Besides the meltdown in the financial markets, perhaps of more concern to physicists is a meltdown at CERN, specifically in the connection between two magnets during powering tests being conducted at 11:17 last Friday the 19th. Here’s the daily report from that day on the LHC beam commissioning site. By the next day it had become clear that it would be necessary to warm back up the sector to deal with the problem, leading to this press release. It was immediately clear that doing this would take at least a couple months, and make it impossible to have physics collisions at the LHC this fall. Today, a new press release confirms this:
The time necessary for the investigation and repairs precludes a restart before CERN’s obligatory winter maintenance period, bringing the date for restart of the accelerator complex to early spring 2009. LHC beams will then follow.
The press releases refer only to a “large helium leak” and the failure of an electrical connection, making the problem sound rather minor. I tried contacting a physicist at CERN to find out if they had any more information, but was told that he or she was under instructions not to discuss anything about what had happened beyond what was in the press releases, and that CERN was specifically concerned that information might show up in blogs. This policy seems to be being unevenly enforced, since today the Everything Blog carries the following report:
I was in a meeting at CERN when someone ran to the front of the room with a computer, then after letting the speaker finish and setting up the computer to project the press release/e-mail (agonizing moments: it was a Mac), they let us know. I was worried that the sector with the helium explosion had collapsed like an old mine— there were rumors going around that this is a weak point in the tunnel. (Of course there would be such rumors.)
I have learned a few more graphic details about the event in the last few days. First off, it was two tonnes of helium, not one. But I’ve also learned that this was a more explosive and dramatic event than I had imagined— helium is fortunately an inert gas, but the temperature gradient caused it to explode violently, probably causing physical damage to the nearby components. And now that section of the LHC is an ice tunnel, maybe with stalagtites hanging down and a Yeti moaning in the distance.
Up until now, the policy at the LHC has been to be quite open about the commissioning process, with detailed technical information provided on web-sites that were freely accessible. For instance, there’s detailed news about how beam commissioning was going up until the accident available here. Going forward, it will be interesting to see how CERN deals with the problem of letting not-so-good news out to the public. Just about one year ago, I wrote about some earlier LHC problems, and it has always worried me a bit that having a huge LHC publicity onslaught before the machine was actually ready and working might not have been a good idea. Going through the often painful process of solving the problems likely to show up in a project of this scale may provide a different education of the public than the one people were hoping for.
Update: Yesterday there was a LHCC meeting at CERN, broken up into an open and closed session. The slides from the talks are available here, and give a wealth of information about the state of the machine and detectors, and what they were able to accomplish during the short period that they had a beam. There’s no info about the accident in the slides, but video of the talks is here, and at the end of the talk by Lyn Evans (9-18min into the video) he gave a report on the accident and answered questions. The problem has been traced to an electrical fault in the magnet busbar, and bizarrely occurred during the test of the last circuit of the last sector that was being commissioned for 5 TeV operation.
Evans says that the machine will be down until “early spring”. Before the accident, the plan had been to bring the LHC back up in early June, after various work needed on the injection system. The current plan is to try and get this work done instead this fall, so that they can start up more quickly in the spring.
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