arXiv subjects

M. Tobiyama

Publications and source records attributed to M. Tobiyama.

3 recordsLinked to original sources

arXiv2010

KEKB Beam Collision Stability at the Picosecond Timing and Micron Position Resolution as observed with the Belle Detector

Using the Belle detector we study the characteristics of beam collisions at the KEKB 3.5 GeV $e^+$ on 8 GeV $e^-$ asymmetric energy collider. We investigate the collision timing {\tip} and its $z$-coordinate along the beam axis {\zip} as a function of the position of the colliding bunch in a beam train. The various {\tip} and {\zip} behaviors observed by Belle are attributed to beam loading effects in the radio frequency cavities that accelerate the beams with a beam abort gap. We report these results in detail and discuss the prospects for the SuperKEKB collider.

physics.ins-det↗

arXiv2007

Compensation of the Crossing Angle with Crab Cavities at KEKB

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.

physics.ins-det↗

arXiv2005

Observation of Vertical Betatron Sideband due to Electron Clouds in the KEKB LER

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 blow-up 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 blow-up 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.

physics.acc-ph↗