Accelerators
Mark Mandelkern
For producing beams of energetic particles
• Protons, antiprotons and light ions
• heavy ions
• electrons and positrons
• (secondary) neutral beams (photons, neutrons, neutrinos)
Some accelerator applications
• particle and nuclear physics• synchrotron radiation
– materials science, biology
• medical radiation therapy• isotope production• plasma heating• high energy X-ray production
– non-destructive testing, food sterilization
Accelerators in particle physics
• probe small-scale structure• = h/p10-13 cmp(MeV/c)• electrons, positrons
– Pointlike (also neutrinos), no strong interactions
– costly to accelerate (synchrotron radiation)
• protons and antiprotons– complicated structures make interpretation difficult
– easier to accelerate to ultra-high energies
Accelerator types
• electrostatic– battery, lightning, van de Graff, Pellatron: to about 30
MeV; for nuclear physics and isotope production
• cascade– Cockcroft-Walton: to several MeV; cheap; for X-ray
sources and injectors
• Linear– RFQ
– drift-tube(Wideroe, Alvarez):preaccelerators, LAMPF
– Waveguide:electrons only(SLAC, NLC)
Pelletron
Van de Graff
Cockcroft-Walton principle
ISIS Cockcroft-Walton
Wideroe Linac
Alvarez Linac
Radiofrequency Quadrupole RFQ
SLAC Linac
SLAC Waveguide
Phase Stability
Circular Accelerators
• betatron– electrons only, cheap, portable, to ~500 MeV
• cyclotron– Protons to ~500 MeV (TRIUMF, PSI)
• Synchrotron– 100 GeV electrons (LEP)– 1 TeV protons and antiprotons (FNAL)– 7 TeV protons (LHC)
Cyclotron animation
First cyclotron
TRIUMF
Strong focusing principle
Strong focusing animation
HEP Accelerator Systems
• FNAL Tevatron(1 TeV p)– CW(750 keV):Linac:Booster(8 GeV):Main
Injector(120 GeV): Tevatron Ring
• CERN SPS/LEP(400 GeV p/100 GeV e+-)
– RFQ (750 keV):Linac (50 MeV):PS(28 GeV):SPS:LEP
FNAL Tevatron Tunnel
Synchrotron radiation
W=(e2/)(4R) loss per turn
Ec=(hc/232R) peak energy
E/mc2
LEP: 100 GeV/beam: R=4.9km W~3 GeV Ec~ 90 keV(hard X-ray) 288 SC RF cavities
evatron: E=1 TeV R=1.1km W~ 10 eV Ec~0.4 eV
LHC: E=7 TeV R=4.9 kmW~5 keV, Ec~27 eV
Colliders
• Circular
– e- e+ below 10 GeV (BEPS/PEP-2/KEKB)
– 1 TeV p/1 TeV pbar (Tevatron-FNAL),
– 27.5 GeV e-/920 GeV p (HERA-DESY)
– 105 GeV e-/105 GeV e+ (LEP-CERN)
– 7 TeV p/7TeV p (LHC-CERN)
• Linear
– 50 GeV e-/50 GeV e+ (SLC-SLAC)
– ~1 TeV e-/~1 TeV e+ (NLC-?)
Why Colliders?
• Fixed target (pp)– Ecm
2=mb2+mt
2+2Ebmt
– Eb=1 TeV mb=mt=0.938 GeV Ecm=43.3 GeV
• Symmetrical Collider – Ecm=Eb+Et
– Eb=Et= 1 TeV Ecm=2 TeV
How Colliders?
Event Rate = LL=f n1n2/(4xy)
n1 n2 particles per bunch
x,y rms horizontal (vertical) beam profile
Thus intense bunched beams with tiny beam spots at the interaction points
LEP
LHC
SLC/NLC
