[en] Highlights: • A novel rolling schedule, 135° clock rolling, was presented in this paper. • The orientation dependence in tantalum was alleviated by changing rolling paths sequentially with a rotation angle of 135°. • The substructural evolutions of θ-fiber and γ-fiber grains under unidirectional and 135° clock rolling were analyzed. • The orientation-dependent stored energy was analyzed in a quantitative way. Grains with γ-fiber texture (〈111〉 direction // normal direction (ND)) and θ-fiber texture (〈100〉 direction // ND) show different subdivision behaviors during unidirectional rolling, which leads to orientation-dependent stored energy. This orientation dependence in tantalum can be largely alleviated by a novel approach named 135° clock rolling, which is attributed to two reasons. One is that the clock rolling can weaken the micro-shear bands and destroy the parallel dislocation boundaries in γ-fiber grains, thus reducing their stored energies; and the other is that the clock rolling changes the stability of θ-fiber orientations and introduces plenty of “veins” into θ-fiber grains, thereby increasing corresponding stored energies. Therefore, 135° clock rolling narrows the stored energy difference between these two types of grains, which is beneficial for homogenizing the annealing microstructure of tantalum.

No abstract available

[en] We report observation of a high performance scenario in the National Spherical Torus Experiment with very small edge-localized modes (ELMs). These ELMs have no measurable impact on stored energy and are consistent with high bootstrap current operation with line average density approaching Greenwald scaling. The ELM perturbation is observed to typically originate near the lower divertor region, as opposed to the outer midplane for ELMs described in the literature. If extrapolable, this scenario would provide an attractive operating regime for next step fusion experiments

[en] Dipole magnets with fields beyond 16T will require superconducting coils that are at least 40 mm thick, an applied pres-stress around 150 MPa and a protection scheme for stored energy in the range of 1-2 MJ/m. The coil size will have a direct impact on the overall magnet cost and the stored energy will raise new questions on protection. To reduce coil size and minimize risk, the coil may have to be graded. Grading is achieved by splitting the coil into several layers with current densities that match the short sample field in each layer. Grading, especially at high fields, can be effective; however it will also significantly raise the stress. In this paper we report on the results of a study on the coil size and field relation to that of the stress and stored energy. We then extend the results to graded coils and attempt to address high stress issues and ways to reduce it

[en] A unique large-aperture neodymium glass rod amplifier is experimentally studied. The small-signal gain distribution is measured at different pump energies. The aperture-averaged gain is found to be 2.3. The stored energy (500 J), the maximum possible pump pulse repetition rate, and the depolarisation in a single pulse and in a series of pulses with a repetition rate of one pulse per five minutes are calculated based on the investigations performed. It is shown that the use of this amplifier at the exit of the existing laser can increase the output pulse energy from 300 to 600 J. (lasers)

[en] The electron backscatter diffraction technique has been used to characterize the microstructure of deformed grains in cold-rolled, Cu-added, bake-hardenable steel. A new scheme based on the kind and number of average orientations, as determined from a unique grain map of the deformed grains, was developed in order to classify deformed grains by type. The α-fiber components, γ-fiber components and random orientations, those which could not be assigned to either γ-fiber or α-fiber components, were used to define the average orientation of unique grains within individual deformed grains. The microstructures of deformed grains in as-rolled specimens were analyzed based on the Taylor factor, stored energy, and misorientation. The relative levels and distributions of the Taylor factor, the stored energy and the misorientation were examined in terms of the types of deformed grains. - Highlights: • We characterized the microstructure of Cu-added BH steel using EBSD. • A new scheme was developed in order to classify deformed grains by type. • Stored energy and misorientation are strongly dependent on the type of deformed grains. • Microstructure was examined in terms of the types of deformed grains

[en] In the helical-axis heliotron configuration, bumpiness of the confinement field ε _b is introduced to control the plasma transport. The plasma performance were experimentally investigated in Heliotron J for three configurations with ε _b = 0.01, 0.06 and 0.15 at ρ = 2/3. The obtained volume-averaged stored energy depends on the configuration. To understand the observed difference in global energy confinement, the ε _b-control effects on the edge plasma is discussed. For ε _b = 0.01, the plasma density and temperature in the peripheral region is low compared to other cases. This poor plasma edge relates to the observed low stored energy or poor energy confinement for ε _b = 0.01

[en] Measurements on plasma focus ion beams include various advanced techniques producing a variety of data which has yet to produce benchmark numbers. Recent numerical experiments using an extended version of the Lee Code has produced reference numbers and scaling trends for number and energy fluence of deuteron beams as functions of stored energy E₀. At the pinch exit the ion number fluence (ions m^-2) and energy fluence (J m^-2) computed as 2.4-7.8×10²⁰ and 2.2-33×10⁶ respectively were found to be independent of E₀ from 0.4 – 486 kJ. This work was extended to the ion beams for various gases. The results show that, for a given plasma focus, the fluence, flux, ion number and ion current decrease from the lightest to the heaviest gas except for trend-breaking higher values for Ar fluence and flux. The energy fluence, energy flux, power flow and damage factors are relatively constant from H₂ to N₂ but increase for Ne, Ar, Kr and Xe due to radiative cooling and collapse effects. This paper reviews this work and in a concluding section attempts to put the accumulating large amounts of data into the form of a scaling law of beam energy E_beam versus storage energy E₀ taking the form for deuteron as: E_beam = 18.2E₀^1.23; where E_beam is in J and E₀ is in kJ. It is hoped that the establishment of such scaling laws places on a firm footing the reference quantitative ideas for plasma focus ion beams. (author)

[en] In stellarators, increasing the density is beneficial for the energy confinement. While there is no single reason for this observation, it is still very robust across different devices and this is reflected in the empirical energy confinement time scaling for stellarators, ISS04. In order to study whether this is also true for Wendelstein 7-X, the density scaling of the energy confinement time is analyzed and compared to ISS04 for the first divertor experiments. When the density is increased beyond a critical density, however, radiative collapses are frequently observed. Existing analytical models for the critical density are revisited to assess whether they can predict the accessible density range. Furthermore, since close to the collapse the radiation losses increase substantially, the impact on the global energy confinement is investigated. It is found that in plasmas with high radiation the density scaling of the energy confinement time becomes weaker, the reason for this observation is not yet clear. In the second half of the first divertor campaign, boronization was applied to W7-X for the first time. This broadened the operational window, allowing for operation at higher density and, hence, higher stored energy. (paper)

[en] Electromagnetic metamaterials are generally defined and classified in terms of their effective parameters. They are evaluated in the far-field which limits the evaluation of its near field interaction in some applications such as metamaterial inspired design. An alternative approach proposed in this paper is based on the modal stored energy of metamaterial inclusion. This approach is based on the surface current distribution which would address the challenge of metamaterial near-field application. This paper describes a method for quantifying the modal stored energy of arbitrary-shaped metamaterial inclusions based on the theory of characteristic modes. The theory of characteristic modes is independent of excitation, gives good physical insight into the behaviour of an inclusion and would be helpful for near-field application of metamaterials. The modal stored energy approach is also compared with the common effective parameter approach. It shows similarity in terms of the physical and qualitative analysis when far-field assumptions are accounted for. The broadside-coupled split-ring resonator and the S-shaped inclusion are considered. The physical and qualitative analysis based on the modal stored energy approach shows a good agreement with the effective parameter approach. (paper)