We demonstrate the focusing of a free-space THz beam emerging from a leaky parallel-plate waveguide (PPWG). Focusing is accomplished by grading the launch angle of the leaky wave using a PPWG with gradient plate separation. Inside the PPWG, the phase velocity of the guided TE1 mode exceeds the vacuum light speed, allowing the wave to leak into free space from a slit cut along the top plate. Sin...

Ultrasonic guided wave methods are being widely explored for inspection of large structural areas using a sparse array of surface-mounted transducers. However, structural health monitoring (SHM) with guided waves can be problematic because variable operational conditions can significantly affect the measured ultrasonic signals. Although homogeneous temperature variations have been well-research...

We report measurements of the ratio of the perpendicular velocity to the parallel velocity, a = ul /ull, of a relativistic electron beam gyrating in a magnetic field by the use of ( 1) Cerenkov emission from a glass plate, detected by a gated microchannel plate image intensifier camera, and (2) electron-beam-induced radiation darkening pattern on the same glass plate. The measurements are based...