But while we were waiting for the cryogenics to recover [after the transformer failure], we were commissioning the very last sector, the sector 34. We’d already taken seven sectors up to 5.5 TeV, which we considered to be good for 5 TeV operation. And on the last sector, I think you know very well, we were ramping between 5 and 5.5 TeV, and we had a fault. The first manifestation was a massive quench, but the massive quench was quite normal, because the incident, which I will explain in a moment, provoked the quench protection system to fire the quench heaters in about a hundred magnets, and they all quenched and it behaved perfectly, I think it was a perfect test of our quench protection — if unsolicited, a perfect test of our quench protection system. And there there is no problem at all. I think the fact that the system behaved as it should and the magnets quenched, that would not have been a problem. The problem is the incident that caused it all was an electrical fault, which caused a penetration of the helium vessel, so helium went from the liquid into the vacuum of the cryostat, and from there through the quench relief valves into the tunnel. And we’ve now analyzed all the signals, and we know to within one magnet where the fault was. It’s got to be a big fault. I think at this level of current, there shouldn’t be any problem at all. There’s got to be a big electrical fault. We think that it’s in the busbar, in the busbar splice, but we cannot be sure until we open up and examine. So the consequence was the discharge of helium from the magnet into the insulation vacuum, and from there into the tunnel, which is where the big discharge of helium into the tunnel comes from. Now we are warming up the sector, I think the magnet which is at fault, or the busbar of that magnet which is at fault of course, we will open it up and examine it. There is collateral damage for sure, I think that high presure into the — like that, is certainly provoked some other damage which we will have to fix. Warming up will take at least three weeks, and then of course the repair we don’t know how long it will take, but I think it doesn’t need a rocket scientist to realize that this will take us into the winter shutdown, I mean into December, and one thing we cannot do is to run through the winter, I think, for many reasons. For basically as the DG [Director General of CERN] announced yesterday, we are certainly down until early Spring. So what we are doing now, apart from gearing up to make whatever repair is necessary, is to try to readjust the schedule of the maintenance of the machine, not the LHC but the injector chain, in order to get them up as early as possible next year, because up until this accident, we would only have come up in June of next year to start the LHC. So we want to come up as early as we possibly can, and this has now got to be reorganized, that we shut down the injectors, we perform the maintenance that we would have performed from January to March, we bring it much forward. So I think that’s about all I can say for now. I’m certainly willing to answer questions.
[...]
2008-10-03 | achtphasen | 01:04:02 | 
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2008-10-05 | 19:21 
