Linacs for microtrons and pulse stretchers

For many applications, continuous (CW) beams of electrons are strongly preferred over the low duty cycle beams available for RF linacs. The two preferred methods for realizing high-energy CW beams are (1) a pulsed linac followed by a pulse-stretcher ring, and (2) a recirculating CW accelerator. In both methods, a high performance electron linac is required. Recent advances in the technology and understanding of standing wave structures appear to make them preferable to travelling wave linacs for the pulse-stretcher method. Recirculating linacs, whether of the racetrack microtron type or some other topology, are built with CW standing wave linacs. Both room temperature and superconducting structures have been used. Recent exciting advances in superconducting structures make them the structures of choice for high energy CW electron accelerators