A little over a year after the highly publicized start-up and break-down of the LHC, the damage has been repaired, new protection systems are in place, and all sectors are cold and ready for beam. Yesterday, the first injection test of 2009 was completed— beams of protons and heavy ions were successfully threaded into the LHC beampipe from its predecessor, the Super Proton Synchrotron (SPS). The beams were allowed to flow as far as the first experiments in both directions, ALICE on the clockwise side, LHCb on the other.
New York City, 1956
Leaning on a Chinese restaurant at a busy street corner in Greenwich Village, I crossed my legs, tipped my hat low, and quietly panicked. This case is turning into a nightmare: dozens of suspects, growing daily, and they all seem to swap places when you’re not looking. A pion couldda done it; pions seem to be some kind of front for the nuclear force that Madame Curie was playing with before she died. But leave a pion to itself and it disintegrates into a muon and a neutrino, neither of which claims to have ever heard of nuclear forces. Radiation in the form of muons and neutrinos has been raining down on us since the beginning of time, and it’s never even hurt. If pions are just glowing with nuclearness, where does the nuclearness go when they die?
For that matter, what is a particle, anyway? I have to admit, I wasn’t suspicious when I first heard the word— I thought they were talking about little rocks or marbles or something. But rocks don’t just change into different kinds of minerals on their own, except for Curie’s rocks, that is. What are these particles? The physicists themselves don’t seem to know: everyone I ask gives a different answer. They seem to be some shadowy energy-clouds, sometimes insubstantial and sometimes infinitely hard. What kind of world are we living in, anyway?
I felt a crumpled slip of paper in my pocket. Pulling it out, I read the well-worn handwriting under my breath, “Seek the Dragon Lady.” I scanned the crowd. I’d bet none of them knew the half of what’s going on, right under their noses! Well, not just their noses, but everywhere in fact. “Any of you folks know a Dragon Lady?”
“Are you looking for Madame Wu?” The young man startled me. From the high-necked sweater and the pipe in the corner of his mouth, I’d reckon he was a student.
Ithaca, NY, 1948
After a wrong turn in Albuquerque, I caught up with Bugs Bunny, alias Richard Feynman, somewhere near the ends of the earth. Up to my elbows in snow-drifts, I spied on the little window to his office, in which he seemed to be doing normal professor-things, plus wild gesticulations. I decided on a particularly frozen morning that I would have to risk visibility if I was to get answers, so I enrolled at Cornell, posing as a G.I. bill student. In Professor Feynman’s introductory physics lectures, I could see that there was something remarkable happening here. People researching physics is about as natural as fish studying water: it’s the very stuff we’re made of. He had a knack of getting down to the ground floor, asking the basic questions, just as much in a block sliding down a plane as in neutrinos.
His teaching assistant, a quirky bow-tied Brit by the name of Freeman Dyson, knew the man personally, so I inquired. “Oh, he’s working on something, yes. The trouble is he just won’t publish, no matter how much I cajole him. He says he’s depressed, but Dick depressed is just a little more cheerful than any other person exuberant. It’s the Bomb, I think, and of course Arlene, his poor wife who died in New Mexico. I probably shouldn’t be telling you this, but Dick and Arlene got married knowing she hadn’t long to live, she having T.B. Bit like Dick to give it a go anyway.”
“What do you suppose he’s up to?”
“Well, he’s got his own private quantum theory for starters. Quantum theory, that’s the theory of the atom and electrons. Until recently, no one’s been able to make it work with Einstein’s relativity; it’s riddled with infinities, you know. Schwinger’s done some remarkable work reconciling the two— all operator theory and renormalization, I’m still trying to understand it. Somehow, there’s a way to replace the infinities with experimental measurements, then the beast is well behaved and gives very nice results. Dick manages calculate the same thing with these funny little pictures, and he puts plus signs between them like they were real mathematical formulae. Quite a ball at conferences: squiggle plus squiggle equals whatever. I mean to pick his brain about it before he flies off to Brazil.”
“Yes, he’s taking a visiting professorship. Says he hates the cold.”
On my way home that evening, I saw a shadow linger on my doorstep, then dart away. I broke into a run to pursue it, but not a trace was left, not even footprints in the snow. With one exception, that is: crinkled under the door and sodden with melt-water was a little envelope. Inside was a note, which read,
“The killer is left-handed.
Los Alamos, 1946
I should have sought Dr. Fermi right away, back when it was easy. When Mademoiselle Curie gave me the lead, Enrico was a quiet university professor in Rome. Since then, he’s got a lot harder to find, and it seems that the professor has government ties— secrets as big as the men who hide them. I chanced upon a tip leading me to a project in Manhattan, and though I found Fermi on the books as a Columbia professor, I had just missed the man himself. Asking an associate about where in the New World this Italian Navigator might be, he turned bright red and insisted that there was absolutely nothing in the basement. Nothing at all.
Sometimes you just get lucky. I asked one of his students to give me a tour of the basement, and was shown a room-sized apparatus for creating artificial radiation. “Artificial radiation?”
“Radiation is just ordinary particles, accelerated to high speeds. Naturally radioactive elements like radium spontaneously break off parts of themselves and shoot them at us, but we can accelerate them on our own with rapidly oscillating electric fields.”
“So this,” I asked, “is a sort of ‘particle-accelerator?'”
“I guess you could call it that.”
I was on the right track! “What do you use it for?”
“Well, Dr. Fermi did a lot of experiments with neutron capture, but by far the most exciting was the splitting of uranium atoms by a neutron beam. He disappeared soon after that.”
So Enrico wasn’t content to let atoms do all of the dirty work— this cat shoots back!
I was called to investigate the recent death of a famous physicist: Marie Curie, born Manya Skłodowska. When I arrived on the scene, she was in her death-bed, her face long and grey, a ghostly shadow in the warm light of the mountain sanatorium. Her daughter Eve was there. “It’s so quiet,” she said, “so fearfully motionless—”
We made our introductions, but she was obviously distracted. “So motionless, those hands. No longer nervously shaking, constantly moving, always working…”
I took a look at the hands, still and limp on the bed. They were hardened, calloused, deeply burned and thick-skinned. “What is this?” I asked myself, but I must have said it out loud because Eve heard me.
“Radium,” she said.
“Those were her last words— ‘Was it done with radium or with mesothorium?’ As she was stirring her tea with a spoon— no, no, not a spoon, but a glass rod or some delicate laboratory instrument… She had drawn away from human beings; she had joined those beloved ‘things’ to which she had devoted her life, and joined them forever.”
A cup of tea and now dead? That didn’t sound good. “Poisoned?” I asked. I never mind stating the obvious.
“Yes, poisoned. By radium. In the laboratory, she always used to say, ‘That polonium has a grudge against me.'”
“Radium— or polonium?”
In a meeting at Chamonix last week, CERN, the LHC collaboration, and the LHC experiments came up with a 2009 schedule. “Second beams” (as opposed to first beams last year) will start a little later than expected: September 2009 instead of July. Then the goal is to have first collisions at the end of October, making the delay due to The Incident almost exactly one year.
Then after that, the good news starts in earnest. Instead of having a long shutdown over the 2009-2010 winter, as CERN usually does, the shutdown will be short, and we continue running and collecting data until we have something close to 200 pb-1 at 10 TeV, which will probably take about a year, until fall of 2010. That’s great, because it’s just enough for some of the basic discoveries: Z’ and W’ above 1 TeV, Higgs -> WW (if the Tevatron doesn’t see it first), the low-mass region of SUSY/mSUGRA parameter space (the “LM#” points), contact interactions in jets, and maybe a very optimistic extra-dimensions model (see my “Early Discoveries at CMS” talk at Dark Matter and the LHC conference). Running at 6 TeV collision energies was considered, and thankfully rejected, as that would be just below the interesting threshold for a lot of this. (The LHC’s design energy is 14 TeV, which is scheduled for 2011.)
At the risk of sounding naive, I think it’s really going to happen this time. The LHC people must know a lot more about the actual behavior of the beams from their real-data test last year, and given how disappointing last year’s setback was, I’m sure they’ll do everything they can to avoid anything like it. In other words, the argument is based on social reasons, not technical ones, but guessing when we’ll have data is a social science.
A few days ago, CERN released pictures from the LHC incident. Here’s one from the DG’s talk. There are a few more, plus a video of the repairs, in their press release. This interconnect between two magnets is normally straight.
If you add up the energy stored in the magnets during the 5 TeV test, it comes to about 6 MJ, of which 4 MJ was dumped into a system designed to absorb energy on a rapid demagnetization. Unfortunately, 2 MJ is the amount of energy a 3-ton SUV has when it crashes at 90 miles per hour. Twenty-nine magnets need actual repairs, which is not too bad of a load for a factory that built over 1,600 in the past 7 years. A lot of the talks about this focus on new preventative measures to identify spots of high resistance (several more have been found, though they were all within specifications, unlike the one that caused the accident) and to absorb more energy in the case of future accidents.
The new start-date for powering tests is the end of June, 2009, with beam again in July (a 10-month delay).
From a personal perspective, though, it turns out that the beam collected last September was exactly enough for the tests I needed to do. (Whew! for me, at least.)
- Confirmation that the cause was an electrical fault, rather than a magnet quench. When temperatures rose, the magnets certainly quenched in response, but the initial cause was “an electrical arc which punctured the helium enclosure, leading to a release of helium into the insulation vacuum of the cryostat.”
- Sentences that begin, “After 0.39 seconds”, “at 0.46 seconds”, and “at 0.86 seconds…”
- At most 5 quadrupole and 24 dipole magnets will need to be repaired, though more may need to be removed to clean off “contamination by a soot-like dust.” There are enough spare magnets and components for all of these repairs. (Whew!)
- In all, 6 tonnes of helium were lost out of the 15 tonnes that were in that sector. The last 4 leaked slowly, before the enclosure could be closed.
Again, I’m not a CERN representative, I’m just very interested in the outcome of this project, as may be some of the readers of this blog.
A few days after the first LHC collisions, I dug into our growing dataset and made an animation from the signals we captured in the CMS detector of muons from LHC beam-halo events. The result looks like a computer simulation, but these are real measurements from the detector, observations from 10:33-10:42 PM Geneva-time on September 11, 2008. In that sense, it’s a live video. During this period, LHC beam #2 circulated for 9 minutes, 6 million times around the ring without getting off track. All the cheering on September 10th was about getting the beam to go once around the ring without getting off track.
The animation can be found at the bottom of the CMS Media page.
Red dots are the signals in the detectors, yellow lines are the best-fit curves through them, representing the path taken by the muons. Notice that the muons are more often vertical when the beam is off (because they’re cosmic rays) and horizontal when the beam is on (because they’re from proton collisions with gas atoms and collimators far upstream in the LHC). The rate also increases dramatically.
After yesterday’s post, the first comment was actually a ping from the Not Even Wrong blog, quoting my paragraph describing the electrical failure in the LHC. Peter Woit used it as an example of a leak (information, not helium) through a CERN policy discouraging the blogging of sensitive information. It is not sensitive information, and it does not go substantially beyond what is given in the press release, which reveals the basic cause of the accident as it’s currently understood and the decision that there must be significant down-time to repair the damage. (And most of that down-time is for re-cooling, not the repairs themselves.)
My description is more colorful than the press release because I am not the official face of CERN. As described in a much-earlier post, I am not even an LHC person, but a member of the CMS collaboration, so for LHC news, I’m an “outsider” who happens to live close to the source. That is what I thought would be valuable about this blog: it would give people who are interested in the development of the LHC (namely, mathematicians who have heard of field theory), the same kind of closeness that the experimenters down the hall have. It is not a conduit for collaboration secrets, and I have been extremely pedantic in what I have revealed. (I started by reading the CMS Constitution, and I have checked everything I say to make sure it’s on a public website somewhere, however obscure. If I’m not sure about the internal-versus-external status of a website, I check it in my iPod, which doesn’t know any of my passwords. Veeery pedantic.)
It is quite reasonable for scientific collaborations to have private information, because they are the kinds of social organizations for whom it would be best for everyone to reveal well-digested information at a late time, but better for an individual, worse for the group, to release exciting information early. We need to control that, with our own good-will preferably, and that’s how it’s currently instituted. The world interest in the LHC, the unprecedented size of the collaborations, and the new existence of blogging introduces a temptation for individual scientists to be self-proclaimed Promethei, and that’s a problem, not a good thing.
To illustrate what I mean with a perhaps not-applicable example, do you remember five to ten years ago when large extra dimensions were a new idea? People first started thinking that maybe the hierarchy problem doesn’t exist, and maybe the Plank scale is actually just a few TeV (those of you who are physicists or part-physicists)? Then someone went one step further and said, “well if so, maybe the new particles we’ll see at the LHC will be black holes.” And physicists thought about that and how they would Hawking-radiate in fascinatingly spherical patterns and how that would be cool, but in the end, not consistent with existing observations. Of course no attempt could or should be made to keep scientific discourse like that secret, but when it left the physicists, it became the headline “LHC to Make Black Holes, Eat Earth (page C-1)” and a frenzy that even lead to a death. Somehow that sort of thing happens to ideas and information, and there is strangely no way to reign it in; no amount of truth mops it up. It is utterly reasonable for the LHC collaboration to want to do an investigation before they let their members speak openly about it.
I don’t want to be responsible for “LHC Explodes, Experts Say (page E-13).” Given what I know as a nearby outsider, the problem is exactly as bad as the press release says it is: a broken electrical connection, a huge helium leak, and possibly some damage to the magnets. The extent cannot be known until it is investigated. Why is it taking so long? I can guess: a helium-rich environment is an oxygen-poor environment, and the moment they switched on the beams, they turned the tunnel into a radiation zone that will need to be mapped before it can be safely traversed.
Of course, I’m also disappointed and nervous, because I have a lot at stake. So do the LHC people. And we all have an interest in carefully-evaluated information; I mean, we’re scientists after all!