FermilabFermilab’’ss TevatronTevatron && LargeLarge HadronHadron ColliderCollider (LHC)(LHC)
Teruki Kamon PHYS 627
Taken from slides by Ron Moore, Paul Derwent, Mike Syphers (FNAL) (Apr 2005) Modified/updated by Teruki Kamon for PHYS 627
Hadron Collisions at the Tevatron and the LHC 1
AA littlelittle bitbit ofof EinsteinEinstein……
Recall the well-known equation: E = mc 2
Measure energy in “electron volts” = eV (1 eV ≈ 1.6 x 10−19 Joule) 2 Measure mass in units of eV/c … (1 eV/c2 ≈ 1.78 x 10−36 kg)
…but often use units where c ≡ 1, so mass can also be measured in eV
For a moving particle: 1 v 2 2 2 2 γ = β ≡ E = (mc ) + ( pc) = γ mc 1 − β 2 c 2 2 Total Energy = Rest Energy + Kinetic Energy E = mc + (γ − 1 )mc
Ultra-relativistic: γ >> 1 can neglect rest mass
Hadron Collisions at the Tevatron and the LHC 2 FixedFixed TargetTarget vs.vs. CollidersColliders w/ow/o calculuscalculus
Hadron Collisions at the Tevatron and the LHC 3
FixedFixed TargetTarget vs.vs. CollidersColliders w/w/ calculuscalculus Fixed Target Center of Mass Energy
Energy E s = 2mE
ultrarelativistic limit
Head-On Collision
Energy E Energy E s = 2E
Compare protons @ 1 TeV:
Fixed Target: ECM = 43 GeV Collider: ECM = 2000 GeV
Big advantage for colliders! ⇒ Most efficient use of beam energy for physics!
Challenge to get a high collision rate to look for interesting (rare) processes
Fixed target still essential for secondary beams: antiprotons, kaons, µ’s, ν’s
Hadron Collisions at the Tevatron and the LHC 4 Hadron Collisions at the Tevatron and the LHC 5
σ int σ int σ int A
3.46 x 109 crossings Skip
Hadron Collisions at the Tevatron and the LHC 6 LuminosityLuminosity N N L = f 1 2 Luminosity is measure of the collision rate in a collider 4πσ 2 − 2 −1 Units are cm s f is collision frequency 32 − 2 − 1 × Peak luminosity ~ 1.2 10 cm s N 1, N 2 are # particles in each beam 32 − 2 − 1 Goal ~ 4.0 ×10 cm s σ is beam size −24 2 32 − 2 − 1 − 1 10 cm = 1 barn; 10 cm s = 360 nb /hr To reach higher luminosity…
More beam
May be hard…Tevatron needs more antiprotons
Higher collision frequency (more bunches)
Not for Tevatron – will keep using 36 bunches of protons and antiprotons
Smaller beam
Tevatron beams are ~30 µm wide at interaction points
Linear colliders have nm size beams
All can be hard to achieve due to instabilities that may develop Want high luminosity to study rare processes
Luminosity × Cross Section = Event Rate 32 −2 − 1 e.g., 1 × 10 cm s × 10 pb = 3.6 events/hr Hadron Collisions at the Tevatron and the LHC 7
ModelModel ofof AcceleratorAccelerator Accelerating device + magnetic field to bring it back to accelerate again
+=
Hadron Collisions at the Tevatron and the LHC 8 Hadron Collisions at the Tevatron and the LHC 9
WhereWhere isis thethe FermilabFermilab??
Hadron Collisions at the Tevatron and the LHC 10 Looking Down on the Fermilab Accelerator Complex
~5 mi. CDF
D0
Hadron Collisions at the Tevatron and the LHC 11
CloselyClosely LookingLooking DownDown onon thethe FermilabFermilab
Wilson Hall
Tevatron
Main 1 km Injector
Hadron Collisions at the Tevatron and the LHC 12 NuMI (120 GeV protons) MiniBoone (8 GeV) 1 6 2
3 7 5 4
9
Accelerator Highest Energy Cockroft Walton 750 keV 8 Linac 400 Mev 10 Booster 8 GeV Main injector 150 GeV TEVATRON 980 GeV
MachineMachine EnergiesEnergies ((cc == 1)1)
Comparing relativistic β, γ for electrons and protons at various energies…
electron proton rest mass 511 keV 938 MeV
Machine KE βγβγ Cockroft-Walton 750 keV 0.926794588 2.47 0.707389304 1.00 FNAL Linac 400 MeV 0.999999186 784 0.818829208 1.43 FNAL Booster 8 GeV 0.999999998 15657 0.994538328 9.53 Main Injector 150 GeV 1 293543 0.999980691 161 ILC 500 GeV 1 978475 0.999998247 534 Tevatron 980 GeV 1 1.918E+06 0.999999543 1046 LHC 7 TeV 1 1.761E+07 0.999999995 9596 VLHC? 100 TeV 1 1.957E+08 1 106611
1 keV = 103 eV 1 MeV = 106 eV 1 GeV = 109 eV 1 TeV = 1012 eV Mass of top quark ≈ 175 GeV
Hadron Collisions at the Tevatron and the LHC 14 HiHi--riserise BuildingBuilding
•25 keV H− ion source •750 keV Cockcroft- Walton accelerator
Hadron Collisions at the Tevatron and the LHC 15
CockcroftCockcroft--WaltonWalton
•25 keV H− ion source •750 keV Cockcroft-Walton accelerator
Hadron Collisions at the Tevatron and the LHC 16 LinacLinac
Accelerate H− ions to 400 MeV − 116 MeV Alvarez linac (201.25MHz) H ions 400 MeV side-coupled cavity linac (805 MHz)
Hadron Collisions at the Tevatron and the LHC 17
BoosterBooster
Booster: 8 GeV Synchrotron Runs at 15 Hz Stripper foil at injection removes electrons from H− ions Accelerates protons from 400 MeV to 8 GeV Most protons (>75%) going through Booster are delivered to MiniBoone (eventually NuMI)
Hadron Collisions at the Tevatron and the LHC 18 Main Injector & Recycler Ring
Recycler Main Injector
Hadron Collisions at the Tevatron and the LHC 19
MainMain InjectorInjector (MI)(MI)
Replaced Main Ring (formerly in Tevaron tunnel)
Higher repetition rate for stacking pbars
Simultaneous stacking and fixed target running Many operating modes 12 Pbar production: ~ 6-7 x 10 120-GeV protons to pbar target
“Slip-stacking” – merge two booster batches of beam on 1 MI ramp cycle
“Tevatron protons/pbars”:
Accelerate 8 GeV to 150 GeV 9 Coalesce 7-9 proton bunches at 90% eff into “270-300 x 10 proton” bunch 9 Coalesce 5-7 pbar bunches at 75-90% eff into “20-80 x 10 antiproton” bunch
Transfer 8-GeV protons/pbars to the Recycler
Provide protons for neutrino production
8-GeV protons for MiniBoone
120-GeV protons for NuMI
120-GeV protons to Switchyard (fixed target area) Hadron Collisions at the Tevatron and the LHC 20 DebuncherDebuncher && AccemulatorAccemulator
Debuncher
Two rings
Accumulator
Hadron Collisions at the Tevatron and the LHC 21
PbarPbar (Antiproton)(Antiproton) SourceSource
(1) > 6 x 1012 120-GeV protons per pulse strike Ni target every 2-3 sec; (2) Li lens (740 Tesla/m) collects negative secondaries; (3) Pulsed dipole “PMAG” bends pbars down AP-2 line to Debuncher ε≈(14-18) x 10−6 pbars/proton on target Pbars “debunched”, cooled briefly in Debuncher prior to Accumulator Hadron Collisions at the Tevatron and the LHC 22 PbarPbar (Antiproton)(Antiproton) SourceSource Stack rate = 6-14 mA/hr Depending on stack size; Limited by stochastic cooling systems in Accumulator Transverse beam size increases linearly with stack size - That’s a drawback… In a really good 24 hour period, nearly 200 x 1010 pbars can be accumulated.
−12 −24 Pbar Production Rate = 3.3 x 10 g/day (Mpbar ≈ 1.67 x 10 g) 800 million years to make 1 g of antimatter!
Hadron Collisions at the Tevatron and the LHC 23
TevatronTevatron OverviewOverview
Proton-pbar collisions (Ebeam = 980 GeV)
Revolution time ~ 21 µs
Virtually all of the Tevatron magnets are superconducting (Cooled by liquid helium, operate at 4 K)
150 GeV beams are injected from MI
Protons injected from P1 line at F17; Pbars injected from A1 line at E48 36 bunches of proton and pbars circulate in same beam pipe, but separated by “electrostatic separators”
3 trains of 12 bunches with 396 ns separation (see the next page)
2 low β (small beam size) intersection points (CDF and D0)
8 RF cavities (near F0) to keep beam in bucket, acceleration
1113 RF buckets (53.1 MHz ⇒ 18.8 ns bucket length) Hadron Collisions at the Tevatron and the LHC 24 ProtonProton BunchBunch PositionsPositions 3 trains of 12 bunches with 396 ns separation
P12 P13
P1 P24 P25 P36
Hadron Collisions at the Tevatron and the LHC 25
ProtonsProtons andand PbarsPbars atat HEPHEP
Proton Collide Collide bunches @ CDF @ D0 P1-P12 A25-A36 A13-A24 A P13-P24 A1-A12 A25-A36 2 4~ P25-P36 A13-A24 A1-A12 P1 3 P25~P36
Hadron Collisions at the Tevatron and the LHC 26 ProtonProton--PbarPbar CollisionCollision PointPoint
Hadron Collisions at the Tevatron and the LHC 27
First Collisions at the Tevatron Run 493 Event 11
Run 493 Event 15
October 13, 1985
Hadron Collisions at the Tevatron and the LHC 28 LargeLarge HadronHadron ColliderCollider
HighlightsHighlights
~27km circumference
1232 bends
Main bends are 14.3 meters long
The strength of each magnet is 8.33 Tesla
Huge synchrotron radiation loss. SynchrotronSynchrotron RadiationRadiation Accelerated charges produce radiation.
r e ⎡ nr × (nr × β&)⎤ Useful equations for ideal conditions in SI E a = ⎢ ⎥ c R ⎣ ⎦ ret qvB v = r c r r c r 2 & S = E × B = E nr γm 4π 4π a 2 2 dP c r 2 e 2 e 2 = RE = nr × (nr × β&) = vr& sin 2 Θ dΩ 4π a 4πc 4πc 3 2 2 e 2 P = vr& 3 c 3 Above we integrated over the angle Θ, and below switched to more familiar units SI
2 r 2 q ⎛ dp ⎞ 4 1 dE dpr = ⎜ ⎟ ⎛ q ⎞ 2 2 Pγ 2 3 From here were can get if << 6π m c dt Pγ ∝ ⎜ ⎟ U B ε ο ⎝ ⎠ ⎝ m ⎠ c dτ dτ
Go to, for example, Jackson’s Classical Electrodynamics book, find more convenient expression in terms of v, ρ, γ
Hadron Collisions at the Tevatron and the LHC 31