I’m here today to talk about flooring. The kind people walk on. I’ve seen a lot of floors in my time, from the linoleum tile my dear old mother installed all by herself in our humble kitchen when I was a wee lad, all the way to the 2000-year old tile floor in the Vatican Museum that supports millions of visiting feet per year with nary a scratch … after being transported thousands of miles by slaves and horses, that is! I’ve walked on a lot of floors throughout the entire world, and I can say with absolute honesty that every single one of ‘em has succeeded in supporting my weight; that every last one of ‘em has remained flat and avoided caving in under my feet, thanks to the laws of gravity, strong building materials, and good workmanship. Because I say that the only thing you would ever ask a floor to do is, well, nothing at all! You would ask that floor to stay flat and motionless, and to bear your weight across it, repeatedly, for years on end. You would never ask that floor to cave in under your feet; to crumble pathetically under the weight of a hundred kilo or so; to turn to rubble in the course of nominal daily usage. That’s why floor-makers get paid; I’ll go so far as to venture that’s the only reason they get paid. I claim that the only thing required of a floor is not to cave in. Well, if you’re in agreement with that statement, then you’ll agree that the upper floor of CERN’s Restaurant 2 has utterly, abjectly failed in its incredibly simple mission. This is truly the first floor I have ever encountered that has been unable to bear the strain of human feet, and the failure of it and its builders fills me with a deep-seated disgust and enduring concern.

Sorry about all the silence the last couple weeks.  These days our day jobs are getting pretty busy.

Beam dump at Point 6

After the question “what is 7 TeV?” came up in the comments on our imminent collisions post I though it would be fun to take a tour of some common quantities in energy physics. All of this appears in other sources such as “LHC: The Guide” (2008) and, many talks such as “LHC Status and Commission Plans”.

First of all, let’s stay humble. The size of the LHC and its experiments are often enumerated for dramatic effect with numbers like

• 27 km in circumference,
• 100 m underground,
• 8 stories high,
• 12,500 tons, etc.

But all this huge equipment is just support for the diminutive stars:

• bunches of 10¹¹ protons,
• each 7 cm long and 1 mm in diameter (about the size of a mechanical pencil lead).

That really isn’t much stuff considering that macroscopic things contain around 10²³ atoms. At rest this bunch of protons is just 1.6×10^-13 g of matter. Given this tiny mass and the pencil-lead dimensions you end up with a density of roughly 4×10^-7 g/m³, which is absolutely nothing considering that hydrogen gas is  200 million times denser at 90 g/m³ (the LHC can run for many months using the protons from one bottle of hydrogen gas). To increase the odds that these protons run into each other the bunches are focused to a diameter of about 16 μm just before they cross. Still, collisions are rare, with everything running well there will be at best 20 interactions per crossing (and only a tiny fraction of these interactions will be of any interest to scientists). On the otherhand, the LHC can be filled with 2808 bunches spaced about 7 m apart, and with all these bunches moving at just a hair under the speed of light we can end up with 600 million interactions each second.

So, what about this 7 TeV thing? A teraelectronvolt (TeV), or 10¹² electronvolts (eV), is a unit of energy. What we are measuring is the energy available in individual proton interactions. The LHC was designed to operate up to 7 TeV per proton, or 14 TeV total. But, for the next couple years the protons will be accelerated up to a speed where each proton carries 3.5 TeV of energy, and for just a moment while two protons collide we will have 7 TeV of energy in one place ready to make new particles (a Higgs boson, dark matter, or maybe something completely new).

A TeV is actually a very tiny amount of energy. A popular analogy is to a flying mosquito, one proton has the same energy as a handful of mosquitoes,

On the other hand, we have to give these protons some credit. They are a lot smaller than a mosquito. In fact, if you consider energy density these interactions are record breaking. A simple way to look at this is in terms of energy per particle interaction. Chemical energy is what runs batteries, bombs, and us; but chemical reactions involve only around one electronvolt of energy per atom. Potentially, each of the LHC protons brings 7 trillion times more energy to their little party.

Of course there can be quite a few  protons spinning around the LHC at one time, and though only a few interact each time the bunches cross, we can wonder how much total energy is in the beam.  This is important for two practical reasons that have nothing to do with the science:

• What would happen if the beam were to somehow go astray and hit the beam pipe and surrounding apparatus?
• How can we safely remove the beam in the normal course of work?

The short answer to the first question is pretty simple: bad things. The beam can punch through 2 meters of solid copper [slides 23-25]. But, it should be noted that it is essentially impossible for a person to be hit by a beam, even if they tried. This is because the beam travels in a vacuum pipe that does a very good job of keeping air out, not to mention human hands. In addition, no one can get anywhere close to tunnels with active beam without breaking safety interlocks that cause it to be dumped immediately. The danger is really only to the equipment. Of course they found exceptions to this in Soviet Russia.

When it’s time to inject a fresh beam of protons or the beam must be removed quickly for safety it is diverted toward a very large chunk of carbon that is liquid cooled and shielded in a 1000 tons of metal and concrete. A nice article about the beam dumps can be found in IEEE Spectrum.

So, to the energies…

You will notice that for all this crazy amount of energy in the beam (almost 200 car-accidents worth) there are even bigger energies lurking at the LHC. The magnetic field of the ATLAS toroid stores 10 times as much energy, and 10 times beyond that is the energy stored in all the LHC magnets.  In fact, the average pair of Swiss people consume more energy every year in chocolate than our measly beams can provide.

(One thing I love about these numbers has nothing to do with high energy physics: you might have been surprised that there is over 5 times as much energy in chocolate as there is in TNT. What is important about an explosion is not as much that a lot of energy is released, but instead that it is released very quickly.)

I have to give a shout-out to I Can Haz Large Hadron Collider.  My favorite image from the site is the following;  needless to say, it is the apex of all our hopes and dreams as physicists.

Howdy lovers,

Well, today’s the day!  The LHC people have decided, along with all the experimenters, that it’s time to collide some protons at 7 TeV.  Actually, the hoopla was originally scheduled to start this morning at 09h00 (CERN time).  That plan was amended several times, so that physicists I talked to all had different ideas of the actual start time for colliding the beams (I heard 03h00 at some point).  The initial attempts this morning to ramp the beam have both failed due to unforeseen errors in the quench protection system (QPS) and some other electronics, but they’re now saying they expect beam (and collisions!) to be ready around noon or 13h00.  So, that means that our early risers in the US might be privy to all the good shit.

For your viewing pleasure, we’ve compiled a list of links to various webcasts broadcasting the day’s activities:

• LHC First Physics Webcast (be sure to click around to the various webcams, at the bottom of the page)
• Our beloved OP Vistars (Page1 is often the most informative)
• CMS cameras: One Two Three
• ATLAS public page, home to a nice feed and some pretty pictures
• ATLAS event displays
• A pretty informative CERN Twitter feed
• The LHC Announcer (this dude talks to you about the LHC activities)

So, click away.  We’ll try to keep you updated, maybe copying some of the pretty photos of the day here for you to see.  Let us know if you find other interesting webcasts to link here, either by commenting or by e-mailing dipole@cernlove.org.

Happy collisions!

UPDATE: We have collisions!  At 13h22, the LHC people declared “STABLE BEAMS,” and we’ve been seeing 7 TeV collisions ever since.  The press release is here, and the champagne is everywhere.

Fearne: What’d you want to talk about. We can talk about anything.
Peaches: Ummm, the Large Hadron Collider.
Fearne: The what?
Peaches: You know they have made this thing called the Large Hadron Collider. It’s in Texas or something, where they are trying to create a black hole in space.
Fearne: Right, you want to talk about space.
Peaches: Yeah.
Fearne: Go for it.
Peaches: Well, I’ve always been interested in Quantum physics, and about theories of, you know, how we came to be and why… Um, which is I guess how I got involved in spirituality and stuff and that way and the religious path I choose to go down and stuff.
Fearne: Which is what?
Peaches: I don’t want to talk about it.
[later] I am a scientologist, I’ve been a scientologist for a while now.

[Thanks to Reddit]

About a week ago, the LHC was preparing itself for its inaugural 2010 current ramp to values consistent with 3.5 TeV energy proton beams.  While this was simply an opening act for the feature presentation (actual 3.5 TeV + 3.5 TeV collisions) next week, it certainly was an exciting and optimistic event celebrated widely at CERN and around the world.  Record energies were reached in the field of particle acceleration, and the timing was perfect considering the growing awareness of the 2010-2011 LHC physics programme.

One media outlet that decided to express its enthusiasm for the huge success of the LHC’s initial foray into the high energy realm was the British online newspaper The Telegraph.  Here is the article they published the day after the successful 3.5 TeV commissioning; really, things are pretty tame in this write-up — catchy headline, video of cute physicists, and lots of fervent anticipation for next week’s collision extravaganza.  However, when this article first appeared on the website of The Telegraph, their elation with the world record breaking energy ramp-up was much more apparent:

If that didn’t strike you as odd, have a look at that headline one more time.

Actually, this is quite a natural joke to be made, if you think about it.   I was surprised to find that, while ‘large hadron collider’ yields around 900k Google hits, ‘large hardon collider’ only finds 63.4k!  I can only hope that our fellow internet comrades will up the efforts to capitalize on this goldmine.  Sexual innuendos mix quite well with physics jargon.  How do you think the term hadron was derived in the first place?  I feel like we’re not far from hearing the phrases ‘beam dump’ and ‘that’s what she said’ used together quite regularly.

On the other hand, the top hit of that Google search surely sets the bar pretty high: http://largehardoncollider.com/

Everyone knows that bunnies are cute and fluffy; why then do human-constructed likenesses of them turn out to be so utterly terrifying? Appearing harmless and adorable in nature, a bunny writ large is at best creepy and at worst, devastating. And yet we insist on creating ever larger monuments to the long-eared ones. It’s possible that our widespread practices of rabbit idolatry perversely reflect some deep and ancient animosity between the races; after all, a child’s first impulse, when given a small (possibly edible) bunny effigy, is to bite off its head. Like other dangerous and potentially world-ending pursuits, CERN finds itself right in the center of the ongoing human vs. bunny struggle, with rabbit flesh prominently featured as a dish on the lab’s rotating menu. Now the world’s tallest chocolate bunny has been erected a stone’s throw away from the LHC in the outskirts of Geneva. Physicists and laypersons alike were encouraged to worship at the feet of this delicious and unholy monstrosity. While other countries may claim to have constructed the most massive, I sincerely doubt anyone can beat this 5-meter tall chocolate bunny.

I fear that our overweening pride has not only threatened the destruction of the universe, but that this graven image shall reach unto the heavens as the ancient tower of Babel, its pointy ears penetrating the event horizon of some intergalactic time warp, bringing down Armageddon upon our heads.

Some of our readers not plugged-in to the everyday scene of physics at the high energy frontier might be confused remembering that we promised you some bad-ass proton collision action somewhere around 14 February, which was over a month ago, and realizing that, indeed, the beloved 7 TeV data is still nowhere to be found.  In fact, the media has been so focused on the 1-year shutdown expected for the LHC in 2012 (and seriously, it’s not because of the Mayan calendar…) that no one has really posed the obvious question: “Umm, hey… wasn’t there supposed to be stuff happening already this year?”

Have no fear, friends.  Your friendly LHC scientists are simply making sure they are working with a well-oiled machine, and these kinds of delays are completely normal.  January and February were used for commissioning the machine at low current, and further developing the Quench Protection System (QPS); here’s a nice article by SymmetryBreaking giving some more information about the LHC’s QPS.  Having a robust protection against accidents such as the one in September 2008 is clearly a high priority.  Beam was re-introduced to the LHC a few weeks ago, and the progress is steadily imrpvoing, however carefully the technicians are working.

Tonight is a special night, however.  For the first time in 2010, we are witnessing the LHC dry-ramping* to the current which corresponds to a 3.5 TeV proton energy; this is the target energy for collisions in the 2010-2011 run.  Of course, live coverage is brought to you by OP Vistars.  In case you missed it, here’s a snapshot in the early stage of the ramp.

(*Dry-ramping implies the current in the magnets of the LHC are being ramped up, but that there is no proton beam circulating at the time.)

Kick the tires and light the fires.

We here at CERN Love are as giddy as schoolgirls about this.

As a non-physicist, you may think that physicists spend their time writing equations on chalkboards, tweaking complicated machines, or scribbling equations on chalkboards. If you read Dan Brown, you probably think they run around in white lab coats. However, hands-on work involving machines and equipment is often given to undergraduate interns and graduate students, while PhD physicists conduct their work a little differently…

• CERN physicists spend most of their work day in meetings, not in labs or their offices.
• There are so many meetings that committees have been formed to hold meetings to figure out how to reduce the number of meetings (I am not making this up).
• Physics analysis is done on laptops during meetings, because it has to get done sometime, and physicists are always in meetings.
• Nobody pays attention to the speaker because they’re submitting physics analysis jobs and creating ugly ROOT graphs on their laptops; they know they can always get the slides later from Indico, the conference management tool everybody uses to post their slides.
• The presenters know nobody is listening so instead of creating readable PowerPoint slides or learning the most basic presentation skills, they write entire blocks of fully formed text in their PowerPoint slides using miniscule font sizes and read verbatim from the slides in an often inaudible monotone. They know that if anyone wants to see their results, they’ll just read the slides on Indico later. Generally the presenter faces the screen, with his/her back to the audience.

This behavior habitual and completely ingrained. I was once in a tutorial for physicists held in a computer lab, where every seat had a desk with a dedicated computer terminal. The participants all filed into the room, sat down at their computer terminals, got out their laptops, put them in front of the computer terminals, and plugged their laptops in at the same time, blowing the room’s electrical circuits.

We have already noted that “the building numbers here don’t make a damn bit of sense. If they do follow any kind of scheme, it’s not a scheme that helps you find buildings.” So, suppose you have a workshop to attend in the AB auditorium in building 6.  You might know where building 5 is, but one learns very quickly that that sort of information doesn’t do you the tiniest bit of good at CERN. Instead, your only resource is undoubtedly the ancient “WWW Map” of CERN.

(By the way, I once spent twenty minutes wandering the halls of building 6 trying to find the infamous AB auditorium.  Not to be outdone, at CERN the room numbers can be just as confusing as the building numbers.)

I actually find CERN’s building map page mostly effective and a cute little throwback to a time before Google Maps.  It’s the horseshoe crab of web pages, ugly but effective. Go ahead and open Netscape 1.0 (or maybe something even older) and find yourself a building, if that happens to be your thing. It’s all just GIFs and links (image maps are used in some places, but not nearly as much as you would expect), and most of the time it gets you where you need to go.

Of course though, there are some serious and silly limitations,

• Clicking top map zooms out revealing the only other zoom level available.  Clicking bottom maps inexplicably takes you back to the home page. Panning is never an option.
• If you land in the Prevessin site the bottom right map doesn’t indicate this at all. From the home page try CERN Clubs Spaces > Picnic area; if you don’t have an inkling that this is on the Prevessin site then you are going to be very confused for a while.
• The orientations of the other two maps are not consistent with the the overview map in the bottom right (the only one with north properly straight up). Why they did this I don’t have a clue; my only guess is that they wanted to layout the Meyrin site a little more horizontally. This is a big reason why the previous picnic area example is so confusing, the shape of the Prevessin site is not as obvious when presented in multiple orientations.
• At least at first glance, there are no simple everything-in-a-pdf versions of the maps. There is a very prominent link to a 3D PDF that takes a while to download and render, after which you realize the 3D in this case is a useless gimmick. I have run across a PDF with 3D content a total of zero times outside of this page; there must be a very good reason for this. Actually, there are PDF maps of all the sites, but the only place you can find them is via a very subtle link at the bottom of the map page after you have clicked on a point of interest or searched for a building. There is no link at all from the main page.  (Contrary to what it says, they are accessible outside of CERN, one slightly pleasant surprise.)

Hoping to discover what other information might be available, I found my way to the GS Department Patrimony and Site Information page. The page is littered with promising links that when poked reveal themselves to be dead and rotting. But, there is one handy find: a GPS navigation page provides a CSV file with the latitude and longitude of all the buildings for uploading to your navigation system. (Relevant to the discussion in our building number post, there is also a page listing the construction date of each of the buildings, but that page is not accessible outside of CERN so I won’t bother linking.)

Finally, a tip: keep watching CERN Love. We are working on a geographical component to the site that hopefully will be handy and informative. We also hope to publish some interactive informational pages that will be very relevant to the start up of the LHC. Both should appear in the next couple weeks.