The latest milestone in commissioning the Large Hadron Collider (LHC), the world’s most powerful particle accelerator and the subject of a major physics project next year, has been achieved after CERN director general Robert Aymar sealed the last interconnect in the world’s largest cryogenic system.

The LHC’s cryogenic system has the unenviable task of cooling up to 36,800 tonnes of materials to a temperature of -271°C – just 1.9°C above absolute zero. To realise this challenging brief, over 10,000 tonnes of liquid nitrogen and 130 tonnes of liquid helium will be deployed through a cryogenic system including over 40,000 leak-tight welds.

This latest landmark signifies the end of a 2 year programme of work to connect all the main dipole and quadrupole magnets in the LHC.

Lyn Evans, LHC project leader, enthused, “This is a huge accomplishment. Now that it is done, we can concentrate on getting the machine cold and ready for physics.”

The LHC machine is a colossal unit stretching 27km and divided into 8 sectors, each of which can be cooled down to its operating temperature of 1.9°C above absolute zero and then powered-up individually. One sector was cooled down, powered and warmed up earlier this year (2007) and served as an imperative learning process for subsequent sector tests. With the complex nature of this technically challenging project however, the transition from construction to operation is a lengthy process.

Aymar explained this after saying, “There is no big red button, and there are inevitably hurdles to be overcome as we bring the LHC into operation. Every part of the system has to be brought on-stream carefully, with each sub-system and component tested and repaired if necessary.”