam resonances. The basic specifications of such a system, the expected luminosity increase, a preliminary design of the crab cavities and the architecture of the dedicated RF system are presented.
MOPLS030	Recent Progress of KEKB	610
	Y. Funakoshi KEK, Ibaraki
	We summarize the machine operation of KEKB during the past one year, focusing on progress for this period.
MOPLS031	Beam Orbit Control System for the KEKB Crab Cavities	613
	M. Masuzawa, Y. Funakoshi, T.T. Nakamura, J.-I. Odagiri KEK, Ibaraki
	KEKB is an electron-positron collider with an 8 GeV electron ring (HER) and a 3.5 GeV positron ring (LER). The two beams currently collide at one interaction point with a finite horizontal crossing angle of 11 mrad. The design luminosity of 10 /nb/sec was first reached in May 2003 and the peak luminosity exceeded 16 /nb/sec in December 2005. Simulations predict a luminosity boost if a crab crossing scheme is introduced. The installation of two superconducting crab cavities, one in each ring, is scheduled in March 2006 in order to implement the crab crossing scheme. For stable operation, the horizontal beam position in the crab cavity must be carefully controlled. This is needed to avoid loss of control of the crabbing mode field due to beam loading. A beam position feedback system at the crab cavity has been prepared and tested. Its performance will be discussed in this report.
MOPLS032	Beam-beam Limit and the Degree of Freedom	616
	K. Ohmi, K. Oide KEK, Ibaraki E. Perevedentsev BINP SB RAS, Novosibirsk
	Beam-beam limit is caused by chaotic diffusion due to the strong nonlinear force of beam-beam interaction. Degree of freedom in the colliding system is essential for the diffusion. We discuss the diffusion using several models.
MOPLS033	Beam-beam Limit and Feedback Noise	619
	K. Ohmi, Y. Funakoshi, S. Hiramatsu, K. Oide, M. Tobiyama KEK, Ibaraki
	Beam-beam interaction is strongly nonlinear, therefore particles in the beam experience chaotic motion. A small noise can be enhanced by the chaotic nature, with the result that unexpected emittance growth can be observed. We study the noise of transverse bunch by bunch feedback system and related luminosity degradation. Similar effects caused by crab cavity noise is also discussed.
MOPLS037	Beams Injection System for e⁺e^- Collider VEPP-2000	622
	D.E. Berkaev, V.V. Druzhinin, I. Koop, A.P. Lysenko, F.V. Podgorny, V.P. Prosvetov, P.Yu. Shatunov, Y.M. Shatunov, D.B. Shwartz BINP SB RAS, Novosibirsk
	Electron-positron collider VEPP-2000 is under commissioning at the Budker Institute of Nuclear Physics. The paper presents the injection system of the collider delivering the beam from the booster storage ring BEP with maximum energy 900 MeV. A matching of the beam injection with the storage ring optics is done with respect to a nonlinear kicker field. Features of beam diagnostic and transfer line magnets including pulse septums (100 mksec; 30 kGs) and fast kickers (20 nsec; 70 kV) are described. Results of the magnetic measurements and their comparison to calculated data are given.
MOPLS038	Beam Energy Calibration in Experiment on Precise Tau Lepton Mass Measurement at VEPP-4M with KEDR Detector	625
	A. Bogomyagkov, V.E. Blinov, S. Karnaev, V. Kiselev, E.V. Kremyanskaya, E. Levichev, O.I. Meshkov, S.I. Mishnev, I. Morozov, N.Yu. Muchnoi, S.A. Nikitin, I.B. Nikolaev, A.G. Shamov, D.N. Shatilov, E.A. Simonov, A.N. Skrinsky, V.V. Smaluk, Yu.A. Tikhonov, G.M. Tumaikin, V.N. Zhilich BINP SB RAS, Novosibirsk
	Experiment on mass measurement of tau lepton requires an absolute energy calibration. The resonant depolarization technique is used for most accurate (1 keV) but once at a time energy calibration. The measured energy is used for calibration of the germanium detector for Compton backscattering energy monitoring. The developed Compton backscattering facility allows continuous energy monitoring with accuracy of 50 keV for 10 minutes of data acquisition. The tau lepton threshold is in the vicinity of integer spin resonance, which minimizes polarization lifetime in the presence of vertical orbit distortions. Therefore, spin matching of the VEPP-4M is required. The achieved lifetime is sufficient for absolute energy calibration.
MOPLS040	Magnet Structure of the VEPP-2000 Electron-positron Collider	628
	P.Yu. Shatunov, D.E. Berkaev, A.A. Borisov, I. Koop, N.A. Mezentsev, E. Perevedentsev, Y.M. Shatunov, D.B. Shwartz BINP SB RAS, Novosibirsk A. Valishev Fermilab, Batavia, Illinois
	Electron-positron collider VEPP-2000 with beam energy up to 1 GeV is under commissioning at Budker Institute. This paper presents magnetic elements of the storage ring including 13T focusing superconducting solenoids in interaction regions. Features of magnet elements design and magnetic measurements results are given together with comparison to previously calculated data.
MOPLS041	MAD-X/PTC Lattice Design for DAFNE at Frascati	631
	F. Schmidt CERN, Geneva E. Forest KEK, Ibaraki C. Milardi INFN/LNF, Frascati (Roma)
	In absence of a program that takes as an input the desired or known location of the magnets in the tunnel, accelerator designers have been using MAD8/X that looks at a ring as a sequence of magnets without a connection to the tunnel. In many simple examples that is just fine, but once more complicated structures are treated one is bound to play tricks with MAD. Here PTC comes to the rescue. It is shown how pieces of this machine that exist in MAD-X format are used in PTC to create this double ring, as found in the tunnel, with a proper survey in the forward and backward direction. Special elements have been implemented in MAD-X to allow the full PTC description of the machine. It is discussed how this real PTC model differs from the 'fake' MAD-X model and how well PTC describes the real machine.
MOPLS042	Longitudinal Beam Stability for CESR-c	634
	R. Holtzapple, J.S. Kern, P.J.S. Stonaha Alfred University, Alfred, New York B. Cerio Colgate University, Hamilton, New York M.A. Palmer Cornell University, Laboratory for Elementary-Particle Physics, Ithaca, New York
	The Cornell Electron-Positron Storage Ring (CESR) operates at 1.9 GeV per beam for high energy physics collisions. To maintain high luminosity it is essential for the bunch trains to be longitudinally stable. Measurements of longitudinal stability with a single, multiple, and colliding trains have been performed using a dual sweep streak camera and are presented in this paper.
MOPLS043	Studies of the Beam-beam Interaction at CESR	637
	J.A. Crittenden Cornell University, Department of Physics, Ithaca, New York M.G. Billing CESR-LEPP, Ithaca, New York
	The Cornell Electron Storage Ring facility operates 2-GeV multi-bunch electron and positron beams in a single beam-pipe. Electrostatic separators are used to separate the two counter-rotating beams at the parasitic crossings. When the beam energy was lowered from 5 GeV in 2003, the strength of the beam-beam interaction became a more important factor in beam-current limitations, resulting in extensive experimental and calculational studies of their characteristics. The CESR lattice design procedure has been modified recently to account explicitly for their dynamic consequences. We describe our modelling of the beam-beam interaction, experimental validation techniques, and investigations into compensation strategies.
MOPLS044	Luminosity Variations along Bunch Trains in PEP-II	640
	F.-J. Decker, M. Boyes, W.S. Colocho, A. Novokhatski, M.K. Sullivan, J.L. Turner, S.P. Weathersby, U. Wienands, G. Yocky SLAC, Menlo Park, California
	In spring of 2005 after a long shut-down, the luminosity of the B-Factory PEP-II decreased along the bunch trains by about 25-30%. There were many reasons studied which could have caused this performance degradation, like a bigger phase transient due to an additional RF station in the Low-Energy-Ring (LER), bad initial vacuum, electron cloud, chromaticity, steering, dispersion in cavities, beam optics, etc. The initial specific luminosity of 4.2 sloped down to 3.2 and even 2.8 for a long train (typical: 130 of 144), later in the run with higher currents and shorter trains (65 of 72) the numbers were more like 3.2 down to 2.6. Finally after steering the interaction region for an unrelated reason (overheated BPM buttons) and the consequential lower luminosity for two weeks, the luminosity slope problem was mysteriously gone. Several parameters got changed and there is still some discussion about which one finally fixed the problem. Among others, likely candidates are: the LER betatron function in x at the interaction point got reduced, making the LER x stronger, dispersion reduction in the cavities, and finding and fixing a partially shorted magnet.
MOPLS045	Achieving a Luminosity of 10³⁴/cm²/s in the PEP-II B-factory	643
	J. Seeman, J. Browne, Y. Cai, W.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, V. Pacak, M.T.F. Pivi, C.H. Rivetta, M.C. Ross, P. Schuh, K.G. Sonnad, M. Stanek, M.K. Sullivan, P. Tenenbaum, D. Teytelman, J.L. Turner, D. Van Winkle, M. Weaver, U. Wienands, W. Wittmer, M. Woodley, Y.T. Yan, G. Yocky SLAC, Menlo Park, California M.E. Biagini INFN/LNF, Frascati (Roma) W. Kozanecki CEA, Gif-sur-Yvette
	For the PEP-II Operation Staff: PEP-II is an asymmetric e⁺e^- collider operating at the Upsilon 4S and has recently set several performance records. The luminosity has exceeded 1x10³⁴/cm²/s and has delivered an integrated luminosity of 728/pb in one day. PEP-II operates in continuous injection mode for both beams, boosting the integrated luminosity. The peak positron current has reached 2.94 A and 1.74 A of electrons in 1732 bunches. The total integrated luminosity since turn on in 1999 has reached over 333/fb. This paper reviews the present performance issues of PEP-II and also the planned increase of luminosity in the near future to over 2 x 10³⁴/cm²/s. Upgrade details and plans are discussed.
MOPLS047	Design of an Asymmetric Super-B Factory	646
	J. Seeman, Y. Cai, A. Novokhatski, A. Seryi, M.K. Sullivan, U. Wienands SLAC, Menlo Park, California M.E. Biagini, P. Raimondi INFN/LNF, Frascati (Roma)
	Submitted for the High Luminosity Study Group for an Asymmetric Single-pass Super-B Factory: Parameters are being studied for a high luminosity e⁺e^- collider operating at the Upsilon 4S that would deliver a luminosity of over 10³⁶/cm²/s. This collider would use a novel combination of linear collider and storage ring techniques. In this scheme an electron beam and a positron beam are first stored in fast-damping and low-emittance damping rings, then extracted, accelerated, compressed and focused to the interaction point. After collision the two beams are decelerated and re-injected in the damping rings to be damped and extracted for collision again. The explored beam parameters are similar to those used in the design of the International Linear Collider, except for the beam energies. Design parameters for very flat beams and round beams have been studied.
MOPLS048	Doubling the PEP-II Luminosity in Simulations	649
	Y. Cai, J. Seeman, K.G. Sonnad, U. Wienands SLAC, Menlo Park, California
	The PEP-II luminosity reached 1x10³⁴cm-2s-1 in October 2005. The question of how to increase the luminosity using modest improvements in the PEP-II accelerator in the coming years is the subject of this paper. We found that the parasitic collisions significantly degrade the simulated luminosity as the beam currents are increased from 3A and 1.7A to 4A and 2.2A in the low and high energy rings, respectively. Using the beam-beam code BBI, we systematically optimized the luminosity and showed that a luminosity of over 2x10³⁴cm-2s-1 is achievable within the limits of machine parameters.
MOPLS049	Anomalous High Radiation Beam Aborts in the PEP-II B-factory	652
	M.K. Sullivan, Y. Cai, S. DeBarger, F.-J. Decker, S. Ecklund, A.S. Fisher, S.M. Gierman, S.A. Heifets, R.H. Iverson, A. Kulikov, N. Kurita, S.J. Metcalfe, A. Novokhatski, J. Seeman, K.G. Sonnad, D. Teytelman, J.L. Turner, U. Wienands, D. Wright, Y.T. Yan, G. Yocky SLAC, Menlo Park, California
	The PEP-II B-factory at SLAC has recently experienced unexpected beam losses due to anomalously high radiation levels at the BaBar detector. The problem was finally traced to the occurrence of very high pressure (>100 nTorr) spikes that have a very short duration (few seconds). We describe the events and show analysis predicting where in the vacuum system the events originated and describe what was discovered in the vacuum system.
MOPLS050	Combined Phase Space Characterization at the PEP-II IP using Single-beam and Luminous-region Measurements	655
	A.J. Bevan Queen Mary University of London, London Y. Cai, A.S. Fisher, C. O'Grady, J.M. Thompson, M. Weaver SLAC, Menlo Park, California W. Kozanecki CEA, Gif-sur-Yvette B.F. Viaud Montreal University, Montreal, Quebec
	We present a novel method to characterize the e ± phase space at the IP of the SLAC B-factory, that combines single-beam measurements with a detailed mapping of luminous-region observables. Transverse spot sizes are determined in the two rings with synchrotron-light monitors & extrapolated to the IP using measured lattice functions. The 3-D luminosity distribution, as well as the spatial dependence of the transverse-boost distribution of the colliding beams, are measured using e⁺ e^- –> mu+ mu- events reconstructed in the BaBar tracking detectors; they provide information on the luminous spot size, the e^- angular divergence & the vertical emittance. The specific luminosity, which is proportional to the inverse product of the overlap IP beam sizes, is continuously monitored using Bhabha-scattering events. The combination of these measurements provide constraints on the horizontal & vertical spot sizes, angular divergences, emittances & beta functions of both beams at the IP during routine high-luminosity operation. Preliminary results of this combined-spot size analysis are confronted with measurements of IP beta-functions & overlap IP beam sizes at low beam current.
MOPLS051	Tracking Down a Fast Instability in the PEP-II LER	658
	U. Wienands, R. Akre, S.C. Curry, S. DeBarger, F.-J. Decker, S. Ecklund, A.S. Fisher, S.A. Heifets, A. Krasnykh, A. Kulikov, A. Novokhatski, J. Seeman, M.K. Sullivan, D. Teytelman, D. Van Winkle, G. Yocky SLAC, Menlo Park, California
	During Run 5, the beam in the PEP-II Low Energy Ring (LER) became affected by a predominantly vertical instability with very fast growth rate of 10…60/ms - much faster than seen in controlled grow-damp experiments - and varying threshold. The coherent amplitude of the oscillation was limited to approx. 1 mm pk-pk or less and would damp down over a few tens of turns; however, beam loss set in even as the measured amplitude damped, causing a beam abort. This led to the conclusion that the beam was actually blowing up. The presence of a 2 nu_s line in the spectrum suggested a possible head-tail nature of the instability, although chromaticity was not effective in raising the threshold. In this paper we will describe the measurements and data taken to isolate and locate the cause of the instability and, eventually, the discovery and fix of the root cause.
MOPLS052	Luminosity Improvement at PEP-II Based on Optics Model and Beam-beam Simulation	661
	Y. Cai, W.S. Colocho, F.-J. Decker, Y. Nosochkov, P. Raimondi, J. Seeman, K.G. Sonnad, M.K. Sullivan, J.L. Turner, M. Weaver, U. Wienands, W. Wittmer, M. Woodley, Y.T. Yan, G. Yocky SLAC, Menlo Park, California
	The model independent analysis (MIA) has been successfully used at PEP-II to understand machine optics and improve the luminosity. However, the rate of success was limited because the improvement of optics does not necessarily lead to increase of luminosity. Recently, we were able to reconstruct MIA model in a full optics code, LEGO, and used it to calculate complete lattice and beam parameters. These parameters were fed to the beam-beam code, BBI, to understand the luminosity histories at PEP-II over the past year. Using these tools, we optimized the luminosity by varying the beam parameters such as emittance. Finally, we implemented an optimized solution with a set of asymmetric horizontal orbit bumps into the machines during a delivery shift with a few percentage gain in luminosity. The solution was retained at PEP-II machines along with the luminosity. Later, these asymmetric bumps also played a vital role in reaching 1x10³⁴cm-2s-1 as the beam currents increased.
MOPLS053	Beta-beat Correction Using Strong Sextupole Bumps in PEP-II	664
	G. Yocky SLAC, Menlo Park, California
	A method for correcting lattice beta mismatches has been developed for the PEP-II collider using orbit offsets in strong sextupoles. The solution is first predicted in the MAD program by modeling closed orbit bumps in the plane of correction at the sextupoles strongest in that plane. The derived solution is then tested in the machine to confirm the prediction and finally dialed into the machine under high-current conditions.
TUODFI02	DAFNE Experience with Negative Momentum Compaction	989
	M. Zobov, D. Alesini, M.E. Biagini, A. Drago, A. Gallo, C. Milardi, P. Raimondi, B. Spataro, A. Stella INFN/LNF, Frascati (Roma)
	There are several potential advantages for a collider operation with a lattice having a negative momentum compaction factor (alfa): bunches can be shorter and have a more regular shape; longitudinal beam-beam effects and synchrobetatron resonances are predicted to be less dangerous; requirements on sextupole strengths can be relaxed because there is no head-tail instability with the negative chromaticity. Since the lattice of the Frascati e⁺e^- Phi-factory DAFNE is flexible enough to provide collider operation with alfa < 0, we have exploited this possibility to study experimentally the beam dynamics. The negative momentum compaction lattices have been successfully implemented and stable 1 A currents have been stored in both the electron and positron rings without any problem for RF cavities and feedback systems operation. First collisions have been tested at low currents. In this paper we describe the experimental results and compare them with expectations and numerical simulations. Present limitations to DAFNE operation with alfa < 0 are also discussed.
	Transparencies
TUODFI03	Operational Status of CESR-c	992
	J.A. Crittenden Cornell University, Department of Physics, Ithaca, New York
	We summarize recent running experience at the Cornell Electron Storage Ring operating as a high-statistics production-threshold factory for mesons containing charm quarks. Since beginning operation at beam energies near 2 GeV in late 2003, CESR has accumulated world-record samples of D and D$_s$ meson decays and has also operated in an energy-scanning mode, making unique contributions to the presently very active field of charm spectroscopy. CESR lattice design is characterized by the versatility provided by the variety of beam-line components applied to the challenges imposed by the beam-beam interactions at the parasitic crossing points in the pretzel orbits and the necessity of powerful superconducting wiggler magnets used to tune damping and emittance. We describe the observed tune-plane, beam-current and luminosity limits, as well as our understanding of their sources and near-term plans for operational improvements.
	Transparencies
FRXBPA01	HERA and the Next Generation of Lepton-ion Colliders	3621
	F.J. Willeke DESY, Hamburg
	This talk will present a summary of the physics insights gained from the lepton-hadron collider HERA and review major beam dynamics issues and lessons learned in view of LHC operation, including technical aspects related to the large number of superconducting magnets or the influence of various design choices on the overall machine performance. It will also address future plans for lepton-ion colliders, including eRHIC at BNL and the CEBAF-based ELIC, with emphasis on their luminosity reach and challenges. The talk will also mention possible high energy lepton-ion collisions, for example colliding a 1 TeV proton (or ion) beam from the Tevatron or Super-SPS with a 20-75 GeV electron beam from the ILC or CLIC (first stage).
	Transparencies