CERN, Geneva
The LHC stored beam contains 362 MJ of energy at the top beam energy of 7 TeV, presenting a significant risk to the components of the machine and the detectors. In response to this threat, a sophisticated system of machine protection has been developed to minimize the danger, and detect potentially dangerous situations. In this paper, the protection of the experiments in the LHC from the machine is considered, focusing on pilot beam strikes on the experiments during injection and on the dynamics of hardware failure with a circulating beam, with detailed time-domain calculations performed for LHC ring power converter failures and magnet quenches. The prospects for further integration of the machine protection and experimental protection systems are considered,along with the risk to near-beam detectors from closed local bumps.
CERN, Geneva
Several forwards detectors have been installed in the LHC long straight sections located on each side of the experimental caverns. Most of these detectors have been designed by the LHC experiments to study the forwards physics while some of them are dedicated to the measurement of the LHC luminosity. The integration and installation of the forwards detectors have required an excellent coordination between the experiments and the different CERN groups involved into the design and installation of the LHC accelerator. In some cases the integration of these detectors has required a modification of the standard beam lines in order to maximise the physics potentiality of the detectors. Finally, additional systems have been installed in the LHC tunnel to ensure the operation of the forwards detectors in a high radiation environment.
UMAN, Manchester
CERN, Geneva
Uppsala University, Uppsala
The CLIC beam delivery system focuses 1.5 TeV electron and positron beams to a nanometre-sized cross section when colliding them at the interaction point (IP). The intense focusing leads to large beam-beam effects, causing the production of beamstrahlung photons, coherent and incoherent electron-positron pairs, as well as a significant disruption of the main beam. The transport of the post-collision beams requires a minimal loss extraction line, with high acceptance for energy deviation and divergence. The current design includes vertical bends close to the IP in order to separate the charged particles with a sign opposite to the main beam into a diagnostic-equipped intermediate dump, whilst transporting the photons and the main beam to the main dump. Photon and charged particle losses on the collimators and dumps result in a complex radiation field and IP background particle fluxes. In this paper, the electromagnetic backgrounds at the IP, which arise from these losses, are calculated, and the potential impact on the detector is discussed.
CERN, Geneva
The TOTEM experiment at the LHC will operate at down to 10 σ from the beam in the forward region of the CMS experiment. The associated beam loss monitors (BLMs) are crucial to monitor the position of the detectors and to provide a rapid identification of abnormal beam conditions for machine protection purposes. In this paper, the response of the TOTEM BLMs is considered and the protection thresholds are defined, with calculations made of the expected signal from protons grazing the TOTEM pot as a function of pot distance from the beam, and of the BLM signal from proton collisions at the CMS beam interaction point.
UMAN, Manchester
STFC/DL/ASTeC, Daresbury, Warrington, Cheshire
The Accelerator Test Facility (ATF2) at KEK aims to experimentally verify the local chromaticity correction scheme to achieve a vertical beam size of 37nm. The facility is a scaled down version of the final focus design proposed for the future linear colliders. In order to achieve this goal, high precision tuning methods are being developed. One of the methods proposed for ATF2 is a novel method known as the ‘rotation matrix’ method. Details of the development and testing of this method, including orthogonality optimisation and simulation methods, are presented.
UMAN, Manchester
The LHC Collimators are designed to remove halo particles such that they do not impinge onto either detectors or other vulnerable regions of the storage ring. However, the very high 7 TeV energy means that their design is critical, as is the modelling of the absorption, scattering and wakefield effects upon the passing bunches. Existing simulations are being performed using Sixtrack and K2. We compare these simulations with results obtained using the MERLIN code, which includes a fuller description of the scattering and wakefield processes.