Abstracts Brochure - CERN

MOPLS136
MOPLS137
MOPLS138
26-Jun-06 16:00 - 18:00 MOPLS — Poster Session
emittances and the dynamic aperture back to the ideal value. The correction using dipolar correctors and several
skew quadrupole correctors allows a minimization of the closed-orbit distortion, the cross-talk between vertical and
horizontal closed orbits, the residual vertical dispersion and the betatron coupling.
Ion Effects in the Damping Rings of ILC and CLIC
We discuss ion trapping, rise time of the fast
F. Zimmermann, W. Bruns, D. Schulte (CERN)
beam-ion instability, and ion-induced incoherent
tune shift for various incarnations of
the ILC damping rings and for CLIC, taking into account the different regions of each ring. Analytical calculations
for ion trapping are compared with results from a new simulation code.
Tracking Studies to Determine the Required Wiggler Aperture for the ILC Damping Rings
The injection efficiency of an ILC damping
I. Reichel, A. Wolski (LBNL)
ring is closely tied to its acceptance. To maximize
both, one wants a physical aperture as
large as possible in the wiggler magnets, as these are the limiting physical apertures in the ring. On the other hand,
a small aperture in the wiggler magnets is needed to achieve the required field profile, a high magnetic field that is
very linear over the whole physical aperture of the magnet. Tracking studies were done for all proposed ILC damping
ring lattices to determine their required apertures. Although a half-aperture of 8 or 10 mm had been proposed, our
studies showed that, for most lattices, a 16 mm half-aperture is required. (For some lattices a 12 mm half aperture
might suffice.) We present here the results of our studies, which led to adopting a 16 mm half-aperture in the current
ILC damping ring baseline design.
Space Charge and Equilibrium Emittances in Damping Rings
The unusual combination of small beam size
M. Venturini, A. Wolski (LBNL)
and long ring circumference may cause space
charge to have noticeable effects on the beam
dynamics of the ILC (International Linear Collider) damping rings. One possible consequence is a modification of the
vertical equilibrium emittance resulting from a non-ideal lattice. One simple way to account for this effect is to model
space charge in the linear approximation within the framework of Oide’s envelope (or Chao’s matrix) formalism,
whis is commonly used to calculate equilibrium emittances in lepton storage rings. However, this model would likely
overestimate the effect as a linear approximation for space charge is accurate only in a small neighborhood of a bunch
center. For a more accurate modelling, we propose to make use of Sacherer’s envelope equations consisting of a
closed set of equations for the second moments of a beam distribution that account for the nonlinear dependence of
the space-charge force. Here we will illustrate how Sacherer’s equations can be combined with Oide’s formalism and
apply the result to the ILC damping rings.
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