The fishbone and beam guidance. The fishbone is a component in the accelerator, which switches the path of the beam between the experimental rooms of Ganil. The beam is transported and guided towards the rooms, along long pipes under vacuum, by means of magnetic elements: dipoles (magnets) used to rotate the beam, as well as quadrupoles, which keep it on axis and focus it. Other pieces of equipment known as beam diagnostic boxes are used along the line to measure its energy, its flux, that is the number of particles per second, and its spatial and temporal dimensions.