Abstracts Brochure - CERN

MOPLS025
MOPLS026
MOPLS027
26-Jun-06 16:00 - 18:00 MOPLS — Poster Session
Experience in Reducing Electron Cloud and Dynamic Pressure Rise in Warm and Cold Regions
in RHIC
S.Y. Zhang, L. Ahrens, J.G. Alessi, M. Bai, M. Blaskiewicz, P.
Cameron, K.A. Drees, W. Fischer, J. Gullotta, P. He, H.-C. Hseuh,
H. Huang, R.C. Lee, V. Litvinenko, W.W. MacKay, T. Nicoletti, B.
Oerter, F.C. Pilat, V. Ptitsyn, T. Roser, T. Satogata, L. Smart, L. Snydstrup,
P. Thieberger, D. Trbojevic, J. Wei, K. Zeno (BNL)
114
Significant improvement has been achieved
for reducing electron cloud and dynamic
pressure rise at RHIC over several years;
however, there remain to be factors limiting
luminosity. The large scale application
of non-evaporable getter (NEG) coating in
RHIC has been proven effective in reducing
electron multipacting and dynamic pressure rise. This will be reported together with the study of the saturated
NEG coatings. Since beams with increased intensity and shorter bunch spacing became possible in operation, the
electron cloud effects on beam, such as the emittance growth,are an increasing concern. Observations and studies are
reported. We also report the study results relevant to the RHIC electron cloud and pressure rise improvement, such
as the effect of anti-grazing ridges on electron cloud in warm sections, and the effect of pre-pumping in cryogenic
regions.
Monitoring of Interaction-point Parameters Using the Three-dimensional Luminosity Distribution
Measured at PEP-II
B.F. Viaud (Montreal University) W. Kozanecki (CEA) C. O’Grady,
J.M. Thompson, M. Weaver (SLAC)
The 3-D luminosity distribution at the IP of
the SLAC B-Factory is monitored using e +
e − -> e + e-, mu+ mu- events reconstructed
online in the BaBar detector. The transverse
centroid and spatial orientation of the luminosity ellipsoid provide a reliable monitor of IP orbit drifts. The longitudinal
centroid is sensitive to small variations in the average relative RF phase of the beams and provides a detailed
measurement of the phase transient along the bunch train. Relative variations in horizontal luminous size are detectable
at the micron level. The longitudinal luminosity distribution depends on the e± overlap bunch length and
the vertical IP beta-function beta*y. In addition to continuous online monitoring of all the IP parameters above, we
performed detailed studies of their variation along the bunch train to investigate a temporary luminosity degradation.
We also used controlled variations in RF voltage and beam current to extract separate measurements of the e + and
e − bunch lengths. The time-history of the beta*y measurements, collected over a year of routine high-luminosity
operation, are compared with HER & LER phase-advance data periodically recorded in single-bunch mode.
Beam-beam Simulations for a Single Pass SuperB-factory
M.E. Biagini (INFN/LNF) P. Raimondi, J. Seeman (SLAC) D.
Schulte (CERN)
A study of beam-beam collisions for an asymmetric
single pass SuperB-Factory is presented*.
In this scheme an electron and a
positron beam are first stored and damped
in two damping rings, then extracted, compressed and focused to the IP. After collision the two beams are re-injected
in the DR to be damped and extracted for collision again. The explored beam parameters are similar to those used
in the design of the International Linear Collider, except for the beam energies. Very flat beams and round beams