Talk:Large Hadron Collider

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- Texture 17:09, 3 Feb 2004 (UTC)

Detecting very small particles

-Decent stuff but they will need fast computers to test for such particles. -anon1

Obvioulsy, which is the reason why the CERN is developping distributed computing systems, "The Grid" [1] Rama 16:57, 13 December 2005 (UTC)

Nowadays you build a bunch of custom hardware to pick out the interesting events, which get stored. The computers are for "off-line" analysis and storage; they do have to be fast, but the idea is to get the real time-sensitive detection stuff done in hardware rather than software. - mako 00:36, 14 December 2005 (UTC)

Well, it's done in hardware up to a certain point, but the decisions on the order of 1 second are still done with processor farms. -- SCZenz 06:56, 14 December 2005 (UTC)

Amendments

loss of only 10−7 of ..... I suppose we aren't talkin apples but MJ here. I figure we could postfix and convert it straight in kJ?Slicky 07:11, 28 February 2006 (UTC)

Location?

I didn't see it listing anywhere the location of this facility...

It's in Geneva, Switzerland Turboyoshi 21:23, 23 April 2006 (UTC) Well, It is actually close to Geneva, but not in Geneva. Of course the circle spans quite an area between France and Switzerlandyanneman 00:36, 1 July 2006 (UTC)

LHC figure

I made a figure about LHC. I think that appropriate for this article. I made it's SVG version as well, but it didn't work well (my Firefox shows it correctly). -- Harp 15:35, 3 April 2006 (UTC)

Clarification requested

Is it a large collider of hadrons or a collider of large hadrons? This is not obvious from the article! Cheers -- SamSim 22:13, 23 May 2006 (UTC)

It's a large collider of hadrons. Zargulon 22:28, 23 May 2006 (UTC)

It's a proton collider more specifically, and protons only come in one "size." ;) -- SCZenz 15:22, 28 May 2006 (UTC)

Technically, they're very small protons. The energy you make a particle, the smaller it gets.--Loodog 17:23, 31 May 2007 (UTC)

Science Collaboration of the Week

Hi all. I work on an LHC experiment, namely ATLAS, and I am happy to help with this article. I don't have infinite time, but there are three ways I can help:

1. If there are specific pieces of information you need, or questions you have, I may know already where to find them.
2. A significant amount of background information relevant to all of the LHC is in the ATLAS experiment article, which I brought up to featuerd status a while back. Perhaps some of it could be used/rewritten for the LHC more generally.
3. I'm at CERN right now, so possibly I can go take some pictures if there's something for which a picture is needed. Bear in mind that I can't get better access to the experimental halls or tunnels than any member of the public, which is to say I'd have to apply for a tour. But do go ahead and ask if there's some specific thing you think would be cool; it may be such a picture can already be found in the public domain somewhere, too, and I'll know where it is. -- SCZenz 15:28, 28 May 2006 (UTC)

• • Yes, please do take pictures. As long as you agree to release them under the GFDL, we need your pictures! The current one in the article is not very good for the purpose, so get snapping! —Vanderdecken∴∫ξφ 11:14, 6 June 2006 (UTC)

Template for LHC-experiments

What do you think, would it be good to put a template into the LHC-experiments like this:

ATLAS	CMS	LHCb	ALICE	TOTEM

-- Harp 10:36, 30 May 2006 (UTC)

Looks good (but I'm no judge as to accuracy, completeness etc.). Can we somehow discourage people from clicking the text in the picture, expecting to get to the respective articles? Make the font underneath bigger/bolder? Or if anyone knows how to implement the functionality of the "area" html tag here? - Samsara (talk • contribs) 10:44, 30 May 2006 (UTC)

I had a small trial to use area maps, I don't succeeded. I think it is hard, because the full image is a link. But if it is possible, I can change the text to a html-link like style. (The vector graphic (SVG) version is at the commons too, but it can't render the Wikimedia software perhaps because of the several layer. -- Harp 12:40, 30 May 2006 (UTC)

It looks very nice. I disambiguated ALICE in the above. -- SCZenz 12:59, 30 May 2006 (UTC)

Maybe something like the Germany map in World_Cup_2006#Venues could be tried. rbonvall 12:02, 19 July 2006 (UTC)

Large Hadron Collider
(LHC)

Plan of the LHC experiments and the preaccelerators.
LHC experiments
ATLAS	A Toroidal LHC Apparatus
CMS	Compact Muon Solenoid
LHCb	LHC-beauty
ALICE	A Large Ion Collider Experiment
TOTEM	Total Cross Section, Elastic Scattering and Diffraction Dissociation
LHCf	LHC-forward
MoEDAL	Monopole and Exotics Detector At the LHC
FASER	ForwArd Search ExpeRiment
SND	Scattering and Neutrino Detector
LHC preaccelerators
p and Pb	Linear accelerators for protons (Linac 4) and lead (Linac 3)
(not marked)	Proton Synchrotron Booster
PS	Proton Synchrotron
SPS	Super Proton Synchrotron

Here is Template:LHC (at right). (I used some code from Template:Hadron colliders). -- Harp 09:21, 31 May 2006 (UTC)

I changed, I you like the shorter version, you can find it in the history of the template. But if you like the longer better, perhaps it would be usfeul to put the energies of linacs, PS, SPS... in the table. Any other suggestion? What is better word: preaccelerator or injector? I think only the previous one is the injector of the LHC, so I used the preaccelerator, but I don't know wheter it is an official phrase. -- Harp 10:29, 31 May 2006 (UTC)

I have put the template into the expertiment articles. I will put it into the LHC as well. -- Harp 08:56, 1 June 2006 (UTC)

I have a table about LHC. I have collected the facts I think could be mention in the article. Perhaps some of them should be in the template.

General parameters of LHC

Energy at collision	7 TeV
Energy at injection	450 GeV
Dipole field at 7 TeV	8.33 T
Luminosity	1×1034 cm-2s-1
Current (proton)	0.56 A
Bunch spaceing	7.48 m
Bunch separation	24.95 ns
Number of protons /bunch	1.1×1011
Luminosity lifetime (reduce to 1/e)	10 h
Energy loss per turn	6.7 keV
Total radiated power per beam	3.8 kW
Stored energy per beam	350 MJ

Some parameters I think don't need to mention, or I don't know what means:

Coil inner diameter, aperture (300 K)	56 mm
Distance between aperture axes (1.9 K)	194 mm
Beam beam parameter	3.6×10−3
Normalized transverse emittance (r.m.s.)	3.75 μm
Total crossing angle	300 μrad
Beam separation in arcs (1.9 K)	194 mm

Ref section

Per the MoS, I believe the section currently labeled as "references" should be labelled "Notes" and go to the end of the article. Perhaps the actual references for those can then be added back into the ref section. I'll double check the MoS and provide a link shortly. --DanielCD 03:22, 4 June 2006 (UTC)

Wikipedia:Footnotes and Wikipedia:Citing Sources. It seems to be a flexible policy, but I'll change the name of the section to "Notes and references" for now. If actual general refs are added, then we can make a separate section. --DanielCD 03:26, 4 June 2006 (UTC)

Popular culture references

Shouldn't some reference be made as to the prominence of the LHC and CERN in Dan Brown's book Angels and Demons? The mention of the accelerator creating antimatter, the theory of the process used etc. should be included. Not to mention the fallout that this gave CERN, redirecting concerns that antimatter had been made in 5 gram amounts that were not secured and so on. Many refernces can be found with our friend Google. —Vanderdecken∴∫ξφ 11:20, 6 June 2006 (UTC)

It's covered in some detail in CERN. -- SCZenz 12:43, 6 June 2006 (UTC)

I'm really sick of these stupid "pop culture" sections in Wikipedia. Can't geeks forgo their obsession with trivia and add only information that matters? -- 71.235.238.180

Then they wouldn't be geeks. ;-) I oppose adding a popular culture section to any article. If there is something extremely relevant in popular culture about the subject, it can be worked into the rest of the article. -- Kjkolb 14:04, 7 November 2006 (UTC)

No one cares about that terrible book Kupesoft 16:27, 1 December 2006 (UTC)

Loss and AD

"Loss of only 10⁻⁷ of the beam is sufficient to quench a superconducting magnet..." On what timescale? Per second, per hour...

LEIR, AD - I think it is an other story. The LHC don't need antiproton.

-- Harp 12:36, 13 June 2006 (UTC)

I think it is not about the timescale. If only a portion (I don't know the correct ratio) of a single beam bunch gets out of the path and hits the magnet once, it is enough to quench the superconductor. þħɥʂıɕıʄʈ^ʝɘɖı 09:03, 14 June 2006 (UTC)

LHC countries

Armenia, Australia, Austria, Azerbaijan Republic, Belarus, Belgium, Brazil, Bulgaria, Canada, China, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, France, Georgia, Germany, Greece, Hungary, India, Israel, Italy, Japan, Korea, Morocco, Netherlands, Norway, Pakistan, Poland, Portugal, Romania, Russia, Slovak Republic, Slovenia, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, United States, Uzbekistan

from http://lhc-machine-outreach.web.cern.ch/lhc-machine-outreach/components/lhc-manufacturing.htm

Updated LHC information

It might be interesting to know the startup program for the LHC, later and at lower energies than was previously believed. You can find good material for the article in that post. I'll add that link to the article Franjesus 18:29, 20 June 2006 (UTC)

LHC starting energy

The article says the LHC will start in November 2007, which is correct, but also "when it will become the world's largest and highest energy particle accelerator". This is not true. The latest LHC schedule foresees 450 GeV collisions in 2007. The full energy will only be achieved in 2008. Until then the Tevatron will keep the energy world record. I don't know how to reshuffle the introduction to correct this while keeping the present clarity. Pkoppenb 13:41, 28 October 2006 (UTC)

I've made the change. - mako 01:25, 29 October 2006 (UTC)

Clarification of diminishing returns

"After some years of running, any particle physics experiment typically begins to suffer from diminishing returns. This is because the statistical precision achievable in the presence of background by any given experiment scales with the square root of the run time."

Can someone clarify exactly what this means? It's a bit difficult to parse, particularly the "in the presence of background" bit. What background? As far as I can tell, it's saying that if you repeat a given experiment, each subsequent repetition of the experiment gives you less and less new information, relatively. Is that it, or is this something specific to accelerator experiments, or is it something else entirely? chrismear 20:01, 20 November 2006 (UTC)

LHC simulation

I've uploaded an image from the LHC homepage - fortunately it is public domain - to the Commons. commons:Image:CMS Higgs-event.jpg Is it a simulation of a Higgs-event, isn't it? The original page don't have any description. Could you find me a description?

I think, that it is useful image for this article, and for Higgs boson too. -- Harp 15:05, 5 December 2006 (UTC)

I find a description. I insert into the page of the image. -- Harp

Swiss francs?

Okay people, why does this article put the cost of the LHC in Swiss Francs? How much dollars or euros is that? AppleHaven 23:24, 8 March 2007 (UTC)

Yeah. Could it be put in Euros or USD for pete's sake? And maybe include a total cost to date figure instead of spitting out half a dozen overexpenditure figures on top of an original estimate? NaK-Pump 01:00, 11 April 2007 (UTC)

• Maybe because CERN is (mostly) base in Switzerland, and even the French part is under Swiss jurisdiction? Or more simply the fact that the article cited was giving the figures in Swiss Francs? -- KTC 00:43, 15 May 2007 (UTC)

Some strange thing at the beginning

"Protons are then injected at 1.4 GeV into the Proton Synchrotron (PS) at 26 GeV. The Low-Energy Injector Ring (LEIR) will be used as an ion storage and cooler unit. The Antiproton Decelerator (AD) will produce a beam of anti-protons at 2 GeV, after cooling them down from 3.57 GeV."

Is it true, that we need LEIR for storage ion beams for the LHC? Why we need antiprotons (I think the LHC needn't, just the experiment at the AD). I think this part of the article is confusing. If some of them are true, we need source of citation. -- Harp 13:25, 28 March 2007 (UTC)

Some LHC numbers

A lot of these are taken from http://edms.cern.ch/file/445830/5/Vol_1_Chapter_2.pdf and http://sl.web.cern.ch/SL/sli/Cycles.htm. Also see http://accelconf.web.cern.ch/accelconf/p99/PAPERS/MOCL6.PDF for details of the LHC injection kickers:

• Beam circumference: 26658.883 m. Other sources say that it grows by 1 mm during high tide due to earth tides, but I don't know if that's a max or min number.
• Beam revolution frequency: 11245.5 Hz (speed of light divided by above number). The protons don't actually travel at exactly the speed of light, but the difference is too small for an encyclopedia article to worry about.
• Beam revolution time: 88.924462 us
• This is divided into 3564 buckets of nominally 25 ns (actually 24.95 ns).
• Some 2808 of those buckets (78/99, or 78.8% of the total) actually contain bunches of protons. A bunch fills only a few ns of a 25 ns bucket.
• The pattern of which buckets contain protons is complex. Gaps must be left between bursts of bunches so that magnets can be turned on to redirect the bursts without spraying protons wildly during the transition. The gaps get longer when higher-powered magnets are needed to redirect higher-powered beams. Think of it as needing a gap in a train to throw a railroad switch.
• Additionally, the bucket-filling pattern should have 4-fold symmetry, so at each of the experimental intersection points, a full bucket in one ring always meets a full bucket coming the other way in the other ring.
• The Proton Synchrotron is 84 buckets in circumference, of which 72 are filled with protons and 12 are empty to allow 300 ns for the PS ejection kicker to turn on and redirect the protons to the SPS. (See http://doc.cern.ch/annual_report/2000/vol2/PS.pdf and http://epaper.kek.jp/e00/PAPERS/WEOAF102.pdf for a description of the PS loading process.)
• The Super Proton Synchrotron contains 924 buckets (11 times the circumference of the PS). It is filled with 3 or 4 72-bunch bursts from the PS, with gaps of 8 buckets between bursts. This is limited by the 220 ns SPS injection kicker magnet switching time. The SPS is not filled; after 232 (for a 3-batch) or 312 (for a 4-batch) buckets, there is a large gap in the SPS.
• The spacing between batches in the LHC is limited by the 940 ns LHC injection kicker rise time. This is a 38- or 39-bucket gap.
• A 3-batch consists of 72 buckets with beam (72b), then 8 empty buckets (8e), repeated 3 times, plus an additional 30 empty buckets at the end. 72b+8e+72b+8e+72b+38e, a total of 270 buckets.
• A 4-batch is similar, but consists of 72b+8e+72b+8e+72b+8e+72b+39e, a total of 351 buckets.
• A pattern of two 3-batches plus one 4-batch makes 891 buckets, exactly 1/4 of the full LHC circumference.
• The "334" batch pattern is repeated 4x around the LHC ring, except that one 4-batch is replaced by a 3-batch to provide a 119-bucket "abort gap", to match the 3000 ns LHC beam dump kicker turn-on time. This violates the 4-fold symmetry goal, but providing 4 abort gaps would be even more wasteful.
• The largest batch that could fit into 1/4 of the LHC ring while still providing the necessary injection kicker gap is (891-30)/80 = 10.7625 80-bucket PS loads, and the 3-3-4 pattern achieves this maximum. (I'm not sure why they don't fill the SPS more, such as with a 5-5 pattern. Heck, the SPS could hold a 10-batch with a 132-bucket ejection gap.) —The preceding unsigned comment was added by 71.41.210.146 (talk) 05:11, 13 April 2007 (UTC).

Particles Speed

The article states that a proton takes around 90 microseconds to travel around the collider. Perhaps this could be elaborated upon, to give an idea of how fast these particles are going, maybe in comparison to the speed of light. Any other info in relation might be helpful. I am not at all knowledgeable in this area so maybe someone who is could make this edit? Or is there a reason that the article does not go into further detail regarding the statement? --Overpet 20:27, 6 June 2007 (UTC)

I did a quick calculation and from speed= distance/time the speed of the protons came out at exactly 300million meters per second often used as a good approximate of the speed of light, so thats where the 90 microseconds probably comes from. The protons are traveling (or will be) very close to the speed of light.

Proton energy and velocity relation [2].

energy	velocity as the fraction of light speed
1eV	0.00005
1 MeV	0.046
1 GeV	0.876
1 TeV	0.99999956
7 TeV	0.999999991 (LHC)

--Harp 08:48, 29 June 2007 (UTC)

Magnetic monopoles

Page totally skips the search for magnetic monopoles - info here [3]. -Ravedave 02:15, 17 July 2007 (UTC)

Put it in if you want, but the search for magnetic monopoles is considered a relatively unimportant item on the list of thousands of measurements to be made and searches to be conducted. Jeffakolb 22:18, 13 August 2007 (UTC)

Safety Concerns section

The section on safety concerns not only contains a bunch of speculative BS, but repeats the BS multiple times. As a physicist somewhat involved with the project, I'll recuse myself from getting rid of all the BS, but I am going to get rid of redundant parts. -- Jeffakolb 22:25, 13 August 2007 (UTC)