Beyond the God Particle Read Online Free PDF Page A

accidentally and explosively released if the current flow in the magnet were instantaneously disrupted.
    To operate efficiently, the magnets use the principle of superconductivity and must be cooled down to near absolute zero temperature (0° Kelvin, which is 459° Fahrenheit). The magnets are housed inside enormous cryogenic containers, called “cryostats,” which contain the ultra-cold liquid helium. At temperatures approaching absolute zero the special magnet coils, made of copper-clad niobium-titanium cables, become superconducting, and then offer no resistance whatsoever to the flow of electrical current. Without this, the power bill to operate a collider would be unaffordable.
    For the days after the initial beam was circulated, and the Fermilab pajama party on September 10, the accelerator physicists at CERN began to gradually step the machine up to its higher design energy. The precision-engineered coil windings of these magnets must be secure against any tiny movements as the magnetic field becomes stronger. This ultra-strong magneticfield exerts enormous stress on the magnet structure, and the structure must literally contain the force of the field against an explosion. Slight changes in the magnet can create “normal,” or non-superconducting “hot-spots.” These hot-spots could “quench” the magnet, such that it loses its superconductivity, by being driven out of its cold, superconducting state. 10
    In a quench, to prevent an explosion, the enormous electrical current flowing through the magnet coils must be quickly drained out of the system. A “quench protection system” is in place to minimize the effects of any unwanted quench incident. Astonishingly, copper, which is a good conductor of electricity at normal temperatures and is used in the wires of your home, is actually used as an electrical insulator on the superconducting cables, since the current will always flow through the superconductor and not the copper at the low temperatures! If a hot spot quench arises, the current can then be safely carried away through the surrounding copper, minimizing any damage to the system. A quench in any one of the totality of about 5,000 LHC superconducting magnets could disrupt the machine operation for several days with the quench protection system, but would be catastrophic without it.
    Superconducting magnets have to be “trained” to reach higher and higher magnetic fields, as smaller and smaller glitches are relaxed from the coils. The engineers use advanced computer monitoring systems to watch for any possible quenches and induced stresses before they develop into larger problems. The enormous currents that flow within any particular magnet must also pass onto the next magnet. This is done outside of the superconducting environment of the cryostats and requires enormous copper junctions, joined together at face-to-face soldered copper plates. Even these low-tech solder joints are monitored by computers for any changes in temperature during the operation of the system.
    OH, $%&#!
    By September 19, 2008, things had settled back to “business as usual” at CERN. The LHC was being ramped up to full magnetic field strength as the magnets were being trained. Gradually, carefully, and systematically the LHC operators in their Swiss control room, with the precision of watchmakers, pumped more and more electrical current into the massivesuperconducting magnets that steer the beam in its 8-kilometer (5-mile) diameter (that's the same as a 27-kilometer, or 17-mile, circumference ) circle.
    Suddenly… a massive cataclysmic explosion ripped through the tunnel!
    The electrical circuit feeding one magnet to an adjacent one had inexplicably “opened.” Later it would be discovered that the solder joint between external copper plate connectors conducting the electrical current from magnet to magnet had melted. While the monitors had detected some heating in the copper joints, evidently the meltdown of the solder