Large mechanical model of the cyclotron.

Large mechanical model of the cyclotron. Ref.:Modern College Physics by Harvey White, 6rd ed., p. 872-874 The mechanical model of a cyclotron mimics the way a simple cyclotron works. See Fig.1. The top consists of three aluminum parts: two 'D' shaped semi-circles that pivot on either side of a rectangular piece. A machined groove starts in the center and spirals out. When the machine operates, there are two cycles. In cycle 1, a steel ball pops up in the center, the left D lowers down while the right D raises up, the rectangular piece tilts, and the ball rolls down the groove in the rectangle and around the beginning of the spiral. In cycle 2, the left D raises up, the right D lowers down and the rectangular piece tilts in the opposite direction, sending the ball down the groove in the rectangle, increasing its speed for the next part of the spiral. Then everything repeats. The raising and lowering of the Ds is timed to match the motion of the balls so that they speed up in the spiral and end up in the 'exit' hole. The force speeding up the balls is gravity. See Fig.2. The cyclotron designed by Lawrence in 1930 used a magnetic field B perpendicular to two D shaped evacuated cavities ('Dees') to insure that charged particles traveled in nearly circular orbits. A voltage is placed across a gap between the Dees. Charged particles such as protons are introduced at A. This device operates in two cycles. In cycle 1, D1 is charged positively and D2 is charged negatively, and the protons are accelerated towards D2, spiraling clockwise in the magnetic field. In cycle 2, D1 is charged negatively and D2 is charged positively, and the protons are accelerated again, moving into a spiral of increasing radius. Then everything repeats. The alternating voltage on the gap is timed to match the motion of the particles in the magnetic field, raising the particles to a high velocity to exit at W.