OVERVIEW OF THE LHC AND ITS INJECTOR CHAIN E. M Mé étral tral (CERN, AB/ABP/LIS) E. (CERN, AB/ABP/LIS) � Introduction: High-luminosity for ATLAS and CMS î Higgs boson � LEP vs. LHC magnets: LEP vs. LHC magnets: Change of Change of Technology Technology � î Superconductivity and cryogenics � LHC’s challenges in accelerator physics � Beam optics � Synchrotron radiation � e - cloud effects (seen also in the PS & SPS and transfer line in between) � Beam-beam � Collimation � LHC injectors’ challenges î “Preservation” of the transverse emittance + generation of the longitudinal structure (25 ns bunch spacing) � LHC filling scheme and operational cycle � Future work in 2007 & 08: Move from installation to commissioning 1/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (1/11) LAYOUT OF THE LHC + TOTEM Courtesy W. Herr ⇒ Measure the total proton-proton cross-section and study elastic scattering and diffractive physics CMS High- luminosity IP = Interaction Point ⇒ Higgs boson ATLAS LHC-B ALICE Beauty quark Ions ⇒ New phase of physics î CP violation matter expected: Quark-Gluon in B decays Plasma (QGP) 2/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (2/11) � COLLISION in IP1 (ATLAS) ⇒ Vertical crossing angle in IP1 (ATLAS) and horizontal one in IP5 (CMS) 3/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (3/11) � Machine LUMINOSITY Number of events per second N = L events / sec ond generated in the collisions σ event Cross-section for the event under study [cm -2 s -1 ] � The Luminosity depends only on the beam parameters ⇒ It is independent of the physical reaction � Reliable procedures to compute and measure 4/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (4/11) ⇒ For a Gaussian (round) beam distribution Number of Revolution Number of particles bunches per beam frequency per bunch Relativistic velocity factor 2 γ N M f = L b rev r F π ε β * 4 n Geometric reduction factor due to the crossing angle Normalized at the IP transverse beam emittance β -function at the collision point = 34 - 2 - 1 L 10 cm s � PEAK LUMINOSITY for ATLAS&CMS in the LHC = peak 5/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (5/11) Number of particles per bunch N b 1.15 â 10 11 Number of bunches per beam M 2808 Revolution frequency f rev 11245 Hz Relativistic velocity factor g r 7461 ( î E = 7 TeV) b -function at the collision point b * 55 cm 3.75 â 10 -4 cm Normalised rms transverse beam emittance e n Geometric reduction factor F 0.84 Full crossing angle at the IP q c 285 m rad Rms bunch length s z 7.55 cm Transverse rms beam size at the IP s * 16.7 m m 6/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (6/11) T ( ) dt ∫ = L L t INTEGRATED LUMINOSITY � int 0 σ = L number of events ⇒ The real figure of merit = int event � LHC integrated Luminosity expected per year (~10 7 s): [80-120] fb -1 Reminder: 1 barn = 10 -24 cm 2 and femto = 10 -15 7/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (7/11) � The total proton-proton cross section at 7 TeV is ~ 110 mbarns: � Inelastic î s in = 60 mbarns � Single diffractive î s sd = 12 mbarns � Elastic î s el = 40 mbarns � The cross section from elastic scattering of the protons and diffractive events will not be seen by the detectors as it is only the inelastic scatterings that give rise to particles at sufficient high angles with respect to the beam axis � Inelastic event rate at nominal luminosity = 10 34 â 60 â 10 -3 â 10 -24 = 600 millions / second per high-luminosity experiment 8/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (8/11) � The bunch spacing in the LHC is 25 ns î Crossing rate of 40 MHz � However, there are bigger gaps (for the kickers) î Average crossing rate = number of bunches â revolution frequency = 2808 â 11245 = 31.6 MHz � (600 millions inelastic events / second) / (31.6 â 10 6 ) = 19 inelastic events per crossing � Total inelastic events per year (~10 7 s) = 600 millions â 10 7 = 6 â 10 15 ~ 10 16 � The LHC experimental challenge is to find rare events at levels of 1 in 10 13 or more î ~ 1000 Higgs events in each of the ATLAS and CMS experiments expected per year 9/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (9/11) Examples of expected Higgs events Examples of expected Higgs events ATLAS ATLAS high lum i. low lum i. 10/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007 Courtesy C. Rembser
Introduction (10/11) Simulated collision Simulated collision Higgs → 4 Muons Courtesy C. Rembser 11/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Introduction (11/11) The ATLAS detector The ATLAS detector 12/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (1/11) (1/11) LHC is in the same tunnel as LEP before 13/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (2/11) (2/11) � LEP vs LHC: Magnets î A change in technology [ ] [ ] ρ = B T m 3 . 3356 p GeV / c BEAM RIGIDITY 0 Magnetic field Curvature radius Beam momentum of the dipoles LEP LHC r [m] 3096.175 2803.95 p 0 [GeV/c] 104 7000 B [T] 0.11 8.33 Room-temperature Superconducting coils coils 14/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (3/11) (3/11) � Main elements are the 2-in-1 superconducting dipoles and quadrupoles operating in superfluid helium at a temperature of 1.9 K 392 1232 15/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (4/11) (4/11) ~ 0.5 MCHF each 7TeV • 8.33T • 11850A • 7MJ Weight: 37 tons 16/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (5/11) (5/11) � LHC superconducting cables Cable Strand Filaments 17/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (6/11) (6/11) � The cables house 36 strands of superconducting wire � Each strand being exactly 825 m m in diameter. Each strand houses 6300 superconducting filaments of Niobium-titanium (NbTi) � Each filament is about 6 m m thick, i.e. 10 times thinner than a normal human hair � Around each filament there is a 0.5 m m layer of high-purity copper � Copper is an insulation material between the filaments in the superconductive state, when the temperature is below -263C. When leaving the superconductive state, copper acts as a conductor transferring the electric current and the heat � Total superconducting cable required 1200 tons which translates to around 7600 km of cable î Total length of filaments is astronomical: 5 times to the sun and back with enough left over for a few trips to the moon! 18/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (7/11) (7/11) � Full list of superconducting magnets and their function 19/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (8/11) (8/11) Lowering of a dipole 20/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (9/11) (9/11) Installation of the dipoles in the tunnel Dipole-dipole interconnect 21/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (10/11) (10/11) CRYOGENICS � The cryogenic technology uses superfluid helium, which has unusually efficient heat transfer properties, allowing kilowatts of refrigeration to be transported over more than a kilometre with a temperature drop of less than 0.1 K � LHC superconducting magnets will sit in a 1.9 K bath of superfluid helium at atmospheric pressure. This bath will be cooled by low pressure liquid helium flowing in heat exchanger tubes threaded along the string of magnets � In all, LHC cryogenics will need 40 000 leak-tight pipe junctions, 12 million litres of liquid nitrogen will be vaporised during the initial cooldown of 31 000 tons of material and the total inventory of liquid helium will be 700 000 litres 22/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
Superconductivity and cryogenics (11/11) (11/11) Cryogenic distribution line (QRL) 23/80 Elias Métral, seminar at MAX-lab, Lund, Sweden, 21/03/2007
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