PARTICLES AND FIELDS

Before considering accelerators in detail a brief reminder of the physics of the motion of charged particles in magnetic and electric fields is given.

(a) MAGNETIC FIELDS

When a charged particle of mass m moves in a magnetic field of flux density B at a velocity v there is a force on it. If the field is at right angles to the motion of the particle this force is:



This force is always at right angles to the motion and so the particle is deflected into a circle of radius R.

Therefore:

(b) ELECTRIC FIELDS

A particle of charge +q in an electric field of intensity E experiences a force Eq towards the negative plate .

If the plates are distance d apart and the p.d between them is V volts then E = V/d and the force is given by:



Unlike a magnetic field, in an electric field a charged particle at rest will still feel a force.