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1. Commissioning of KEKB

Author

Minoru Yoshida, Shigenori Hiramatsu, E. Perevedentsev, Shigeki Kato, Katsunobu Oide, Naoko Iida, Eiji Kikutani, Tatsuro Nakamura, Masafumi Tawada, Toshihiro Matsumoto, Mitsuo Kikuchi, Y. Wu, Masaaki Suetake, Kazuhito Ohmi, S. Uno, Noboru Yamamoto, Tsuyoshi Suwada, J. Haba, Toshiyuki Mitsuhashi, Takuya Kamitani, S. Yoshimoto, S. Kamada, Atsushi Enomoto, Kenji Hosoyama, Kazunori Akai, Shin-ichi Kurokawa, Kazuro Furukawa, Hitomi Ikeda, Yukiyoshi Ohnishi, Frank Zimmermann, N. Akasaka, J.W. Flanagan, Makoto Tobiyama, Yujiro Ogawa, Yoshihiro Funakoshi, Mika Masuzawa, Norihito Ohuchi, T. Ieiri, Satoshi Ohsawa, Masakazu Yoshioka, H. Fukuma, Toshihiro Mimashi, Yusuke Suetsugu, Haruyo Koiso, Masaki Tejima, Kotaro Satoh, and Takaaki Furuya

Subjects
Physics, Nuclear physics, Nuclear and High Energy Physics, Luminosity (scattering theory), KEKB, Detector, Beam instability, Beam emittance, Instrumentation, B-factory
Abstract

KEKB has been operated since December, 1998, to deliver BB pairs for a physics detector. In this paper,we describe the commissioning procedure of KEKB.

Published
2003
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2. Compensationof the crossing angle with crab cavities at KEKB

Author

T. Abe, K. Akai, M. Akemoto, A. Akiyama, M. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, T. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Inagaki, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama, K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, H. Koiso, Y. Kojima, I. Komada, T. Kubo, K. Kudo, N. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, S. Ohsawa, Y. Ohsawa, Y. Ohnishi, N. Ohuchi, K. Oide, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno, M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, Mi. Yoshida, S. Yoshimoto, K. Yoshino, E. Perevedentsev, and D. N. Shatilov

Subjects
Physics, Nuclear physics, KEKB, Luminosity (scattering theory), Astrophysics::High Energy Astrophysical Phenomena, Physics::Accelerator Physics, High Energy Physics::Experiment, Collision, Linear particle accelerator, Beam (structure)
Abstract

Crab cavities have been installed in the KEKB B-factory rings to compensate the crossing angle at the collision point and thus increase luminosity. The beam operation with crab crossing has been done since February 2007. This is the first experience with such cavities in colliders or storage rings. The crab cavities have been working without serious issues. While higher specific luminosity than the geometrical gain has been achieved, further study is necessary and under way to reach the prediction of simulation.

Published
2007
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3. Beam operation with crab cavities at KEKB

Author

T. Abe, T. Agho, K. Akai, M. Akemoto, A. Akiyama, M. Arinaga, K. Ebihara, K. Egawa, A. Enomoto, J. Flanagan, S. Fukuda, H. Fukuma, Y. Funakoshi, K. Furukawa, T. Furuya, K. Hara, T. Higo, S. Hiramatsu, H. Hisamatsu, H. Honma, T. Honma, K. Hosoyama, T. Ieiri, N. Iida, H. Ikeda, M. Ikeda, S. Inagaki, S. Isagawa, H. Ishii, A. Kabe, E. Kadokura, T. Kageyama, K. Kakihara, E. Kako, S. Kamada, T. Kamitani, K. Kanazawa, H. Katagiri, S. Kato, T. Kawamoto, S. Kazakov, M. Kikuchi, E. Kikutani, K. Kitagawa, H. Koiso, Y. Kojima, I. Komada, T. Kubo, K. Kudo, N. Kudo, K. Marutsuka, M. Masuzawa, S. Matsumoto, T. Matsumoto, S. Michizono, K. Mikawa, T. Mimashi, S. Mitsunobu, K. Mori, A. Morita, Y. Morita, H. Nakai, H. Nakajima, T. T. Nakamura, H. Nakanishi, K. Nakanishi, K. Nakao, S. Ninomiya, Y. Ogawa, K. Ohmi, S. Ohsawa, Y. Ohsawa, Y. Ohnishi, N. Ohuchi, K. Oide, M. Ono, T. Ozaki, K. Saito, H. Sakai, Y. Sakamoto, M. Sato, M. Satoh, K. Shibata, T. Shidara, M. Shirai, A. Shirakawa, T. Sueno, M. Suetake, Y. Suetsugu, R. Sugahara, T. Sugimura, T. Suwada, O. Tajima, S. Takano, S. Takasaki, T. Takenaka, Y. Takeuchi, M. Tawada, M. Tajima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, Mi. Yoshida, S. Yoshimoto, K. Yoshino, E. Perevedentsev, and D. N. Shatilov

Subjects
Physics, Nuclear physics, KEKB, Calibration, Beam (structure), Voltage
Abstract

KEKB has been operating with crab cavities for the first time in the world. This paper represents beam operation with the crab crossing.

Published
2007
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4. Beam-beam effects observed at KEKB

Author

Y. Funakoshi, K. Ohmi, T. Agho, K. Akai, K. Ebihara, K. Egawa, A. Enomoto, J. Flanagan, H. Fukuma, K. Furukawa, T. Furuya, J. Haba, S. Hiramatsu, T. Ieiri, N. Iida, H. Ikeda, T. Kageyama, S. Kamada, T. Kamitani, S. Kato, M. Kikuchi, E. Kikutani, H. Koiso, M. Masuzawa, T. Mimashi, A. Morita, T. T. Nakamura, K. Nakanishi, H. Nakayama, Y. Ogawa, Y. Ohnishi, N. Ohuchi, K. Oide, M. Ono, M. Shimada, M. Suetake, Y. Suetsugu, T. Sugimura, T. Suwada, M. Tawada, M. Tejima, M. Tobiyama, N. Tokuda, S. Uehara, S. Uno, Y. Yamamoto, Y. Yano, K. Yokoyama, Ma. Yoshida, Mi. Yoshida, S. Yoshimoto, E. Perevedentsev, and D. N. Shatilov

Subjects
Physics, Beam diameter, Optics, KEKB, business.industry, business, Beam (structure)
Abstract

At KEKB, a dedicated machine experiment on crab crossing has been carried out for about 4.5 months. Some of the beam-beam effects observed with crab crossing, which include a beam lifetime issue, are discussed in comparison with those with a finite crossing angle of plusmn11 mrad.

Published
2007
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5. Betatron Sidebands due to Electron Clouds Under Colliding Beam Conditions

Author

H. Fukuma, E. Perevedentsev, J.W. Flanagan, S. Uno, Makoto Tobiyama, Shigenori Hiramatsu, Y. Funakoshi, K. Ohmi, S. Uehara, and H. Ikeda

Subjects
Physics, Luminosity (scattering theory), Physics::Instrumentation and Detectors, Physics::Optics, Quantum Physics, Electron, Condensed Matter::Mesoscopic Systems and Quantum Hall Effect, Betatron, Spectral line, Nuclear physics, Positron, KEKB, Bunches, Physics::Accelerator Physics, Atomic physics, Beam (structure)
Abstract

Recently, 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.[1] When the LER is operating in single-beam mode (no colliding bunches in the HER), these sidebands are sharply peaked. When the bunches are in collision for physics running, the sidebands are still present but are found to be smeared out. The bunch-by-bunch specific luminosity is lower for bunches with sidebands than for those without sidebands. In this paper, the behavior of the sidebands in collision and the effects on luminosity are discussed.

Published
2006
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6. Simulation Analysis of Head-Tail Motion Caused by Electron Cloud

Author

E. Perevedentsev, H. Fukuma, K. Ohmi, J.W. Flanagan, Shigenori Hiramatsu, M. Tobiyama, and H. Ikeda

Subjects
Physics, Positron, Atomic orbital, Magnet, Physics::Accelerator Physics, Head (vessel), Side band, Solenoid, Atomic physics, Signal, Instability
Abstract

Synchro-beta side band signal caused by electron cloud instability has been observed at KEK-B factory. The side-band appears above the threshold of beam size blow-up and disappears by exciting solenoid magnets which covers whole ring. The side-band is an evidence of strong head-tail instability caused by electron cloud. The side-band appears in tune spectrum with positive shift ν β + aν s (1 β − aν s (a > 0). We study the synchro-beta spectrum using a code, PEHTS, which simulates single bunch electron cloud instability.

Published
2006
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7. Strong-strong simulation of beam-beam interaction for roundbeams

Author

E. Perevedentsev, K. Ohmi, and A. Valishev

Subjects
Physics, Source code, Luminosity (scattering theory), Computer simulation, business.industry, media_common.quotation_subject, Numerical analysis, law.invention, KEKB, Optics, law, Physics::Accelerator Physics, High Energy Physics::Experiment, Thermal emittance, Collider, business, Beam (structure), media_common
Abstract

This paper presents the results of numerical simulations of beam-beam interaction in a e+-e- machine with round colliding beams. The calculations were done with the particle-in-cell computer code which was developed for the KEKB B-factory. The code was modified to include the effect of the machine nonlinearity and dynamical radiation emittance. A simulation study of the round beam collider VEPP-2000 justified the choice of the chromaticity correction scheme, working point and optics capable of achieving the design luminosity

Published
2004
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8. Beam-beam experience at DAΦNE

Author

C. Milardi, D. Alesini, C. Biscari, Susanna Guiducci, Angelo Stella, M. A. Preger, S. Bertolucci, Marilisa De Serio, G. Mazzitelli, F. Sannibale, A. Ghigo, E. Perevedentsev, G. Di Pirro, Alessandro Stecchi, Fabio Marcellini, Alessandro Drago, Cristina Vaccarezza, Mikhail Zobov, Adriana Gallo, and Manuela Boscolo

Subjects
Physics, Nuclear physics, Physics::Accelerator Physics, Beam (structure)
Abstract

This paper summarizes the results of experimental observations and measurements of beam-beam interactions in DA/spl Phi/NE, the Frascati Phi-factory. The achieved results are reported with analysis of present limitations in both single and multibunch operation modes and compared with numerical simulations.

Published
2002
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9. Beam-Beam Experience at DAPHINE

Author

Alessandro Drago, S. Bertolucci, F. Sannibale, Susanna Guiducci, Manuela Boscolo, Marilisa De Serio, D. Alesini, E. Perevedentsev, Adriana Gallo, A. Ghigo, G. Di Pirro, M. A. Preger, Alessandro Stecchi, Fabio Marcellini, Angelo Stella, Mikhail Zobov, Cristina Vaccarezza, C. Milardi, C. Biscari, and G. Mazzitelli

Subjects
Physics, Nuclear physics, Luminosity (scattering theory), Physics::Accelerator Physics, Statistical physics, Beam (structure)
Abstract

This paper summarizes the results of experimental observations and measurements of beam-beam interactions in DAPHINE, the Frascati Phi-factory. The achieved results are reported with analysis of present limitations in both single and multibunch operation modes and compared with numerical simulations.

Published
2002
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10. Wake-field and fast head-tail instability caused by an electron cloud

Author

K. Ohmi, Frank Zimmermann, and E. Perevedentsev

Subjects
Physics, Positron, Proton, Ionization, Secondary emission, Vlasov equation, Physics::Accelerator Physics, Electron, Wake, Atomic physics, Instability, Accelerators and Storage Rings
Abstract

In positron and proton storage rings, electrons produced by photoemission, ionization, and secondary emission accumulate in the vacuum chamber during multibunch operation with close spacing. A positron or proton bunch passing through this "electron cloud" experiences a force similar to a short-range wake field. This effective wake field can cause a transverse-mode-coupling instability, if the electron-cloud density exceeds a threshold value. In this report, we compute the electron-cloud induced wake in a region without external magnetic field both analytically and via computer simulation, for parameters representing the low-energy positron ring of KERB and the LHC proton beam in the CERN SPS. We study the linearity and time dependence of the wake function and its variation with the size of the electron cloud. Using a broadband resonator model for the electron-cloud wake field, we then evaluate theoretical expressions for the transverse-mode-coupling instability based on the linearized Vlasov equation, and for the instability threshold of fast transverse blow up including its dependence on chromaticity. copy 2001 The American Physical Society.

Published
2002

11. Beam Measurement

Author

S.Y. Lee, S. Kurokawa, E. Perevedentsev, and S. Turner

Subjects
Physics, Nuclear physics, Large Hadron Collider, law, Particle accelerator, Joint (geology), Beam (structure), law.invention
Published
1999
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14. Commissioning of KEKB

Author

Naoko Iida, Yunhai Cai, Satoshi Ohsawa, Shin-ichi Kurokawa, Yasuchika Yamamoto, K. Yokoyama, Kazumi Egawa, Demin Zhou, J. Haba, Shigenori Hiramatsu, Sadaharu Uehara, Mitsuo Kikuchi, Masakazu Yoshioka, E. Perevedentsev, Haruyo Koiso, Masaki Tejima, Mika Masuzawa, Masaaki Ono, Katsunobu Oide, Toshiyuki Oki, Kiyokazu Ebihara, Tatsuro Nakamura, Miho Shimada, Takako Miura, Yoshiharu Yano, H. Fukuma, T. Ieiri, Yoshihiro Funakoshi, Masafumi Tawada, Masaaki Suetake, Zhanguo Zong, Hitomi Ikeda, Osamu Tajima, Kyo Shibata, Takaaki Furuya, Kazuro Furukawa, Akio Morita, Michiru Nishiwaki, Yukiyoshi Ohnishi, S. Kamada, Yujiro Ogawa, Takashi Sugimura, Kazuhito Ohmi, Atsushi Enomoto, Mitsuhiro Yoshida, Norihito Ohuchi, Shoji Uno, S. Yoshimoto, Tatsuya Kageyama, Yoshiyuki Morita, N. Tokuda, J.W. Flanagan, Masanori Satoh, Tetsuo Abe, Tsuyoshi Suwada, Kotaro Satoh, Kenji Hosoyama, Masato Yoshida, Takuya Kamitani, Toshihiro Matsumoto, Kazunori Akai, M. Iwasaki, Toshihiro Mimashi, Yusuke Suetsugu, Kota Nakanishi, Eiji Kikutani, Yuji Seimiya, Makoto Tobiyama, and Shigeki Kato

Subjects
Nuclear physics, Physics, Luminosity (scattering theory), KEKB, Electromagnetic coil, Detector, General Physics and Astronomy, Solenoid
Abstract

KEKB has been operated since December, 1998, to deliver B ¯ B pairs for a physics detector. In this paper,we describe the commissioning procedure of KEKB.

Published
2013
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15. Achievements of KEKB

Author

K. Yoshino, Eiji Kako, Hiroshi Sakai, Hitoshi Fukuma, Kota Nakanishi, Takashi Sugimura, Noboru Yamamoto, Y. Sakamoto, Kazumi Egawa, S. Isagawa, Shigeki Kato, A. Shirakawa, Eiji Kikutani, H. Nakanishi, S. Takasaki, M. Arinaga, Kyo Shibata, Takuya Kamitani, Shigemi Inagaki, Akio Morita, Tetsuo Shidara, Kazunori Akai, Hiroyuki Honma, Yasunobu Ohsawa, T. Ieiri, Naoko Iida, Toshiyuki Ozaki, Toshiyuki Mitsuhashi, Kazuhito Ohmi, S. Mitsunobu, T. Kawamoto, Eiji Ezura, M. Sato, S. Kamada, Shoji Uno, Mitsuhiro Yoshida, Shinichiro Michizono, N. Tokuda, K. Mikawa, I. Komada, S. Takano, Masaaki Suetake, Toshiyasu Higo, Atsushi Enomoto, Demin Zhou, Katumi Nakao, Osamu Tajima, Ken-ichi Kanazawa, Tateru Takenaka, Haruyo Koiso, Masaki Tejima, Yasunao Takeuchi, Miho Shimada, Yoshiharu Yano, Kiyosumi Tsuchiya, Yuuji Kojima, Toshiyuki Oki, Kiyokazu Ebihara, Teruya Honma, Satoshi Ohsawa, Hiromi Hisamatsu, M. Ikeda, Kazuro Furukawa, Toshihiro Mimashi, Takako Miura, T. Kubo, Masakazu Yoshioka, Katsunobu Oide, K. Yokoyama, H. Nakayama, E. Kadokura, Yusuke Suetsugu, Ryuhei Sugahara, Tatsuro Nakamura, S. Yoshimoto, Hitoshi Ishii, K. Mori, Shuji Matsumoto, Mika Masuzawa, T. Sueno, Shigeki Fukuda, Mitsuo Akemoto, Sergey Kazakov, Yingzhi Wu, J. Haba, A. Akiyama, Masafumi Tawada, Hirotaka Nakai, Tsuyoshi Suwada, E. Perevedentsev, Mitsuo Kikuchi, Yuji Seimiya, Hitomi Ikeda, Norimasa Akasaka, K. Marutsuka, Yunhai Cai, Sadaharu Uehara, Kazufumi Hara, Makoto Tobiyama, Kenji Hosoyama, Shigenori Hiramatsu, Zhanguo Zong, Tatsuya Kageyama, Hiromitsu Nakajima, Yoshihiro Funakoshi, Michiru Nishiwaki, Tetsuo Abe, Frank Zimmermann, J.W. Flanagan, Masanori Satoh, Hiroaki Katagiri, Yukiyoshi Ohnishi, Kiyoshi Kitagawa, Takaaki Furuya, Yujiro Ogawa, Masato Yoshida, Atsushi Kabe, Toshihiro Matsumoto, Shin-ichi Kurokawa, Yasuchika Yamamoto, Y. Takeuchi, Yoshiyuki Morita, Kotaro Satoh, K. Kudo, Mitsuru Shirai, Norihito Ohuchi, Kazuhisa Kakihara, Masaaki Ono, and Samo Stanic

Subjects
Physics, Upgrade, KEKB, business.industry, Electrical engineering, General Physics and Astronomy, business
Abstract

The machine commissioning of KEKB started in December 1998 and its operation was terminated at the end of June 2010 to upgrade KEKB to SuperKEKB. In this paper, we summarize the history of KEKB and show the achievements made there.

Published
2013
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16. The LEP impedance model

Author

E. Peschardt, E. Rossa, E. Perevedentsev, Karel Cornelis, D. Brandt, F. Tecker, V. Danilov, Bruno W Zotter, A. Hofmann, D. Wang, L. Rivkin, and C. Juillard

Subjects
Physics, Resistive touchscreen, Transverse plane, Nuclear magnetic resonance, Phase angle, Physics::Accelerator Physics, Wave impedance, Betatron, Electrical impedance, Accelerators and Storage Rings, Beam (structure), Characteristic impedance, Computational physics
Abstract

The bunch current in LEP is limited by collective effects slightly below its design value. To understand this limitation, a set of experiments has been carried out to obtain a model of the impedance seen by the circulating beam. From measurements of the current dependance of the synchrotron and betatron frequencies information about the longitudinal and transverse reactive impedance has been obtained. The growth rate of the m=1 head-tail instability has been observed to gain some knowledge of the resistive transverse impedance. The dependence of the transverse mode-coupling threshold on bunch length has been measured. The energy loss per turn of a stable bunch is given by the longitudinal resistive impedance and has been measured by recording the change of the synchronous phase angle with current. All these quantities represent integrals over products of bunch mode spectra and impedances. By measuring them for different bunch lengths the frequency dependence of the impedances can be estimated. From these results a model of the LEP impedance has been obtained which can be used to estimate the current limitation under different operating conditions. >

Published
1993

17. Beam-beam experience at KEKB

Author

Makoto Tobiyama, Noboru Yamamoto, E. Perevedentsev, N. Akasaka, Y. Wu, Norihito Ohuchi, Tsuyoshi Suwada, Mitsuo Kikuchi, Haruyo Koiso, Masaki Tejima, Shigeki Kato, Shin-ichi Kurokawa, Kazuro Furukawa, Naoko Iida, Takuya Kamitani, S. Yoshimoto, S. Uno, K. Akai, Shinichiro Michizono, Frank Zimmermann, J.W. Flanagan, Katsunobu Oide, D. Pestrikov, Mika Masuzawa, Atsushi Enomoto, Shigenori Hiramatsu, Tatsuro Nakamura, Hitoshi Fukuma, Yukiyoshi Ohnishi, K. Ohmi, T. Ieiri, Eiji Kikutani, Yujiro Ogawa, Masaaki Suetake, Karl Bane, M. Yoshida, H. Ikeda, N. Huang, Toshihiro Matsumoto, Y. Funakoshi, Masakazu Yoshioka, Kenji Hosoyama, J. Haba, Toshihiro Mimashi, Yusuke Suetsugu, Satoshi Ohsawa, K. Satoh, C. H. Yu, and Masafumi Tawada

Subjects
Physics, Nuclear physics, KEKB, Luminosity (scattering theory), business.industry, law, Electrical engineering, Particle accelerator, business, Linear particle accelerator, Beam (structure), law.invention
Abstract

KEKB has achieved the peak luminosity of 4.1 x 10{sup 33} cm{sup -2} sec{sup -1} and the present capability for delivering integrated luminosity is 224 pb{sup -1}/day. This paper describes (1) the recent performance and the problems of KEKB and (2) the comparison of beam-beam simulations with experiments at KEKB.

18. Status report on DAΦNE

Author

Adriana Gallo, G. von Holtey, A. Clozza, S. Di Mitri, Mikhail Zobov, Marilisa De Serio, D. Alesini, Angelo Stella, S. Bertolucci, G. Delle Monache, C. Biscari, R. Boni, F. Sgamma, F. Sannibale, Luigi Pellegrino, Fabio Marcellini, Manuela Boscolo, Cristina Vaccarezza, M. A. Preger, Pantaleo Raimondi, C. Milardi, Susanna Guiducci, G. Mazzitelli, Alessandro Drago, Gabriele Benedetti, Alessandro Stecchi, Claudio Sanelli, Ruggero Ricci, M. Vescovi, E. Perevedentsev, A. Ghigo, and G. Di Pirro

Subjects
Nuclear physics, Physics, Luminosity (scattering theory), Detector, Phase (waves), Physics::Accelerator Physics, High Energy Physics::Experiment, Astrophysics::Cosmology and Extragalactic Astrophysics, Status report, Optical coupling
Abstract

DA/spl Phi/NE, the Frascati LNF /spl Phi/-factory, is providing luminosity for the KLOE experiment since July 2000. A steady increase of daily integrated luminosity in KLOE has been obtained, due to interspersed machine physics studies. The main results are: increase of single bunch luminosity by reduction of the effects of nonlinear terms in the machine, background reduction, refill of the colliding beams while keeping the KLOE detector taking data and increase of stable stored current. A fraction of machine time has been used to tune luminosity and reduce background in the DEAR configuration. The luminosity delivered to DEAR was sufficient to conclude the first phase of the experiment.

19. Observation of vertical betatron sideband due to electron clouds in the KEKB low energy ring.

Author

Flanagan JW, Ohmi K, Fukuma H, Hiramatsu S, Tobiyama M, and Perevedentsev E

Abstract

The effects of electron clouds on positively charged beams have been an active area of research in recent years at particle accelerators around the world. Transverse beam-size blowup due to electron clouds has been observed in some machines and is considered to be a major limiting factor in the development of higher-current, higher-luminosity electron-positron colliders. The leading proposed mechanism for beam blowup is the excitation of a fast head-tail instability due to short-range wakes within the electron cloud. We present here observations of betatron oscillation sidebands in bunch-by-bunch spectra that may provide direct evidence of such head-tail motion in a positron beam.

Published
2005
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20. Wake-field and fast head-tail instability caused by an electron cloud.

Author

Ohmi K, Zimmermann F, and Perevedentsev E

Abstract

In positron and proton storage rings, electrons produced by photoemission, ionization, and secondary emission accumulate in the vacuum chamber during multibunch operation with close spacing. A positron or proton bunch passing through this "electron cloud" experiences a force similar to a short-range wake field. This effective wake field can cause a transverse-mode-coupling instability, if the electron-cloud density exceeds a threshold value. In this report, we compute the electron-cloud induced wake in a region without external magnetic field both analytically and via computer simulation, for parameters representing the low-energy positron ring of KEKB and the LHC proton beam in the CERN SPS. We study the linearity and time dependence of the wake function and its variation with the size of the electron cloud. Using a broadband resonator model for the electron-cloud wake field, we then evaluate theoretical expressions for the transverse-mode-coupling instability based on the linearized Vlasov equation, and for the instability threshold of fast transverse blow up including its dependence on chromaticity.

Published
2002
Full Text
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