Last magnet goes underground

On 26 April, the last superconducting magnet for the LHC was lowered into the accelerator tunnel.

The final precipitous descent, as the last of the LHC's 1746 magnets is lowered into the LHC tunnel, marking the culmination of two years' work.

Not many of the guests at the ceremony on 26 April would have been well-versed in the subtleties of the Welsh language, but they all intuitively understood the inscription on the banner draped across the top of the PM12 shaft. Since 7 March 2005, this well-known banner has borne the inscription 'Magned cyntaf yr LHC' (first magnet for the LHC), in honour of the LHC's (Welsh) Project Leader, Lyn Evans; now the inscription has been changed to 'Magned olaf yr LHC' (last magnet for the LHC). And so, on Thursday 26 April 2007, the last magnet, a 15-metre-long, 34-tonne superconducting dipole bearing the number 2401, was lowered into the LHC tunnel to the applause of the hundreds of guests attending this final lowering ceremony. The PM12 shaft was sunk for the express purpose of lowering these colossal superconductors into the tunnel and has seen 1232 dipoles pass its threshold over the last two years, 1746 magnets in total.

AT Department's Vacuum Group Leader Pierre Strubin, TS Department's Installation Coordination Group Leader Claude Hauviller, LHC Project Leader Lyn Evans, and CERN Director-General Robert Aymar, each took their turn at the microphone, underlining the vast quantities of components assembled, transported and installed over the past months. Before commencing their journey underground, the magnets were fitted with beam screens and underwent final tests and welds in the SM12 hall, which tops the PM12 shaft. '45 kilometres of beam screens and 65,000 components were processed in this building,' Pierre Strubin said. 'It was a real hive of activity, with 40 people going about their business from 7 in the morning until 8 in the evening.'

The lowering operation was a massive challenge also due to the quantity, size and fragility of the items to be transported, not to mention the very tight deadlines. 'The teams worked 24/7, installing up to 35 magnets per week, a feat which everybody, including me, considered impossible,' said Claude Hauviller. It took nearly 10,000 truck journeys to transport the magnets from the various locations where they were stored in France and Switzerland. Hauviller adds: 'some 40,000 km were travelled in total, roughly the circumference of the Earth - at 10 kilometres per hour!' Once underground, another 30,000 kilometres were travelled, at just 2 kph. All the speakers paid tribute to the commitment of the teams and the assistance provided by the local authorities in what was a truly Herculean task.

Magnet No. 2401 was duly slotted into its final position in the UJ22 cavern, where the TI2 transfer tunnel links up with the LHC.

The last magnet before its descent into the tunnel, and the as-yet unmodified banner. Left, Claude Hauviller, Head of the TS Department's Installation Coordination Group, addresses the guests who attended the event.