This Demonstration shows a plot of synchrotron radiation for perpendicular to . The 3D plot indicates a spherical plot of the power distribution per solid angle of an accelerated charge. The acceleration is positive and directed perpendicular to the velocity. An important example of this corresponds to motion in a circle—a current example is furnished by the LHC particle accelerator at CERN. The expression evaluated is the Liénard–Wiechert field for a relativistic charge. The velocity of the charge (in units of ) is controlled by moving the slider. Move the image around in order to view the field from various angles. For relativistic particles the radiation sweeps around, rather like the headlights on a train as it moves.