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I love my LHC
April 25, 2009 6:13 AM   Subscribe

Episode 4 - Problems "Okay, sometimes I almost want to give up everything." A fascinating insight into the Large Hadron Collider (loving the soundtracks too). YTL
posted by tellurian (22 comments total) 22 users marked this as a favorite

Previously on metafilter projects.

'tis very cool.

I haven't had a chance to catch up, but the graphics on the table in the first episode were a nice touch.
posted by pharm at 6:40 AM on April 25, 2009

wow. A series of films about physics that manages to get me teary-eyed...

I also love the little animations. That simple style way better than flashy 3D graphics.
posted by kolophon at 7:01 AM on April 25, 2009

"is" better, that is.

But it was asked by FissionChips on projects, why is there still no rss-feed? I want to follow this, but subscribing by email is a no-no.
posted by kolophon at 7:31 AM on April 25, 2009

I didn't realize that the LHC exploded. It's funny listening to them try to avoid that word- "huge volume ratio from liquid to gas.."
posted by bhnyc at 8:00 AM on April 25, 2009

Love the animation.
posted by lithiummind at 8:18 AM on April 25, 2009

the addition of the chopin nocturne is a nice touch, compared with the first episode. perhaps the episode's content – unexplained, catastrophic mechanical failure – was too depressing to get through without it.
[brief pause]
I know that's why I commute to it .
posted by kickback at 8:35 AM on April 25, 2009

Well, I dunno. I think I've heard of this thing before, and it sounds pretty dangerous to me.
posted by washburn at 8:51 AM on April 25, 2009

Another perspective on the LHC and the search for the Higgs Boson is presented in the really great PBS film The Atom Smashers which follows a team of Physicists working on the Tevatron at Fermilab.
posted by basicchannel at 9:08 AM on April 25, 2009

It's funny listening to them try to avoid that word- "huge volume ratio from liquid to gas.."

Yes. CERN acted *very* strangely after this accident. Everyone involved in high energy physics knows that this stuff is hard. After Fermilab upgraded the Tevatron complex with the Main Injector and Recycler rings, they expected to quickly see higher luminosities*. Instead, it took years for the complex to regain the luminosities they had before the upgrade, and by that time, they had become so adept at creating antiprotons that the recycler ring -- built to capture, cool and reinject antiprotons** into the collider -- never was used as a recycler. Instead, it's now just a larger antiproton storage ring.

After all of that, in the last two years, the Tevatron has been running amazingly well. But it took a great deal of time to get it running that well. Run I of the TeV was from 1983 to 1995, Run 11 started in 1999, and continues today.

Superconducting colliders have several steps. First is orbits -- getting everything settled so that beam actually makes it around. First Orbit is much like First Light on a telescope -- hey, it's on, but we've got a lot of work to do before science happens. You have two first orbits on a collider, one for each direction on the ring. IIRC, the LHC made full clockwise orbits, but the first attempts at counterclockwise was when the accident happened.

Second is protection. Superconducting magnets are touchy, and if something goes wrong, they "quench" and stop superconducting. This is a big, big problem. The amount of current flowing through these magnets is huge -- several thousands amps -- and if the magnet becomes resistive, that energy has to be moved elsewhere or it will destroy the magnet. Quench protection is a combination of two things -- the first is a heating system to make the *whole* magnet normal, not just one part, to buy you time for the second step, which is a bypass around the magnet to dump the energy. *** Also part of this is getting things settled so that the magnets don't quench often.

Third is tuning. You have a system that can orbit beams, and the magnets are working. Now, you work on focusing the beams, and bringing them to collision. In the case of the TeV, another big part of this was creating the pbars they need for the collisions. The LHC deliberately chose to be a proton-proton collider because of the difficulty of creating the number of antiprotons.

All of this takes years. The TeV is a mature accelerator, and it shows -- they're getting more integrated luminosity in a week than the complex achieved in the first two years of operations.

The LHC is a very new machine. Indeed, it still hasn't captured the power record -- it will be the most powerful collider in the world, but the orbits they were making for initial tests were at about 400GeV, rather than the 990GeV the Tevatron makes.****

It will become the most powerful machine, and it'll see much farther into Terascale energies than the TeV can. But it's going to be a few years before it's running well. These are big, tricky beasts with no tolerance for imprecision, and every time we make them bigger -- the Main Ring to LEP to TeV to LHC to Advanced LHC to whatever, we're going to find new things -- but first we're going to find new, clever and fascinating ways for very expensive machines to fail very dramatically.

* Luminosity: Measure of particle interactions.

** I keep wanting to write pbars here, that being the term in the trade. Antiparticles are represented by the symbol for the normal particle with a bar over is, the symbol for a proton is "p", thus, "p-bar". Antielectrons aren't ebars, though, they picked up a cooler name early on, the positron. Issac Asimov read about this when he was writing a robot story, thus, the positronic brain.

*** This is what broke the LHC. The core problem is the bypass circuits protected the magnets, but not the interconnections between magnet strings. That's believed to be the part that failed, and when it did, it failed dramatically, and then the massive induction in the ring insisted that the current keep flowing, despite the missing conductor. That caused a massive energy dump into the liquid helium cooling the magnets, which boiled off. That exposed the other problem -- the vents on the magnets weren't big enough for this scale of a quench, the pressure rise was too quick, and the cryostats failed from the pressure. That was the event that caused the biggest damaged.

Fixing the bypass issue isn't hard. Fixing the vent issue is -- it's "rebuild every cryostat in the ring." Also, they found a significant issue, all that helium displaced the oxygen in a far larger area than they ever thought it would, leading to a serious rethink of safety precautions and what areas can and cannot be inhabited when the machine is running.

**** The TeV isn't lying, it does make over 1TeV when it operated in fixed target mode. And note that in collider mode, there are two beams, in opposite directions, so they hit with 1.98TeV.
posted by eriko at 9:11 AM on April 25, 2009 [18 favorites]

I realized I digress right off the point I wanted to make. The "acting strangely" part was the secrecy after the accident. Everyone knows how hard this is, and failures happen. The normal mode is to let everyone help find out why, not only to help you get the machine online faster, but so that everyone else can make sure it doesn't happen on other machines.

CERN went very quiet after this, rather than making phone calls to the other big labs to ask for help. It's still not clear why they did so.
posted by eriko at 9:13 AM on April 25, 2009 [1 favorite]


This restores my faith in the internet.

Thank you!
posted by vertigo25 at 10:49 AM on April 25, 2009

eriko -- I think they're not being very open about it because there's a lot of FUD, and they fear losing support over this. LHC is largely funded by governments the world over (including the US's Departments of Defense and Energy) -- if the public decides to cave into all of this ridiculous fear mongering, it could jeopardize their funding.

In any case, these are fantastic videos -- the overall production is excellent and engrossing. It makes me miss working in particle physics.
posted by spiderskull at 11:44 AM on April 25, 2009

pĖ… can be entered by using the combining character U+0305, FYI.
posted by Rhomboid at 3:19 PM on April 25, 2009 [1 favorite]

Thanks for posting these excellent videos, I'd have never expected a documentary about particle physics to stir me quite so much. It's thrilling watching people doing and talking about what they love.
posted by teem at 7:42 PM on April 25, 2009

The whole series is pretty good - Thanks for posting this, tellurian!
posted by carter at 7:54 PM on April 25, 2009

Just adding that this is indeed really great.
posted by Alex404 at 10:19 PM on April 25, 2009


The science is so new, they haven't even invented an international pictorial warning symbol for it, yet.
posted by steef at 6:43 AM on April 26, 2009

Thanks Tellurian, excellent.
And congrats, gravelshoes, great moviemaking.
posted by bru at 6:54 AM on April 26, 2009

Oh and thanks eriko: your very clear explanations made me watch the video.
posted by bru at 6:55 AM on April 26, 2009

Thanks for all the comments - it can be difficult to gauge reaction on a project like this and it's great to hear you're enjoying it.

That's a great explanation of the incident Eriko, and I agree with spiderskull's reason for the big silence from the LHC afterwards. The only way these giant experiments can happen is through fantastically expensive international collaborations which rely a lot on public support of their tax money being used to pay for them. CERN stirred up a media frenzy with the turn on, and the breakdown was incredibly embarrassing for them after such a blast of publicity. Thankfully there doesn't seem to have been any serious media backlash so far. I'm less clear on their decision not to contact other labs - perhaps they feel they have all the expertise they need, or perhaps it is something more political. Relations with the Tevatron do seem to have become somewhat strained recently.

I'm sorry about the lack of rss - it was on my to do list but got lost somewhere along the way. Will get on it!
posted by gravelshoes at 3:08 PM on April 26, 2009

Thanks gravelshoes, we really do need it :)

When you do have the RSS ready, please post here AND in the Projects post.
posted by intermod at 9:32 PM on April 26, 2009

Just finished watching the 4 episodes. This is a beautiful, thought provoking documentary. I hope that at some point it gets packaged as a full length (say, an hour) documentary and enters the regular distribution channels, e.g. PBS in the US, so tht many more people see it. The analogies employed to explain what particle physics research is are truly wonderful.

Or maybe I'm just a sucker for melancholic piano soundtracks.
posted by intermod at 5:20 AM on April 27, 2009

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