Abstracts Brochure - CERN

MOPLS031
MOPLS032
MOPLS033
MOPLS034
26-Jun-06 16:00 - 18:00 MOPLS — Poster Session
Beam Orbit Control System for the KEKB Crab Cavities
M. Masuzawa, Y. Funakoshi, H. Koiso, T.T. Nakamura, J.-I. Odagiri
(KEK)
116
KEKB is an electron-positron collider with
an 8 GeV electron ring (HER) and a 3.5 GeV
positron ring (LER). The two beams currently
collide at one interaction point with a finite
horizontal crossing angle of 11 mrad. The design luminosity of 10 /nb/sec was first reached in May 2003 and the
peak luminosity exceeded 16 /nb/sec in December 2005. Simulations predict a luminosity boost if a crab crossing
scheme is introduced. The installation of two superconducting crab cavities, one in each ring, is scheduled in March
2006 in order to implement the crab crossing scheme. For stable operation, the horizontal beam position in the crab
cavity must be carefully controlled. This is needed to avoid loss of control of the crabbing mode field due to beam
loading. A beam position feedback system at the crab cavity has been prepared and tested. Its performance will be
discussed in this report.
Beam-beam Limit and the Degree of Freedom
Beam-beam limit is caused by chaotic dif-
K. Ohmi (KEK)
fusion due to the strong nonlinear force of
beam-beam interaction. Degree of freedom
in the colliding system is essential for the diffusion. We discuss the diffusion using several models.
Beam-beam Limit and Feedback Noise
Beam-beam interaction is strongly nonlinear,
K. Ohmi, Y. Funakoshi, S. Hiramatsu, K. Oide, M. Tobiyama (KEK) therefore particles in the beam experience
chaotic motion. A small noise can be enhanced
by the chaotic nature, with the result that unexpected emittance growth can be observed. We study the noise
of transverse bunch by bunch feedback system and related luminosity degradation. Similar effects caused by crab
cavity noise is also discussed.
Beam-beam Tail Due to Collision with Non-Gaussian Beam
Beam-beam tail has been evaluated by weak-
K. Ohmi, T. Abe, M. Tawada (KEK) D.N. Shatilov (BINP SB RAS) strong simulation with Gaussian model. For
very high beam-beam parameter, an equilibrium
beam distribution could be a non-Gaussian distribution. The non-Gaussian distribution is determined by
another strong-strong simulation. We study beam-beam tail using a weak-strong simulation with the non-Gaussian
distribution.