Magnets are used in accelerators to deflect the beam of electrons or other charged particles. The magnetic force on a moving charged particle can be found using the right hand rule. Place the fingers of your right hand pointing in the direction of the magnetic field, i.e. out of the north pole or into the south pole of a magnet. Point your thumb in the direction of motion of the charged particle. Your palm will then push in the direction of the magnetic force on a positive particle.
Negative particles move the opposite way.
The particles move to the left so the thumb points left. The particles are negatively charged so they are forced away from the front and toward the back. Notice the pattern of glowing glass is bent toward the back.