Eric Prebys/LARP 2/17/2016

 CERN has taken unprecedented steps to control information about this event, including altering the electronic LHC log to remove details.  CERN personnel have been threatened with disciplinary action if they violate these policies.  In the interest of allowing our personnel at CERN to continue to work effectively, I am only including information that has already appeared in a CERN press release or reputable news source (mostly the Times Online*), or information that remains in the LHC logbook. * 2/17/2016 Eric Prebys - All Experimenters' Meeting

Incident in LHC sector 34 Geneva, 20 September During commissioning (without beam) of the final LHC sector (sector 34) at high current for operation at 5 TeV, an incident occurred at mid-day on Friday 19 September resulting in a large helium leak into the tunnel. Preliminary investigations indicate that the most likely cause of the problem was a faulty electrical connection between two magnets, which probably melted at high current leading to mechanical failure. CERN ’s strict safety regulations ensured that at no time was there any risk to people. A full investigation is underway, but it is already clear that the sector will have to be warmed up for repairs to take place. This implies a minimum of two months down time for LHC operation. For the same fault, not uncommon in a normally conducting machine, the repair time would be a matter of days. Further details will be made available as soon as they are known. * 2/17/2016 Eric Prebys - All Experimenters' Meeting

 On Friday, Sept. 19, shortly after 11AM CEDT, a massive quench occurred in sector 34 of the LHC, resulting in  All quench heaters firing  Loss of vacuum  Multiple fire and ODH alarms  The working theory is that a quench occurred in a splice between magnets, which evolved into a massive arc flash.  Over the weekend, fire brigade and key technical personnel entered the tunnel, with the goal of reestablishing power and safety systems and to assess the mechanical integrity of the magnets and stands.  The event caused significant motion of magnets and deformation of magnet stands!!!  As of today, power has been restored, Oxygen levels are safe, and most safety systems are back online.  Preparing for more general accesses to plan for repairs.  This event is completely unrelated to the transformer failure which occurred the previous week. 2/17/2016 Eric Prebys - All Experimenters' Meeting

 CERN is a long way from being able to give an accurate time estimate to resume operation.  Two months would be the absolute minimum to warm up, change a magnet, and cool down.  The scale of the damage will clearly extend that time.  There is no word, as yet, as to the systematic repercussions of the event.  eg, will some sort of protection measures be required to prevent this in the future? 2/17/2016 Eric Prebys - All Experimenters' Meeting