LHC: forwards and onwards

Following the recent incident in Sector 3-4, which has brought the start-up of the LHC to a halt, the various teams are working hard to establish the cause, evaluate the situation and plan the necessary repairs. The LHC will be started up again in spring 2009 following the winter shutdown for the maintenance of all the CERN installations.

The LHC teams are at work on warming up Sector 3-4 and establishing the cause of the serious incident that occurred on Friday, 19 September. Preliminary investigations suggest that the likely cause of the problem was a faulty electrical connection between two magnets. The connections probably melted, leading to a mechanical failure and a large leak of helium into the tunnel. However, the teams will not be able to carry out a full evaluation and assess the repairs needed until the sector has been warmed up again and inspected. "We are not worried about repairing the magnets as spare parts are available", said Lyn Evans, the LHC Project Leader.

As it will take three weeks to bring the sector to room temperature before repair work can begin, it will not be possible to restart the LHC before the winter maintenance period. The objective is thus to start the machine up again in the spring once the CERN accelerator complex has been recommissioned. "We will bring the maintenance work on the accelerators forward so that we can start up again as quickly as possible in the spring", said Lyn Evans.

The incident occurred when Sector 3-4 was being commissioned for operation at 5 TeV. The LHC commissioning team had taken advantage of a suspension of beam operation to test the magnets at a high current of more than 9000 amps. These essential electrical tests began in June 2007 and all the other sectors passed with flying colours. This was the last circuit of the last sector to be tested, making its failure all the more frustrating.

Although this setback only a week after the spectacular start of operation with beam is a psychological blow, it was by no means beyond the bounds of possibility for a machine as innovative and complex as the LHC. The quality standards that had to be met both during the construction of the magnets and the interconnection work were exceptional, as befitted an exceptional machine. No fewer than 123,000 interconnections were needed for the 27 km circuit, including 65,000 electrical connections with superconducting cables. This complexity has been underlined in the many messages of support that CERN has received.

Following the incident, the Director-General paid tribute to the teams that have worked on the construction, installation and commissioning of the LHC. "The speed of the LHC’s first operation with beam is testimony to years of painstaking preparation and to the skill of the teams involved in building and running CERN’s accelerator complex", he underlined. "I have no doubt that we will overcome this setback with the same degree of rigour and application".