A quasi-optical transmission line for plasma scattering measurements using a submillimetre wave gyrotron

A new transmission system has been designed to enable a submillimetre wave gyrotron (P 100 W, f = 354 GHz) to be used for plasma scattering. The optimized probe beam can be scanned across the plasma by rotating and moving the final mirror. Calculations using the Huygens equation for scalar diffraction show that this system can produce a well-collimated beam whose full width at half maximum is 12 mm.