• M. Iwasaki, Y. Funakoshi, J. Haba, N. Iida, K. Kanazawa, H. Koiso, Y. Ohnishi, K. Shibata, S. Tanaka, T. Tsuboyama, S. Uno, Y. Ushiroda
  KEK, Ibaraki
• H. Aihara, C. Ng, S. Sugihara
  University of Tokyo, Tokyo
• H. Nakano, H. Yamamoto
  Tohoku University, Graduate School of Science, Sendai

SuperKEKB is the upgrade plan of the current B-factory experiment with the KEKB accelerator at KEK. Its luminosity is designed to be 8x10³⁵ /cm²/s (40 times higher than KEKB) and the integrated luminosity is expected to be 50 ab-1. In SuperKEKB, it is important to evaluate the beam induced BG and design the interaction region (IR) to assure the stable detector operation. To estimate the beam induced BG, we construct the beam-line simulation based on the GEANT4 simulation. In this paper, we report the BG evaluation and the IR design for SuperKEKB.

• 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

• P. Jain
  Sokendai, Ibaraki
• H. Fukuma, K. Kanazawa, Y. Suetsugu
  KEK, Ibaraki

Electron Cloud (ECLOUD) deteriorates the performance of proton and positron storage rings. Therefore it is desirable to understand the ECLOUD buildup in a given machine. The data taken by Retarded Field Analyzer (RFA) with a multi channel plate showed that the signal had the peaks coinciding with the positron bunch pattern if a high voltage of -2kV is applied to the retarded grid*. This suggests that the cloud electrons get maximum kick near the positron bunch. A computer program has been developed to study the near bunch ECLOUD density at KEKB LER (Low Energy Ring). In simulations, secondary electron emission is modeled according to the Furman and Pivi's model**. In this paper we compare the simulation results of the ECLOUD buildup with the experiments performed in KEK under different beam-optics elements.

* K. Kanazawa et al., PAC05, 10⁵⁴.
** M. Furman and M. Pivi, PRST-AB, 5, 124404 (2002).

• J.R. Calvey, Y. Li, J.A. Livezey, J. Makita, R.E. Meller, M.A. Palmer, R.M. Schwartz, C.R. Strohman
  CLASSE, Ithaca, New York
• S. Calatroni, G. Rumolo
  CERN, Geneva
• K.C. Harkay
  ANL, Argonne
• K. Kanazawa, Y. Suetsugu
  KEK, Ibaraki
• M.T.F. Pivi, L. Wang
  SLAC, Menlo Park, California

Over the course of the CesrTA program, the Cornell Electron Storage Ring (CESR) has been instrumented with several retarding field analyzers (RFAs), which measure the local density and energy distribution of the electron cloud. These RFAs have been installed in drifts, dipoles, quadrupoles, and wigglers; and data have been taken in a variety of beam conditions and bunch configurations. This paper will provide an overview of these results, and give a preliminary evaluation of the efficacy of cloud mitigation techniques implemented in the instrumented vacuum chambers.

• K. Kanazawa, H. Fukuma
  KEK, Ibaraki

The near beam electron cloud density in a magnetic field was estimated with a simple electron current detector at KEKB LER. The estimation is based on the assumption that high energy electrons which hit a chamber wall come directly from the region around the beam after the interaction with a circulating bunch. The first successful application of this idea for a drift space was reported at PAC05 by the authors. In a solenoid field of 50 G, the near beam cloud density is reduced by about four orders of magnitude compared to the no field case. In a quadruple magnet, the density around the beam is by two orders of magnitude lower than the density in a typical drift space, as most simulations show.

• K. Shibata, K. Kanazawa
  KEK, Ibaraki

As part of the design works of the interaction region (IR) of SuperKEKB (the upgrade of KEKB B-factory (KEKB)), the loss factor and impedance of beam ducts for the interaction point (IP duct) were calculated by GdfiedL. The IP duct is round and connected to beam ducts for electron and positron beams with a diameter of 20 mm via Y-shaped crotch ducts at both ends. The lengths of the straight section and crotch section are about 200 mm, respectively. The beam crossing angle is 83 mrad. Calculations for two types of IP duct were performed. Both ducts are almost same in design except for the diameter of the straight section (20 mm and 30 mm). The loss factors were about 0.001 V/pC in both cases when the bunch length was 6 mm. The longitudinal impedances showed that there were no modes trapped longitudinally in IP duct. However, from the results of the transverse impedance and eigenmode calculation, it was found that many TE modes can be trapped at the crotch section if the beam is off-center of the beam duct. For comparison, the loss factor and impedance of the IR beam duct of KEKB are also being calculated now. Full details of the calculation results will be provided in this report.

• 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