Protecting the world’s largest particle accelerator

When CERN’s Large Hadron Collider is fully operational, it will accelerate countercirculating protons to energies of 7 TeV, the highest particle energy ever achieved by human ingenuity. By macroscopic standards, 7 TeV (10^-6 J) is tiny. But each beam produced at the LHC will ultimately include some 3 × 10¹⁴ protons; should it go awry, it could seriously damage the LHC and the delicate particle detectors that the accelerator hosts. For that reason, as described in a new paper by Robert Appleby and colleagues at CERN, the LHC includes an elaborate safety system that regulates the beams, monitors them, and dumps them out of harm’s way if they go off course. To give an idea of the system’s complexity, the authors note that 17 distinct subsystems must continually give a virtual OK to a central processer, or else the beam will be dumped. In addition to describing the LHC’s safety features, Appleby and colleagues calculate how the beams would respond to various possible accidents—improperly set magnetic fields, for example—and ask if the protection system would respond quickly and accurately enough to avert disaster. Although no system can protect against all failures, the researchers conclude that the accelerator and its associated detectors are as safe as could reasonably be expected. In addition to the simulated studies, scientists are testing the protection system with real 3.5-TeV beams whose intensity is gradually being ramped up. (R. B. Appleby et al., Phys. Rev. ST Accel. Beams 13 , 061002, 2010 http://dx.doi.org/10.1103/PhysRevSTAB.13.061002 .)