CERN, Geneva
Electron cloud build-up is a major limitation for the operation of the SPS with LHC beam above nominal intensity. These beams are envisaged in the frame of the LHC luminosity upgrade and will be available from the new injectors LPSPL and PS2. A series of studies have been conducted in order to identify possible means to suppress electron multipacting by coating the existing SPS vacuum chambers with thin films of amorphous carbon. After a description of the experimental apparatus installed in the SPS, the results of the tests performed with beam in 2008 will be presented.
CERN, Geneva
With the successful circulation of beams in the Large Hadron Collider (LHC), its vacuum system becomes the World’s largest vacuum system under operation. This system is composed of 54 km of UHV vacuum for the two circulating beams and about 50 km of insulation vacuum around the cryogenic magnets and the liquid helium transfer lines. The LHC complex is completed by 7 km of high vacuum transfer lines for the injection of beams from the SPS and their dumping. Over the 54 km of UHV beam vacuum, 48 km are at cryogenic temperature (1.9 K), the remaining 6 km are at ambient temperature and use extensively non-evaporable getter (NEG) coatings, a technology that was born and industrialised at CERN. The cryogenic insulation vacuums, less demanding technically, impress by their size and volume: 50 km and 15000 m3. Once cooled at 1.9 K, the cryopumping allows reaching pressure in the 10-4 Pa range. This paper describes the LHC vacuum system, its behaviour in presence of beams as well as the detailed actions undertaken to recover its integrity after the electrical short which happened in a quadrupole bus-bar on 19th of September 2008.
CERN, Geneva
Beam losses in high-energy particle accelerators are responsible for beam lifetime degradation. In the LHC beam losses will create a shower of particles while interacting with materials from the beam pipes and surroundings, resulting in a partial activation of material in the tunnel. Efforts have been made during the accelerator design to monitor and to reduce the activation induced by beam losses. Traceability for all vacuum components has been established providing a tool to follow-up individually each component or subcomponents installed in the tunnel, regardless of their future destination e.g. recycling or disposal. In the latter case, the history of vacuum components will allow calculating the beam-induced activation and permit comparisons with in-situ and ex-situ measurements. This zoning will also help to reduce collective and individual radiation doses to personnel during interventions. The paper presents the vacuum system layout and describes the LHC vacuum zoning and its implementation using an ORACLE© database.