Talk:Large Hadron Collider/Archive 3

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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 [1].

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 [2]. -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)

I replaced that with Supersymmetry, which is one of the major scenarios which is highly anticipated so I thought it deserved a mention (and maybe CP violation studies too). I don't think anyone takes magnetic monopoles seriously anymore, but please feel free to put in some well-referenced monopole material if you want. Rotiro (talk) 20:39, 6 February 2008 (UTC)

Oh wow, I know Pinfold and his crew but I had no idea they were looking for monopoles. I take it back ... one group is looking for monopoles. I guess it's good that someone is trying that. Rotiro (talk) 20:42, 6 February 2008 (UTC)

Now that everybody knows about the monopole search, I don't think we need quite so many citations about it. I'm getting rid of some. Rotiro (talk) 23:18, 15 February 2008 (UTC)

Big numbers

Are the figures at the bottom of Technical Design correct? Those seem to be very very large numbers for the beam and particle energies. John

CaptinJohn 13:46, 26 October 2007 (UTC)

hence the "large" in large hardon collider. —Preceding unsigned comment added by 74.12.157.200 (talk) 02:16, 20 November 2007 (UTC)

Research

Should we really refer to one possible non-peer-reviewed theory by a non-notable scientist? 152.16.10.179 16:06, 16 November 2007 (UTC)

Creation of magnetic monopoles that could catalyze proton decay

Article says that one of the concerns is creation of magnetic monopoles that could catalyze proton decay.

Can anybody describe the mechanism that would make magnetic monopoles catalyze proton decay? --161.53.6.108 15:06, 30 November 2007 (UTC)

Physics for the layman - collision energies

"The LHC can also be used to collide heavy ions such as lead (Pb) with a collision energy of 1,150 TeV."

Could someone perhaps elaborate how the collision energy of lead ions can reach 1,150 TeV when the colliding protons reach only 14 TeV? I kind of get it that the mass of the lead ions must contribute to the collision energy (or I might be completely wrong here), but some explanation on the energies required to accelerate the ions would be extremely helpful! Thanks.

Westworldviewer (talk) 13:08, 6 December 2007 (UTC)

A lead ion has a charge of +82, whereas a proton only has +1. The only way to accelerate a particle is by using its electric charge like a "handle", so the more charge it has, the easier it is to accelerate. Rotiro (talk) 20:45, 6 February 2008 (UTC)

Re: Death of technician in "Construction accidents and delays"

Considering he died helping to build CERN, I think it's only fair that "a technician" is referred to by his name - José Pereira Lages. citation

PapaCheez (talk) 23:40, 6 December 2007 (UTC)

Amend description of ALICE

{{editprotected}}

ALICE is a fairly general purpose detector, albeit one optimized for nucleon collisions rather than particle collisions, and one thing it isn't is small. I'd rephrase:

Six detectors are being constructed at the LHC. They are located underground, in large caverns excavated at the LHC's intersection points. Two of them, ATLAS and CMS are large, "general purpose" particle detectors. The other four (LHCb, ALICE, TOTEM, and LHCf) are smaller and more specialized.

to

Six detectors are being constructed at the LHC. They are located underground, in large caverns excavated at the LHC's intersection points. Two of them, ATLAS and CMS are large, "general purpose" particle detectors. ALICE is a large detector designed search for a quark-gluon plasma in the very messy debris of heavy ion collisions. The other three (LHCb, TOTEM, and LHCf) are smaller and more specialized.

71.41.210.146 (talk) 03:50, 9 December 2007 (UTC)

This page is semiprotected; any username more than a few days old can edit it. There is no need for administrator assistance to edit this page. — Carl (CBM · talk) 04:01, 9 December 2007 (UTC)

But, since a user without an account couldn't do the editing, I put in the suggested changes. Also, I unprotected the page. Thanks for your suggestions, 72.41.210.146! -- SCZenz (talk) 20:58, 9 December 2007 (UTC)