Beryllium erosion and redeposition in ITER H, He and D-T discharges

The Monte-Carlo code ERO2.0 was used to simulate steady-state erosion and transport of beryllium (Be) in the ITER main chamber. Various plasma scenarios were tested, including a variation of the main species (hydrogen, deuterium, helium), plasma conditions (density, temperature, flow velocity) and magnetic configurations. The study provides valuable predictions for the Be transport to the divertor, where it is expected to be an important contributor to dust formation and fuel retention due to build-up of co-deposited layers. The Be gross and net erosion rates provided by this study can help identifying first wall regions with potentially critical armour lifetime.

Evaluation of Helium Plasma Surface Modification on Tensile Bond Strength of Denture Base Materials: A Scanning Electron Microscope Study

The purpose of this study was to compare the effect of helium plasma treatment on tensile bond strength between polymethylmethacrylate and soft liner material. For the tensile test, acrylic samples (30 x 10 x 10 mm³; n=100) were prepared. Acrylic samples were divided into five surface groups (n = 10/group) and treated by different concentrations of helium plasma: G I: Control group (untreated), G II: 100% Helium plasma-treated group, G III: 90% Helium plasma-treated group, G IV: 85% Helium plasma-treated group, G V: 80% Helium plasma-treated group. After plasma treatment, the soft liner was processed between two acrylic resin blocks according to the manufacturer's instructions and polymerized. The surface properties were evaluated by scanning electron microscopy and atomic force microscopy. All samples were submitted to a tensile test using a universal testing machine. After failure, the surface properties were evaluated by stereomicroscope. One-way analysis of variance was used to compare the groups. p <0.05 value was considered statistically significant. While the highest mean tensile bond strength value was obtained with the G III (1.56 ± 0.13 MPa), the lowest value was observed with the G I (0.95 ± 0.2 MPa). In addition, it was observed that the surface roughness increased the most in G III.

Characteristics of Plasma Dynamics in Current Sheets Formed in Helium Plasma

The characteristic features of plasma acceleration in the current sheets are discussed on the basis of an analysis of the structure of electrodynamic forces at successive stages of the evolution of the current sheets formed in the plasma with helium ions. Of particular interest is the generation of reverse currents at the side edges of the sheet and the appearance of forces, which are braking previously accelerated plasma flows.