Abstracts Brochure - CERN

WEPCH — Poster Session 28-Jun-06 16:00 - 18:00
Models to Study Multi-bunch Coupling through Head-on and Long-range Beam-beam Interactions
In the LHC almost 6000 bunches will collide
in four interaction points where they experi- T. Pieloni, W. Herr (CERN)
ence head-on as well as clustered long range
interactions. These lead to a coupling between all bunches and coherent beam-beam effects. For two colliding bunches
this is well understood. However, for a large number of bunches colliding with different collision patterns, it results
in a complex spectrum of oscillation frequencies with consequences for beam measurements and Landau damping.
To study the coherent beam-beam modes, three complementary models have been developped and will be described
in this report. Two of these methods rely on self-consistent multi-bunch and multi-particle tracking while the third is
a semi-analytic model based on a complex matrix algorithm. The three methods together provide useful information
about the beam-beam coupling of multi bunch beams and together provide a deeper insight into the underlying
physics.
Measurement and Correction of the 3rd Order Resonance in the Tevatron
At Fermilab Tevatron BPM system has been
recently upgraded resulting much better accuracy
of beam position measurements and
improvements of data acquisition for turn-
F. Schmidt (CERN) Y. Alexahin, V.A. Lebedev, D. Still, A. Valishev
(Fermilab)
by-turn measurements. That allows one to record the beam position at each turn for 8000 turns for all BPMs (118
in each plane) with accuracy of about 10 -20 µm. In the last decade a harmonic analysis tool has been developed at
CERN that allows relating each FFT line derived from the BPM data with a particular non-linear resonance in the
machine. In fact, one can even detect the longitudinal position of the sources of these resonances. Experiments
have been performed at the Tevatron in which beams have been kicked to various amplitudes to analyze the 3rd
order resonance. It was possible to address this rather large resonance to some purposely powered sextupoles. An
alternative sextupole scheme allowed the suppression of this resonance by a good factor of 2. Lastly, the experimental
data are compared with model calculations.
Beam Dynamics in Compton-ring Gamma Sources
Electron storage rings with a laser cavity
are promising intensive sources of polarized
hard photons to generate polarized positron
beams. The dynamics of electron bunches
circulating in a storage ring and interacting
E.V. Bulyak, P. Gladkikh, V. Skomorokhov (NSC/KIPT) K. Moenig
(DESY Zeuthen) T. Omori, J.U. Urakawa (KEK) F. Zimmermann
(CERN)
with high-power laser pulses is studied both analytically and by simulation. Common features and difference in the
bunch behavior interacting with an extremely high power laser pulse (polarized positron source for the ILC project)
and a moderate pulse (source for CLIC) are shown. Also considerations on particular lattice designs for both rings
are presented.
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