| Paper |
Title |
Page |
| TUPP053 |
Radiolocation of a HOM Source in the PEP-II Rings
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1664 |
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- A. Novokhatski, J. Seeman, M. K. Sullivan
SLAC, Menlo Park, California
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A signal from the antenna situated in the LER (Low Energy Ring) helped to find a broken shielded bellows in the HER (High Energy Ring) during a single HER bunch operation.
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| TUPP054 |
A Model of an Electrical Discharge in the Flange Contacts with Omega Seals at High Currents in PEP-II
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1667 |
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- A. Novokhatski, J. Seeman, M. K. Sullivan
SLAC, Menlo Park, California
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During operation with high currents at HER (High Energy Ring), high temperature elevation was found at almost every location of the vacuum chamber flange contacts. Omega RF seals were strongly damaged or even evaporated by sparks and electrical discharge. We suggest a physical model, which may explain this effect.
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| TUPP055 |
Loss Factor of the PEP-II Rings
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1670 |
| |
- A. Novokhatski, M. K. Sullivan
SLAC, Menlo Park, California
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RF power balance method is used to measure the synchrotron radiation losses and the wake field losses. We present the history of the loss factor during the last several runs, which reveals many interesting correlations with vacuum chamber improvement and processing.
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| WEPP041 |
High-current Effects in the PEP-II Storage Rings
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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
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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.
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| WEPP044 |
Commissioning the 90° Lattice for the PEP II High Energy Ring
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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
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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.
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| WEPP039 |
Design of a 1036 cm-2 s-1 Super-B Factory
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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
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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.
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