An Introduction To Particle Accelerators

1
An Introduction To Particle Accelerators

• A-Level Physics

2
A Question

• Q. Where is the nearest particle accelerator to
  this classroom?
• A.

3
Accelerating with high voltages

• Particles can be accelerated to high speeds and
  thus high energy
• The energy is measured in electron-Volts
• 1 eV 1.602x10-19 J
• An industrial sized Van de Graaff generator can
  accelerate electrons up to a few Mega
  electron-Volts

4
The Van de Graaff Generator

• This shows Robert Van de Graaffs original high
  voltage generator at MIT in 1933

5
Why do we need particle accelerators?

• If particles have large velocity, the wavelength
  decreases. So they can be used to study atomic
  spacing.
• High energy particles can be smashed into each
  other, allowing other particles to be studied!

6
How do accelerators work?

• Electric fields (creating electromagnetic waves)
  attract charged particles and speed them up.
• Magnetic fields can be used to change their
  direction.

7
Obtaining particles to accelerate

• Electrons Heating a metal causes electrons to
  boil off thermionic emission.
• Protons They can easily be obtained by ionizing
  hydrogen.
• Antiparticles High energy particles are collided
  with solid materials and antiparticles are
  ultimately produced.

8
Accelerating Particles

• In a Linear Accelerator (Linac), a carefully
  selected frequency of alternating voltage is
  placed across a series of cylindrical electrodes
  to accelerate a particle.
• Linac Game

9
Accelerating Particles 2

• The particles can also be considered to be
  surfing the electromagnetic wave

10
Accelerator Design

• There are two main types of accelerator
  experiment
• Fixed Target
• - e.g. Rutherfords
• alpha scattering
• experiment.
• Colliding Beams
• - can use much
• more energy!

11
Linac or Synchrotron?!

• Linear accelerators (Linacs) are used for
  fixed-target experiments, as injectors to
  circular accelerators, or as linear colliders.

A Linac at the University of California
12
Linac or Synchrotron?!

• The largest Linac is at Stanford University, USA.
• It can accelerate particles up to 50 GeV

13
Linac or Synchrotron?!
Particle energy at Fermilab, USA Vaan de
Graaf H- ions to about 1 MeV Linac H- ions
to about 500 MeV Booster synchrotron protons to
about 10 GeV Main injector protons to about
150 GeV Tevatron synchrotron protons (and p-) to
1 TeV

• The particle beams from a circular accelerator
  (synchrotron) can be used for particle colliding
  experiments or extracted from the ring for
  fixed-target experiments.

This is the European Synchrotron Radiation
Facility (ESRF) in Grenoble, France
14
CERN

• Accelerators at CERN
• LINAC23 Hadron Linacs
• PSB Proton Synchrotron Booster
• PS Proton Synchrotron
• SPS Super Proton Synchrotron
• LHC Large Hadron Collider
• Other things
• AD Antiproton Decelerator
• CMS Compact Muon Solenoid
• ALICE A Large Ion Collider Experiment

15
What can they do?

• Linacs and Synchrotrons can be used together or
  alone

16
Accelerating Particles 3

• Heat energy provides the work function for
  thermionic emission.
• Electric fields accelerate particles

17
Accelerating electrons

• PE lost KE gained
• qV ½ mv2

e.g. A thermionic diode has a p.d. of 5kV placed
across its electrodes. Calculate the maximum
velocity of the electrons.
v (2qV/m) ½ v (2 x 1.6x10-19 x 5000 /
9.1x10-31) ½ v 4.2x107 ms-1
18
Accelerating electrons

• The greater the acceleration of the electron, the
  greater its energy.
• KE ½ mv2
• Q. What happens when velocity approaches the
  speed of light?
• Mass increases! (Velocity can never equal the
  speed of light).
• KE ½ mv2 still applies.

19
Bending Beams of Particles

• For a beam of particles to move through a
  circular path, they must each experience a
  centripetal force.
• Q. Does this force increase the energy of the
  particles?
• The centripetal force is provided by a magnetic
  field perpendicular to the direction of the
  particles.
• Demo Bending a beam of electrons in a CRT
  monitor or Teltron tube.

20
The Cyclotron

• Cyclotrons accelerate particles in a circular
  path up to around 10MeV.
• They are relatively small and so can be used in
  hospitals to provide beams of (deuterons
  creating) neutrons for cancer therapy.
• http//www.nscl.msu.edu/tech/accelerators/index.ht
  ml

21
(No Transcript)
22
(No Transcript)