Ex Situ LIBS Analysis of WEST Divertor Wall Tiles after C3 Campaign

Fuel retention monitoring in tokamak walls requires the development of remote composition analysis methods such as laser-induced breakdown spectroscopy (LIBS). The present study investigates the feasibility of the LIBS method to analyse the composition and fuel retention in three samples from WEST divertor erosion marker tiles after the experimental campaign C3. The investigated samples originated from tile regions outside of strong erosion and deposition regions, where the variation of thin deposit layers is relatively small and facilitates cross-comparison between different analysis methods. The depth profiles of main constituents W, Mo and C were consistent with depth profiles determined by other composition analysis methods, such as glow-discharge optical emission spectroscopy (GDOES) and secondary ion mass spectrometry (SIMS). The average LIBS depth resolution determined from depth profiles was 100 nm/shot. The averaging of the spectra collected from multiple spots of a same sample allowed us to improve the signal-to-noise ratio, investigate the presence of fuel D and trace impurities such as O and B. In the investigated tile regions with negligible erosion and deposition, these impurities were clearly detectable during the first laser shot, while the signal decreased to noise level after a few subsequent laser shots at the same spot. LIBS investigation of samples originating from the deposition regions of tiles may further clarify LIBS’ ability to investigate trace impurities

Temporal and spectral characteristics of atmospheric pressure argon plasma jet

An investigation of atmospheric pressure argon DBD plasma jet generated at 6 kHz sinusoidal voltage was carried out. On the basis of recorded electrical, optical and spectral characteristics spatiotemporal evolution of plasma jet in negative and positive half-cycles of voltage was studied. It was found that the dynamics of argon jet propagation outside the tube differs considerably from that found by other authors in the case of helium jet. The difference was explained with the influence of Penning reactions between metastable state He atoms and air molecules in He jet. On the basis of radiative transitions N2 (C-B, 0-0) and OH(A-X, 0-0) the rotational temperatures of N2(C, 0) and OH(A, 0) were estimated along jet axis. In regions where Ar-air mixing was negligible or low, the rotational temperatures of both molecules coincide and were close to the gas temperature

Oxidation of nitrogen oxide in hybrid plasma-catalytic reactors based on DBD and Fe

In the present study, Fe2O3 was used as catalyst for the removal of NO in a hybrid plasma- catalytic reactor. The catalyst was located either directly inside the hybrid plasma-catalytic reactor or in a separate catalytic reactor, which followed ozone producing and injecting plasma reactor. Ozone production in such a reactor was dependent on the state of the electrode surface. The fresh catalyst ensured an order of magnitude smaller ozone concentration in the outlet of the hybrid reactor. After a short treatment of the catalyst with NO2, its ability to destroy ozone diminished but was regained after heating of the reactor up to 100 °C. Similarly to earlier results obtained with TiO2, the removal of NO in the hybrid reactor with Fe2O3 was enhanced compared to that in an ordinary plasma reactor. In the ozone injection reactor, oxidation of NO to NO2 took place with considerably higher efficiency compared to the hybrid reactor. The use of catalyst in the ozonation stage further improved the oxidation of NO2 to N2O5. The time-dependence effects of NO removal during plasma and ozone oxidation were explained by reactions between NO2 adsorbed on surface, with surface-bound NO3 and gas phase NO as the reaction product

Treatment of industrial exhaust gases by a dielectric barrier discharge

Volatile organic compounds (VOCs) in industrial exhaust gases were treated by a dielectric barrier discharge (DBD) operated with two different mobile power supplies. Together with the plasma source various gas diagnostics were used, namely fourier transform infrared (FTIR) spectroscopy, flame ionization detector (FID) and GC-MS. The analysis revealed that some exhaust gases consist of a rather complex mixture of hydrocarbons and inorganic compounds and also vary in pollutants concentration and flow rate. Thus, analysis of removal efficiencies and byproduct concentrations is more demanding than under laboratory conditions. This contribution presents the experimental apparatus used under the harsh conditions of industrial exhaust systems as well as the mobile power source used. Selected results obtained in a shale oil processing plant, a polymer concrete production facility and a yacht hull factory are discussed. In the case of total volatile organic compounds in oil processing units, up to 60% were removed at input energy of 21–37 J/L when the concentrations were below 500 mg/m3. In the yacht hull factory up to 74% of styrene and methanol were removed at specific input energies around 300 J/L. In the polymer concrete production site 195 ppm of styrene were decomposed with the consumption of 1.8 kJ/L. These results demonstrate the feasibility of plasma assisted methods for treatment of VOCs in the investigated production processes but additional analysis is needed to improve the energy efficiency