This experiment shows the effect that shaping the magnetic field has on focusing the cyclotron’s beam. If the beam wanders off of the mid-plane, the magnetic field pushes it back, but of course it then overshoots and goes below the mid-plane. The magnetic field pushes the beam back up, and so it goes. The beam oscillates about the mid-plane in the vertical (axial) direction as it spirals out in the horizontal plane. These images show that action and is one of the most fundamental accelerator demonstrations this cyclotron provides.
This paper describes the first observation of betatron motion in our cyclotron.
This paper goes more into the details of the betatron motion demonstrations with the 12-Inch Cyclotron