| Paper |
Title |
Page |
| 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.
|
|
| MOPLS138 |
Space Charge and Equilibrium Emittances in Damping Rings
|
882 |
| |
- M. Venturini
LBNL, Berkeley, California
- K. Oide
KEK, Ibaraki
- A. Wolski
Liverpool University, Science Faculty, Liverpool
|
|
| |
The unusual combination of small beam size and long ring circumference may cause space charge to have noticeable effects on the beam dynamics of the ILC (International Linear Collider) damping rings. One possible consequence is a modification of the vertical equilibrium emittance resulting from a non-ideal lattice. One simple way to account for this effect is to model space charge in the linear approximation within the framework of Oide's envelope (or Chao's matrix) formalism, whis is commonly used to calculate equilibrium emittances in lepton storage rings. However, this model would likely overestimate the effect as a linear approximation for space charge is accurate only in a small neighborhood of a bunch center. For a more accurate modelling, we propose to make use of Sacherer's envelope equations consisting of a closed set of equations for the second moments of a beam distribution that account for the nonlinear dependence of the space-charge force. Here we will illustrate how Sacherer's equations can be combined with Oide's formalism and apply the result to the ILC damping rings.
|
|
| WEOFI01 |
Beam Dynamics Measurements in the Vicinity of a Half-integer Resonance
|
1902 |
| |
- T. Ieiri, J.W. Flanagan, H. Fukuma, H. Ikeda, Y. Ohnishi, K. Oide, M. Tobiyama
KEK, Ibaraki
|
|
| |
The operating point of the betatron tune set near a half-integer is a crucial parameter to make high luminosity in electron/positron ring colliders. Dynamic beam-beam effects would change the optics parameters of the colliders, depending on the betatron tune and the beam-beam parameter. On the other hand, existence of the half-integer stopband makes the beam unstable. Therefore, beam behavior near a half-integer might provide interesting issues from the viewpoint of beam dynamics. We measured a frequency response of the beam across a half-integer for measuring the betatron tune at KEKB. A sharp spike just at a half-integer was observed in the tune spectrum. We believe that the spectrum would be a nonlinear resonance caused by some off-momentum particles in a bunch, not by a coherent motion of a whole bunch. The horizontal beam size measured using a synchrotron radiation monitor indicated a slight increase when the tune approached a half-integer. The variations in the beam size are discussed, considering both dynamic beam-beam effects and a beta beat due to the half-integer stopband.
|
|
|
Transparencies
|
| WEPCH026 |
Recent Progress of Optics Measurement and Correction at KEKB
|
1981 |
| |
- A. Morita, H. Koiso, Y. Ohnishi, K. Oide
KEK, Ibaraki
|
|
| |
We present the progress of the optics measurement and the correction scheme of the KEKB operation for example off-momentum beta correction.
|
|
| THPCH050 |
Further Studies on Betatron Sidebands due to Electron Clouds
|
2898 |
| |
- J.W. Flanagan, H. Fukuma, Y. Funakoshi, S. Hiramatsu, T. Ieiri, H. Ikeda, K. Ohmi, K. Oide, M. Tobiyama
KEK, Ibaraki
|
|
| |
We have observed vertical betatron sidebands in the transverse beam spectra of positron bunches at the KEKB LER which are associated with the presence of electron clouds in single-beam studies*, and which are also associated with a loss of luminosity when the KEKB beams are in collision**. The sidebands may be signals of a fast head-tail instability due to short-range wakes within the electron cloud, providing a diagnostic for exploring the mechanism for transverse beam blow-up due to electron clouds. We report here on further studies on the behavior of the sidebands under varying beam conditions, including varying initial beam size below the beam blow-up threshold, chromaticity, RF voltage and fill pattern.
*J. W. Flanagan et al. PRL 94, 054801 (2005).**J. W. Flanagan et al. Proc. PAC05, p. 680 (2005).
|
|
| THPCH051 |
The Effect of the Solenoid Field in Quadrupole Magnets on the Electron Cloud Instability in the KEKB LER
|
2901 |
| |
- H. Fukuma, J.W. Flanagan, T. Kawamoto, T. Morimoto, K. Oide, M. Tobiyama
KEK, Ibaraki
- F. Zimmermann
CERN, Geneva
|
|
| |
The electron cloud instability which causes vertical beam blowup in the KEKB LER is largely suppressed by applying a weak solenoid field to vacuum chambers in the drift region. However the blowup is still observed when the bunch spacing is reduced to 3.27 rf buckets or shorter. A question is where the remaining electron clouds are. To investigate the electron clouds in the quadrupole magnets, solenoids made of flat cables were developed and installed in 88 quadrupole magnets. The field strength of the solenoid is 17 Gauss. The effect of the solenoid field on the blowup is now under beam study. So far no clear effect of the solenoids on the luminosity and the sideband accompanied by the blowup is found. We report on the solenoid system, the results of the experiments and comparison of the experimental results with simulations.
|
|
| WEPCH141 |
Accelerator Physics Code Web Repository
|
2254 |
| |
- F. Zimmermann, R. Basset, E. Benedetto, U. Dorda, M. Giovannozzi, Y. Papaphilippou, T. Pieloni, F. Ruggiero, G. Rumolo, F. Schmidt, E. Todesco
CERN, Geneva
- D.T. Abell
Tech-X, Boulder, Colorado
- R. Bartolini
Diamond, Oxfordshire
- O. Boine-Frankenheim, G. Franchetti, I. Hofmann
GSI, Darmstadt
- Y. Cai, M.T.F. Pivi
SLAC, Menlo Park, California
- Y.H. Chin, K. Ohmi, K. Oide
KEK, Ibaraki
- S.M. Cousineau, V.V. Danilov, J.A. Holmes, A.P. Shishlo
ORNL, Oak Ridge, Tennessee
- L. Farvacque
ESRF, Grenoble
- A. Friedman
LLNL, Livermore, California
- M.A. Furman, D.P. Grote, J. Qiang, G.L. Sabbi, P.A. Seidl, J.-L. Vay
LBNL, Berkeley, California
- D. Kaltchev
TRIUMF, Vancouver
- T.C. Katsouleas
USC, Los Angeles, California
- E.-S. Kim
PAL, Pohang, Kyungbuk
- S. Machida
CCLRC/RAL/ASTeC, Chilton, Didcot, Oxon
- J. Payet
CEA, Gif-sur-Yvette
- T. Sen
Fermilab, Batavia, Illinois
- J. Wei
BNL, Upton, Long Island, New York
- B. Zotter
Honorary CERN Staff Member, Grand-Saconnex
|
|
| |
In the framework of the CARE HHH European Network, we have developed a web-based dynamic accelerator-physics code repository. We describe the design, structure and contents of this web repository, illustrate its usage, and discuss our future plans.
|
|
| THPCH116 |
Continuous Circumference Control and Timing System for Simultaneous Electron-positron Injection at the KEKB
|
3074 |
| |
- M. Suetake, H. Koiso, Y. Ohnishi, K. Oide
KEK, Ibaraki
|
|
| |
We have continuously controlled ring circumference with a new method of synthesizer control at the KEKB. The new method stands for continuous controlling of reference frequency of synthesizers. Due to the new circumference control, we stabilized the KEKB circumference within about 6 micrometers. In Fall 2006, KEKB will introduce simultaneous electron-positron injection scheme. We have to change the timing system of KEKB to control the injection phase with pulse-to-pulse injection. We show the plan of the new timing system due to the simultaneous injection scheme.
|
|