Abstract
The Large Hadron Collider (LHC) at CERN will collide two counter-rotating proton beams, each with an energy of 7 TeV. The energy stored in the superconducting magnet system will exceed 10 GJ, and each beam has a stored energy of 362 MJ which could cause major damage to accelerator equipment in the case of uncontrolled beam loss. Safe operation of the LHC will therefore rely on a complex system for equipment protection. The systems for protection of the superconducting magnets in case of quench must be fully operational before powering the magnets. For safe injection of the 450 GeV beam into the LHC, beam absorbers must be in their correct positions and specific procedures must be applied. Requirements for safe operation throughout the cycle necessitate early detection of failures within the equipment, and active monitoring of the beam with fast and reliable beam instrumentation, mainly beam loss monitors (BLM). When operating with circulating beams, the time constant for beam loss after a failure extends from ≈ms to a few minutes—failures must be detected sufficiently early and transmitted to the beam interlock system that triggers a beam dump. It is essential that the beams are properly extracted on to the dump blocks at the end of a fill and in case of emergency, since the beam dump blocks are the only elements of the LHC that can withstand the impact of the full beam.
Highlights
There are several general requirements for the protection systems: 1. Protect the accelerator equipment: the first priority is to protect equipment from damage, in the Large Hadron Collider (LHC) ring, and during the transfer from the pre-accelerator SPS to the LHC
For the beam loss monitors (BLM) that will be installed in the superconducting part of the LHC, the threshold will be adjusted in order to request a beam dump before the beam loss quenches a magnet
The energy stored in the LHC beams is two orders of magnitude larger than for other colliders, and operating with a stored beam energy of some 100 MJ in the presence of magnets that would quench if some millijoules of energy are released is one of the major challenges
Summary
The motivation to construct the LHC at CERN comes from fundamental questions in particle physics. The search for the Higgs boson and for other particles requires the LHC to provide proton– proton collisions at the centre-of-mass energy of 14 TeV and a luminosity in the order of 1034 cm−2 s−1, a significant challenge for the accelerator. For the LHC, the operation with large stored energy in the beams in the presence of superconducting magnets with a very low quench margin is a particular challenge for the collimation system, which needs to have an unprecedented efficiency [6] To achieve this efficiency, the position of close to 200 collimator jaws needs to be optimized in order to capture particles with large amplitudes that would otherwise be lost around the accelerator. The LHC beams are prepared in the CERN accelerator complex [7], pre-accelerated in the SPS from 26 to 450 GeV and transferred through two lines of about 3 km length to the LHC injection points
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