Royal Society 16th May 2011

The Large Hadron ColliderThe Large Hadron ColliderLyn Evans Imperial College/CERN

The birth of the LHCThe birth of the LHC

Lyn Evans2

It is generally accepted that the kick-off It is generally accepted that the kick-off of the LHC Project was the Lausanne of the LHC Project was the Lausanne Workshop in March 1984 where particle Workshop in March 1984 where particle physicists and machine builders got physicists and machine builders got together for the first time.together for the first time.

In reality, the LHC adventure started In reality, the LHC adventure started much earlier…much earlier…

ISRISR

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Interaction pointwith crossing angle

Lyn Evans

Approval of the LHCApproval of the LHC

Lyn Evans4

In December 1993, a plan was In December 1993, a plan was presented by the Director General presented by the Director General designate Chris Llewellyn Smith to the designate Chris Llewellyn Smith to the CERN Council to build the machine CERN Council to build the machine over a ten-year period by reducing the over a ten-year period by reducing the other experimental program of CERN other experimental program of CERN to the absolute minimum, with the to the absolute minimum, with the exception of the full exploitation of the exception of the full exploitation of the LEP collider. An external expert panel LEP collider. An external expert panel endorsed the design.endorsed the design.

Lyn Evans5

Although the plan was generally well Although the plan was generally well received, it became clear that two of the received, it became clear that two of the largest contributors, Germany and the largest contributors, Germany and the United Kingdom, were very unlikely to United Kingdom, were very unlikely to agree to the budget increase required. agree to the budget increase required. They also managed to get Council voting They also managed to get Council voting procedures changed from a simple procedures changed from a simple majority to a double majority, where majority to a double majority, where much more weight was given to the large much more weight was given to the large contributors so that they could keep contributors so that they could keep control.control.

Lyn Evans6

In June 1994, the proposal to build the LHC was In June 1994, the proposal to build the LHC was made once more to Council. Seventeen member made once more to Council. Seventeen member states voted to approve the project. However, states voted to approve the project. However, because of the newly adopted double voting because of the newly adopted double voting procedure, approval was blocked by Germany procedure, approval was blocked by Germany and the UK, who demanded substantial and the UK, who demanded substantial additional contributions from the two host states, additional contributions from the two host states, France and Switzerland, claiming that they France and Switzerland, claiming that they obtained disproportionate returns from the CERN obtained disproportionate returns from the CERN budget. They also requested that financial budget. They also requested that financial planning should proceed under the assumption planning should proceed under the assumption of 2% annual inflation, with a budget of 2% annual inflation, with a budget compensation of 1%, essentially resulting in a compensation of 1%, essentially resulting in a 1% annual reduction in real terms.1% annual reduction in real terms.

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In order to deal with this new constraint, we were In order to deal with this new constraint, we were forced to propose a “missing magnet” machine forced to propose a “missing magnet” machine where only two thirds of the dipoles would be where only two thirds of the dipoles would be installed in a first stage. The deadlock concerning installed in a first stage. The deadlock concerning extra host-state contributions was broken when extra host-state contributions was broken when France and Switzerland agreed to make extra France and Switzerland agreed to make extra voluntary contributions in the form of a 2% annual voluntary contributions in the form of a 2% annual inflation adjustment, compared with the 1% inflation adjustment, compared with the 1% adjustment from the other member states. The adjustment from the other member states. The project was approved for two-stage construction, project was approved for two-stage construction, to be reviewed in 1997 after the size of the to be reviewed in 1997 after the size of the contribution offered by non-member states contribution offered by non-member states interested in joining the LHC program would be interested in joining the LHC program would be known.known.

Japan becomes an ObserverJapan becomes an ObserverJune 1995June 1995

Lyn Evans8

Japan becomes an Observer of CERN and announces a financial contribution to the LHC. The Japanese Minister for Education, Sciences and Culture offers a Daruma doll to CERN’s Director-General. According to Japanese tradition, an eye is painted on the doll to mark the beginning of the LHC project and the second eye must be drawn at the time of its completion. Japan makes two other major financial contributions to the LHC project in 1996 and 1998.

19961996

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MarchMarch India makes a financial contribution to the

construction of the LHC.

And in June, Russia announces a financial contribution to the project.

DecemberDecember Canada announces a financial contribution for the

LHC, while a protocol of co-operation is defined for participation of the United States.

In December 1997, the US declares a contribution.

Lyn Evans10

A final sting in the tail came in June 1996 from A final sting in the tail came in June 1996 from Germany who unilaterally announced that, in order Germany who unilaterally announced that, in order to ease the burden of reunification, it intended to to ease the burden of reunification, it intended to reduce its CERN subscription by between 8% and reduce its CERN subscription by between 8% and 9%. Confining the cut to Germany proved 9%. Confining the cut to Germany proved impossible. The UK was the first to demand a impossible. The UK was the first to demand a similar reduction in its contribution in spite of a similar reduction in its contribution in spite of a letter from the UK Minister of Science during the letter from the UK Minister of Science during the previous round of negotiations stating that the previous round of negotiations stating that the conditions are “reasonable, fair and sustainable”. conditions are “reasonable, fair and sustainable”. The only way out was to allow CERN to take out The only way out was to allow CERN to take out loans, with repayment to continue after the loans, with repayment to continue after the completion of LHC construction.completion of LHC construction.

Lyn Evans11

In December 1996 Council, Germany declared that In December 1996 Council, Germany declared that “a greater degree of risk would inevitably have to “a greater degree of risk would inevitably have to accompany the LHC”. The project was approved accompany the LHC”. The project was approved for single-stage construction with the deficit for single-stage construction with the deficit financed by loans. It was also agreed that the final financed by loans. It was also agreed that the final cost of the project was to be reviewed at the half-cost of the project was to be reviewed at the half-way stage with a view to adjusting the completion way stage with a view to adjusting the completion date. With all contingency removed, it was date. With all contingency removed, it was inevitable that a financial crisis would occur at inevitable that a financial crisis would occur at some time, and this was indeed the case when the some time, and this was indeed the case when the cost estimate was revised upwards by 18% in cost estimate was revised upwards by 18% in 2001. 2001.

The LHC and its detectorsThe LHC and its detectors

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Aerial view of Point 5Aerial view of Point 5 Gallo-roman vestiges 1998 Gallo-roman vestiges 1998

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Roman coins found duringRoman coins found during a archeological excavations at Point rcheological excavations at Point

5 5

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ATLAS cavern inauguration ATLAS cavern inauguration 20032003

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End of civil engineering works in Point End of civil engineering works in Point 55

(1st February 2005)(1st February 2005)

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23 km of superconducting 23 km of superconducting magnetsmagnets

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Cryodipole cross-sectionCryodipole cross-section

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Superconducting accelerator Superconducting accelerator magnetsmagnets

Lyn Evans

In a superconducting magnet, the field level and geometry is basically given by the current distribution in the coils.

To match the geometry of the beam tubes, the coils are saddle-shaped & elongated.In the LHC, two sets of coils create opposite fields in the neighbouring apertures.24

……at the physics laboratory of at the physics laboratory of Leyden, helium was first liquifiedLeyden, helium was first liquified

Lyn Evans

Heike Kamerlingh Onnes

“Door meten tot weten”To knowledge through measurement

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Discovery of superconductivity Discovery of superconductivity 8th April 19118th April 1911

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7000 km of superconducting cable 7000 km of superconducting cable Nb-TiNb-Ti

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Superfluid heliumSuperfluid helium

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2.3K

2.17K

« In my PhD work in Toronto on superconductivity, I had often seen the sudden cessation of boiling at the lambda temperature Tλ but had paid it no particular attention. It never occured to me that it was of fundamental significance. »

J. Allen, Physics World, November 1988, p 29.

J. F. AllenJ. F. Allen

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Dipole cold massesDipole cold masses

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Descent of the last magnetDescent of the last magnet 26 April 2007 26 April 2007

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30’000 km underground at 2 km/h!

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Transport in the tunnel with an optical guided vehicle

Transfer on jacksTransfer on jacks

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Dipole dipole interconnectDipole dipole interconnect

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10 September 200810 September 2008

5 DGS5 DGS

Electrical spliceElectrical splice

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Cable Junction Box Cross-section

Upper Tin/Silver Soldering alloy Layer

Inter-Cable Tin/Silver Soldering Alloy Layer

Superconducting Cable in Copper

Stabilizer

Upper Copper Profile

Lower Copper U Profile

Lower Tin/Silver Soldering Alloy Layer

Completed Junction

Busbar spliceBusbar splice

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Busbar spliceBusbar splice

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The electron cloud effect The electron cloud effect

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Reduction of one decade in about 17h (periods with constant number of bunches)

V. Baglin et al.

Vacuum pressure evolution with Vacuum pressure evolution with 50 ns50 ns

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Emittance preservation Emittance preservation Limited blow-up observed after some hours at injection (injected emittances are in the range 2.5-3 mm), even with 800 and >1000 bunches. Clear improvement due to reduced activity in the arcs. Low chromaticity (~4)

We started like that...

Day 1 – 300 bunchesDay 3 – 800 bunches

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