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Mehen
28th September 2006, 22:42
http://www.nzherald.co.nz/topic/story.cfm?c_id=325&objectid=10400645


The Large Hadron Collider - a 27km-long circular particle accelerator at the CERN experimental facility near Geneva, will smash protons into one another at unimaginable speeds trying to replicate in miniature the events of the Big Bang.

http://media.apn.co.nz/webcontent/image/jpg/cern_facility.jpg

lowlifecat
28th September 2006, 23:04
* Scientists aim to reproduce miniature versions of the so-called Big Bang, which is thought to have started the universe.

* To do this they will smash protons together at huge speeds along a 27km tube known as a particle accelerator.

* They hope to create tiny black holes or find extra dimensions in the universe.

* They estimate the possibility of accidentally destroying the planet as extremely low.

* The risk is calculated at about 10 to the minus 40 - a 1 in 10,000,000,000,000,000,000,000,000,000,000,000,000 ,000 chance.

not enough zeros in that estimate.

Dr Mordrid
29th September 2006, 01:10
One of the predictions for the LHC (Large Hadron Collider) is the creation of mini-black holes. If Hawking is right and black holes emit radiation they will evaporate quickly. He's probably correct in that cosmic rays more energetic than the LHC hit the atmosphere every day and it's not raining mini-black holes.

Fat Tone
29th September 2006, 04:08
Without having thought about this too much, why cant these rings be much smaller and have the particles travel in a helix, i.e. they circuit many times, picking up speed as they go, before the collision?

Nowhere
29th September 2006, 04:17
They do that already, several passes are a norm.

As to the size...the bigger the accelerator is, the smaller are the losses of energy when accelerating particles. And this problem isn't only "classical" (the more particle would have to turn, the more energy that would waste which could otherwise accelerate particle) - when particle gains speed, it gains also mass, which in turn wastes more energy at keeping the particle turning.

Fat Tone
29th September 2006, 04:20
Thanks Nowhere, that makes sense.

So they aren't linear because they'd have to be several times longer, once for each circuit, though they could be a little shorter as no losses due to turning. What proportion though?

Nowhere
29th September 2006, 04:24
Well, some are/were linear...but because particle passes only once through them in can't be accelerated much (and there's limit on possible size/lenght) and AFAIK modern ones/future ones are circles.

BTW, keeping particles in correct path (not hitting walls of accelaratod, which would eventually require repairs) is quite a challenge...but you can help! :)
http://lhcathome.cern.ch/

edit: I actually checked the number - on typical experiments in LHC particles will travel 400 million revolutions (and that's in the big ring of LHC alone, not counting the smaller ones from which particles are injected)

Dr Mordrid
29th September 2006, 08:47
http://www.scienceagogo.com/news/20060825010928data_trunc_sys.shtml


Honey, I Shrunk The Particle Accelerator

Is that a particle accelerator in your pocket or are you just pleased to see me?
>
In a remarkable demonstration of the potential of laser-wakefield acceleration, scientists at the Lawrence Berkeley National Laboratory (LBNL) have accelerated electron beams to energies exceeding a billion electron volts (1 GeV) in a distance of just 1.3 inches (3.3 centimeters).

As a comparison, the Stanford Linear Accelerator Center boosts electrons to 50 GeV, but over a distance of two miles (3.2 kilometers). Traditional accelerators like Stanford's, which use radiofrequency cavities, are limited to about 20 million volts per meter. In the new system, however, the electric field of a plasma wave driven by a laser pulse can reach 100 billion volts per meter, theoretically achieving the same energies as Stanford's accelerator in only one-two-thousandth of the distance. "Billion-electron-volt beams from laser-wakefield accelerators open the way to very compact high-energy experiments and superbright free-electron lasers," said researcher Wim Leemans.
>
"It's the tip of the iceberg," said Leemans. "We are already working on injection [inserting an already energetic beam into an accelerating cavity] and staging," the handoff of an energetic beam from one capillary to the next and subsequently to others, until very high energy beams are achieved. Leemans' group and their Oxford collaborators look forward to the challenge with confidence, predicting energies of 10GeV with an accelerator less than a meter long.

Fat Tone
29th September 2006, 10:16
edit: I actually checked the number - on typical experiments in LHC particles will travel 400 million revolutions (and that's in the big ring of LHC alone, not counting the smaller ones from which particles are injected)

Erm, I guess doing that in a linac would be a little expensive ;)

Nowhere
30th September 2006, 07:55
not enough zeros in that estimate.
Oh, and...why not enough? There are many cataclysms which are much, much more probable...

One of the predictions for the LHC (Large Hadron Collider) is the creation of mini-black holes. If Hawking is right and black holes emit radiation they will evaporate quickly. He's probably correct in that cosmic rays more energetic than the LHC hit the atmosphere every day and it's not raining mini-black holes.
I'll just add that he's definatelly correct. Example: oh-my-god particles.