By Michael Schlumpf

"It's really very special when one can actually see the result of years of work," says the ETH employed General Integration Co-ordinator Gérard Faber, standing in the CMS construction hall in Cessy (France). Last week, the European Organisation for Nuclear Research (CERN) celebrated the arrival of the last of five magnet modules. These are components of the Compact Muon Solenoid detector (CMS) (3) , itself a gigantic core component of the new particle accelerator, the Large Hadron Collider (LHC) (4) , due to be set in operation in 2007. Assembly of the magnet will be completed this year and connected to the LHC. First tests will then be conducted in the construction hall.

The superconducting magnetic coil of the CMS detector into which all of the individual tracking devices will be placed.

When LHC becomes operational researchers hope that it will provide them with new knowledge about the very beginnings of the universe. 15 billion years ago the big bang led to the formation of the universe from particles. Protons will collide with one another in the tunnel of the particle accelerator thus imitating conditions that existed roughly a hundredth billionth of a second after the big bang. Rays of protons will cross paths 40 million times per second and researchers estimate that each crossing will lead to 25 proton-proton collisions. The particle detector's job is to track and measure these collisions, as well as new particles that will ensue from each collision. This calls for a enormous computer performance.

Gérard Faber in front of the construction hall in Cessy. In the background the construction site for the new technology building.

"A new technology building is being erected in Cessy to house whole banks of computers, which will be connected to the detector with multiple glass fibre cables," explains Faber with regard to a further aspect of the undertaking. During one second of MS running a data volume equivalent to 10,000 copies of the entire Encyclopaedia Britannica will be processed every second. Researchers hope that this data will provide some fundamental insights into physics. The Institute for Particle Physics at ETH Zurich has also contributed in a great measure to the development and production of various tracking devices.

Gérard Faber explains the construction of the CMS to Ambassador Jürg Streuli, permanent Swiss representative at the UNO in Geneva.

At present, the individual components of the detector are still lying in the construction hall and much remains to be done before the 27 kilometre long LHC is operative. After tests have been carried out in the construction hall the gigantic detector will be dismantled into 15 parts, each weighing up to 2000 tons, and built into the particle accelerator 90 metres below the surface of the ground. "The pieces will be moved around on a system of "air-pads" that raises them about a centimetre into the air so they can be moved about easily," explains Faber. When all elements are ready they will be sunk into the already constructed underground hollow using a large gantry crane and then reassembled. Measuring 21 metres in length and with a diameter of 15 metres the assembled detector will weigh in, unbelievably, at over 12,500 tons.

The CMS detector will come to rest 90 metres below ground in this hall. Individual components will be lowered down through the big hole in the roof.

A superconducting magnetic coil builds the core of the solenoid detector. The coil, with an inner diameter of 6 metres, a length of 12.5 metres and a field strength of 4 tesla, will generate the largest magnetic field ever constructed, approximately 100,000 times the strength of the magnetic field of the Earth. The magnetic coil inside the solenoid will be cooled to 4.2 Kelvin, equal to minus 296 degrees Celsius and thus colder than the temperature of the universe. This enables the magnetic coil to store 2.6 gigajoules, which would suffice to smelt 18 tons of gold. Professor Felicitas Pauss and her colleagues at the ETH Institute for Particle Physics are co-responsible with three other teams of international scientists for the development and construction of the coil.

The running of the detector will devour four megawatts of power. "Unfortunately a lot of heat is wasted that could be used to heat the entireregion," Faber regrets, adding, "I very much hope that we will be able to make use of it sometime in future".

"I find it stimulating to work with people from all over the world," says Faber. He has worked at CERN for over 18 years, and on the CMS integration since 1994. 36 nations, 160 institutions and 2008 scientists and engineers are working at an intensive pace to complete the detector. Interested people around the world are awaiting the results with impatience.