LHC Status Lyndon R. Evans LHC 2003 / 4th International Symposium on LHC: Physics and detectors FNAL, 1-3 May 2003. Civil Engineering at Point 1. Civil Engineering at Point 5. Civil Engineering. All excavation finished. Caverns will be delivered on schedule:
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Lyndon R. Evans
LHC 2003 / 4th International Symposium on LHC: Physics and detectors
FNAL, 1-3 May 2003
Civil Engineering at Point 1
Civil Engineering at Point 5
Electrons, from synchrotron radiation or ionisation, can be accelerated in the potential well of the bunches, creating secondaries on impact with the beam screen.
For 25 nsec bunch separation, this can result in an exponential build-up and is a source of heat input into the cryogenic system.
Electron bombardment has a “scrubbing” effect, reducing the SEY and increasing the threshold. This has clearly been observed in the SPS.
Simulations (Zimmermann et al.) now predict many features that can be verified experimentally.
In the warm regions, the chamber will be coated with a new getter materail, TiZrV (Benvenuti) that activates at much lower temperature (200° C) than conventional getters.
Once activated, the SEY is low enough to avoid e-cloud build-up.