World's Largest Supercooled Magnet Activated

An anonymous reader writes to mention a C|Net article about the activation of the world's largest superconducting electromagnet. Switched on today at Geneva's CERN lab, the experiment is part of the Large Hadron Collider (LHC) project. The magnet, called ATLAS, worked on its first start up. From the article: "In use, the magnet will be used to bend the paths of particles formed from the collision of protons or lead ions accelerated to near light speeds in 27km diameter subterranean contra-rotating circular beams. The ATLAS experiment is one of five in the LHC, and engages 1,800 scientists from 165 universities and laboratories in 35 countries."

Worlds largest bulk magnetic media eraser...

[binaryspiral (784263)]

And every single magnetic based media for ten miles was instantly erased.

A faint "bwa ha ha ha... vhs tapes and floppy disks suck!" was heard from from the evil scientists' lair.

Oblig

[h2g2bob (948006)]

It was as though millions of credit cards suddenly cried out in terror and were suddenly silenced.

Re:Oblig

[legoburner (702695)]

aaahhh... that would be the reason they switched to chip-and-pin instead of the magnetic strip on European credit cards. Now it all makes sense!

Re:

[camperdave (969942)]

I can't figure out how to mod you up, so you'll just have to settle for kudos. Most Excellent post!

Re:Worlds largest bulk magnetic media eraser...

[Fred_A (10934)]

No wonder I had to degauss this morning...

I live inside the ring...

[Paul Bristow (118584)]

My house is actually inside the circle made by the ring, albeit at ground level, not 100m down. So far, My computers still work, but I guess the HDD's could be gradually demagnetising a bit on each turn.

So far, so goo£%^$.... NO CARRIER

It's taking a long time

[BadAnalogyGuy (945258)]

The original team working on this tried to load the software from floppies.

Re:

[RuBLed (995686)]

Now that it is functional, I doubt that those floppies would work now. I hope they made backups.

why

[tezbobobo (879983)]

I know the article says what it will be used for, but why do we need to bend the particles path, and why does the magnet need to be super cooled?

Re:

[Peden (753161)]

All in the name of research baby. "The internet" as we know it was in part created at CERN, if that does not merit researching high energy particles, I don't know what does. http://www.hitmill.com/internet/web_history.html [hitmill.com]

Re:why

[hcdejong (561314)]

IANAPP (particle physicist), but bending the particles' path is often done to determine mass: heavier particles will be pulled off their course less than lighter particles, so they'll impact the detector in a different place.

The magnet needs supercooling because a huge magnetic field is easier to achieve with a superconductor than with a conventional magnet.

Re:

[bmgoau (801508)]

Actually No, particle accelerators such as this are called cyclotrons and their ring shape is such that any particle placed within them can orbit a central point until the deisered velocity can be reached by proceeding through the same series of magnets over and over again, often close the speed of light. This is opposed to a cheaper and simpler liniar accelerator, which shoots particles down a long and stright tunnel.

This is because we already know the mass of the particles (such as molecular and atomic io

Re:why

[hcdejong (561314)]

Actually, no. The LHA is not a cyclotron. In a cyclotron [wikipedia.org], the particles travel in a spiral, in an area sandwiched between two huge electromagnets. The size of the magnet limits the size of the cyclotron.
The LHA consists of a tube running through a series of magnets, a bit like a linear accelerator. The tube is bent into a circle so you can have the particles do multiple laps around the accelerator to increase their energy.

Re:

[Gromius (677157)]

No, not in this case (good try but you're thinking clasically). This may be true at low speeds but the particles detected in these experiments that are of interest are relativistic and are moving at signficant fractions of the speed of light (about 0.999c or there abouts) and as such for all intents and purposes have zero mass. These particles are often the decay products of more massive particles. The reason we want to bend them is to measure their momentum (or spectifically their transverse momentum) NOT

Re:why

[Gromius (677157)]

We need to bend the particles path so we can measure its momentum. A charged particle in an magnetic field will have a radius of curvature inversely proportional to the magnetic field and proportional to its momentum, with opposite charged particles curving in different ways. The radius of curvature decreases as the magnetic field increases and increases as the momentum of the particle increases. So for very high momentum particles, the radius of curvature is very large so the particle travels in almost a straight line which makes it very difficult to measure the radius of curvature. Hence you increase the magnetic field to force the particle to "bend" more and make it easier to measure the amount of "bending". So you want as big as magnetic field as possible and at the moment superconducting magnets give the most powerfull fields.

Here, have a look at this picture [fnal.gov] of a particle physics event (not from ATLAS but CDF at the Tevatron but the idea is the same). Lines in the circle are particle tracks, the two pink ones are very high momentum charged particles (in this case electrons). Notice how they are straight. As such we dont have a very good measurement of their momentum. The other grey lines are low momentum particles as they bend a lot since the radius of curvature is small.

Why do we want to measure the momentum of a particle? Well the Higgs boson (if it exists) will decay to 4 muons (basically heavy electrons) (nb: the Higgs can decay to other stuff but for a heavy higgs this is the cleanest signature and will be how its discovered). You want to measure the momentum of these muons and from that you can measure the mass of the particle that produced them. If you get a lot of events at a certain mass above what you expect from background, you've just discovered a new particle, likely to be the Higgs.

Re:why

[romain wartel (918183)]

> why do we need to bend the particles path

I am not a particule physicist, but the particules need be accelerated and are 'pushed' by the magnets before being collided, so they need to circulate many times around the accelerator in order to get sufficient speed.

"A beam might circulate for 10 hours, travelling more that 10 billion kilometres, enough to get to the planet Neptune and back again. At near light-speed, a proton in the LHC will make 11 245 circuits every second."

What is the LHC power consumption?

It is around 120 MW which corresponds more or less to the power consumption for households in the Canton (State) of Geneva."
http://public.web.cern.ch/Public/Content/Chapters/ AskAnExpert/LHC-en.html [web.cern.ch]

> why does the magnet need to be super cooled?

To magnets are used also to maintain the beam within its path, and the requires huge amount of energy to create a magnetic field that is strong enough to prevent the beam to escape. These magnets are using a massive amount of power, and must be cooled down (a lot) do reduce their electrical resistance down to supraconductivity.

"In order to cool the magnets down to -193.16 C (pre-cooling), 10 080 tonnes of liquid nitrogen will be used. Afterwards, the refrigerators turbines will bring the helium temperature down to -268.7 C and fill the magnets with almost 60 tonnes of liquid helium. Once the magnets are filled, the refrigeration units will bring the temperature down to -271.3 C by lowering the saturation pressure - and therefore the temperature - of the liquid helium in a heat exchanger in contact with the static pressurized helium of the magnets' cold masses."
http://public.web.cern.ch/Public/Content/Chapters/ AskAnExpert/LHC-en.html [web.cern.ch]

http://en.wikipedia.org/wiki/Large_Hadron_Collider [wikipedia.org]
For reference, the LHC will also use a massive computing Grid: http://www.cern.ch/LCG/ [www.cern.ch]

Romain.

Re:

[hcdejong (561314)]

You seem to suggest the ATLAS magnet is used to contain the particles within the accelerator itself, which is not the case.

The accelerator does use magnets to contain the particles, just not this one.

The ATLAS experiment [wikipedia.org] is one of the detectors which use the output from the accelerator.

Re:

[Lord Crc (151920)]

I know the article says what it will be used for, but why do we need to bend the particles path

As found on this [atlasexperiment.org] page, the magnet is used to measure the momentum of the particles. I'm not into physics, but I imagine it's a bit like rolling (equally sized) balls along a line, and then have a fan on the side trying to deflect the movement. A large momentum (and thus mass, assuming all the balls travel at the same speed) would lead to less deflection.

Impressive stuff

[Hyksos (595814)]

I've seen the magnet while it was still being constructed. Suffice to say, BIG is an understatement! :)

Re:

[trip11 (160832)]

Bah, the muon detector 'big wheel' is way more impressive (: Ok, not that the magnets aren't cool too.

Re:Impressive stuff

[l0b0 (803611)]

How's this for size? ATLAS calorimeter [flickr.com], the tunnel [flickr.com], one of the tubes [flickr.com], the "crab" [flickr.com], the hole [flickr.com], and the cavern [flickr.com]. Bonus: They do have retina scanners [flickr.com]!

Re:

[10Ghz (453478)]

And now that it's finished, I bet it's quite attractive as well!

The realy deep questions

[Silver Sloth (770927)]

From TFA

the LHC will be the most powerful particle accelerator ever built and will be used to investigate why particles have mass

It's at this point I realise how amazingly little I know about particle physics. In my ignorance I always thought that having mass was an inherant property of being.

Re:The realy deep questions

[tkittel (619119)]

It might have been an inherrent property of all particles (except the massless photon and gluon), but it turns out that the nature of the weak force (normally known from beta decays of nuclei) conflicts with this.

The real understanding of this problem requires knowledge of Quantum Field Theory, but the gist of the problem is as follows:

All known matter particles (fermions) as well as the particles that mediates the weak force (the W and Z) behaves in experiments as if they have masses. However, if they actually do have masses the theory breaks down (it becomes non-renormalizable, and gives non-sensical answers such as "that decay have a branching ratio of 500%". It becomes a bit like sports-commentators, I guess).

The proposed solution to this conundrum, and the one the LHC and ATLAS will try to verify, sounds kind of like a lawyer finding a legal loophole when you first hear it. In essence it is: "All particles are really massless, but some of them behaves as if they have mass". The way to accomplish this is by the so-called Higgs Mechanism, in which particles acquire masses the same way that a light-weight guy walking in a waist-high pool will feel as much or more difficulty walking as a really fat guy walking on dry ground: All particles move around in a soup of Higgs particles and thus acquire the appearance of being massive due to their interactions with this Higgs-soup.

I thought it was kind of cheesy back when I first heard about it, but later I realised that similar effects already are known to happen elsewhere in nature, which kind of makes it more acceptible (for instance, those familiar with the Meissner effect for superconductors might recall how the otherwise massless photon acquires the appearance of mass inside superconductors due to the presence of a soup of electronic cooper-pairs).

But we will have to see when the LHC starts!

ps. I am actually a member of the ATLAS collaboration. Go magnets!

Re:

[myowntrueself (607117)]

All particles move around in a soup of Higgs particles and thus acquire the appearance of being massive due to their interactions with this Higgs-soup.

Oh so the Higgs-soup is kind of like phlogiston or something similar?

Re:

[Mr2cents (323101)]

All particles move around in a soup of Higgs particles and thus acquire the appearance of being massive due to their interactions with this Higgs-soup.

How would that be possible? I thought that this Higgs particle was highly unstable and decays almost immediately. So where does the soup come from?

NB: I'm no expert.

Re:

[imsabbel (611519)]

largest, in size, and strongest by the amount of energy contained (think about it: its has 100s of m^3 with nearly 4T flux)

Re:Strongest magnetic field or Physically Largest?

[gregor-e (136142)]

I received email from Dr. James Gillies of CERN on this:

Dear Gregory,

I believe that the field of the ATLAS magnet is around 2 tesla, but the volume is vastly larger than an MIR magnet. Another experiment at CERN, which has a smaller volume than ATLAS has a field that reaches 4 tesla. In the LHC particle accelerator itself, the field in the magnets is around 9 tesla.

Regards, James Gillies

Energy Consumption

[chriss (26574)]

From TFA:

The LHC will consume some 120 megawatts and is predicted to run for between 15 years and 20 years. It will be rested for three months in winter because the French power station that supplies it is needed for the domestic grid.

So I guess almost all the world's particle physicists will be home for christmas.

This is just a part of Large Hadron Collider

[RuBLed (995686)]

This was once featured on slashdot and for those confused, this is just a part of the world largest (longest) particle accelerator thing and one of the purposes of this huge facility is to generate small blackholes.

http://public.web.cern.ch/Public/Content/Chapters/ Spotlight/SpotlightATLAS-en.html [web.cern.ch]

Re:This is just a part of Large Hadron Collider

[trip11 (160832)]

IAAPP. Just so no one freaks out over this (as they so often do). The black holes that are getting created here will not destroy the earth. First off the theory tells us that black holes with less than, say the mass of the earth, will dissapate and dissapear (this is one of the things we are looking for). So for those of you thinking, what if they are wrong, I present the second argument. The experiment we are trying to set up at ATLAS and the Large Hadron Collider to smash really high energy particles together is done in nature every day. Cosmic rays smash into the earth's upper atmosphere with WAY more energy than we can every hope to achive here in Switzerland. If we can make black holes here, then many have been made in the upper atmosphere. The problem is that they are hard to observe way up there, occurring at random chance. However the fact that the earth is still here is damn good evidence that the back holes don't grow and destroy the earth when they are created.

Re:This is just a part of Large Hadron Collider

[Dread_ed (260158)]

"The black holes that are getting created here will not destroy the earth."

Suuuure! That's what you said the last time the Earth was destroyed.

Re:

[bmgoau (801508)]

Actually, the Large Hadron Super Collider does not have the creation of micro-singularities (aka black holes) in its objectives. Infact, some politions were concerned about this possibility, and scientists involved in the project to build the LHC did reseach into the possibility. They concluded that this accelerator does not have the power needed to collide particles at velocities needed to create small blackholes. Several orders of magnitude more power is requiredto do this.

The LHC is designed to verify ma

Shutdown

[Detritus (11846)]

How do you shutdown the magnet without destroying it? According to my rough calculation, it stores energy equivalent to about 500 kg of TNT.

Re:

[KokorHekkus (986906)]

The electromagnet not used to hold anything together. The energy is just "stored" in the coils and when you remove the power supply the field dissipates. Now, should you short-circuit the coils - that would be interesting.

Re:

[Detritus (11846)]

One situation that I was thinking about was the case of a super-conducting magnet heating up and losing its superconductivity. I've read about MRI machines suffering expensive damage when they aren't shutdown properly.

Re:

[KokorHekkus (986906)]

That is an interesting question. One way could be to use separate cooling systems for each coil and if there is a cooling system failure you could shunt the energy from the failing coil to the rest of them and then proceed with an orderly shutdown. Anyone else have any suggestions? (Or actualy *gasp* know? :)

Re:Shutdown

[tomstdenis (446163)]

All you have to do is shunt the power to a secondary plasma relay and then the induction coils will shut down normally.

Oh wait ... this isn't Star Trek?

Tom

Re:

[imsabbel (611519)]

I read about it years ago, so my memory is abit hazy.

But they do have extensive field-quench protection systems. (they need it, as its by far the biggest liquid helium installation in the world).

One way they protect themselvs is that they are well below the critical temperature for the magnet at the current density they use. They also use liquid helium evaporation cooled to about 2K. And they have huge venting tanks for quench protection.

The sublimation heat of helium is not that big, but they have 10s of t

Re:

[squoozer (730327)]

I once worked with a guy who used to maintain fairly large superconducting NMR magnets. According to him they procedure was essentially as follows Step 1: Connect wires to the magnet taking great care not to quench the magnet in the process (e.g. stop it super conducting). Step 2: Place a large resistive load between the wires and bleed off the stored energy.

Apparently you only screw up step one once.

Re:

[Rich0 (548339)]

I believe the wires mentioned in step 1 lead to a small header coil that heats a very small section of magnet wire just above the critical temperature. The resistive load is then the section of magnet wire itself - which now is resistive. However, you wouldn't want to use a "large" resistive load. Standard NMRs run hundreds of amps so you don't want much resistance at all.

If you generate too much heat the situation goes exponentially out of control as the entire magnet rapidly heats up (as each portion o

Re:Shutdown

[trip11 (160832)]

There is about 1 GJ of energy stored in the magnet when it is at full strength. I don't remember my TNT converstions, but admitedly that is a lot. The energy is disapated through resistors and that heat is dumped into a LOT of mass all while actively cooling everything. Here is a pretty picture of the current as a function of time during the test (notice how fast it was shut down) http://jenni.web.cern.ch/jenni/BT.9Nov06.jpg/ [web.cern.ch] The axis are in amps and minutes by the way. And yes, that is ~20,000 amps. As another intresting LHC note, the magnets in the accerator store ~11GJ of energy which is disapated into something like 50 tonns of steel. This is (breaking out the obscure unit conversions) the energy of something like 40 bullet trains traveling at full speed, or a nuclear aircraft carrier traveling at full speed. The energy stored in the actual beam of protons is also not anywhere near negligible and systems had to be designed to dump all of this energy as well.

ATLAS webcams

[fresita (1031476)]

http://atlas.ch/webcams.html [atlas.ch] With images from when they began.

Ah ha!

[SnarfQuest (469614)]

That explains it! There I was, walking around in my suit of armor, when suddenly, WHAM! Stuck against the wall! And now, every time I pass the kitchen, the silverware shoots out at me!

Re:

[Nevtje(hr (869571)]

Walking around in your -what-?

Dude, I think you've been playing too much World of Warcraft.

Field strength and other detials

[HalfFlat (121672)]

I was wondering what the magnetic field strength of this magnet would be, but the FA is a light on details. But there's a pamphlet [cern.ch]!

Peak field strength for the barrel toroid magnet is 3.9 Tesla. And apparently it will take 30 days to cool the thing down with liquid helium to operating temperature.

Re:

[Rich0 (548339)]

For those not into magnets, 3.9 tesla isn't all that much - maybe bigger than a typical hospital MRI, but by NMR standards it is pretty small - NMRs go up to around 20 tesla or so, and experimental non-superconducting magnets have gone to 25-30T (or even higher for brief periods). The non-superconducting magnets aren't useful for NMR or a lot of other physics since they tend to fluctuate quite a bit - they use water-cooled electromagnets and a HUGE amount of electricity. I remember reading about one that

Re:

[imsabbel (611519)]

Well, its not weak. Sure there are MUCH stronger ones, but usually at the cost of size.
There is even a 20T magnet 30 meter away from me right now, but the volume of the bore is only the size of a can of coke.

The energy density goes square with the flux, but linear with the volume, so the size makes the magnet quite special.

Everytime I read about particle accelerators

[Centurix (249778)]

I always think of this toy we bought our cat, it's like a round disc with a tube around the edge with ping pong balls in it and a few holes in the side so kitty can chase the balls around for minutes and minutes.

I imagine a group of scientists standing at one point next to the tube with a hole, waiting and watching.

1800 scientists

[drooling-dog (189103)]

...and engages 1,800 scientists from 165 universities and laboratories in 35 countries.

That's going to be quite an author list when they finally publish...