Relativistic effects on reflectometry density profile measurements have been evaluated for planned ITER operating scenarios. Standard X-mode, right-hand cutoff reflectometry reconstruction can produce large errors (up to 35% for Te(0) = 24 keV plasmas) in high-temperature ITER plasmas if relativistic effects are ignored. It will therefore be essential to account for these effects in ITER. The errors created in density profile reconstruction have been analysed using simulated temperature profiles, including uncertainties, as an input to a standard inversion routine. Modelling using random errors with maxima of ±10% across the electron temperature profile leads to errors in the inverted density profile ranging from zero at the edge to a maximum RMS error of ∼1% at the magnetic axis. In addition to this, a novel iterative inversion technique is demonstrated which eliminates the dependence on external Te information and allows Te itself, and hence electron pressure Pe, to be extracted from the reflectometry measurement. The new technique utilizes phase data from both O- and X- mode propagation and has been successfully demonstrated numerically in peaked plasma profiles, as well as in the edge pedestal region. Integration of this novel approach with other planned measurement systems will serve to improve confidence in electron density and temperature measurements in ITER.
Assessment of microwave power flow for reflectometry measurements in tokamak plasmas