Forward Scattering Measurement Based on Terahertz Microwave Interferometer on KTX Reversed Field Pinch

Electron density fluctuation has been measured based on the collect forward scattering method using a single-chord microwave interferometer system on the Keda Torus eXperiment (KTX) reversed field pinch. The interferometer system is a heterodyne one with two terahertz solid-state sources with frequency around 650 GHz, and the transmitted beam and forward scattering beam are received simultaneously by a Schottky planar diode mixer with sensitivity about 500 mV/mW. Constrained by the beamwidth and geometry limitation, the measurable wave vector range is
$k_{w}\le 5 {\mathrm {cm}}^{-1}$
with a resolution
$\Delta k\approx 2.07\,{\mathrm {cm}}^{-1}$
. MHD activities are detected via this forward scattering technique. The results are consistent with other diagnostics, such as the chord averaged electron density, the edge magnetic probe, and high-speed charge-coupled device (CCD) camera.