ABSTRACT
A table top device for producing high peak power (tens of megawatts to a gigawatt) T-ray beams is described. An electron beam with a rectangular longitudinal profile is produced out of a photoinjector via stacking of the laser pulses. The beam is also run off-crest of the photoinjector rf to develop an energy chirp. After passing through a dielectric loaded waveguide, the beam's energy becomes modulated by its self-wake. In a chicane beamline following the dielectric energy-bunching section this energy modulation is converted to a density modulation-a bunch train. The density modulated beam can be sent through a power extraction section, like a dielectric loaded accelerating structure, or simply can intercept a foil target, producing THz radiation of various bandwidths and power levels.
ABSTRACT
We analyze the radiation from a charged particle crossing the boundary between an ordinary medium and a "left-handed" metamaterial. We obtain exact and approximate expressions for the field components and develop algorithms for their computation. The spatial radiation in this system can be separated into three distinct components, corresponding to ordinary transition radiation having a relatively large magnitude, Cherenkov radiation, and reversed Cherenkov-transition radiation (RCTR). The last one is explained by reflection and refraction of reversed Cherenkov radiation at the interface. Conditions for generating of RCTR are obtained. We note properties of this radiation that have potential applications in the detection of charged particles and accelerator beams and for the characterization of metamaterial macroscopic parameters (epsilon, mu).
