Tunable microwaves from Cerenkov wakes in magnetized plasma

Summary form only given, as follows. The Cerenkov wake excited by a particle beam or short laser pulse in a perpendicularly magnetized plasma is analyzed. The wake has both electrostatic and electromagnetic components and couples to a vacuum microwave at the plasma/vacuum boundary. The transmission coefficient depends on the boundary scale length and the ratio of /spl omega//sup c///spl omega//sub p/. The frequency of the forward going radiation is approximately /spl omega//sub p/, and its amplitude is /spl omega//sup c///spl omega//sub p/ times the amplitude of the wake excited in the plasma (for a sharp boundary). The possibility of tapering the magnetic field and density profile to optimize the output coupling is then discussed for a continuous boundary. We also use 1D PIC simulations to verify the scaling laws. Since plasma wakes as high as a few GeV/m are produced in current experiments, the potential for a high power (i.e., Gwatt) coherent microwave to THz radiation source exists.