Cern 16 April 2009 The last repaired dipole for Sector 3-4 has been lowered into the LHC tunnel.

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The last repaired dipole for Sector 3-4 has been lowered into the LHC tunnel.

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The 39th and final repaired dipole magnet was lowered into Sector 3-4 and installed on Thursday 16 April. This is the last of the LHC’s easily recognizable 15-metre-long blue superconducting dipoles required for the 3-4 repair. Only two more Short Straight Sections (SSS) remain to be installed in 3-4.

Since the start of the repair work in Sector 3-4, the Vacuum Group have been cleaning the beam pipes to remove metallic debris and soot created by the short circuit last September. Firstly all 4800 m of the beam pipes in Sector 3-4 were surveyed cm by cm to document the damage before the cleaning work started. The cleaning process involves passing a brush through the pipe to clean the surface mechanically, followed by a vacuum to remove any debris both inside and outside the beam pipe. This procedure is repeated ten times, followed by a final check with an endoscopic camera. So far 68% has been completed.

Work to install the new pressure release ports has now started in the areas outside the arc sections – in particular on the inner triplets (the focusing magnets either side of the collision point). The ports have been slightly modified to fit the geometry of these magnets.

A new test has been developed to measure the electrical resistance of the connection joining the ‘busbars’ of the superconducting magnets together. The busbar consists of a superconducting cable surrounded by a larger copper block known as a ‘stabilizer’. The copper helps to conduct electricity in the event that part of the superconducting cable becomes normally-conducting (for example during a quench). The new test allows the electrical continuity of this copper part to be checked. This provides another important quality control safety check for the electrical connections.