Summary:
Multi-bunch Electron Cloud effects in the ILC
BDS -- Juhao Wu
- Juhao presented an analytic calculation of
beam orbit variation in one dimension due to interaction of the bunches with
an electron cloud due to finite vacuum in the system. Solutions of the
equations of motion were expressed as series expansions and the lowest order
term examined. The buildup of the electron cloud as function of
distance along the BDS was parameterized. Only US Warm beam parameters
study presented as ILC bunch spacing makes issue negligible. Study
showed that a cloud density threshold of ne~1012 m-3
was required to observe orbit variations.
Effect of post-IP solenoid on 20 mrad
extraction optics and beam loss - Yuri Nosochkov
- Yuri divided the post IP solenoid field in slices and
looked at what it would do to the beam in the extraction line. If
uncorrected, y-orbit and y-dispersion at Compton IP would be less than
optimal and be a function of y'. He concluded that its effects could be
cancelled by the introduction of relatively large field dipole windings on
the extraction SC quads Very small modification (~0.05%) of the quad fields
would be required to compensate for weak focusing of the solenoid field.
There is only a minor increase in beam loss in the extraction line for the
nominal/high 500 GeV and nominal 1 TeV IP parameter sets. More
detailed analyses which include the yoke-mounted anti-solenoid around QD0
need to be done.
MARS simulation of BDS - Mikhail Kostin
- Mikhail modeled the ILC BDS in MARS at 250 GeV/beam
using STRUCT generated particle losses on the betatron and energy
collimators SP2, SP4 and SPEX. A muon distribution at the IP without tunnel
filling spoiler magnets is presented as are energy depositions at the
spoilers and protection collimators. Although still statistically
insignificant, the muon spoilers provide a muon background reduction of
8000. He notes that the radiation load is most severe at the quad
immediately downstream of the first protection collimator PC1 and that the
life time limit of 4 MGy will be reached in just 14 days at the standard 10-3
halo level assumed in the calculation. A further optimization of the
protection collimators is needed.
Tom Markiewicz for Andrei Seryi,
05/12/05