CERN LHC Project Report 190 (1998),
presented at the Sixth European Particle Accelerator Conference
(EPAC98, session MOP02C), Stockholm, 22-26 June 1998
Numerical Simulations for the Beam-Induced Electron Cloud in the LHC Beam Screen
O. Brüning
June 1998
Abstract:
The following work summarises simulation results obtained at CERN
for the beam-induced electron cloud
and looks at possible cures for the heat load in the LHC beam screen.
The synchrotron radiation in the LHC creates a continuous flow of
photoelectrons. These electrons are accelerated by the electric field of
the bunch and hit the vacuum chamber
on the opposite side of the beam pipe where they create secondary electrons
which are again accelerated by the next bunch.
For a large secondary emission yield the above mechanism leads to an
exponential growth of the electron cloud which is limited by
space charge forces.
The simulations use a two-dimensional mesh
for the space charge calculations and
include the effect of image charges on the vacuum chamber wall.
Depending on the quantum yield for the production of photoelectrons,
the secondary emission yield and the reflectivity,
the heat load can vary from 0.1 W/m to more than 15 W/m.
Keywords: multi-bunch-effects synchrotron-radiation cryogenics
RF-structure beam-losses
F. Ruggiero
28 June 1998