LHC – Take 2

By John Conway | December 9, 2008 12:30 pm

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CERN has issued a press release detailing the extent of the damage from the September 19 incident, the plans for retrofitting the magnets to ensure it does not happen again, and a new schedule. The skinny: the machine should be back up and running in July of next year, resuming the commissioning that was underway when the incident occurred. There are now some impressive photos of the damaged components, showing what tens of megajoules of energy can accomplish in a few seconds.

Six tons of helium was released in the incident, and is presumably gone into outer space now, since at atmospheric temperatures the helium atoms readily attain escape velocity. (Helium is not a renewable resource, per se, though it is continually being produced within the earth from radioactive decay.)

But what caused the incident to begin with? Here is a quote from a talk by Robert Aymar, the outgoing CERN Director General:

On 19 September 2008 morning, the current was being ramped up to 9.3 kA in the main dipole circuit at the nominal rate of 10 A/s, when at a value of 8.7 kA, a resistive zone developed in the electrical bus in the region between dipole C24 and quadrupole Q24. No resistive voltage appeared on the dipoles of the circuit, so that the quench of any magnet can be excluded as initial event. In less than 1s, when the resistive voltage had grown to 1 V and the power converter, unable to maintain the current ramp, tripped off, the energy discharge switch opened, inserting dump resistors in the circuit to produce a fast power abort. In this sequence of events, the quench detection, power converter and energy discharge systems behaved as expected.

Since the interconnect bus subsequently vaporized, it has been difficult to tell exactly what triggered the event. The retrofits to the magnets will improve the quench detection and helium pressure relief systems, but I’ve not heard what, if anything, CERN will do to prevent other interconnects from “developing resistive zones.” Hence the question: will it happen again? It is clear that the new systems will help prevent serious damage to the machine, but there are thousands of these interconnects, so…

Anyway, quite a number of magnets have been removed from the tunnel and are being refurbished and will be reinstalled in the coming months. The experiment I work on, CMS, is in the “open” state now with the end caps pulled back, allowing access to the inner detectors. Our team on the forward pixel detectors plans to remove and reinstall our detectors, making minor electrical and cooling repairs and modifications, starting in February. The photo of the detectors being installed last summer shows the beam pipe, the installation fixtures, and the detector half-cylinder going in, like a ship in a bottle.

Once more, from the top, this time with feeling!

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CATEGORIZED UNDER: News, Science, Technology
  • mandeep gill

    John- thx for the update, and i’m glad to hear CERN is making steady progress on this.. though i have *not* liked at all the secrecy surrounding the whole affair. I know even some of the highest levels of people on the detectors haven’t been accurately given a picture of what happened, and i have also gotten this sense from colleagues at my institution (OSU) as well as personal friends who work at LHC — and this is simply *not* how we in HEP ought handle problems/accidents in our field, i strongly feel. openness and transparency is one of the key hallmarks of what ennobles and uplifts and makes special what we do, vs. in corporations or on the Dark Side (not to mention it’s one of the reasons the Web was *developed* within HEP).

    Yes — it *sucks* that this is such a long delay. it sucks that many peoples’ lives are put on hold for months. sucks that we won’t know anything about BTSM physics for about a half year to a year longer — but does management really have to go around in a ‘press release-y’ manner while not really letting on the extent of the damage? sure, they may not have been certain initially — but it’s clear this was *pretty bad*, and not any individual’s fault (as far as i can see, yet). but CERN funding is quite stable (unlike from the DOE, because of yearly Congressional oversight etc.), so this should help a lot, i do think.

    Most of *all* — i hope that CERN will learn from all this, take it *very* carefully on the next ramp-up, not rush things, even if it might take a few extra weeks — or months — and make *DAMN* sure that such a massive problem does not arise again. many of us (at least i) almost *expected* one of these, from the most complicated and highest energy experiment/collider ever built — but man oh man, it would suck bigtime for *another* one of these at this scale to happen.

    We can just take heart that no one was hurt, and that this is on the ground vs. in space, and a little easier to access. and do the best we can, and then — cross our fingers, and then *pray hard* (even if for some that might only be to the FSM).

    I’m not claiming i know all the issues, details, or right way about this — i’m just expressing some personal feelings about how some of this has been handled, and some of how i know many others also feel about this. other informed input is welcome.

    [NB: i was on Babar, now am in cosmology and don't work on LHC, but have a huge amount of my life energy invested in caring about what comes out of it]

  • http://dorigo.wordpress.com Tommaso

    Hi Mandeep,

    I also was concerned with the “secrecy” surrounding the incident. I suspect the CERN management found out they had invested too much energy into their celebrations of September 10th, and now felt they had to protect their credibility in some way, letting time pass a bit before passing detailed news on the extent of the damage. Also, that was not really well known for a while, because safety issues prevented early surveys.

    That said, I myself did complain about the silence and up-tightness of the CERN management in my blog earlier this fall, precisely for the reasons you mention. We however have to be careful because the LHC is a great tool to make people aware of science and its importance. If we screw things up, the scope of the damage to science is larger than whatever it is by itself, because it will propagate as a nasty message. I can already hear people complaining about the money spent in building the LHC: imagine if it ends up not working!

    Cheers,
    T.

  • graviton383

    Here, Here. I agree with both you guys…if they are not careful & there is another similar screwup after a years delay it could cause irreversible damage to our credibility as a field. This we can’t tolerate as we’re already under fire from manysources…and lots not forget how demoralizing this is, ESPECIALLY to the young people in our field. I heard that CERN rushed LHC turn-on by ~2 months for political reasons.

  • Ras

    My problem was how much of the regular media (and much of CERN press releases) compressed the event as a “helium leak”. If it hadn’t been for Cosmic Variance I wouldn’t have had the correct (and more worrisome) perspective. Although I had presumed that the quench event was in the magnets, in part because I have had some experience in worrying about what happens in that case (in much smaller magnets for that matter). I would have thought that the interconnect bus would have been less of an issue, (and less energy density to dissipate). Clearly more for me to learn about… will there be an open report on the actual causes?

  • http://lablemminglounge.blogspot.com/ Lab Lemming

    For people who mostly interact with helium via party balloons, 6 tons of helium would fill about 7.8 million 8-inch balloons, at standard temperature and pressure.

  • Lawrence Crowell

    There are long term issues with running out of helium! The national helium reserve was set up in the 30′s to keep Nazi Germany from using it in dirigibles, as seen with the Hindenberg. The element should be more tightly regulated IMHO, for low temp physics and super conducting applications are more important.

    L. C.

  • goomba

    This is great news ! Data in 2009! I can see the bubbly flowing into the little styrofoam cups already…

  • http://lablemminglounge.blogspot.com/ Lab Lemming

    How much helium is Yucca Mtn. expected to produce once it gets filled up?

  • Lawrence Crowell

    He from Yucca mountain? I suspect we can expect about as much He as what the ITER will produce :-) Helium balloons are evil. Plastic balloons are a sort of pollution and those silver metal-plastic laminated types get snagged in power lines and cause current arcs and power outs. He is a precious resource needed for research and MRI machines.

    Presumably the He problem and quenching which occurred will not be repeated. Crank ‘er up, see what goes wrong and learn. Maybe we will get some real physics before the decade is out.

    Lawrence B. Crowell

  • Roman

    The report says:
    “Overall, the discharge cross-section will be eventually increased 40-fold, thus allowing to cope with a helium discharge twice as high as that of the 09.19 incident while keeping overpressure within allowed limits.”
    Does this mean that the original discharge cross-section was at least 20-fold under designed?

  • Sili

    the interconnect bus subsequently vaporized

    I <3 Physics – as the kids might say.

    On the subject of Helium – where'll we get it once the wells run dry? Should I ferret away He in my cellar rather than Iridium and Osmium for my old age?

  • Pingback: What 10 Megajoules Worth of Damage To the LHC Looks Like | Bite-Dose

  • http://lablemminglounge.blogspot.com/ Lab Lemming

    “Should I ferret away He in my cellar rather than Iridium and Osmium for my old age?”

    Leave the Os in the cellar, keep the He in the attic.

    As for the waste, 15% of the actinides should eventually end up as He, but for Th you’ll have to wait a while…

  • http://www.mpe.mpg.de/~erwin/ Peter Erwin

    The national helium reserve was set up in the 30’s to keep Nazi Germany from using it in dirigibles, as seen with the Hindenberg

    According to Wikipedia, the National Helium Reserve was set up in 1925 (which is of course before the Nazis came to power). It was created primarily as a source for US airships. The US government later decided not to sell helium to Nazi Germany, forcing the latter to rely on hydrogen for the Hindenburg and other German airships. (The situation, as I understand it, is that private industry wasn’t willing to go into the helium extraction business, so the US government decided to set up an entity to promote it.)

  • Pingback: Vídeo e imágenes de las reparaciones en el LHC. |

  • Gregg Weber

    If helium is released into space above escape volocity should there not be a plume of helium spiraling away from the earth at about CERNs latitude and declination? If that were so could it be detected shortly after the release event by people doing spectroscope work on stars so that those reading would produce absorption bands. This would prove the existance of such escaping helium and also corupt measurments of the helium in the stars atmosphere.

  • Markk

    “If helium is released into space above escape volocity should there not be a plume of helium spiraling away from the earth at about CERNs latitude and declination?”

    No helium was released into space at any velocity. What the comments about helium being above escape velocity are implying is this – the distribution of speeds of a helium atoms (molecules – they are the same) in Earth’s atmosphere has a significant portion of the distribution curve at speeds above escape velocity. So when the helium from LHC diffuses through the whole atmosphere, and some of the atoms get to the top parts of the atmosphere a hundred kilometers up, they will escape at a higher rate than all the other gasses in the atmosphere, which are also escaping, but at a lower rate since they are heavier molecules and thus going slower.

    This takes a long time – decades, centuries, millenia plus.

  • Pingback: Photos Show What 10 Megajoules Worth of Damage To the LHC Looks Like [Large Hadron Collider] | The-Informer

  • Pingback: LHC 2009 Restart | Cosmic Variance | Discover Magazine

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