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