large hadron collider at cern - university of edinburghplayfer/lhclect.pdf · steve playfer...

Steve Playfer University of Edinburgh 15th Novemebr 2008

Large Hadron Collider at CERN

27km circumference depth 70-140m

17.03.2010 1 Status of the LHC - Steve Playfer

LHC vital statistics •  Will eventually collide two 7 TeV proton beams with

beam currents of 600mA E=mc2 gives 14TeV=>0.15g (a fly) Total energy stored in beam is 350MJ (90kg of TNT) •  Uses 1232 superconducting NbTi dipole magnets to

bend beams round the ring •  Beam pipe has vacuum of 10-13 atmospheres •  Total power required to run LHC is 120MW •  Total cost to construct LHC was 3Billion Euros (not including tunnel which was constructed for LEP)

More details on design at http://lhc.web.cern.ch/lhc/

Current status at http://www.lhcportal.com/ 17.03.2010 3 Status of the LHC - Steve Playfer

LHC Dipoles •  Magnets are cooled to

1.9K by superfluid 3He

•  Field ramps from 0.5T to 8.3T during injection •  Both beams are in the

same cryostat


ALICE Experiment

SPS ring injects 400GeV protons

Cool-down time is 4 weeks/sector

Today all the magnets are cold


Four Experiments (ALICE, ATLAS, CMS, LHCb)

LHC RF Cavities •  Needed to accelerate beams from 400GeV to

7TeV after injection •  Also needed to replace synchrotron energy losses during stable beam delivery (collisions) •  8 cavities/beam •  Frequency 400 MHz •  Accelerating gradient 5MV/m


LHC Operation •  Proton beams are injected from the SPS at 400GeV

and then accelerated to 7TeV. This is known as a “fill”. •  The lifetime of the stored beams is ~10 hours. •  There will eventually be 2808 bunches of protons in

each direction. Each bunch contains 1011 protons and travels round the ring in 0.9ms.

•  The bunch spacing is ~7m or 25ns, the bunch length is 7.5cm, and the crossing rate is 40MHz at each of the four interaction points (ATLAS, CMS, LHCb, ALICE).

•  At full luminosity (1034/cm2/s) there will be several interactions during each bunch crossing.

•  The expected data rate is 100MB/s per experiment or ~10 PetaBytes/year!


LHC turn-on 10/9/08 Big media publicity day (I was at the Scottish parliament)

Proton beams were circulated in each direction for a short time.


The incident on 19/10/08

•  Burnt a hole in a cryogenic circuit causing a large liquid Helium leak (6 Tonnes)

•  Energy released as pressure wave was sufficient to damage several magnets

•  Safety interlocks restricted damage to one sector

•  During power testing of a dipole magnet at high current (9kA) there was an electrical arc due to sudden high resistance.

Dissipated 400MJ of energy very quickly.


The culprit: a bus-bar joint

17.03.2010 Status of the LHC - Steve Playfer 10

 24’000 bus-bar joints in the LHC main circuits.

 10’000 joints are at the interconnection between magnets. They are welded in the tunnel.

Nominal joint resistance: • 1.6 K 300pΩ • 300K ~10µΩ

For the LHC to operate safely at a certain energy, there is a limit to the maximum value of the joint resistance.

2008/9 - LHC repair and consolidation

17.03.2010 Status of the LHC - Steve Playfer

11

14 quadrupole magnets replaced

39 dipole magnets replaced

204 electrical inter-connections repaired

Over 4km of vacuum beam tube cleaned

New longitudinal restraining system for 50 quadrupoles

Almost 900 new helium pressure release ports

6500 new detectors and 250km cables for new Quench Protection System to protect from busbar quenches

November/December 2009


20th Nov Day 0 Both beams circulating after 6 hours 23rd Nov Day 3 First pilot collisions at 450 GeV 29th Nov Day 9 Beams ramped to 1.18 TeV 6th Dec Day 16 Stable collisions @ 450 GeV for the experiments 8th Dec Day 18 Both beams ramped to 1.18 TeV – first collisions

Low luminosity, but all four experiments observed collisions

First papers (on inclusive charged track multiplicity) have already appeared.

Results are being presented this week (Moriond QCD)

2010-2011 Run


  (Ambitious) goal : each experiment collects an integrated luminosity of 1 fb-1 of data

  Peak luminosity 2x1032/cm2/s (same as Tevatron)   700 bunches with 108 p/bunch (30MJ of stored energy)   There will be a short heavy ion run in November 2010   Beam Energy will be 3.5TeV (maximum safe level

before further improvements to machine in 2012)

Beams injected this month. About to accelerate them to 3.5TeV.

First collisions at the end of the month?

1031/cm2/s

April July November

1032/cm2/s

2010

LHC Detectors •  ATLAS is a general purpose detector (GPD)

46mx25mx25m, 7000Tonnes, central magnetic solenoid 2T and muon toroids 4T

•  CMS is another GPD, 21mx15mx15m, 12500Tonnes, central magnetic solenoid 4T –  GPDs look for new heavy particles –  Each collaboration has 2000 physicists (10% from UK)

•  LHCb is a forward spectrometer with a dipole bending magnet (4Tm) –  Designed to study b quarks –  Collaboration has 700 physicists (20% from UK)

•  ALICE is designed to look at heavy ion collisions 17.03.2010 14 Status of the LHC - Steve Playfer

ATLAS


CMS


Décembre 2005

LHCb

Muon detectors

Bending Magnet

Vertex Locator

Tracking System

Calorimeter Particle ID (RICH)



Λ → p π

First Physics Results


Number of charged tracks as a function of (pseudo)rapidity is rather flat

ALICE EPJC 65:111 (2010)

National Geographic News (4th Dec)

‘….a machine called ALICE....

found that a proton-proton collision

recorded on November 23rd

created the precise ratio of matter and antimatter particles

predicted from theory..’


W.H.Bell (Moriond QCD 2010)


C.Roland (Moriond QCD 2010)

CMS First Results

Transverse momentum spectrum is as expected

LHCb First Results


Inclusive KS production in the forward direction

M.Knecht (Moriond QCD 2010)

Long Term LHC Schedule •  Big shutdown in 2012 to make machine safe to

operate at full beam energy of 7 TeV •  Then there will be long 18 month runs separated by

shorter 6 month shutdowns •  Peak luminosity will gradually increase (x2/year?) •  There will improvements to the injectors (2015-2020) •  Eventually there will be upgrades to the detectors

(2016-2020?)


My optimistic scenario… -  Find evidence for supersymmetry in 2011 -  Find Higgs boson(s) by 2014

Why the LHC won’t destroy the world Centre of mass energy of proton-proton collisions ECM=14TeV

Can be achieved by colliding a high energy proton with a proton at rest ECM = sqrt(2Epmp) with Ep ~105 TeV

Primary cosmic rays (protons) interact with the Earth’s upper atmosphere. Highest observed energy cosmic rays are Ep ~108 TeV which gives ECM>>14TeV.

There are even more energetic collisions in the centres of galaxies, black holes etc.

LHC collisions are the highest energy in a laboratory 17.03.2010 26 Status of the LHC - Steve Playfer

large hadron collider at cern - university of edinburghplayfer/lhclect.pdf · steve playfer...

Documents