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Impact of Sodium Cationization on Gas-Phase Conformations of DNA and RNA Cytidine Mononucleotides
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Probing plasmon excitations in copper nano-clusters with spectroscopic ellipsometry
Get PDFLight induced plasmon excitations of copper nano-clusters have been probed using spectroscopic ellipsometry. Copper clusters of typically 20 nm diameter were created on the surface of a silicon wafer by means of physical vapour deposition. The growth of the clusters as well as the chemical interaction with atmosphere are monitored. Clear plasmon excitations are observed with resonance positions in the range from 1.85 to 2.1 eV for copper in its metallic state. The resonance position and amplitude scale linear with deposited amounts. Changes in resonance position and amplitude are observed when copper nano-clusters are exposed to atmosphere and a sub-nanometer thin copper oxide is formed. The resonance position red-shifts 0.4 eV (180 nm wavelength) after one day of exposure with respect to its metallic state. Spectroscopic ellipsometry is shown to have good sensitivity to ultra-thin (down to sub-nanometer thick) metal-oxide layers as well as to nanometer size changes of the copper nano-clusters. This puts the technique in a position where real-time monitoring of plasmon active material in gaseous or liquid environments of, for example, (photo-) catalytic processes becomes accessible.</p
Atmospheric pressure-plasma enhanced chemical vapour deposition of silica. Characterisation and control of porosity in multi-layer encapsulation films
No full textHigh Z neoclassical transport: Application and limitation of analytical formulae for modelling JET experimental parameters
Get PDFHeavy impurities, such as tungsten (W), can exhibit strongly poloidally asymmetric density profiles in rotating or radio frequency heated plasmas. In the metallic environment of JET, the poloidal asymmetry of tungsten enhances its neoclassical transport up to an order of magnitude, so that neoclassical convection dominates over turbulent transport in the core. Accounting for asymmetries in neoclassical transport is hence necessary in the integrated modeling framework. The neoclassical drift kinetic code, NEO [E. Belli and J. Candy, Plasma Phys. Controlled Fusion P50, 095010 (2008)], includes the impact of poloidal asymmetries on W transport. However, the computational cost required to run NEO slows down significantly integrated modeling. A previous analytical formulation to describe heavy impurity neoclassical transport in the presence of poloidal asymmetries in specific collisional regimes [C. Angioni and P. Helander, Plasma Phys. Controlled Fusion 56, 124001 (2014)] is compared in this work to numerical results from NEO. Within the domain of validity of the formula, the factor for reducing the temperature screening due to poloidal asymmetries had to be empirically adjusted. After adjustment, the modified formula can reproduce NEO results outside of its definition domain, with some limitations: When main ions are in the banana regime, the formula reproduces NEO results whatever the collisionality regime of impurities, provided that the poloidal asymmetry is not too large. However, for very strong poloidal asymmetries, agreement requires impurities in the Pfirsch-Schlüter regime. Within the JETTO integrated transport code, the analytical formula combined with the poloidally symmetric neoclassical code NCLASS [W. A. Houlberg et al., Phys. Plasmas 4, 3230 (1997)] predicts the same tungsten profile as NEO in certain cases, while saving a factor of one thousand in computer time, which can be useful in scoping studies. The parametric dependencies of the temperature screening reduction due to poloidal asymmetries would need to be better characterised for this faster model to be extended to a more general applicability.</p
The role of carrier gas flow in roll-to-roll AP-PECVD synthesized silica moisture barrier films
No full textMoisture barrier films are deposited on a polymer foil by roll-to-roll Atmospheric Pressure Plasma Enhanced CVD reactor using a N2, O2, TEOS gas mixture. The film microstructure and permeation properties are studied as a function of the carrier gas flow rate with both static and dynamic film transport. The microstructure is analyzed by spatially resolved attenuated total reflectance (ATR)-FTIR and correlated with the vertical density gradient obtained in the dynamic films and the moisture barrier performance. It is shown that by varying the carrier gas flow rate the vertical density gradient, or the network porosity, can be tuned by governing the convective transport inside the reactor consequently densifying the inorganic film at fixed energy cost (i.e. Yasuda parameter) of the process. Moreover, adopting the bilayer architecture allows to achieve the same moisture barrier properties of 2 · 10−3 g·m−2·day−1 (40 °C, 90% RH) at only half the film thickness of a single layer barrier films, which consequently leads to a throughput increase of almost two times.</p
The effect of oxygen on the efficiency of planar p-i-n metal halide perovskite solar cells with a PEDOT:PSS hole transport layer
No full textImpact of plastic deformation on retention under pure D or He high flux plasma expose
No full textThe retention of deuterium (D) and helium (He) is studied in pure tungsten after high flux mono-plasma exposure. The recrystallized and plastically deformed tungsten samples are studied to clarify the impact of the material microstructure, in particular dislocation density, on the trapping and release of D and He. Thermal Desorption Spectroscopy (TDS) measurements are performed to reveal the release stages and quantify the retention. Preliminary transmission electron microscopy study was applied to clarify the microstructural modifications induced by the plasma exposure to support the discussion and conclusions. It has been demonstrated that plastic deformation causes considerable suppression of He release within the explored limit of the TDS temperature-1300 K. This is opposite to what is found for the pure D exposure, where the plastic deformation evidently enhances the D retention, given equivalent exposure conditions in terms of surface temperature and ion fluence
Tuning of conversion and optical emission by electron temperature in inductively coupled CO2 Plasma
Get PDFThis paper focuses on how the electron temperature and other plasma properties affect optical emission and CO2 conversion in CO2 plasma. Such plasma-mediated reactions can enable efficient CO2 reuse. We study CO2 and CO plasmas generated by inductively coupled radiofrequency power (30-300 W) at low pressures (6-400 Pa). By varying the argon admixture, we can study the effect of the electron temperature, Te, on the conversion and emission properties using optical emission spectroscopy, mass spectrometry, and electrical probe measurements. Importantly, we can observe several parameters simultaneously: Te, CO2 conversion, chemiluminescence from CO2, and dissociation products and optical emission from several atomic and CO transitions and from the C2 Swan system. On the basis of these results, we establish a correlation between Te, the CO2 conversion, and the optical emission spectra. A low Te enhances CO2 conversion and Swan band emission. In contrast with published studies, our results show that the CO2 and C2 vibrations are not in local equilibrium. This means that the vibrational temperatures of CO2 and C2 should differ.</p
Nano-hardness, EBSD analysis and mechanical behavior of ultra-fine grain tungsten for fusion applications as plasma facing material
Get PDFTungsten and its alloys have been extensively studied in order to be used in plasma facing components for future fusion nuclear reactors such as ITER and DEMO. In this work, an evaluation of nano-hardness, microstructure/texture and mechanical behavior using nano-indentation, electron backscatter diffraction (EBSD) and tensile test was performed. The investigated materials were ultra-fine grain lab-scale tungsten and ITER-specification commercial tungsten products, taken as reference in the as-received and annealed (at 1300 °C for 1 h) conditions. Three ultra-fine grain (UFG) tungsten grades were produced under different spark plasma sintering conditions, namely at 2000 °C and 70 MPa, at 1700 °C and 80 MPa and, finally, at 1800 °C and 80 MPa. EBSD analysis provides very relevant data as it is known that the crystallographic orientation affects some features of the surface damage caused by fusion-relevant plasma exposure. The present results will serve as a reference for future studies that will be carried out using plasma-exposed samples in order to correlate the observed damage with the microstructural characteristics and mechanical behavior.</p