Microwave Reflectometry Based On Amplitude Modulation

Reflectometry is a technique, based on the radar principle, with a response mainly sensitive to the plasma regions where the microwaves are reflected. The reflectometry technique used in plasma devices measures the phase of a wave reflected by a plasma cut-off layer at a given electron density. It has become a promising experimental technique for the measurement of the electron density profile in plasma devices, due to its good spatial and temporal resolution, together with the moderate access requirements and its ability to perform profile inversion along a single line of sight. Since its first implementation on a plasma device for electron density profile measurement, the high cut-off X-mode polarization has convinced many scientists to use this technique on most of the main devices, such as ASDEX, DIII-D, Gamma 10, TJII, TFTR, W7AS etc, and it is planned for edge and scrape of layer profile determination on ITER. HT-7 tokamak is a circular cross-section limiter superconducting tokamak with a 1.22m major radius and 0.27m minor radius. Many experiments such as IBW heating and LHW heating have been conducted in predominantly deuterium target with a toroidal magnetic field BT up to 2.OTesla, plasma current I
_p
up to 200kA and central line averaged electron density n
_e
(0) = (0.5-6.0)×10
¹⁹
m
^-3
. In order to obtain density profiles in these experiments, a microwave reflectometry based on amplitude modulation, is being developed on HT-7 tokamak. The reflectometry was designated according to HT-7 specifications for profile measurements over a rather large range.