Particle accelerators

Question 1

What is a linear accelerator?How does it work?

Answer 1

• A linear accelerator is a long straight tube containing a series of electrodes.- Alternating current is applied to the electrodes so that their charge continuously changes between + and – The alternating current is timed so that the particles are always attracted to the next electrode in the accelerator and repelled from the previous one.- A particle’s speed will increase each time it passes an electrode - so if the accelerator is long enough particles can be made to approach the speed of light.- The high-energy particles leaving a linear accelerator collide with a fixed target at the end of the tube.

Question 2

What is a cyclotron?How does it work?

Answer 2

• A cyclotron uses two semicircular electrodes to accelerate protons or other charged particles across a gap.- An alternating potential difference is applied between the electrodes-as the particles are attracted from one side to the other their energy increases.- A magnetic field is used to keep the particles moving in a circular motion.- The combination of the electric and magnetic fields makes the particles spiral outwards as their energy increases.

Question 3

What are synchrotrons?How do they work?

Answer 3

A synchrotron can produce particle collisions with much higher energies than either a linear accelerator or a cyclotron.- Electromagnets keep the particles moving in a circular path in focused beams.- In this way, synchrotrons can produce particles with energies reaching from 500GeV to several TeV.

Question 4

How does special relativity affect particle accelerators?

Answer 4

• Special relativity is where the idea that energy is equivalent to mass comes from. It means that the more you increases the kinetic energy of a mass, the more massive it gets. This happens to any object with kinetic energy, but it’s only noticeable at speed approaching c.- Particle accelerators have to alter their magnetic and electric fields to compensate for the relativistic mass of the accelerating particles.

Question 5

What is the relativistic factor?

Answer 5

The relativistic factor is the total energy of a particle divided by the rest energy of the particle. For particles travelling at low speeds (v<<c), the r-factor will be very close to 1.Gamma = Etot/ErestErest = mc^2