Abstracts Brochure - CERN

THPCH047
THPCH048
THPCH049
29-Jun-06 16:00 - 18:00 THPCH — Poster Session
*A. W. Chao, SLAC-PUB 2946, (1982).**L. B. Felsen and N. Marcuvitz, Polytech. Inst. Brooklyn Rept. PIB 705 (1959);
J. Schwinger, J. Appl. Phys. ,22, 806 (1951).
Maps for Electron Clouds: Application to LHC
T. Demma, S. Petracca (U. Sannio) F. Ruggiero, G. Rumolo, F. Zimmermann
(CERN)
400
Electron Cloud studies performed so far were
based on very heavy computer simulations
taking into account photoelectron production,
secondary electron emission, electron
dynamics, and space charge effects providing a very detailed description of the electron cloud evolution. In a recent
paper* it has been shown that, for the typical parameters of RHIC, the bunch-to-bunch evolution of the electron cloud
density can be represented by a cubic map. Simulations based on this map formalism are orders of magnitude faster
than those based on usual codes. In this communication we show that the map formalism is also reliable in the
range of typical LHC parameters, and discuss the dependence of the polynomial map coefficients on the physical
parameters affecting the electron cloud (SEY, chamber dimensions, bunch spacing, bunch charge, etc.).
*U. Iriso and S. Peggs. "Maps for Electron Clouds", Phys. Rev. ST-AB 8, 024403, 2005.
Transverse Coupled Bunch Instability Driven by 792-MHz Cavity HOM in NewSUBARU
Electron Storage Ring
A. Ando, S. Hashimoto, S.H. Hisao, T. Matsubara, Y. Miyahara,
Y. Shoji (NewSUBARU/SPring-8, Laboratory of Advanced Science
and Technology for Industry (LASTI))
The 792-MHz HOM of the RF cavity can drive
horizontal coupled bunch instability in the
NewSUBARU electron storage ring. This instability
is now avoided by tuning the HOM
frequency with an additional tuner (HOM
tuner). Detailed characteristics of this instability were investigated by changing the HOM frequency, betatron tune,
chromaticity and magnitude of the stored current at the energy of 1 GeV. The experiments were performed with 6bunch
equi-space filling to clarify the mode number. Bunch oscillations show saw-tooth patterns when the stored
current is not so large. The measured results are compared with an analytical calculation using a rigid bunch model
and Sacherer’s formalism. The fundamental aspects can be well explained by the calculation, but there exist many
problems that cannot be explained by the rigid bunch model.
Simulation Study of Transverse Coupled-bunch Instabilities due to Electron Cloud in
KEKB LER
In this paper we report simulation results
X.W. Dong, S.-I. Kurokawa, K. Ohmi (KEK)
on the transverse coupled-bunch instabilities
(TCI) at the KEKB Low Energy Ring (LER).
The formation of electron cloud and related transverse coupled-bunch instabilities were investigated based on various
solenoid field models. Studies on electron cloud in Quadrupole which caused TCI are also presented in this paper.