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Dive into the research topics where Y. Funakoshi is active.

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Featured researches published by Y. Funakoshi.


Nuclear Instruments & Methods in Physics Research Section A-accelerators Spectrometers Detectors and Associated Equipment | 2003

The KEKB injector linac

Isamu Abe; N. Akasaka; M. Akemoto; S. Anami; A. Enomoto; J. Flanagan; Shigeki Fukuda; H. Fukuma; Y. Funakoshi; K. Furukawa; Hirofumi Hanaki; Hiroyuki Honma; N. Iida; M. Ikeda; K. Kakihara; Norihiko Kamikubota; T. Kamitani; H. Katagiri; T. Kawamoto; M. Kikuchi; Hitoshi Kobayashi; H. Koiso; T. Matsumoto; S. Michizono; K. Nakahara; Hiromitsu Nakajima; K. Nakao; Y. Ogawa; Y. Ohnishi; S. Ohsawa

Abstract An 8-GeV electron/3.5-GeV positron injector for KEKB was completed in 1998 by upgrading the existing 2.5-GeV electron/positron linac. The main goals were to upgrade its accelerating energy from 2.5 to 8 GeV and to increase the positron intensity by about 20 times. This article describes not only the composition and features of the upgraded linac, but also how these goals were achieved, by focusing on an optics design and commissioning issues concerning especially high-intensity single-bunch acceleration to produce positron beams.


ieee particle accelerator conference | 2007

Beam-beam effects in crab crossing and crab waist schemes

K. Ohmi; M.E. Biagini; Y. Funakoshi; P. Raimondi; M. Zobov

To boost up the luminosity performance in B factories, crab crossing and crab waist schemes are proposed. The crab crossing scheme compensates crossing angle, while the crab waist scheme compensates nonlinear terms induced by crossing angle with sextupole magnets. We discuss which nonlinear terms in the beam-beam map are enhanced by the crossing angle and which terms are compensated by the crab waist sextupole.


PACS2001. Proceedings of the 2001 Particle Accelerator Conference (Cat. No.01CH37268) | 2001

Present status and beam-stability issues of the KEKB injector linac

T. Suwada; N. Akasaka; A. Enomoto; Y. Ogawa; J. Flanagan; H. Fukuma; Y. Funakoshi; K. Furukawa; T. Ieiri; N. Iida; T. Kamitani; M. Kikuchi; T. Matsumoto; Tatsuro Nakamura; Y. Ohnishi; S. Ohsawa; K. Satoh; M. Suetake; H. Koiso; K. Oide

The KEKB injector linac was completely upgraded for the KEK B-Factory (KEKB) project in March, 1998. Many difficulties have been overcome during the elaborate commissioning of the upgraded linac since the end of 1997. The 3.5-GeV positron and 8-GeV electron beams have been injected to the KEKB rings with good performance. Much effort has also been continuing to stabilize the intensity and quality of the beams. Some experimental results on the beam stability issues am shown together with the recent operation status in this report. A beam test on a new scheme of a two-bunch injection was started in order to increase the positron intensity since March, 2001.


Proceedings of the 2005 Particle Accelerator Conference | 2005

Recent Progress at KEKB

Y. Funakoshi; K. Akai; K. Ebihara; K. Egawa; A. Enomoto; J. Flanagan; H. Fukuma; K. Furukawa; Takaaki Furuya; J. Haba; S. Hiramatsu; T. Ieiri; N. Iida; Hitomi Ikeda; T. Kageyama; S. Kamada; T. Kamitani; Shigeki Kato; M. Kikuchi; E. Kikutani; H. Koiso; M. Masuzawa; T. Mimashi; A. Morita; T. Nakamura; H. Nakayama; Y. Ogawa; K. Ohmi; Y. Ohnishi; N. Ohuchi

We summarize the machine operation of KEKB during past one year focusing on progress for this period.


BEAM HALO DYNAMICS, DIAGNOSTICS, AND COLLIMATION: 29th ICFA Advanced Beam Dynamics Workshop on Beam Halo Dynamics, Diagnostics, and Collimation HALO'03 | 2003

Collision with finite crossing angle at KEKB

K. Ohmi; M. Tawada; Y. Funakoshi

KEK B factory (KEKB) achieved the luminosity of 1034 cm−2s−1 with a finite crossing angle scheme. The crossing angle made easy the design of the interaction region for a narrow bunch spacing, with the result that it gave a gain of high collision repetition. The crossing angle did not degrade the beam‐beam performance up to the beam‐beam parameter of ξ ≈ 0.05. We review the beam‐beam effect of KEKB as a successive case of collision with finite crossing angle.


Proceedings of the 1999 Particle Accelerator Conference (Cat. No.99CH36366) | 1999

The first results of optics matching using wire scanners for the KEKB beam transport line

N. Iida; Y. Funakoshi; M. Kikuchi; K. Satoh; T. Suwada; T. Kawamoto

In the beam transport lines from the injector linac to KEKB rings, four wire scanners were installed for each of positron and electron line. The vibrations and non-linearities of the wire holders were suppressed to be small enough for beam size measurements. Optics matchings were made wing the wire scanners. Better transmission from the linac to the rings was obtained. By detecting shower due to Bremsstrahlung near the detector, the beam sizes were successfully measured without any beam tunings dedicated for background.


Proceedings of the 2005 Particle Accelerator Conference | 2005

Betatron Sidebands due to Electron Clouds Under Colliding Beam Conditions

J. Flanagan; K. Ohmi; H. Fukuma; Y. Funakoshi; S. Hiramatsu; Hirokazu Ikeda; M. Tobiyama; S. Uehara; S. Uno; E. Perevedentsev

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.


Proceedings Particle Accelerator Conference | 1995

Single-beam collective effects in the KEK B-factory

Y. H. Chin; K. Akai; Y. Funakoshi; K. Oide; K. Satoh

In this paper, we deal with the issues of single-beam collective effects (the bunch lengthening and the transverse mode-coupling instability) and coupled-bunch beam instabilities due to RF cavities and the resistive-wall beam pipes in the KEK B-factory. The transition problem and coupled-bunch instabilities due to photo-electrons will be discussed in other publications.


arXiv: Accelerator Physics | 2014

Operational experience with crab cavities at KEKB

Y. Funakoshi

KEKB was in operation from December 1988 to June 2010. The crab cavities were installed at KEKB in February 2007 and worked very stably until the end of KEKB operation. Operational experience of the crab cavities with beams is described.KEKB was in operation from December 1988 to June 2010. The crab cavities were installed at KEKB in February 2007 and have worked very stably until the end of the KEKB operation. Operational experience of the crab cavities with beams is described.


AIP Conference Proceedings | 2008

Longitudinal bunch deformation of a multi-bunched beam in the TRISTAN Accumulation Ring

Takashi Obina; K. Satoh; T. Kasuga; Y. Funakoshi; M. Tobiyama

A remarkable bunch deformation has been observed in the TRISTAN Accumulation Ring (AR) during multi-bunch operations. When two bunches that have different populations are stored in the ring, the bunch length of the weaker bunch is longer than that of the stronger one. The phenomenon can be explained as an effect of wake fields due to higher-order modes (HOMs) of accelerating cavities. We tried to find out the frequency of the mode and the strength of the wake field, and introduced a new technique called a test bunch measurement. The estimated field strength from the experiment shows a reasonable agreement with the calculation of HOM impedance.

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