Lesson 16, Topic 3
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Particle Accelerators

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Particle accelerators launch elementary particles, such as electrons and protons, to high velocities and energies by means of electric or electromagnetic fields.

  • Linear accelerators: Straight-line path of travel.
  • Circular accelerators: Circular path of travel.

Discovery of the Electron, Proton and Neutron

  1. The electron was discovered by Thomson using cathode ray tubes, which are essentially electron accelerators.
  2. Radioisotopes emitting alpha particles are natural accelerators which helped to discover the proton and neutron.
    1. Rutherford discovered the nucleus (thus proton) by firing alpha particles at gold atoms.
    2. Chadwick discovered the neutron by firing alpha particles at beryllium atoms.

Verification of the Standard Model of Matter

  1. Particles accelerated to near light-speed.
  2. The high-energy particles are made to collide.
  3. Kinetic energy momentarily converted to matter (mass), creating new particles which may be studied:
    1. Directly
    2. And indirectly, from decay products

Types of Modern Particle Accelerators

Operation of Particle Accelerators

  1. Electric fields accelerate particles
  2. Magnetic fields steer particles

There are some important things to note about this.

  • Linear accelerators don’t need magnetic fields – only straight-line motion
  • Cyclotrons use constant magnetic fields to deflect particles in a spiral (circular path of increasing radius)
  • Synchrotrons, like the LHC, require increasing magnetic fields to deflect particles in a circular path of constant radius