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| MOOCH01 |
Beam Based Alignment at the KEK-ATF Damping Ring
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36 |
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- M. Woodley, J. Nelson, M.C. Ross, J.L. Turner
SLAC, Menlo Park, California
- K. Kubo
KEK, Ibaraki
- A. Wolski
LBNL/AFR, Berkeley, California
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The damping rings for a future linear collider will have demanding alignment and stability requirements in order to achieve the low vertical emittance necessary for high luminosity. The Accelerator Test Facility (ATF) at KEK has successfully demonstrated the <5 pm vertical emittance specified for the GLC/NLC Main Damping Rings [*]. One contribution to this accomplishment has been the use of Beam Based Alignment (BBA) techniques. The mode of operation of the ATF presents particular challenges for BBA, and we describe here how we have deduced the offsets of the BPMs with respect to the quadrupoles. We also discuss a technique that allows for direct measurements of the beam-to-quad offsets.
* "Extremely Low Vertical-Emittance Beam in the Accelerator Test Facility at KEK", K. Kubo, et al., Phys.Rev.Lett.88:194801,2002
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Video of talk
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Transparencies
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| MOOCH03 |
Status of a Linac RF Unit Demonstration for the NLC/GLC X-band Linear Collider
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42 |
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- D.C. Schultz, C. Adolphsen, D.L. Burke, J. Chan, S. Doebert, V.A. Dolgashev, J.C. Frisch, R.K. Jobe, D.J. McCormick, C.D. Nantista, J. Nelson, M.C. Ross, T.J. Smith, S.G. Tantawi
SLAC, Menlo Park, California
- D.P. Atkinson
LLNL, Livermore, California
- Y.H. Chin, S. Kazakov, A. Lounine, T. Okugi, N. Toge
KEK, Ibaraki
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Designs for a future TeV scale electron-positron X-band linear collider (NLC/GLC) require main linac units which produce and deliver 450 MW of rf power at 11.424 GHz to eight 60 cm accelerator structures. The design of this rf unit includes a SLED-II pulse compression system with a gain of approximately three at a compression ratio of four, followed by an overmoded transmission and distribution system. We have designed, constructed, and operated such a system as part of the 8-Pack project at SLAC. Four 50 MW X-band klystrons, running off a common 400 kV solid-state modulator, drive a dual-moded SLED-II pulse compression system. The compressed power is delivered to structures in the NLCTA beamline. Four 60 cm accelerator structures are currently installed and powered, with four additional structures and associated high power components available for installation late in 2004. We describe the layout of our system and the various high-power components which comprise it. We also present preliminary data on the processing and initial high-power operation of this system.
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Video of talk
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Transparencies
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| MOPLT139 |
Beam-based Alignment and Beta Function Measurements in PEP-II
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866 |
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- G. Yocky, J. Nelson, M.C. Ross, T.J. Smith, J.L. Turner, M. Woodley
SLAC, Menlo Park, California
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Careful optics studies and stringent lattice control have been identified as two key components to increasing PEP-II luminosity. An accurate, trusted BPM system is required for both of these strategies. To validate the existing BPM system and to better understand some optical anomalies in the PEP-II rings, an aggressive program of beam-based alignment (BBA) has been initiated. Using a quad-shunt BBA procedure in which a quadrupole?s field strength is varied over a range of beam positions, relative offsets are determined by the BPM readings at which quadrupole field changes no longer induce a closed orbit shift. This procedure was verified in the HER and is well underway in the LER IR. We have found many surprisingly large BPM offsets, some over one centimeter, as well as a number of locations where the current nominal orbit is several millimeters from the quadrupole center. Tune versus quadrupole field data were taken during the BBA process in the LER IR, and the non-linear response in each case is compared to simulation to infer local beta functions.
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| MOPLT107 |
Nanosecond-timescale Intra-bunch-train Feedback for the Linear Collider: Results of the FONT2 Run
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785 |
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- P. Burrows, T. Hartin, S.M. Hussain, S. Molloy, G.R. White
Queen Mary University of London, London
- C. Adolphsen, J.C. Frisch, L. Hendrickson, R.K. Jobe, T. Markiewicz, D.J. McCormick, J. Nelson, M.C. Ross, S. Smith, T.J. Smith
SLAC, Menlo Park, California
- R. Barlow, M. Dufau, A. Kalinin
CCLRC/DL/ASTeC, Daresbury, Warrington, Cheshire
- G. Myatt, C. Perry
OXFORDphysics, Oxford, Oxon
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We report on experimental results from the December 2003/January 2004 data run of the Feedback On Nanosecond Timescales (FONT) experiment at the Next Linear Collider Test Accelerator at SLAC. We built a second-generation prototype intra-train beam-based feedback system incorporating beam position monitors, fast analogue signal processors, a feedback circuit, fast-risetime amplifiers and stripline kickers. We applied a novel real-time charge-normalisation scheme to account for beam current variations along the train. We used the system to correct the position of the 170 nanosecond-long bunchtrain at NLCTA, in both 'feed forward' and 'feedback' modes. We achieved a latency of 53 nanoseconds, representing a significant improvement on FONT1 (2002), and providing a demonstration of intra-train feedback for the Linear Collider.
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| MOPLT143 |
Results and Plans of the PEP-II B-Factory
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875 |
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- 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
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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.
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| THPLT154 |
Design of an X-ray Imaging System for the Low-Energy Ring of PEP-II
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2816 |
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- 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
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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.
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| MOPLT136 |
Reliability Simulations for a Linear Collider
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857 |
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- N. Phinney, T.M. Himel, M.C. Ross
SLAC/NLC, Menlo Park, California
- P. Czarapata, H. Edwards, M. Huening
Fermilab, Batavia, Illinois
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A new flexible tool for evaluating accelerator reliability was developed as part of the US Linear Collider Technology Comparison Study. The linear collider designs considered were based on the GLC/NLC X-band and TESLA Superconducting proposals, but modified to meet the US physics requirements. To better model some of the complexities of actual operation, a simulation program was written, which included details such as partial fixes or workarounds, hot-swappable repairs, multiple simultaneous repairs, cooldown periods before access, staged recovery from an outage, and both opportunistic and scheduled machine development. The main linacs and damping rings were modeled in detail with component counts taken from the designs, and using MTBFs and MTTRs from existing accelerator experience. Other regions were assigned a nominal overall failure rate. Variants such as a single tunnel or conventional positron source were also evaluated, and estimates made of the sensitivity to recovery or repair times. While neither design was predicted to be sufficiently reliable given present experience, the required improvements were estimated to increase the overall project cost by only a few percent.
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| MOPLT142 |
Analysis of KEK-ATF Optics and Coupling Using LOCO
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872 |
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- M. Woodley, J. Nelson, M.C. Ross
SLAC/NLC, Menlo Park, California
- A. Wolski
LBNL/AFR, Berkeley, California
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LOCO is a computer code for analysis of the linear optics in a storage ring based on the closed orbit response to steering magnets. The analysis provides information on focusing errors, BPM gain and rotation errors, and local coupling. Here, we discuss the details of the LOCO implementation at the KEK-ATF Damping Ring, and report the initial results. Some of the information obtained, for example on the BPM gain and coupling errors, has not previously been determined. We discuss the possibility of using the data provided by the LOCO analysis to reduce the vertical emittance of the ATF beam.
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