A Cherenkov-emission microwave source

Summary form only given. In an unmagnetized plasma, there is no Cherenkov emission because the phase velocity /spl upsi//sub /spl phi// of light is greater than c. In a magnetized plasma, the situation is completely changed. There is a rich variety of plasma modes with phase velocities /spl upsi//sub /spl phi///spl les/c which can couple to a fast particle. In the magnetized plasma, a fast particle or particle beam excites a Cherenkov wake that has both electrostatic and electromagnetic components. Preliminary simulations indicate that at the vacuum/plasma boundary, the wake couples to a vacuum microwave with an amplitude equal to the electromagnetic component in the plasma. For a weakly magnetized plasma, the amplitude of the outcoupled radiation is approximately wc/w/sub p/ times the amplitude of the wake excited in the plasma by the beam, and the frequency is approximately w/sub p/. Since plasma wakes as high as 100 MeV/m are expected in near-term experiments, the potential for a high-power, coherent microwave to THz source exists. A brief overview of the scaling laws are presented, followed by 1-D and 2-D PIC simulations. Prospects for a tuneable microwave source experiment based on this mechanism at the UCLA plasma wakefield accelerator facility are discussed.