CERN, Geneva
The unprecedented design intensities of the LHC require several important advances in beam collimation. With its more than 100 collimators, acting on various planes and beams, the LHC collimation system is the biggest and most performing such system ever designed and constructed. The solution for LHC collimation is explained, the technical components are introduced and the initial performance is presented. Residual beam leakage from the system is analyzed and compared to simulations. It is shown that the observed leakage is in agreement with prior predictions. Measurements are presented which show that collimation efficiencies of better than 99.98 % have been measured with the 3.5 TeV proton beams of the LHC.
CERN, Geneva
The LHC has two dedicated cleaning insertions: IR3 for momentum cleaning and IR7 for betatron cleaning. During the first months of beam experience the presently installed Phase-I system performed as predicted earlier in detailed studies with tracking simulations. As the current system is not sufficient to allow LHC operation with nominal or ultimate intensity at 7TeV/c, simulations with an upgraded system are ongoing to overcome these limitations. In this contribution a collimation scheme with combined momentum and betatron cleaning in IR3 with additional collimators in the IR3 dispersion suppressor is presented. The predicted improvements compared to the Phase-I system and the limitations of this scheme are discussed.
CERN, Geneva
A single-sided mobile diluter (TCDQ) and a horizontal secondary collimator(TCSG) are installed in the extraction region of the LHC to protect the downstream elements from damage in case of asynchronous beam dump. These collimators have to be precisely setup to shield the arc aperture at 450 GeV, the triplet apertures and the tungsten tertiary collimators (TCT) at the low-beta collision points. During the LHC beam commissioning, several machine protection tests were carried out to validate collimator setup and hierarchy at different beam energies and intensities. The outcomes of these measurements are presented in this paper together with the results of particle tracking simulations for asynchronous beam dump. These studies allowed to quantify the leakage expected from dump protection collimators to the downstream elements, and to validate the system performance towards higher beam intensity.
CERN, Geneva
The LHC transfer lines, injection and beam dump systems are equipped with a series of active and passive protection systems. These are designed to prevent as many failures as possible, for example through surveillance and interlocking, or to absorb any beam which is mis-kicked or mis-steered on passive absorbers. The commissioning, validation tests and performance of the different systems are described, and the implications for the protection of the LHC against different failures during beam transfer are discussed.
CERN, Geneva
The collimation system of the CERN Large Hadron Collider (LHC) was built to handled 360 MJ stored in the LHC beams and is one of the most advanced cleaning system built for accelerators. It consist of 88 ring collimators of various designs and materials, for a total of 352 degrees of freedom (4 motors per collimators), that provide a multi-stage cleaning of beam halo as well as a crucial role for the LHC machine protection. Collimator can be moved with functions of time to guarantee the optimum settings during energy ramp and betatron squeeze. The system has been commissioned with beam for the 3.5 TeV LHC run and has ensured a safe operation, providing a close to nominal cleaning performance in the initial LHC operational phases. In this paper, the setup procedure and the setting validation techniques are presented, the operational aspects and challenges are reviewed and the system performance is discussed.