Photocathodes and DC Guns for Next Generation Light Sources

A new class of synchrotron light sources, based on the use of superconducting electron linear accelerators and beam recirculation with energy recovery, is currently under active consideration. The injectors for such accelerators must deliver high brightness electron beams with appropriate RF time structure and the full average beam current. Various photoemission cathodes have been demonstrated to produce high brightness electron beams, suitable high frequency RF time structure, and high average current, and thus are a natural choice for this application. Such cathodes may be used in either DC or RF electron gun structures. The technical challenge is to develop a photoemission electron source which satisfies all the electron beam requirements simultaneously, and which offers an acceptable operational lifetime.