• K. Ohmi, T. Ieiri, Y. Ohnishi, Y. Seimiya, M. Tejima, M. Tobiyama, D.M. Zhou
  KEK, Ibaraki

Optics parameters at the interaction point, beta, x-y coupling, dispersion and their chromatic aberrations, seriously affect the beam-beam performance as is shown in experiments and simulations. The control of the optics parameters is essential to maintain the high luminosity in KEKB. They drift day by day, or before and after the beam abort. They were often monitored at intervals of the operation with taking the study time. They are recently measured during the physics run using a pilot bunch without collision. We show the measured the optics parameters and their variations and discuss the relation to the luminosity.

• K. Ohmi
  KEK, Ibaraki

Super B factories are designed with very low emittance and very low beta function at the interaction point. The two beams collide with a large crossing angle, thus the overlap area of the beams is limited at a small part of their length. Simulation of the beam-beam effects is hard because of the longitudinal slice of the beam is the order of 100. We discuss two methods for the simulation. One is a simplified method, which is mixture of the particle in cell and Gaussian approximation. The other is fully strong-strong simulation using the particle in cell. The shifted Green function is used to calculate the beam-beam force for less overlap of the beam distribution. Luminosity and its degradation due to IP optics errors in Super B factories are discussed.

• Y. Susaki, K. Ohmi
  KEK, Ibaraki

Single bunch instability caused by electron cloud can depend on emittance, because the electron oscillation period in positron bunch is large. The single bunch instability should appear as a head-tail motion with synchro-beta frequency. We discuss the single bunch instability in low emittance rings, CesrTA, Super B factories and ILC damping ring with focusing the threshold and synchro-beta oscillation.

• K. Ohmi, H. Koiso
  KEK, Ibaraki

Progress of Graphic Processor Unit (GPU) is marveled. The performance is 1TFlops per unit. Simulation of electron gun can be performed by particle-particle interactions, in which the calculation cost is NxN. Since the calculation of each interaction is very simple, GPU can demonstrate its ability. We show simulation results and discuss the possibilities to extend other simulations.

• D.M. Zhou, H. Koiso, A. Morita, K. Ohmi, Y. Ohnishi, Y. Seimiya
  KEK, Ibaraki

Using a weak-strong beam-beam code, in which the symplectic maps for the linear coupling and chromatic aberrations were implemented, the luminosity degradation caused by the linear and chromatic X-Y couplings at the interaction point (IP) were evaluated for the SuperKEKB project under design. The linear and chromatic X-Y couplings were estimated through modeling the machine errors using random seeds, based on a baseline design of the SuperKEKB rings. It was found that the linear and chromatic X-Y couplings can potentially degrade the luminosity performance.

• D.M. Zhou, T. Abe, H. Ikeda, M. Kikuchi, K. Ohmi, K. Oide, K. Shibata, M. Tobiyama
  KEK, Ibaraki
• G.V. Stupakov
  SLAC, Menlo Park, California

Coherent synchrotron radiation (CSR) is generated when a bunched beam traverses a dipole magnet or a wiggler/undulator. It can degrade the beam quality in both storage rings and linacs through enhancing the beam energy spread and lengthening the bunch length, even cause single-bunch microwave instabilities. Using several methods, CSR impedances in the positron damping ring (DR) of the SuperKEKB which is under design were calculated. From the impedances due to CSR, resistive wall and various vacuum components, quasi-Green function wake potentials were constructed and used in simulations of Particle-In-Cell (PIC) tracking. We present the CSR related results in this paper.

• M. Kikuchi, T. Abe, K. Egawa, H. Fukuma, K. Furukawa, N. Iida, H. Ikeda, T. Kamitani, K. Kanazawa, K. Ohmi, K. Oide, K. Shibata, M. Tawada, M. Tobiyama, D.M. Zhou
  KEK, Ibaraki

Super-KEKB, an upgrade plan of the present KEKB collider, has recently changed its scheme from 'high current' option to 'nano-beam' scheme. In the latter the current is relatively low(4A/2.3A for LER/HER ring) compared to that of the high-current option(9.4A/4.1A), while the vertical beam size is squeezed to 60 nm at the interaction point to get the high luminosity. The emittance of the injected beam should be low and, since the Tousheck lifetime is very short(600 sec), the intensity of the positron beam is as high as 8 nC/pulse. For the electron beam a low-emittance high-intensity RF gun is adopted. For the positron beam a damping ring has been proposed. The design of the damping ring has been performed for the high-current option*. In this paper an updated design for the nano-beam scheme is presented.

* Nucl. Instr. Meth. A 556 (2006) 13-19

• M.A. Palmer, J.P. Alexander, M.G. Billing, J.R. Calvey, C.J. Conolly, J.A. Crittenden, J. Dobbins, G. Dugan, N. Eggert, E. Fontes, M.J. Forster, R.E. Gallagher, S.W. Gray, S. Greenwald, D.L. Hartill, W.H. Hopkins, D.L. Kreinick, B. Kreis, Z. Leong, Y. Li, X. Liu, J.A. Livezey, A. Lyndaker, J. Makita, M.P. McDonald, V. Medjidzade, R.E. Meller, T.I. O'Connell, S.B. Peck, D.P. Peterson, G. Ramirez, M.C. Rendina, P. Revesz, D.H. Rice, N.T. Rider, D. L. Rubin, D. Sagan, J.J. Savino, R.M. Schwartz, R.D. Seeley, J.W. Sexton, J.P. Shanks, J.P. Sikora, E.N. Smith, C.R. Strohman, H.A. Williams
  CLASSE, Ithaca, New York
• F. Antoniou, S. Calatroni, M. Gasior, O.R. Jones, Y. Papaphilippou, J. Pfingstner, G. Rumolo, H. Schmickler, M. Taborelli
  CERN, Geneva
• D. Asner
  Carleton University, College of Natural Sciences, Ottawa, Ontario
• L. Boon, A.F. Garfinkel
  Purdue University, West Lafayette, Indiana
• J.M. Byrd, C.M. Celata, J.N. Corlett, S. De Santis, M.A. Furman, A. Jackson, R. Kraft, D.V. Munson, G. Penn, D.W. Plate, M. Venturini
  LBNL, Berkeley, California
• B.T. Carlson
  Grove City College, Grove City, Pennsylvania
• T. Demma
  INFN/LNF, Frascati (Roma)
• R.T. Dowd
  ASCo, Clayton, Victoria
• J.W. Flanagan, P. Jain, K. Kanazawa, K. Kubo, K. Ohmi, H. Sakai, K. Shibata, Y. Suetsugu, M. Tobiyama
  KEK, Ibaraki
• D. Gonnella
  Clarkson University, Potsdam, New York
• W. Guo
  BNL, Upton, Long Island, New York
• K.C. Harkay
  ANL, Argonne
• R. Holtzapple
  CalPoly, San Luis Obispo, CA
• J.K. Jones, A. Wolski
  Cockcroft Institute, Warrington, Cheshire
• D. Kharakh, J.S.T. Ng, M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California
• M.C. Ross, C.-Y. Tan, R.M. Zwaska
  Fermilab, Batavia
• L. Schächter
  Technion, Haifa
• E.L. Wilkinson
  Loyola University, Chicago, Illinois

The Cornell Electron Storage Ring (CESR) has been reconfigured as a test accelerator (CesrTA) for a program of electron cloud (EC) research at ultra low emittance. The instrumentation in the ring has been upgraded with local diagnostics for measurement of cloud density and with improved beam diagnostics for the characterization of both the low emittance performance and the beam dynamics of high intensity bunch trains interacting with the cloud. Finally a range of EC mitigation methods have been deployed and tested. Measurements of cloud density and its impact on the beam under a range of conditions will be presented and compared with simulations. The effectiveness of a range of mitigation techniques will also be discussed.

Slides

• Y. Funakoshi, T. Abe, K. Akai, Y. Cai, K. Ebihara, K. Egawa, A. Enomoto, J.W. Flanagan, H. Fukuma, K. Furukawa, T. Furuya, J. Haba, T. Ieiri, N. Iida, H. Ikeda, T. Ishibashi, M. Iwasaki, T. Kageyama, S. Kamada, T. Kamitani, S. Kato, M. Kikuchi, E. Kikutani, H. Koiso, M. Masuzawa, T. Mimashi, T. Miura, A. Morita, T.T. Nakamura, K. Nakanishi, M. Nishiwaki, Y. Ogawa, K. Ohmi, Y. Ohnishi, N. Ohuchi, K. Oide, T. Oki, M. Ono, M. Satoh, Y. Seimiya, K. Shibata, M. Suetake, Y. Suetsugu, T. Sugimura, Y. Susaki, T. Suwada, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, M. Yoshida, S.I. Yoshimoto, D.M. Zhou, Z.G. Zong
  KEK, Ibaraki

KEKB is an e-/e⁺ collider for the study of B physics and is also used for machine studies for future machines. The peak luminosity of KEKB, which is the world-highest value, has been still increasing. This report summarizes recent progress at KEKB.

Slides

• M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California
• C.M. Celata, M.A. Furman, M. Venturini
  LBNL, Berkeley, California
• J.A. Crittenden, G. Dugan, M.A. Palmer
  CLASSE, Ithaca, New York
• T. Demma, S. Guiducci
  INFN/LNF, Frascati (Roma)
• K.C. Harkay
  ANL, Argonne
• O.B. Malyshev
  Cockcroft Institute, Warrington, Cheshire
• K. Ohmi, K. Shibata, Y. Suetsugu
  KEK, Ibaraki
• Y. Papaphilippou, G. Rumolo
  CERN, Geneva

As part of the International Linear Collider (ILC) collaboration, we have compared the electron cloud effect for different Damping Ring designs respectively with 6.4 km and 3.2 km circumference and investigated the feasibility of a shorter damping ring with respect to the electron cloud build-up and related beam instability. These studies were carried out with beam parameters of the ILC Low Power option. A reduced damping ring circumference has been proposed for the new ILC baseline design and would allow to considerably reduce the number of components, wiggler magnets and costs. We also briefly discuss the plans for future studies including the luminosity upgrade option with shorter bunch spacing, the evaluation of mitigations and the integration of the CesrTA results into the Damping Ring design.

• K. Ohmi, K. Fan, S. Igarashi, Y. Sato
  KEK, Ibaraki
• H. Hotchi, Y. Shobuda
  JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken

Nonlinear space charge interaction in high intensity proton rings causes beam loss, which limits the performance. Simulations based on particle in cell method has been performed for JPARC-Rapid Cycle Synchrotron and Main Ring. Beam loss estimation during acceleration and resonances analysis are discussed with various simulations using dynamic and frozen models.

• Y. Seimiya, K. Ohmi
  KEK, Ibaraki

Synchro-beta resonances enhance beam sizes dynamically. For accelerators aimed for high luminosity, the effect can be more serious since a difference between vertical emittance and longitudinal emittance tends to be larger. Therefore, it is necessary to estimate a tune spread of the synchro-beta resonances properly. Synchro-beta effect is caused by chromatic aberrations, which characterize how optics parameters, including tune, Twiss parameter, X-Y coupling parameter, and other parameters, depend on the momentum deviation. The chromatic aberrations are actually defined by coefficients of an optics parameter in is expansion in terms of momentum deviation. The synchro-beta resonances caused by chromatic aberrations are discussed in this conference. We use 6-dimensional symplectic map which is obtained from measured optics parameters in order to simulate beam motion precisely*.

* Y. Seimiya and K. Ohmi, TH6PFP020, Particle Accelerator Conference PAC09, 4-8 May 2009, Vancouver, Canada.