Abstracts Brochure - CERN

WEPCH137
WEPCH138
WEPCH139
28-Jun-06 16:00 - 18:00 WEPCH — Poster Session
A Code to Simulate the Collective Effect of Electrons and Ions
A new code for computing the multiple ef-
W. Bruns, D. Schulte, F. Zimmermann (CERN)
fects of slowly moving charges is being developed.
The basic method is electrostatic
particle in cell. The underlying grid is rectangular and locally homogeneous. At regions of interest, e.g., where the
beam is, or near material boundaries, the mesh is refined recursively. The motion of the macroparticles is integrated
with an adapted timestep. Fast particles are treated with a smaller timestep, and particles in regions of fine grids are
also treated with a fine timestep. The position of collision of particles with material boundaries is accurately resolved.
Secondary particles are then created according to user-specified yield functions.
Simulations of Long-range Beam-beam Interaction and Wire Compensation with BB-
TRACK
We present weak-strong simulation results
U. Dorda, F. Zimmermann (CERN)
for the effect of long-range beam-beam collisions
in LHC, SPS, RHIC and DAFNE, as
well as for proposed wire compensation schemes or wire experiments, respectively. In particular, we discuss details
of the simulation model, instability indicators, the effectiveness of compensation, the difference between nominal and
PACMAN bunches for the LHC, beam experiments, and wire tolerances. The simulations are performed with the
new code BBTRACK.
An Adaptative Simulation of the LHC Optics
P. Hagen, M. Giovannozzi, J.-P. Koutchouk, T. Risselada, S. Sanfilippo,
E. Todesco, E.Y. Wildner (CERN)
312
The LHC beam dynamics requires a tight
control of the magnet field quality and geometry.
As the production of the magnets advances,
decisions have to be made on the ac-
ceptance of possible imperfections. To ease decision making, an adaptative model of the LHC optics has been built,
based on the current information available (e.g. magnetic measurements at warm or cold, magnet allocation to
machine slots) as well as on statistical evaluations for the missing information (e.g. magnets yet to be built, measured,
or for non-allocated slots). The uncertainties are included: relative and absolute measurement errors, warm-to-cold
correlations for the fraction of magnets not measured at cold, hysteresis and power supply accuracy. A pre-processor
generates instances of the LHC ring for the MADX program, with the possibility of selecting various error sources.
A post-processor computes ranges for relevant beam optics parameters and distributions. This approach has been
applied to the expected beta-beating, to the possible impact of permeability issues in some quadrupole collars, to the
geometrical displacements of the multipolar correctors and to prioritize the magnetic measurement programme.