Combination Doppler backscattering/cross-polarization scattering diagnostic for the C-2W field-reversed configuration.

A versatile combination Doppler backscattering and Cross-Polarization Scattering (CPS) diagnostic for the C-2W beam-driven field-reversed configuration is described. This system is capable of measuring density fluctuations and perpendicular magnetic field fluctuations across a wide wavenumber range (2.5 ≤ ≤ 50), with typical resolution Δ / ≤ 0.4-0.8. Four tunable frequencies (26 GHz ≤ ≤ 60 GHz corresponding to plasma cut-off densities 0.8 × 10 ≤ ≤ 4.4 × 10 m) are launched via quasi-optical beam combiners/polarizers and an adjustable parabolic focusing mirror selecting the beam incidence angle. GENRAY ray tracing shows that the incident O-mode and backscattered CPS X-mode beam trajectories for C-2W plasma parameters nearly overlap, allowing simultaneous detection of and or from essentially the same scattering volume.