New results on the physics of THz gyrotrons

Basic wave-particle interaction dynamics from linear to chaotic regimes is studied in detail both experimentally and theoretically on a frequency tunable gyrotron developed for DNP-NMR spectroscopy applications and generating THz radiation in continuous mode (150W) at 260GHz. The non-linear dynamics associated to the wave-particle interaction is dominated by self-consistent effects on the longitudinal profile of a given single transverse cavity-mode TE_m,p. This study covers a wide range of control parameters from traveling wave tube (gyro-TWT) to gyro-backward wave oscillator (gyro-BWO) like interactions. The route to chaos via a period doubling cascade dynamics is experimentally observed and is supported by numerical simulations. In presence of phase-locked side-bands a novel regime characterized by the generation of nanosecond pulses has been experimentally identified. This novel regime is consistent with numerical simulations and may open up new applications for gyrotrons.