New density profile reconstruction methods in X-mode reflectometry

Reconstruction method of X-mode ultrashort-pulse reflectometry in LHD

Reflectometry is considered to be one of the key diagnostics to measure density profiles and density fluctuations of fusion oriented plasmas. When an electromagnetic wave is launched into a plasma, the wave is reflected at the corresponding cutoff layer of the ordinary (O) mode or the extraordinary (X) mode. Reflectometry measures the time of flight (TOF) or group delay of the reflected wave. W...

Density profile measurements with X-mode lower cut-off reflectometry in ASDEX Upgrade.

Despite the fact that density profile measurements using X-mode lower cut-off reflectometry are foreseen to be used on ITER, little or no experience is available within the reflectometry community and to our knowledge no results on this subject have been published so far. In ASDEX Upgrade the multichannel broadband reflectometer is equipped with b...

First Density Profile Measurements Using FMCW Reflectometry on JET

Reconstruction of the turbulence radial profile from the reflectometry phase root mean square measurements

Simple expressions allowing estimation of the turbulent density perturbation from the reflectometry phase root mean square (r.m.s.) measurements and accounting for the turbulence correlation length are given. The numerical procedure for precise turbulence radial profile reconstruction for different turbulence wave number spectra and both O-mode and X-mode reflectometry is proposed. It is valida...

Iterative reconstruction methods in X-ray CT.

Iterative reconstruction (IR) methods have recently re-emerged in transmission x-ray computed tomography (CT). They were successfully used in the early years of CT, but given up when the amount of measured data increased because of the higher computational demands of IR compared to analytical methods. The availability of large computational capacities in normal workstations and the ongoing effo...