(per) In mid-September the world’s biggest superconducting magnet coil at CERN near Geneva reached its full field strength: four tesla. Thus the field generated by this ultimate among magnet coils is 100,000 times greater than the Earth’s magnetic field. This was reported by CERN in a press release the week before last.

The magnet weighs 10,000 tons and is six metres in diameter and 13 metres long. It stores 2.5 gigajoules of energy, enough to melt 18 tons of gold. The colossus is part of the Compact Muon Solenoid Detector (CMS) which is used to detect fragments of protons after collisions. Researchers working with ETH Professor Felicitas Pauss from the Institute for Particle Physics are responsible for developing and building the coil in an international collaborative project. The scientists produced the superconducting magnet cable, among other things, during ten years of research work. (1) , (2)

It was a big challenge. The cable for the coil consists of a niobium-titanium alloy and is embedded in ultrapure aluminium to enable it to withstand the current intensity of 20,000 amperes and the extremely low temperature of minus 269 degrees Celsius. Each of the total of 20 cables is 2.5 kilometres long. The construction of the supermagnet was approved in 1996 and began in 1998. It took five years just to wind the cable onto the five modules of the magnet.

The plan is for the CMS Particle Detector, to which the magnet belongs, to begin operating in November 2007. Physicists working at CERN will use it to look for answers to fundamental scientific questions, for example why do particles have mass and what the hitherto unexplored 96 percent of the universe is made of.

A view of the CMS detector inside which the supermagnet is hidden. (Photo: CERN, Geneva)