DIFFER: Publications
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Nucleation mechanism of intra-granular blisters in tungsten exposed to hydrogen plasma
No full textDespite being a subject of long-term research on fusion-reactor structural materials, the behaviour of hydrogen in tungsten under plasma exposure remains unclear. Here, the explicit transmission electron microscopy observations for recrystallised W after hydrogen plasma exposure are successfully obtained. These are the first observations to show the intra-granular blisters are located on the {100} planes. Molecular dynamics simulations confirm the hydrogen blister initiating at dislocation core behaved similarly to those in experiment. We propose that the widely reported intra-granular hydrogen blisters are nucleated at the edge dislocation core and develop along the (100) plane in tungsten
Thermal aspects of CO2 conversion in the vortex-stabilized microwave plasma
No full textunder embargo</p
Cross-field transport in detached helium plasmas in Magnum-PSI
No full textIn this study, enhanced radial transport in a volume-recombining region in detached helium plasmas in a linear device, Magnum-PSI, was investigated. By installing a reciprocating Langmuir probe, electrostatic fluctuations with high spatiotemporal resolutions were measured and analyzed. As a result, the ion-flux profile broadening in the detached state and the coherent plasma structure, which has an internal electric field in the azimuthal direction, were confirmed. By analyzing the emission intensities obtained with a fast framing camera viewing around the probe head, an enhanced fluctuation, which has an azimuthal mode number of m= 1, was found to be correlated with radial plasma ejection. This m= 1 mode rotates by the drift with the radial electric field and magnetic field and is correlated with the m= 0 mode. These two modes behave like a predator and prey; they quasi-periodically appear with about a quarter-period shift. Because the ion flux flowing into the target plate decreases when the radial transport is enhanced, this cross-field transport disperses the ion flux and decreases the maximum heat load applied to the target
Dry Reforming of Methane under Mild Conditions Using Radio Frequency Plasma
Get PDFDry reforming of methane (DRM) is a challenging process wherein methane reacts with CO2 to give syngas. This reaction is strongly endothermic, typically requiring temperatures higher than 500 °C. Catalysts can be used, but the high temperatures (which are a thermodynamic requirement) often lead to catalyst deactivation. Herein, the reaction from another conceptual direction is approached, using low‐power radio frequency inductively coupled plasma (RF‐ICP). It is demonstrated that this system can give high conversions of methane and CO2 at near‐ambient temperatures. Importantly, the energy costs in this system are considerably lower compared with other plasma‐driven DRM processes. Furthermore, it is shown that the yield of hydrogen can be increased by minimizing the C2 compound formation. The factors that govern the DRM process and discuss Hα emission and its influence on H atom recycling in the process are examined.</p
Controlling the Microstructure of Conjugated Polymers in High‐Mobility Monolayer Transistors via the Dissolution Temperature
No full textDeciphering the synergy between plasma and catalyst support for ammonia synthesis in a packed dielectric barrier discharge reactor
No full textProgress and challenges in understanding core transport in tokamaks in support to ITER operations
No full textFusion performance in tokamaks depends on the core and edge regions as well as on their nonlinear feedbacks. The achievable degree of edge confinement under the constraints of power handling in presence of a metallic wall is still an open question. Therefore, any improvement in the core temperature and density peaking is crucial for achieving target performance. This has motivated further progress in understanding core turbulent transport mechanisms, to help scenario development in present devices and improve predictive tools for ITER operations. In the last two decades, detailed experiments and their interpretation via the gyrokinetic theory of turbulent transport have led to a satisfactory level of understanding of the heat, particle, and momentum transport channels and of their mutual interactions. This paper presents some highlights of the progress, which stems from joint work of several devices and theory groups, in Europe and worldwide within the International Tokamak Physics Activities framework. On the other hand, the achievement of predictive capabilities of plasma profiles via integrated modeling, which also accounts for the nonlinear interactions inherent to the multi-channel nature of transport, is a priority in view of ITER. This requires using faster, reduced models, and the extent to which they capture the complex physics described by nonlinear gyrokinetics must be carefully evaluated. Present quasi-linear models match well experiments in baseline scenarios, and thus offer reliable predictions for the ITER reference scenario, but have issues in advanced scenarios. Some of these challenges are examined and discussed. In the longer term, advances in high performance computing will continue to drive physics discovery through increasingly complex gyrokinetic simulations, allowing also further development of reduced models. The development of neural network surrogate models is another recent advance that bridges the gap towards physics-based fast models for optimization and control applications