Review of continuous beam electron machines

Accelerators able to deliver continuous, or nearly continuous electron beams can be separated in two main classes. In the first one, a usually existing pulsed electron linac to which one adds a pulse stretcher ring (PSR), used either with an internal target or with an extracted beam is obtained with a slow extraction system. In the second one, the accelerator is designed from the beginning to get a continuous beam. The basic component is a piece of linear accelerator with a beta equal one structure. Bending magnets oblige the beam to pass several times through this linac. Depending on the bending magnet technology, one will speak of microtrons (or polytrons) or of race-tracks. Some these types of accelerators are outlined. (R.P.) 29 refs.; 1 fig.; 7 tabs