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We describe the results of a multi-scale, multi-physics modeling assessment of SOLPS-ITER, hPIC2, RustBCA and Xolotl, in which five single-crystal tungsten (W) samples were placed in a reciprocating collector probe and exposed to helium (He) plasma in the WEST fusion device. In our models, we considered a pure (100 %) He plasma, as well as one with oxygen (O) present (95% He 5% O) corresponding to the impurity concentration estimated during the C4 He campaign in WEST. Our SOLPS simulations approximately match experimental reciprocating Langmuir probe plasma measurements of plasma density and temperature. Using these plasma parameters as input, hPIC2 and RustBCA predict that the presence of oxygen impurities lead to a 15%–20% decrease in ion and heat fluxes to the surface, and an order of magnitude higher sputtering yields (compared with a pure He plasma). Xolotl predictions for the response of tungsten to plasma surface interactions (PSIs) agree with experimental LAMS analysis, and indicate large near-surface He concentrations, which quickly decay with depth. Our model also shows an increasing role of erosion—in removing the near-surface He—with time. Overall, slightly higher retention is predicted for tungsten exposed to a pure He plasma, with the largest differences in the near-surface gas content caused by the large oxygen-induced erosion. This highlights the important role that impurities play in PSI. Therefore, future work will focus on providing a fully self-consistent description of oxygen (and oxides, etc.) in our models, through multi-species implementation in GITR and inclusion of oxygen and tungsten oxide formation in Xolotl.

This study explores a hypothetical scenario where low-activation refractory multi-component alloys (RMCAs) are considered for use as divertor target materials in fusion reactors. To investigate the surface modifications under divertor service conditions, a multi-phase W–Ta–V–Cr RMCA is irradiated with low-energy helium (He) plasma at varying temperatures to approximately 5.0 × 1025 He·m−2. The W-rich and Cr-rich phases in the multi-phase RMCA mimic the mono-phase W–Ta–V–Cr RMCA and segregation at grain boundaries, respectively. Following irradiation, fuzz layer formation is observed for all phases at temperatures lower than pure W requires. Additionally, nano He bubbles are identified in the fuzz tendrils at 920 °C. The modified layers exhibit reduced V and Cr content with increasing temperature, transitioning into W-Ta binary alloys at 920 °C. Notably, the fuzz layer on the W-rich phase is thinner than that on pure W at 920 °C. While a thinner fuzz layer suggests the alloy’s potential as a divertor target material, challenges include a lower fuzz formation temperature and potential high V and Cr sputtering yield, raising concerns for plasma contamination during fusion reactor operation. This dual perspective highlights both the promise and challenges of utilizing RMCAs as divertor target materials in severe fusion reactor environments.

Conducting metal interconnections are essential to link electronic components or multiple circuits for electronic device fabrication. Scalable, rapid, and sustainable methods for printing adherent metal interconnections on dielectric materials are lacking, which stifles the development of new electronic consumer devices. Here a breakthrough single‐step and rapid process to deposit highly conducting metal tracks is introduced, using an atmospheric pressure plasma jet. The deposition process used a rudimentary aqueous solution of metal salts as ink, that was introduced as a mist into a helium plasma gas. The metal salt was reduced and deposited with spatiotemporal control using a plasma jet generated at radio frequency with 15 W power at room temperature and pressure. The conductive metal layers were highly adhesive on glass, ceramics, polymeric materials, even biological surfaces such as plant leaves and animal skin, depostedwith little damage to the substrate. The conductivity of deposited tracks on glass shows 50.8 ± 8.6% and 5.2 ± 1.6% of bulk silver and copper metal conductivity respectively. Highly adhesive electrically conductive metal track printed on dielectrics using atmospheric pressure plasma microjet through a rapid, single‐step process.

In this paper, a theoretical study of kinetic processes occurring in argon–helium plasma of a pulsed discharge is presented. A model of argon–helium plasma is developed and key mechanisms of the formation and loss of plasma particles are studied. A general scheme of kinetic processes occurring in plasma of inert gases of a pulsed discharge is formed.

A Lagrangian/Eulerian simulation technique for an argon/helium plasma spray including 10–100 micron metal particles has been developed and characterized for manufacturing applications including a unique equilibrium-based approach to the argon ionization problem. Six metals were studied for behavior under a characteristic flow condition to assess the sensitivity of model predictions for application purposes. Particular attention was paid to the thermal properties of the six candidate metals, and a number of uncertainties of varying significance were found in surveying existing source materials for the properties. Methods for determining injection boundary conditions based on measured nozzle parameters are exhibited. Spray dynamics have been affiliated with model properties, which may help guide the exercise of identifying optimal spray conditions for new applications. Particle-mean velocity and temperatures are compared to experimentally obtained data, suggesting the model provides a reasonable approximation of the nozzle dynamics at a low power setting. A number of uncertainties in the modeling characteristics of the nozzle are evaluated through a parametric evaluation. The exercise highlights the importance of input and boundary conditions to the accuracy of the resultant spray.

Cold plasma (CP) treatment for enhancing functional and cooking properties has been investigated on less rice varieties and delays the industrial adoption of this technology. This study treated three types (short-, medium-, and long-kernel) of milled rice from six Chinese varieties with helium plasma (Radio frequency, 13.56 MHz, 140 Pa) at a combination of watt and time, and evaluated the cooking properties, cooked rice texture, kernel appearance quality, and surface morphology, as well as flour thermal and thermomechanical properties. CP treatment at 120 W for 20 s significantly decreased the cooking time and the hardness of cooked rice while increasing adhesiveness, elasticity, and gruel solid loss. CP did not significantly change the appearance of milled rice, except for chalky rice rate, and kept the peak temperature and enthalpy of gelatinization in rice flour. 120W–20s CP significantly increased rice dough development and stability time, starch gelatinization maximum torque, and starch breakdown, but decreased the stability of protein network and starch retrogradation. As CP power strength increased from 120 to 520 W; the surface rupture of a rice kernel became more severe, and small particles aggregated on the rough surface. Compared with the 0 h sample of 120W–20s CP treatment, the repeating CP treatments at 24 h, 48 h, and 30 d significantly decreased water contact angle and free fatty acid content, but increased water absorption rate and chalky rice rate. These results suggest that 120W–20s helium CP improved the cooking properties of milled rice via leading to the rough kernel surface, higher water absorption rate, weak protein network, and a higher speed of starch gelatinization.

We studied the influence of various exposures (1, 2, 3, 5, 10 and 15 min.) effects of cold helium plasma on the state of free radical processes in the biological fluid (human blood). It was found that the nature of the response of antioxidant systems of blood to cold plasma treatment is directly determined by exposure, as evidenced by the results of chemiluminescence assessment of the intensity of free radical processes and total antioxidant activity, as well as the dynamics of the concentration of malonic dialdehyde. At the same time, the short-term processing mode of biological fluid allows us to establish the presence of a two-phase influence of the factor on oxidative processes (“the phenomenon of the antioxidant window”).

In this paper, we report the successful development of non-thermal atmospheric plasma torch employing high voltage power supply. Usually atmospheric plasma is generated at high temperature (>1000 °C) and it is quite a challenge to generate cold plasma (<150 °C). The plasma torch in this assembly uses helium gas. The length of helium plasma glow discharge in this research is studied and optimized, with flow rate varied from 2 to 7 liters per mins, at varied applied voltage of 1.20 to 2.00 kV. The generated cold helium plasma has tunable length of around 5 to 35 mm, as cold as 26 °C. The plasma setup in this study is projected to be suitable for future applications in several fields such as industrial wastewater processing, as well as food processing, or agricultural field.

AbstractThe results of experiments on the impact of fast helium ions (Ei ~ 100 keV) and helium plasma (v ~ 2 × 107 cm/s) on a silicon single crystal plate in the Vikhr plasma focus (PF) installation with radiation power density in the range of q ≈ 106–107 W/cm2 are presented. It is shown that, at low values of q = 106–1011 W/cm2, the damageability of silicon is due to its surface sputtering mainly in the zone of mechanical defects, while with more intense irradiation (108< q ≤ 1011 W/cm2) the processes of melting and evaporation of the surface layer occur with the formation of structural defects in the form of waves, flows, bubbles, craters and microcracks. The specific nature of damage of the Si plate at high power density and a large number of pulsed beam-plasma impacts (q ≥ 109 W/cm2, N = 50) is described. It is associated with the formation of a brittle fine-crystalline surface layer, which is easily separated from the base material and disintegrates in the form of a powder of particles of micron and nanoscale size. This result is a consequence of the action of thermal stresses in combination with the implantation of helium ions into the material as well as the possible influence of shock waves generated in the Si target during hard irradiation regimes. The presence of copper, carbon, and nitrogen on the silicon surface after its beam-plasma treatment, as well as an increase in the electrical resistivity on the irradiated side and backside of the plate, is noted. The results obtained are discussed taking into account the features of the experiments in the PF setup.

Plasma waves generated in the wake of intense, relativistic laser1,2 or particle beams3,4 can accelerate electron bunches to gigaelectronvolt energies in centimetre-scale distances. This allows the realization of compact accelerators with emerging applications ranging from modern light sources such as the free-electron laser to energy frontier lepton colliders. In a plasma wakefield accelerator, such multi-gigavolt-per-metre wakefields can accelerate witness electron bunches that are either externally injected5,6 or captured from the background plasma7,8. Here we demonstrate optically triggered injection9–11 and acceleration of electron bunches, generated in a multi-component hydrogen and helium plasma employing a spatially aligned and synchronized laser pulse. This ‘plasma photocathode’ decouples injection from wake excitation by liberating tunnel-ionized helium electrons directly inside the plasma cavity, where these cold electrons are then rapidly boosted to relativistic velocities. The injection regime can be accessed via optical11 density down-ramp injection12–16 and is an important step towards the generation of electron beams with unprecedented low transverse emittance, high current and 6D-brightness17. This experimental path opens numerous prospects for transformative plasma wakefield accelerator applications based on ultrahigh-brightness beams.