Possibility of plasma undulator driven by an electron beam (Invited Paper)

Comparing a conventional undulator, the concept of plasma undulator is hard to realize because of a small-scaled cavity structure and a longitudinal acceleration field in the plasma cavity. So, the electron beam with betatron motion should stay in the longitudinal center of the plasma cavity. An other issue is the plasma cavity should propagate keeping a stable cavity formation and speed for entire plasma target. Moreover, high photon energy like UV and soft x-ray is much challenge since it requires longer plasma length and higher speed plasma cavity. To satisfy such conditions we investigate the electron beam-driven plasma cavity using PIC simulations. The life-time of the plasma cavity depends on how long the driving electron beam survives. We test several plasma profile, electron beam, and plasma lens parameters by testing matching conditions of the electron beam. In the presentation we also introduce new numerical technique in PIC to eliminate the numerical Cherenkov radiation causing unwanted increases of emittance. Finally we discuss a possibility of FEL from electron’s betraon motions.