01 Circular Colliders

A02 Lepton Colliders

Paper	Title	Page
TUXG01	Last Year of PEP-II B-Factory Operation	946
	J. Seeman SLAC, Menlo Park, California
	The PEP II B-Factory at SLAC has been in operation for a decade, delivering luminosity to the BABAR experiment. The design luminosity was successfully reached after one year of operation and since then it has surpassed over four times design at 1.2 x 1034 cm-2sec-1. History of main achievements, high current operation issues, and lessons for the future factories will be presented.
	Slides
TUOAG01	VEPP-2000 Electron-Positron Collider Commissioning and First Results of Round Colliding Beam Tests	956
	Y. M. Shatunov, D. E. Berkaev, I. Koop, A. P. Lysenko, E. Perevedentsev, A. L. Romanov, P. Yu. Shatunov, D. B. Shwartz, A. N. Skrinsky BINP SB RAS, Novosibirsk
	VEPP-2000 electron-positron collider construction has been completed in the Budker INP at the beginning of 2007 year. First beam was captured in a special lattice without final focus solenoids. In this regime all systems of power supplies, machine control and beam diagnostics were calibrated and tuned. In the same mode vacuum chamber treatment by synchrotron radiation was performed with electron beam current up to 150 mA. The first test of the round beam option was performed at the energy of 508 MeV with the solenoidal field 10 T in two interaction straight sections. Studies of the beam-beam interaction have been done in "weak-strong" and "strong-strong" regimes. Measurements of beam sizes in the both cases have indicated a beam behavior similar to expectations for the round colliding beams.
	Slides
TUOAG02	Commissioning of BEPCII	959
	J. Q. Wang, L. Ma, C. Zhang IHEP Beijing, Beijing
	BEPCII is the upgrade project of Beijing Electron Positron Collider (BEPC), serving continuously for both high energy physics experiment and light soure use. As an e+-e- collider, BEPCII will operate in the beam energy region of 1-2.1 GeV with design luminosity of 1*1033cm-2s-1 at 1.89 GeV. The beam commissioning of BEPCII storage rings started out in Nov. 2006. From Nov. 2006 to Aug. 2007, the phase one commissioning was carried out successfully with the so called backup scheme adopting conventional magnets in the IR intead of the superconducting insertion magnets (SIM). After the SIM was intalled into the interaction region, phase two commissioning began in Oct. 2007. The tuning method for high luminosity but low background was extensively studied during phase two, and the beam current has reached more than 1/3 of the design of 0.91 A. The third phase of beam commissioning is planned in May this year after the detector is moved into the on-line position. It is expected that the luminosity would reach to about 30% of its design specification. This paper describes the procedure of beam commissioning of BEPCII and focuses on results of its second phase.
	Slides
WEPC060	Studies on the Beam Current Dependent Phenomena in the BEPC-II Storage Rings	2130
	Q. Qin, N. Huang, W. B. Liu, Y. D. Liu, Y. M. Peng, J. Qiu, D. Wang, J. Q. Wang, N. Wang, X. H. Wang, Y. Wei, X. M. Wen, J. Xing, G. Xu, C. H. Yu, C. Zhang, Y. Zhang, Z. Zhao, D. M. Zhou IHEP Beijing, Beijing
	The upgrade project of the Beijing Electron Positron Collider (BEPC-II) has been being commissioned since Nov. 2006. Besides the commissioning of the luminosity, which is expected to be 100 times higher than the BEPC, the BEPC-II also provided beam to the synchrotron radiation users as a light source during these two years. Some beam current dependent phenomena, such as bunch lengthening, single beam instabilities, blow-up in collision, etc., in both collision and synchrotron radiation modes are observed in the machine performance. In this paper, some observations and analyses on these phenomena are given.
WEPP035	Study of Beam-beam Issue for KEKB Crab Crossing	2596
	K. Ohmi, J. W. Flanagan, Y. Funakoshi, N. Iida, H. Koiso, A. Morita, Y. Ohnishi, K. Oide, Y. Seimiya KEK, Ibaraki
	A short lifetime at collision is one of the limits on luminosity performance at KEKB in crab crossing mode. The beam-beam halo was evaluated via simulation. The beam lifetime and profile were measured for various beam conditions, vertical emittances, tunes and collision offsets. We discuss why the lifetime is shortened by the beam-beam interaction.
WEPP036	DAΦNE Setup and Operation with the Crab-Waist Collision Scheme	2599
	C. Milardi, D. Alesini, M. E. Biagini, C. Biscari, R. Boni, M. Boscolo, F. Bossi, B. Buonomo, A. Clozza, G. O. Delle Monache, T. Demma, E. Di Pasquale, G. Di Pirro, A. Drago, A. Gallo, A. Ghigo, S. Guiducci, C. Ligi, F. Marcellini, G. Mazzitelli, F. Murtas, L. Pellegrino, M. A. Preger, L. Quintieri, P. Raimondi, R. Ricci, U. Rotundo, C. Sanelli, M. Serio, F. Sgamma, B. Spataro, A. Stecchi, A. Stella, S. Tomassini, C. Vaccarezza, M. Zobov INFN/LNF, Frascati (Roma) N. Arnaud, D. Breton, P. Roudeau, A. Stocchi, V. Variola, B. F. Viaud LAL, Orsay S. Bettoni CERN, Geneva P. Branchini roma3, Rome M. Esposito Rome University La Sapienza, Roma I. Koop, E. B. Levichev, P. A. Piminov, D. N. Shatilov BINP SB RAS, Novosibirsk K. Ohmi KEK, Ibaraki E. Paoloni University of Pisa and INFN, Pisa M. Schioppa INFN Gruppo di Cosenza, Arcavacata di Rende (Cosenza) V. V. Smaluk BINP, Novosibirsk P. Valente INFN-Roma, Roma
	In the second half of 2007 a major upgrade has been implemented on the Frascati DAΦNE collider in order to test the novel idea of Crab Waist collisions. New vacuum chambers and permanent quadrupole magnets have been designed, fabricated and installed to realize the new configuration. At the same time the performances of relevant hardware components, such as fast injection kickers and shielded bellows have been improved relying on new design concepts. The collider has been successfully commissioned in this new configuration. The paper describes the new layout as well as several experimental results about linear and non-linear optics setup and optimization, damping of beam instabilities and discusses the obtained luminosity performances.
WEPP039	Design of a 1036 cm-2 s-1 Super-B Factory	2605
	J. Seeman, K. J. Bertsche, A. Novokhatski, M. K. Sullivan, U. Wienands, W. Wittmer SLAC, Menlo Park, California S. Bettoni CERN, Geneva M. E. Biagini, R. Boni, M. Boscolo, T. Demma, A. Drago, S. Guiducci, P. Raimondi, S. Tomassini, M. Zobov INFN/LNF, Frascati (Roma) A. Bogomyagkov, I. Koop, E. B. Levichev, S. A. Nikitin, P. A. Piminov, D. N. Shatilov BINP SB RAS, Novosibirsk G. Marchiori INFN-Pisa, Pisa E. Paoloni University of Pisa and INFN, Pisa
	Submitted for the High Luminosity Study Group for an Asymmetric 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 1 to 2 x 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 stored in low-emittance damping rings similar to those designed for a Linear Collider (LC) or the next generation light source. A LC style interaction region is included in the ring to produce sub-millimeter vertical beta functions at the collision point. A large crossing angle (±25 mrad) is used at the collision point to allow beam separation. A crab-waist scheme is used to reduce the hourglass effect and restore peak luminosity. Beam currents of about 1.8 A in 1400 bunches can produce a luminosity of 1036/cm2/s with upgrade possibilities. Design parameters and beam dynamics effects are discussed.
WEPP040	New Low Emittance Lattices for the SuperB Accelerator Project	2608
	M. E. Biagini, M. Boscolo, P. Raimondi, S. Tomassini, M. Zobov INFN/LNF, Frascati (Roma) S. Bettoni CERN, Geneva A. Bogomyagkov, I. Koop, E. B. Levichev, S. A. Nikitin, P. A. Piminov, D. N. Shatilov BINP SB RAS, Novosibirsk E. Paoloni University of Pisa and INFN, Pisa J. Seeman, M. K. Sullivan, U. Wienands, W. Wittmer SLAC, Menlo Park, California
	New low emittance lattices (1.6 nm at 7 GeV, 2.8 nm at 4 GeV) have been designed for the asymmetric SuperB accelerator aiming at a luminosity of 1036 cm-2 s-1. Main optics features are two alternating arc cells with different horizontal phase advance, in order to decrease beam emittance and allow at the same time for easy chromaticity correction in the arcs. Emittance can be further reduced by a factor of two for luminosity upgrade. New beam parameters have been chosen to fulfill the transparency conditions for 4x7 GeV beams, different from the asymmetric currents used in operating B-Factories. Beam polarization schemes have been studied and will be implemented in the lattice.
WEPP041	High-current Effects in the PEP-II Storage Rings	2611
	U. Wienands, W. X. Cheng, W. S. Colocho, S. DeBarger, F.-J. Decker, S. Ecklund, A. S. Fisher, D. Kharakh, A. Krasnykh, A. Novokhatski, M. K. Sullivan SLAC, Menlo Park, California
	High beam currents, 2A(HER) & 3A(LER), in PEP-II has been a challenge for the vacuum system. For the ~1 cm long bunches peak currents reach 50 A. Thus modest impedances can give rise to voltage spikes and discharges. A weakness was uncovered during Run 6: rf seals at the "flex flanges" that join the HER arc dipole and quadrupole chambers became a source of an increasing number of HER beam aborts. Vacuum activity was seen and thermal sensors on these flanges saw temperature spikes. Inspection of the seals found arcing and melting, prompting us to replace all of these seals with an improved design using Inconel instead of GlidCop fingers. We believe the GlidCop fingers do not maintain elasticity and hence can not follow chamber motion due to thermal effects. The Run 7 startup confirmed the success of this repair. However, high bunch current in the LER caused breakdown in a LER kicker. This limited the LER bunch current to about 1 mA. Inspection revealed damage to one of the recently added Macor pins that help support the electrodes. Failure analysis revealed heating of the pin & post-facto modeling shows high fields coming from a combination of HOM impedance and high peak currents.
WEPP042	An Improved Design for a SuperB Interaction Region	2614
	M. K. Sullivan, J. Seeman, U. Wienands SLAC, Menlo Park, California S. Bettoni CERN, Geneva M. E. Biagini, P. Raimondi INFN/LNF, Frascati (Roma) E. Paoloni University of Pisa and INFN, Pisa
	We present an improved design for a SuperB interaction region. The new design attempts to minimize the bending of the two colliding beams which results from shared magnetic elements near the Interaction Point (IP). The total crossing angle at the IP is increased from 34 mrad to 50 mrad and the distance from the IP to the first quadrupole is increased. Although the two beams still travel through this shared magnet, these changes allow for a new a new magnetic field design with a septum which gives the magnet two magnetic centers. This greatly reduces the beam bending from this shared quadrupole and thereby reduces the radiative bhabha background for the detector as well as any beam emittance growth from the bending. We decribe the new design for the interaction region.
WEPP044	Commissioning the 90° Lattice for the PEP II High Energy Ring	2617
	W. Wittmer, Y. Cai, W. X. Cheng, W. S. Colocho, F.-J. Decker, S. Ecklund, A. S. Fisher, Y. Nosochkov, A. Novokhatski, M. K. Sullivan, U. Wienands, Y. T. Yan, G. Yocky SLAC, Menlo Park, California
	In order to benefit from further reduction of the vertical IP beta function of the PEP-II HER the bunch length should be reduced. This will be achieved by changing the phase advance from 60 deg to 90 deg in the four arcs not adjacent to the IR region, thus reducing momentum compaction by about 30% and reducing bunch length from a present 12 mm down to 8.5 mm at low beam current. In preparation to implement the 90 deg lattice the main HER quadrupole and sextupole strings and their power supplies have been reconfigured. Compared to the 60 deg lattice it was expected that dynamic aperture and injection will be more difficult. The synchrotron tune initially will be lower but can be brought back by raising the rf voltage. Beam emittance is held at 48 nmr by introducing a significant dispersion beat in the arcs. The lattice was successfully commissioned at currents up to 800mA in August 2007. In this paper we will compare the actual machine with the predicted behaviour, explain the correction strategies used and give an overall assessment of the operation and the benefit of the new lattice configuration.
WEPP045	Suppression of Beam-beam Resonances in Crab Waist Collisions	2620
	M. Zobov, P. Raimondi INFN/LNF, Frascati (Roma) D. N. Shatilov BINP SB RAS, Novosibirsk
	The recently proposed Crab Waist scheme of beam-beam collisions can substantially increase the collider luminosity since it combines several potentially advantageous ideas. One of the basic ingredients of the scheme is the use of dedicated sextupoles in the interaction region for the vertical beta function waist rotation at the interaction point. In this paper we show how this nonlinear focusing helps to suppress betatron and synchrobetatron resonances arising in beam-beam collisions due to particles’ vertical motion modulation by their horizontal oscillations.