Status of the Large Hadron Collider - LHC Machine Advisory ...

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Status of the Large Hadron Collider - LHC Machine Advisory ...

Status of the Large Hadron Collider

Lyndon R. Evans

LHC Machine Advisory Committee

CERN, 11-13 December 2003


LHC Machine Advisory Committee

4.5 K Refrigerators for LHC

Air Liquide

Linde

The four new 4.5 K refrigerators for LHC have been

delivered, commissioned and accepted:

• Tendering in 1998

• Split of the supply between Air Liquide and Linde

• Delivery: 2000-2002

• Commissioning: 2001-2003

• Additional refrigeration capacity at 4.5 K for LHC: 4 x 18 kW

Next Step: Upgrade of the Ex-LEP refrigerators (tendering phase in progress)

L.R. Evans – EDMS Document No. 428144

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LHC Machine Advisory Committee

Preseries 1.8 K Refrigeration Units

Air Liquide

IHI-Linde

The two Preseries 1.8 K refrigeration units for LHC

have been delivered, commissioned and accepted:

• Tendering in 1998

• Split of the supply between IHI-Linde and Air Liquide

• Delivery: 2001

• Commissioning: 2002-2003

• Refrigeration capacity at 1.9 K for LHC: 2 x 2400 W

Next Step: Series procurement (manufacturing in progress)

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LHC Machine Advisory Committee

Cryogenics

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LHC Machine Advisory Committee

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LHC Machine Advisory Committee

Magnet Feed Boxes in SM18

After an industrial re-organization of the manufacturing in September

2002, the new challenging amended delivery schedule has been nearly

respected:

• 8/8 boxes delivered in 2003

• 7/8 boxes commissioned and accepted

Next Step: 12 feed boxes fully operational in April 2003

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LHC Machine Advisory Committee

Cryogenics

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LHC Machine Advisory Committee

Cable

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LHC Machine Advisory Committee

Magnets

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LHC Machine Advisory Committee

Magnets

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LHC Machine Advisory Committee

Magnets

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LHC Machine Advisory Committee

Dipoles

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LHC Machine Advisory Committee

Dipoles

Number of magnets

46

44

42

40

38

36

34

32

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0

Number of quenches to reach 8.33 Tesla at the FIRST cool-down

for the first 92 LHC dipoles cold tested

Specifications demands to

reach nominal field of 8.33 in

not more than two quenches

0 1 2 3 4 5 6 7 Not reached

Number of quenches to reach 8.33T at first cool-down

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LHC Machine Advisory Committee

Dipoles

52

Number of quenches to reach nominal field of 8.33 Tesla

after additional thermal cycle for the first 92 dipoles

48

Number of dipoles

44

40

36

32

28

24

20

16

After thermal

cycle no quench

below nominal

field is allowed

51 dipoles have NOT been

submitted to additional

thermal cycle because of

GOOD performance at the first

excitation run (reaching 9T in

not more than 5 quenches )

12

8

4

0

0 1 2 3 4 5 No Additional

Thermal Cycle

Number of quenches to reach 8.33T after thermal cycle

Rejected

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LHC Machine Advisory Committee

Magnets

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LHC Machine Advisory Committee

Magnets

• Series production of insertion quadrupoles in Japan is now almost

complete.

• FNAL production about half way through.

• Delivery of many warm magnets from Russia and Canada now

finished.

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LHC Machine Advisory Committee

SPS progress

• Impedance reduction programme has given good results.

Longitudinal emittance is reduced and the beam is stable. This will

allow a clean transfer between SPS and LHC without the need of

200 MHz cavities in the beginning.

• An LHC-type beam has been accelerated in the SPS and extracted

into the TI8 transfer line.

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LHC Machine Advisory Committee

The challenge of operation - collimation

• Collimation is needed to remove halo particles from the beams,

protecting the superconducting magnets and controlling

background in the detectors.

• The stored energy in the nominal LHC beam is equivalent to

60 kG of TNT. Collimation must also cope safely with fault

scenarios.

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LHC Machine Advisory Committee

Collimation

Transverse energy density is a measure of damage potential AND proportional to lumi!

Courtesy of R. Assmann

At less than 1% of nominal intensity LHC enters new territory. Machine damage

(e.g. collimators) and quenches must be avoided.

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LHC Machine Advisory Committee

Collimation

Courtesy of R. Assmann

At less than 1% of nominal intensity LHC enters new territory. Collimators must

survive expected beam loss.

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LHC Machine Advisory Committee

Collimating with small gaps

LHC beam will be physically quite close

to collimator material and

collimators are long (up to 1.2 m)!

Typical collimator half gap

LHC impedance

without collimators

Courtesy of R. Assmann

Machine impedance increases

while closing collimators

(Carbon curve).

LHC will operate at the

impedance limit with

collimators closed!

illustrative example

Half gap b [m]

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LHC Machine Advisory Committee

Radiofrequency

• All cavities for the main 400.8 MHz RF system have been delivered

and assembled into modules (two modules of four cavities per

beam).

• Problems with power coupler manufacture have been resolved.

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LHC Machine Advisory Committee

Accelerating System

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LHC Machine Advisory Committee

Vacuum

• 25 nsec bunch separation can cause a resonant build-up of

secondary electrons, depositing heat in the cryogenics.

• Conditions in the SPS are very similar to LHC (except for the

temperature). Good agreement of observations with simulations.

• The required “scrubbing” to reduce SEY has been observed in the

warm regions.

• First results show a longer scrubbing time at cryogenic

temperature.

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LHC Machine Advisory Committee

Electron Cloud Effect

1.E-17

15

1.E-18

12

P / Ibatch

1.E-19

1.E-20

9

6

I Bunch

(10 10 p)

1.E-21

1.E-22

3

50060 (Dipole field)

51833 (Field free)

Bunch Intensity (x 1E10)

0

0 24 48 72 96 120 144 168 192 216 240 264 288

Cumul. time (hours)

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LHC Machine Advisory Committee

Electron Cloud Effect

2.5

SEY

2.3

2.1

1.9

1.7

1.5

1.3

1.1

0.9

0.7

0.5

0 500 1000 1500 2000 2500 3000

Energy (eV)

4 h

10 h

21 h

63 h

90 h

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LHC Machine Advisory Committee

Sector 1-2 & TI2 & Pt 2

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LHC Machine Advisory Committee

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LHC Machine Advisory Committee

Sector 2-3 & 3-4 & Pt 4

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LHC Machine Advisory Committee

Sector 4-5 & 5-6 & Pt 6

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LHC Machine Advisory Committee

Sector 6-7 & 7-8 & Pt 8

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TI8 & Sector 8-1

LHC Machine Advisory Committee

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LHC Machine Advisory Committee

Installation of Machine Elements

in Sector 7-8:

Schedule Change Request

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LHC Machine Advisory Committee

Civil works – ATLAS cavern

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LHC Machine Advisory Committee

Civil works – CMS cavern

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