Philippe Lebrun is Head of the Accelerator Technology Department at CERN. The engineer, who holds a Master of Science from the California Institute of Technology and a doctorate honoris causa from the Wroclaw University of Technology, has more than thirty years experience in superconducting magnets, cryogenics and particle accelerators.
Newsline: In the IO-DA meeting recently held in Geneva you were asked to give a presentation on CERN and the LHC. This was not just because the meeting happened to take place in Geneva. Indeed there are several similarities between the ITER project and the LHC which I would ask you to sketch.
Lebrun: Although the goals of ITER and the LHC are totally different, the two projects share a number of specifics. Firstly, they rely on the same key technologies which constitute their backbones: advanced superconductors, large high-field superconducting magnets, helium cryogenics, high-vacuum technology, radio-frequency systems and electrical power converters, to name the most salient ones. Secondly, the sheer size and cost of both projects imply a large number of industrial contracts in advanced technology, for which competent and interested companies must be qualified and selected worldwide, products must be industrialized and production lines set up, efficient project management implemented and robust quality assurance enforced. Thirdly, both projects are truly global, stemming from political decisions in most regions of the world and pooling resources and contributions — in different forms — to their financing, staffing, construction and operation. As a consequence, they are unique, highly visible and obliged to succeed.
A new window on nature
Before we continue comparing both projects, could you please summarize in your own words what the LHC is about?
The Large Hadron Collider (LHC) is "simply" the largest research instrument ever built. It is a high-energy particle accelerator, installed in an underground tunnel of 26.7 km circumference near Geneva, Switzerland, which brings into collision intense beams of protons and ions, to probe the structure of matter at the scale of the elementary constituents, at an order of magnitude even finer than the present state-of-the-art. It is therefore a new window on nature, which will help provide answers to basic questions about our universe: where does mass come from? Why are we composed of matter rather than anti-matter? What are the "dark matter"and "dark energy" which constitute most of the universe? Besides the accelerator proper, the LHC program consists of four large particle detectors located in underground caverns around the points where the beams are brought into collision, and a powerful, distributed computing grid to process the high volume of data gathered by the detectors.
ATLAS, the largest of the four particle detectors, claims to have the biggest magnets ever built. Could you please give some bullet points that give us an idea what "big" means? How much energy is stored in ATLAS' magnet system?
ATLAS is 44 m in length, 22 m in diameter, with a mass of 7000 t (i.e. comparable to the Eiffel Tower). It uses four superconducting magnets (one solenoid and three toroids) to generate an analyzing field in the large volume where the tracks of the particles emerging from the collisions are observed and measured. The ATLAS barrel toroid is the largest such magnet in the world: powered at 20,500 A, it produces a field of up to 3.9 T, with a stored energy exceeding 1 GJ. (The total energy stored in the ITER magnet system will be 46 GJ.)
Both, the LHC and ITER are international organizations. How is the LHC built up politically? How many countries participate in the project?
The LHC started as a CERN project, i.e. governed and financed by the twenty European Member States represented in the CERN Council. As the LHC attracted interest and will effectively serve researchers from many regions of the world, the Council decided to negotiate special contributions from the main countries concerned (Canada, India, Japan, Russia and the USA), as well as from the Host States, France and Switzerland. These contributions took different forms — in cash, in kind, or in secondment of expert personnel from national institutes — amounting to about one tenth of the value of the project. In the case of the large detectors, CERN co-finances them only at a level of 20%: the remainder comes from the several hundred institutes in some sixty countries that have signed Memoranda of Understanding to become members of the detector collaborations.
The LHC was thus partly built by in-kind contributions from the members. How are the responsibilities and the rights shared? Is your system similar to the ITER in-kind procurement system?
The in-kind contributions to the LHC were formulated, as much as possible, in terms of deliverables. Still, they represented de facto fixed amounts of resources from the national laboratories and funding agencies. In the fortunately few cases where these fixed amounts proved insufficient to achieve the deliverables, the latter had to be de-scoped. The key to success was to develop a true spirit of collaboration with our partners in the national institutes, who really felt part of the project and fully committed to its success. Getting the most from such in-kind contributions was important for us; it will be essential for ITER, as they represent nine-tenths of the value of the project.
Water in-leaks, manufacturing errors, contract breaching — and a roman villa
How long did it take to build the LHC with its four detectors? What were the major obstacles?
The idea of building a more powerful accelerator in the large tunnel of LEP has been around for many years, but the first conceptual studies of the LHC started in the early 1980s. Structured R&D on the key technologies of high-field superconducting magnets and superfluid helium cryogenics took place from 1990 onwards, leading to technical validation and approval of the project for construction by the CERN Council in 1994. Civil engineering started in 1998, once the authorizations from the Host States were obtained. The main procurement contracts were adjudicated between 1998 and 2001, leading to completion of component deliveries by 2006. Over such a time span, there were evidently a number of obstacles and mishaps to overcome of very different natures, from negotiations with local opponents to reduce the visual impact of the buildings, to water leaking into underground works, manufacturing errors discovered late in series production, insolvency of suppliers and breach of contracts, cost overruns, knock-on effects of delivery delays on sequential installation in a long tunnel with few access points, not to mention the archeological discovery of a roman villa on an excavation site, delaying progress of construction work!
Would you like to say a few words about what the problems are you are facing right now, i.e. what happened and how you hope to solve the problem?
We have been commissioning the technical systems of the LHC throughout the year, each 3.3 km sector after the other. On 10 September 2008, the whole machine was powered at a level corresponding the injection energy (450 GeV), and the first proton beams were injected in both rings, and kept in circulation, testifying to the good quality of the magnetic field and beam vacuum, precise alignment of the accelerator, proper control of powering and beam steering systems. Shortly after this, we were completing the commissioning of the last sector at high current, when an electrical fault in the main dipole circuit provoked an arc, leading to electrical and mechanical damage. We have been investigating the event and drawing conclusions from it, and are now engaged in a repair and consolidation program to be carried out during the planned winter shutdown 2008, so as to restart the LHC in spring 2009. return to Newsline #56