View
8
Download
0
Category
Preview:
Citation preview
1Hadron Collisions at the Tevatron and the LHC
FermilabFermilab’’s Tevatron s Tevatron &&Large Large Hadron Collider Hadron Collider (LHC)(LHC)
Teruki KamonPHYS 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 2
A little bit of EinsteinA little bit of Einstein……Recall the well-known equation:
Measure energy in “electron volts” = eV
(1 eV ≈ 1.6 x 10−19 Joule)
Measure mass in units of eV/c2…
(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:
Total Energy = Rest Energy + Kinetic Energy
Ultra-relativistic: γ >> 1 can neglect rest mass
2222 )()( mcpcmcE γ=+=
2mcE =
21
1
βγ
−=
c
v≡β
22 1 mc)(mcE −+= γ
Hadron Collisions at the Tevatron and the LHC 3
Fixed Target vs. Fixed Target vs. CollidersCollidersw/o calculusw/o calculus
Hadron Collisions at the Tevatron and the LHC 4
Fixed Target vs. Fixed Target vs. CollidersColliders
Energy E
FixedTarget Center of Mass Energy
mEs 2=
Energy E Energy EEs 2=
Head-On Collision
ultrarelativistic limit
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
w/ calculusw/ calculus
Hadron Collisions at the Tevatron and the LHC 5
Hadron Collisions at the Tevatron and the LHC 6
3.46 x 109
crossings
Aintσ
intσ intσ
Skip
Hadron Collisions at the Tevatron and the LHC 7
LuminosityLuminosityLuminosity is measure of the collision rate in a collider
Units are cm− 2 s−1
Peak luminosity ~ 1.2 ×1032 cm− 2 s− 1
Goal ~ 4.0 ×1032 cm− 2 s− 1
10−24 cm2 = 1 barn; 1032 cm− 2 s− 1 = 360 nb− 1/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 beamTevatron beams are ~30 µm wide at interaction pointsLinear colliders have nm size beams
All can be hard to achieve due to instabilities that may develop
Want high luminosity to study rare processesLuminosity × Cross Section = Event Ratee.g., 1 × 1032 cm−2 s− 1 × 10 pb = 3.6 events/hr
221
4πσNN
fL =
sizebeam is
beam each in particles # are
frequency collision is
21
σ
NN
f
,
Hadron Collisions at the Tevatron and the LHC 8
Model of AcceleratorModel of AcceleratorAccelerating device + magnetic field to bring it back to accelerate again
+ =
Hadron Collisions at the Tevatron and the LHC 9
Hadron Collisions at the Tevatron and the LHC 10
Where is the Where is the FermilabFermilab??
Hadron Collisions at the Tevatron and the LHC 11
Looking Down on the Looking Down on the FermilabFermilab Accelerator ComplexAccelerator Complex
CDF
D0
~5 mi.
Hadron Collisions at the Tevatron and the LHC 12
Closely Looking Down on the Closely Looking Down on the FermilabFermilab
1 kmMain Injector
Tevatron
Wilson Hall
8 GeVBooster
980 GeVTEVATRON
150 GeVMain injector
400 MevLinac
750 keVCockroft Walton
Highest EnergyAccelerator
NuMI (120 GeV protons)MiniBoone
(8 GeV)
2
3
1
4
5
6
9
7
10
8
Hadron Collisions at the Tevatron and the LHC 14
Machine Energies (Machine Energies (cc = 1)= 1)Comparing relativistic β, γ for electrons and protons at various energies…
rest mass
Machine KE β γ β γCockroft-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
electron511 keV
proton938 MeV
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 15
HiHi--rise Buildingrise Building
•25 keV H− ion source
•750 keV Cockcroft-Walton accelerator
Hadron Collisions at the Tevatron and the LHC 16
CockcroftCockcroft--WaltonWalton
•25 keV H− ion source
•750 keV Cockcroft-Walton accelerator
Hadron Collisions at the Tevatron and the LHC 17
H− ions
LinacLinac
Accelerate H− ions to 400 MeV
116 MeV Alvarez linac (201.25MHz)
400 MeV side-coupled cavity linac (805 MHz)
Hadron Collisions at the Tevatron and the LHC 18
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 19
Main Injector & Recycler RingMain Injector & Recycler Ring
Main InjectorRecycler
Hadron Collisions at the Tevatron and the LHC 20
Main Injector (MI)Main Injector (MI)Replaced Main Ring (formerly in Tevaron tunnel)
Higher repetition rate for stacking pbarsSimultaneous stacking and fixed target running
Many operating modesPbar production: ~ 6-7 x 1012 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
Coalesce 7-9 proton bunches at 90% eff into “270-300 x 109 proton” bunch
Coalesce 5-7 pbar bunches at 75-90% eff into “20-80 x 109 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 21
Debuncher
Accumulator
Debuncher Debuncher & & AccemulatorAccemulator
Two rings
Hadron Collisions at the Tevatron and the LHC 22
PbarPbar (Antiproton) Source(Antiproton) Source
(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 23
PbarPbar (Antiproton) Source(Antiproton) SourceStack 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.
Pbar Production Rate = 3.3 x 10−12 g/day (Mpbar ≈ 1.67 x 10−24 g)
800 million years to make 1 g of antimatter!
Hadron Collisions at the Tevatron and the LHC 24
TevatronTevatron OverviewOverviewProton-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 MIProtons 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, acceleration1113 RF buckets (53.1 MHz ⇒ 18.8 ns bucket length)
Hadron Collisions at the Tevatron and the LHC 25
Proton Bunch PositionsProton Bunch Positions3 trains of 12 bunches with 396 ns separation
P1
P12
P13
P24P25 P36
Hadron Collisions at the Tevatron and the LHC 26
Protons and Protons and PbarsPbars at HEPat HEP
Collide @ D0
Collide @ CDF
Proton bunches
A1-A12A13-A24P25-P36
A25-A36A1-A12P13-P24
A13-A24A25-A36P1-P12
P25~P36
A24~P
13
Hadron Collisions at the Tevatron and the LHC 27
ProtonProton--PbarPbar Collision PointCollision Point
Hadron Collisions at the Tevatron and the LHC 28
First Collisions at the Tevatron
October 13, 1985
Run 493 Event 11
Run 493 Event 15
Large Large Hadron ColliderHadron Collider
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.
Hadron Collisions at the Tevatron and the LHC 31
2
3
2
22
3
22
22
2
ret
3
2
sin444
44
vc
eP
Θvπc
e)βn(n
πc
eER
π
c
dΩ
dP
nEπ
cBE
π
cS
R
)βn(n
c
eE
a
a
a
&r
&r&rrr
rrrrr
&rrr
=
=××==
=×=
⎥⎦
⎤⎢⎣
⎡ ××=
Accelerated charges produce radiation.
ττ d
pd
d
dE
c
r
<<1
22
4
BUm
qP ⎟
⎠⎞
⎜⎝⎛∝γ
m
qvBv
γ=&
2
32
2
6⎟⎠⎞
⎜⎝⎛=
dt
pd
cm
qP
r
επ ογ
Useful equations for ideal conditions in SI
Above we integrated over the angle Θ, and below switched to more familiar units SI
From here were can get if
Synchrotron RadiationSynchrotron Radiation
Go to, for example, Jackson’s Classical Electrodynamics book, find more convenient expression in terms of v, ρ, γ
Recommended