Course outline:

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Physics at Accelerators, SH2307, vt2008. Bengt Lund-Jensen

Physics at Accelerators

Course outline:

The first 4 lectures covers the physics principles of accelerators.

Preliminary plan:

Lecture 1: Accelerators, an introduction. Acceleration principles.

Lecture 2: Transverse beam dynamics.

Lecture 3: Acceleration, longitudinal beam dynamics.

Lecture 4: Beam instrumentation. Accelerators and beam lines. Case studies.

Lecture 5: Electron cooling. Cryring.

Lecture 6: Particle physics.

Lecture 7: Nuclear physics.

Lecture 8: Synchrotron radiation, Maxlab and X-fel. Material physics.

Lecture 9: Atomic physics Lecture 10: ESS.

Lecture 11: Antiprotons.

Lecture 12: Transmutation.

Lecture 13: Medical applications with accelerators.

Lecture 14: Course summary.

Two studies visits and a laboratory session is foreseen.

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Introduction to Accelerators

Some fields of physics experiments and qapplications need beams of particles Concerns:

• Particle type (e.g. e^-, p, heavy ions, photons)

• Energy (energy and energy spread)

• intensity (flux, duty cycle, time structure, beam size)

Basic principle

the Lorentz force

) (E v B e

F^r ⁼ ^r⁺ ^r^× ^r

For v = c, B = 1 T, corresponds to E ~ 3⋅10⁸V/m

⇓

Magnets used for bending beams at high energies

Bending in magnetic field

momentum p

charge q

radius of curvature ρ

magnetic field B

p =q B ρ

with unit charge and momentum in GeV p = 0.3 B ρ

Example:

Large Hadron Collider (LHC)

p = 7⋅10³GeV/c, ρ = 4.3⋅10³m (27 km circumference)

⇒B ≈ 5.4 T

Not all the tunnel is filled with bending magnets, so need a bit higher field:

B ≈ 8.3 T

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(CERN summer student lecture 2007 by S Gilardoni)

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Cockroft & Walton 1932

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Ernest Lawrence 1929

An early cyclotron

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The GW-cyclotron at TSL

Van de Graaffs

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Linear Accelerators

Wideroe linac.

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Acceleration

Use electric field.

Constant potential not possible for very high energies

⇓

Radiofrequency wave

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Focusing using quadrupoles

Electrostatic

Magnetic

Quarupoles focus in one direction and defocus in the other

By combining two quadrupoles with perpenducular focusing directions a net focusing is obtained

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… even dipole magnets can be designed to help focusing

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The CERN Large Hadron Collider,

a new accelerator in the old LEP tunnel

The LEP (Large Electron Positron) collider gave precision physics studies for more than a decade:

• There are 3 neutrino families

• Predicting the top quark mass

• The energy dependence of the coupling constants ⇒ Grand Unification requires new physics

• Lower limits on Higgs boson mass and Supersymmetric particles

• A prediction of the Higgs boson mass.

The Higgs boson still has to be found!

(the last LEP data did not include real signs of the higgs)

LEP was stopped in November 2000 to build LHC

“The King is dead, long live the King”

The LHC programme

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The CERN Large Hadron Collider

Physics at Accelerators, SH2307, vt2008. Bengt Lund-Jensen Parameters

Circumference Dipole Field Collision energy Injection energy Stored beam energy Bunch spacing Number of bunches Particle per bunch Circulating current per beam Bunch radius

Bunch length Beam lifetime Luminosity Luminosity lifetime

Value 26.7 km 8.4T 7.0 TeV 450 GeV 332 MJ 25 ns 2835 10¹¹ 540 mA 16 μm 75 μm 22 h 10³⁴cm^-2s^-1 10 h

A top quark factory

Excellent for CP violation studies with B-hadrons!

Required for the discovery of the Higgs boson.

NEW PHYSICS!!

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Synchrotron radiation

Particles in circular orbit emit ”synchrotron radiation”

Radiated energy per turn:

ρ γ β q ε π

E

² ² ⁴

3 0

∆ = 4

For relativistic particle with energy E (= mγ)

∆E ~ m^-4

Electron with β ≈ 1

∆E = 88.5 E⁴/ρ ( keV, E in GeV) E.g. E = 1000 GeV, ρ = 1000 m

⇒∆E = 8.9 GeV/turn

(not feasible to build e- accelerator for 100 GeV with such small radius)