More Faults Found in LHC, But No Further Delay to Start-up

[/caption]In September 2008, the Large Hadron Collider (LHC) suffered a catastrophic quench, triggered by a faulty connection in the electronics connecting two of the supercooled magnets between Sections 3 and 4 of the 27 km-circumference particle accelerator. The “S34-incident” caused tonnes of helium coolant to explosively leak into the LHC tunnel, ripping the heavy electromagnets from their concrete mounts.

Naturally, this was a huge blow for CERN, delaying the first particle collisions by several months. However, the repair work is progressing well, and hopes are high for commencement of LHC science as early as this summer. Now engineers are working hard to avoid a recurrence of the S34 Incident, tracking down similar electrical faults between the accelerator magnets. It seems like they have found many more faults than expected…

According to a recently published progress report, the LHC repairs are progressing as planned, but more electrical faults have been discovered in other sections of the accelerator. An electrical short has been blamed for the quench four months ago, only weeks after the first circulation of protons around the LHC in the beginning of September 2008. It is now of paramount importance to isolate any further potential shorts in the complex experiment. It would appear engineers are doing a good job in tracking them down.

Ribbons of superconducting niobium-titanium wire is used by the LHC to carry thousands of amps of current to the magnets. Connecting the ribbon from electromagnet-to-electromagnet are splices that are soldered in place. Should one of these splices be weakened by poor soldering, an electrical short can occur, making the magnets lose superconductivity, initiating a quench, rapidly heating the sensitive equipment. Various sections are being re-examined and re-soldered. The good news is that this additional work is not compounding the delay any further.

It has been confirmed that there was a lack of solder on the splice joint. Each sector has more than 2500 splices and a single defective splice can now be identified in situ when the sector is cold. Using this method another magnet showing a similar defect has been identified in sector 6-7. This sector will be warmed and the magnet removed. The warm up of this additional sector can be performed in the shadow of the repair to sector 3-4 and will therefore not add any additional delay to the restart schedule. — CERN

Hopefully we’ll see a second circulation of protons this summer, and according to informal rumours from a contact involved in the LHC science, the first particle collisions could start as early as October 2009. I will listen out for any further official confirmation of this information…

Sources: CERN, Nature.com