Soft X-ray Reflectometry Research Articles

Structure of thin iron layers on gold substrates

Polycrystalline texturized Au/Fe/Au “sandwiches” are prepared by vacuum deposition on glass substrates. The surface structure and surface roughness are monitored during the layer growth by reflection high energy electron diffraction and soft X-ray reflectometry. The crystalline structure and the relative orientation of gold and iron crystals are determined by transmission electron microscopy. Iron films with thicknesses ranging from 1 to 20 nm have the bulk b.c.c. structure with a (110) plane parallel to the (111) surface plane of the gold crystals. The free surface roughness is constant for very thin iron films and increases when the iron thickness is greater than 1.5 nm.

Soft X-ray reflectometry applied to the evaluation of surface roughness variation during the deposition of thin films

Soft X-ray reflectometry applied to the evaluation of surface roughness variation during the deposition of thin films

Fluctuations during JET discharges with H-mode

The appearance and disappearance of H-mode behaviour in JET Tokamak discharges is associated with characteristic instabilities detected by edge magnetic probes, arrays of soft X-ray diodes and reflectometry: edge disruptive-like modes are observed before L-H transitions whereas H-L transitions are accompanied by large bursts of broad-band activity. Other observed fluctuations, shown to be resonant in the central region of the discharge, are not affected by the transitions. The importance of edge fluctuations and induced transport in a magnetic separatrix configuration is thus emphasised.