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Earliest LHC Restart Slated For Late Summer 2009
gaijinsr writes "The damage done in what CERN calls the 'S34 Incident' (and what other people call a major explosion in the cryogenics system) is much more serious than originally admitted: The earliest possible restart date is late summer next year, but with some proposed improvements to avoid repetitions of the incident, it looks more like 2010. They kept this pretty quiet up to now, not the kind of information policy I would expect from CERN."
The universe is saved for a couple of more years! Now's the time to form our new national holiday "Beat the Hell out of the Atheist Murderous Universe-destroying Physicists Day".
The world's burning. Moped Jesus spotted on I50. Details at 11.
They kept this pretty quiet up to now, not the kind of information policy I would expect from CERN.
Ummmm, perhaps scientists don't like to make statements that they aren't reasonably sure of? If there were still some disagreement or doubt about this timetable, I would fully expect them to keep it internal, and would be disappointed if they made a public statement prematurely. It's not like this timetable is exactly time critical today or anything...
SIGSEGV caught, terminating
wait... not that kind of sig.
Keep in mind all information coming out of there has to escape the black hole's pull.
If brevity is the soul of wit, then how does one explain Twitter?
I once worked at on the LHC at CERN and still have some contacts there and in a couple of conversations have come across some rather interesting bits of information. The fault has been isolated to a single connector, however the analysis was rather difficult as a large amount of the suspect conductor was vaporized by the current surge. The wires are supposed to carry 8,700-Amps!!! at full power, the intrinsic resistance in this particular bad joint caused some localized heating which then caused a portion of the conductor to no longer be superconducting. all of the current then passed through a sudden, unexpected load and voile, lots of heat, boiling helium and a chain reaction of nastiness. Looks like the pressure discs ruptured as expected, but they were overwhelmed by the sheer amount of boiling Helium, 6-Tons!, and the vacuum vessel buckled and ruptured causing other magnets to quench. the sheer force of the expansions knocked more than 20 of these steering magnets off of their supports. Slightly more problematic then first reports indeed. There was always an expectation of shutting down the beam for the Winter as the cost of electricity for the experiment is a major operational consideration and rises prohibitively for the experiment during peak heating season. Hope that they can fix their problems and catch any other flaws before they attempt to ramp up again. Here's to the exploration of fundamental principles.
The initial cause of the incident was probably a bad weld in a busbar joint. But they'll never know; the entire busbar was vaporized when it lost superconductivity under load.
The quench protection system wasn't designed to properly handle a failure of the superconducting busbar between two magnets. There's an elaborate system to dump the energy from a magnet that's starting to lose superconductivity into a big resistor bank. They expected occasional problems within the magnet windings, but this failure wasn't in a winding. The quench system is being redesigned.
The cryogenic system needs many more pressure relief valves. In this event, 6 tons of liquid helium was vaporized, which is 30,000 cubic meters at 1 atmosphere. That much helium couldn't get out of the existing relief valves fast enough, sizable parts of the plumbing were damaged, and magnets were pushed off their mounts. Now that was just bad pressure-vessel design. They should have had enough relief valves or rupture discs for the worst-case scenario. That would have localized the problem. Given the huge amount of energy in the magnets, in close proximity to liquid helium, in an experimental machine, this could not be a totally unexpected possibility.
More relief valves are going in, which means the whole ring has to be brought up to room temperature and atmospheric pressure for plumbing work. Then the whole commissioning process has to be repeated, which takes months.
The tunnels are empty of people when power is on, because if all that helium vents, the air is unbreathable. But this event was big enough that it could have affected people in experiment halls at tunnel level. If this had happened during actual use, people could have been killed.
A magnet quench isn't supposed to be a big deal. Early design specs said that restarting after a magnet quench should only take a few hours. Oops.
I work on one of the LHC experiments, so I'm posting anonymously.
1) CERN's communication has been lacking. Especially in deleting reports immediately after the incident on their eLog that had been open. That was a black eye on their image.
2) Plans change as more information comes in, so no one should be surprised by initial statements saying "The earliest possible date is several months" (which would be the case if no magnets needed replacing) followed by Spring '09 if everything goes well. This is now followed by Summer '09 to just repair the problems and late '09/ early '10 if remedial actions are taken.
3) CERN is changing directors in a month or so. The new director will make the decision of cautious startup vs. remediation and more aggressive startup. My expectation is the latter.
The world can wait an extra year for these results. I feel bad for the students and post-docs who are waiting for the data to emerge, though.
I've got my crowbar. Bring it on.