Darya Ivanova

An overview of the comprehensive First Mirror Test in JET with ITER-like wall

The First Mirror Test in Joint European Torus (JET) with the International Thermonuclear Experimental Reactor-like wall was performed with polycrystalline molybdenum mirrors. Two major types of exp ...

Overview of the second stage in the comprehensive mirrors test in JET

The first mirror test for ITER in JET with carbon walls has been completed. Thirty polycrystalline Mo mirrors including four coated with a 1 μm rhodium (Rh) film were exposed to plasma in the diver ...

Survey of dust formed in the TEXTOR tokamak: structure and fuel retention

A detailed survey of erosion and deposition on plasma-facing components was performed in the TEXTOR tokamak. Co-deposits and dust particles were collected from graphite limiters and from several lo ...

Impact of ion cyclotron wall conditioning on fuel removal from plasma-facing components at TEXTOR

Ion cyclotron wall conditioning (ICWC) is based on low temperature and low density plasmas produced and sustained by ion cyclotron resonance (ICR) pulses in reactive or noble gases. The technique i ...

Plasma cleaning of beryllium coated mirrors

Cleaning systems of metallic first mirrors are needed in more than 20 optical diagnostic systems from ITER to avoid reflectivity losses. Currently, plasma sputtering is considered as one of the most promising techniques to remove deposits coming from the main wall (mainly beryllium and tungsten). This work presents the results of plasma cleaning of rhodium and molybdenum mirrors exposed in JET-ILW and contaminated with typical tokamak elements (including beryllium and tungsten). Using radio frequency (13.56 MHz) argon or helium plasma, the removal of mixed layers was demonstrated and mirror reflectivity improved towards initial values. The cleaning was evaluated by performing reflectivity measurements, scanning electron microscopy, x-ray photoelectron spectroscopy and ion beam analysis.

Fuel re-absorption by thermally treated co-deposited carbon layers

Systematic studies have been conducted to address the fuel re-absorption by carbon deposits under repeated exposure to plasma after cleaning procedures. The investigation was done with graphite tiles from ALT-II (Advanced Limiter Test II), i.e. the main limiter at the TEXTOR tokamak. Pure graphite plates were used as the reference material. The experimental programme comprised the following: pre-characterization of specimens; D desorption by baking the tile at 1273K; surface analyses of the fuel-depleted layers; exposure to deuterium in a laboratory plasma device and in TEXTOR; and quantitative assessment of deuterium re-absorption. The main result is that fuel retention in the re-exposed deposits is 30‐40 times lower than that in the original co-deposit, showing that fuel re-absorption does not lead to an immediate re-saturation of deposits. Annealing at high temperatures enhances layer brittleness, leading eventually to detachment of co-deposits.