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 LHC beam loss monitoring system is a safety critical system and ~ 4000 monitors are installed around the ring in order to prevent the superconducting magnets from quenches and protect the machine components from damage. Two different types of beam loss monitors are used: an ionization chamber (IC) and a secondary emission monitor (SEM). The response functions and expected signals have been simulated using Geant4 as well as FLUKA and have been validated and verified with measurements. The Geant4 model of the beam loss monitors has been tested with protons, gammas, neutrons, muon and mixed field beams for steady state and instantaneous losses. Results from the simulations compared to measurement results will be presented. The expected signals for several events (e.g. direct beam impact on collimators, over-injection, high intensity injection) have been checked against real data being taken during the LHC runtime in 2009 and 2010. The very good performance of the system and the agreement with previous simulations will be shown and 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
IHEP Protvino, Protvino, Moscow Region
Due to rapid progress with the LHC commissioning in 2010 set-up beam intensities were soon surpassed and damage potential reached. One of the key systems for machine protection is the beam loss monitoring (BLM) system. Around 4000 monitors are installed at likely or critical loss locations. Each monitor has 384 associated beam abort thresholds (12 integrated loss durations from 40 us to 83 s for 32 energy intervals). A single integrated loss over threshold on a single monitor aborts the beam. Simulations of deposited energy, critical energy deposition for damage or quench and BLM signal response backed-up by control measurements determined the initial threshold settings. The commissioning and optimization of the BLM system is presented. Test procedures were used to verify the machine protection functionalities and optimize the system parameters. Dedicated beam tests and accidental magnet quenches were used to fine-tune threshold settings. The most significant changes to the BLM system during the 2010 run concerned the injection, the collimation and the beam dump region, where hardware changes and threshold increases became necessary to accommodate for increasing beam intensity.
