The straight sections along the closed path in such facilities are not only required for radio frequency cavities , but also for particle detectors ( in colliders ) and photon generation devices such as wigglers and undulators ( in third generation synchrotron light sources ) .
Straight sections are required at spacings around a ring for both radiofrequency cavities , and in third generation setups space is allowed for insertion of energy extraction devices such as wigglers and undulators .