Paper |
Title |
Page |
TUPCH200 |
Amplitude Linearizers for PEP-II 1.2 MW Klystrons and LLRF Systems
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1480 |
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- D. Van Winkle, J. Browne, J.D. Fox, T. Mastorides, C.H. Rivetta, D. Teytelman
SLAC, Menlo Park, California
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The PEP-II B-factory has aggressive current increases planned for luminosity through 2008. At 2.2 A (HER) on 4 A (LER) currents, longitudinal growth rates will exceed the damping rates achievable in the existing low level RF and longitudinal low mode feedback systems. Klystron gain non-linearity has been shown to be a key contributor to these increased growth rates through time domain non-linear modeling and machine measurements. Four prototype klystron amplitude modulation linearizers have been developed to explore improved linearity in the LLRF system. The linearizers operate at 475 MHz with 15 dB dynamic range and 1 MHz linear control bandwidth. Results from lab measurements and high current beam tests are presented. Future development progress and production designs are detailed.
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MOPLS045 |
Achieving a Luminosity of 1034/cm2/s in the PEP-II B-factory
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643 |
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- 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
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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.
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MOPLS051 |
Tracking Down a Fast Instability in the PEP-II LER
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658 |
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- 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
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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.
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THPCH101 |
Modeling and Simulation of Longitudinal Dynamics for LER-HER PEP II Rings
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3032 |
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- C.H. Rivetta, J.D. Fox, T. Mastorides, D. Teytelman, D. Van Winkle
SLAC, Menlo Park, California
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A time domain dynamic model and simulation tool for beam-cavity interactions in LER and HER rings at PEP II is presented. The motivation for this tool is to explore the stability margins and performance limits of PEP II LLRF systems at higher currents and upgraded RF configurations. It also serves as test bed for new control algorithms and to define the ultimate limits of the architecture. The tool captures the dynamical behavior of the beam-cavity interaction based on a reduced model. It includes nonlinear elements in the klystron and signal processing. The beam current is represented by macro-bunches. Multiple RF stations in the ring are represented via one or two single macro-cavities. Each macro-cavity captures the overall behavior of all the 2 or 4 cavity RF stations. This allows modeling the longitudinal impedance control loops interacting with the longitudinal beam model. Validation of simulation tool is in progress by comparing the measured growth rates for both LER and HER rings with simulation results. The simulated behavior of both machines at high currents are presented comparing different control strategies and the effect of non-linear klystrons and the linearizer.
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THPCH103 |
Design and Testing of Gproto Bunch-by-bunch Signal Processor
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3038 |
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- D. Teytelman, R. Akre, J.D. Fox, A. Krasnykh, C.H. Rivetta, D. Van Winkle
SLAC, Menlo Park, California
- A. Drago
INFN/LNF, Frascati (Roma)
- J.W. Flanagan, T. Naito, M. Tobiyama
KEK, Ibaraki
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A prototype programmable bunch-by-bunch signal acquisition and processing channel with multiple applications in storage rings has been developed at SLAC. The processing channel supports up to 5120 bunches with bunch spacings as close as 1.9 ns. The prototype has been tested and operated in five storage rings: SPEAR-3, DAFNE, PEP-II, KEKB, and ATF damping ring. The testing included such applications as transverse and longitudinal coupled-bunch instability control, bunch-by-bunch luminosity monitoring, and injection diagnostic. In this contribution the prototype design will be described and its operation will be illustrated with the data measured at the abovementioned accelerators.
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