CERN took delivery of the last superconducting main magnet for the Large Hadron Collider (LHC) on 27 November. This completes the full set of 1624 main magnets required to build the world's largest and most powerful particle accelerator.
Constructing this gigantic scientific machine is a technological and logistical challenge for CERN and its industrial partners. The LHC accelerator was initially conceived 22 years ago and approved for build 10 years later. Its realisation involved more than 200 manufacturers around the world, producing vast quantities of complex components to tight precision.
The LHC is located inside a circular underground tunnel of 27km circumference approximately 100 metres beneath Switzerland and France. When fully operational, it will reach seven times more energy than the most powerful particle accelerator currently in use. Scientists will use the LHC to recreate the conditions just after the Big Bang, by colliding two beams of protons travelling in opposite directions at close to the speed of light.
Thousands of magnets of different varieties and sizes will be used to navigate the beams of particles around the accelerator. These include the superconducting main magnets, of which 1232 ‘dipole' magnets of 15 metre lengths are used to guide the beams, and 392 ‘quadrupole' magnets of 5 to 7 metre lengths are used to focus the beams.
"The present achievement is an essential milestone. The successful completion of all main magnets for the LHC accelerator results from the dedication and efficient collaboration of teams from CERN, other laboratories and many European industries. This is a promising step towards achieving the three pillars of the LHC – the accelerator, experiments, and computing – and the ultimate goal of scientific discoveries," summarised CERN's Director General Robert Aymar.
Turning a scientific plan on paper into reality is an immensely complex task. The design of the magnets presented one of the most important technological challenges for the LHC. A high magnetic field is required to bend the path of the particle beam around the accelerator. To achieve this, the magnets must perform at the most efficient ‘superconducting' state without loss of energy, which requires chilling to a temperature of -271°C throughout the LHC's operation – this is even colder than outer space!
CERN led the design and production processes of the dipole magnets, assembled by three European partners: Babcock Noell GmbH (Germany), Alstom MSA-Jeumont (a French consortium), and Ansaldo Superconduttori (Italy). "We introduced new techniques that were not yet standard in industry, including a new welding method for special stainless steel. We worked closely with industrial partners to adapt state of the art technologies for large-scale productions, while maintaining stringent standards and economic efficiency," said Lucio Rossi, head of the Magnets, Cryostats and Superconductors group at CERN. Lyn Evans, LHC project leader, added, "This is the end of more than six years of industrial production under very tight quality control. It has required a very close collaboration between the magnet manufacturers and CERN." The quadrupole main magnets were designed by CEA-DAPNIA laboratory (France), within the framework of the French special contribution to the LHC, and assembled by ACCEL Instruments (Germany) with similar challenges.
CERN's industrial partners have also benefited from the project to build the LHC. The processes of research and development, coupled with the knowledge transfer from expertise only found in a world-class particle physics laboratory, have resulted in innovations they can reapply to other products in industry, from magnetic resonance imaging (MRI) machines to car manufacturing.
Assembly processes to complete the LHC are expected to finish by mid-2007, in preparation for the start-up in November 2007. The LHC will be central to the next generation of experiments at CERN, enabling scientific investigations that have never been possible before. A new frontier of knowledge will shed light on the unresolved questions of science, such as the search for the elusive Higgs boson to explain the origin of particle mass, investigating the make up of dark matter, and the existence of extra dimensions of space.
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