1. Particle Accelerators
Designed to accelerate charged particles to higher energies . These high energy particles can then be smashed into a target to probe the nature of matter or the wave properties of the fast moving particles can be used to probe( electron microscope )

2. Principles of Accelerators
Regardless of whether the particle accelerator is linear or circular, the basic parts are the same:
a source of particles (this may be another accelerator)
beam pipes (a guide along which the particles will travel whilst being accelerated)
accelerating structures (a method of accelerating the particles)
a system of magnets (either electromagnets or superconducting magnets as in the LHC)
a target (in the LHC the target is a packet of particles travelling in the opposite direction).
LHC Large Hadron Collider

3. Electric Fields
A charged particle inside an Electric field experiences a force.
The field does work on the charged particle.
The electric work is turned into kinetic energy
work done = charge x potential difference
W = Q x V = ½ mv2

4. Example
-200V
+300V
a) Calculate the work done on the proton by the electric field.
W = Q x V
W = 1.6x10-19 x 500
W = 8.0x10-17 J
proton
Ek gained = work done on proton
Ek = 8.0x10-17 = ½ mv2
2Ek = mv Ek/m =v2
b) Calculate the speed of the proton at the –ve plate if it was initially stationary

5. b) Calculate the speed of the proton at the –ve plate if it was initially stationary
Ek gained = work done on electron
Ek = 8.0x10-17 = ½ mv2
2Ek = mv Ek/m =v2

6. Another unit for Energy
Particle Physicists measure energy in electronvolts, eV.
1eV is the energy gained by an electron when accelerated through a p.d. of 1V.
1eV = Q x V = 1.6 x10-19 x 1 = 1.6 x10-19eV
To probe the nucleus we need particles in the GeV range

7. Electric Field patterns
The arrow shows the direction a free positive charge would accelerate in. The closer the lines the stronger the field.
For a point –ve charge the arrows would point towards the charge

8. More field patterns An +ve and –ve charge of equal magnitude
An +ve and –ve charge of equal magnitude
( similar to the magnetic field around a bar magnet )

9. And more patterns
2 equal charges. Null point between them, no force is experienced here.
Field is uniform for parallel plates.

10. Magnetic Fields
A moving charge has a magnetic field about it. This can interact with another magnetic field . The direction of the charged particle can be controlled.
The magnetic field does no net work on the charged particle, its speed remains constant.

11. Field pattern around a moving charge
© Douglas Morrison
direction of electron flow
Left hand grip rule. The thumb points in the direction of the North Pole,

12. Movement of charged particles
Right Hand Motor Rule : Hold the thumb and first 2 fingers at 900 to each other. Thumb ; direction of motion
1st finger : points North to South
2nd finger : points direction of current