RADAR upper hybrid resonance scattering diagnostics of small-scale fluctuations and waves in tokamak plasmas

The upper hybrid resonance (UHR) scattering technique possessing such merit s as one-dimensional probing geometry, enhancement of cross section, and fi ne localization of scattering region is modified in the new diagnostics und er development to achieve wave number resolution. The fluctuation wave numb er is estimated in the new technique from the scattering signal time delay measurements. The feasibility of the scheme is checked in the proof of prin cipal experiment in a tokamak. The time delay of the UHR scattering signal exceeding 10 ns is observed. The small scale low frequency density fluctuat ions are investigated in the UHR RADAR backscattering experiment. The UHR c ross-polarization scattering signal related to small scale magnetic fluctua tions is observed. The lower hybrid (LH) wave propagation and both linear a nd nonlinear wave conversion are investigated. The small wavelength (lambda less than or equal to0.02 cm) high number ion Bernstein harmonics, resulti ng from the linear wave conversion of the LH wave are observed in a tokamak plasma for the first time. (C) 2001 American Institute of Physics.