Insertion Devices are the heart of the machine and produce the very high intensity X-ray light. They consist of periodic arrays of magnets, which cause the electrons to oscillate around the otherwise straight trajectory. The oscillating electrons emit X-ray light which is directly proportional to the number of magnets - typically 300 or more. Diamond is a third generation light source and is built around the Insertion Devices. At least one Insertion Device is “Inserted” in the storage ring straights before each "I" beam line.