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We have used the local-δf gyrokinetic code GS2 to perform studies of the effect of flux-surface shaping on two highly-shaped, low- and high-β JT-60SA-relevant equilibria, including a successful benchmark with the GKV code. We find that for a high-performance plasma, i.e. one with high plasma beta and steep pressure gradients, the turbulent outwards radial fluxes may be reduced by minimizing the elongation. We explain the results as a competition between the local magnetic shear and finite-Larmor-radius (FLR) stabilization. Electromagnetic studies indicate that kinetic ballooning modes are stabilized by increased shaping due to an increased sensitivity to FLR effects, relative to the ion-temperature-gradient instability. Nevertheless, at high enough β, increased elongation degrades the local magnetic shear stabilization that enables access to the region of ballooning second-stability.

According to the new JIS (or IEC Standards), it is necessary to measure the bounded-square output power (P 1×1) for the determination of the soft tissue thermal index (TIS) for both scanning and non-scanning modes of an ultrasonic diagnostic equipment. However, there is no report about how to measure P 1x1 for an ultrasound probe with an inclined beam-axis (UPIB). We designed an angle-corrected 1 cm × 1 cm absorbing mask in accordance with the spirit of IEC 62359 Ed. 2.0 and established a reasonable process for the measurement of TIS and mechanical index (MI) of a paste type probe (PTP), which is a specially designed UPIB for examination of the blood flow in a carotid artery more conveniently and efficiently. Both the TIS and MI of the PTP were much less than 1.0 at all selectable presettings of the blood flow monitor, the FURUHATA device, suggesting it is as safe as a common ultrasonic Doppler diagnostic device.

In this study, we fabricated p-type diamond Schottky barrier diodes (SBD) and performed selective B doping for the p-type channel and Ohmic region by double ion implantation. SBD were redesigned in the configuration and shape of Ohmic and Schottky electrodes to improve device characteristics. The fabricated device exhibited a rectification ratio of approximately 2400 because of decreasing the parasitic resistance to 2.7 × 107 Ω and the ideality factor to 2.7. The Schottky barrier height was obtained to be 1.04 eV. It is indicated that the diamond SBD fabricated only by B ion implantation is improved by refinement of the electrode structure.

Multi-scale gyrokinetic theory and simulations of a toroidal magnetized plasma have revealed the existence of cross-scale interactions of the trapped electron mode (TEM) and the electron temperature gradient (ETG) turbulence. Reduction of the TEM instability growth rate in the ETG turbulence is clearly identified, and is well represented in the form of effective diffusion. A theoretical model based on the stochastic forcing by the ETG turbulence well describes the turbulent diffusion coefficient observed in multi-scale turbulence simulations.

In this study, we present {11 2 ¯ 2} InGaN underlayers of high In composition and multi-quantum wells (MQWs) grown using the m-plane sapphire substrate. Fully relaxed InGaN templates with high In composition (In: ∼18%) were investigated. We used an InGaN template with an In composition of 16.5%. The photoluminescence (PL) spectrum of MQWs on the InGaN template exhibited higher emission intensity and longer emission wavelength than that on a GaN template. Moreover, an InGaN barrier was found to be more suitable than a GaN barrier for the long-wavelength (red) region in the InGaN underlayer. The intensity of the PL spectrum of InGaN/InGaN MQWs was twice as high as that of InGaN/GaN MQWs in the red emission region. Finally, we analyzed the optical polarization of the MQWs on {11 2 ¯ 2} InGaN underlayers and its characteristics were discussed using theoretical equations.

The effect of surface potential on the carrier mobility and piezoresistance of core–shell silicon carbide nanowires (SiC NWs) was investigated to realize small and sensitive SiC-microelectromechanical systems sensors. The p-type cubic crystalline SiC (3C-SiC) NWs were synthesized via the vapor–liquid–solid method and coated with silicon dioxide (SiO2) or aluminum oxide (Al2O3) dielectric shells to form core–shell structured NWs with different surface potentials. Four-point bending devices (FBDs) with a field-effect transistor (FET) configuration integrating a single core–shell 3C-SiC NW as the FET channel were fabricated to apply an additional electric field and strain to the core–shell 3C-SiC NWs. The fixed oxide charge densities of the SiO2 and Al2O3 shells showed positive and negative values, respectively, which were equivalent to electric fields of the order of several hundred thousand volt per centimeter in absolute values. In the core–shell 3C-SiC NWs with originally low impurity concentrations, the electric field induced by the fixed oxide charge of the shells can determine not only the electrical conduction but also the charge carriers in the NWs. Bending tests using the FBDs showed that the piezoresistive effect of the SiO2-coated NW was almost the same as that of the as-grown 3C-SiC NW reported previously, regardless of the gate voltage, whereas that of the Al2O3-coated NW was considerably enhanced at negative gate voltages. The enhancement of the piezoresistive effect was attributed to the piezo-pinch effect, which was more pronounced in the NW, where the carrier density at the core–shell interface is enhanced by the electric field of the dielectric.

We investigate Sn incorporation effects on the thermoelectrical characteristics of n-type Ge-rich Ge1−x−y Si x Sn y layers (x ≈ 0.05−0.1, y ≈ 0.03) pseudomorphically grown on semi-insulating GaAs(001) substrates by molecular beam epitaxy. Despite the low Sn content of 3%, the Sn atoms play a role in suppressing the thermal conductivity from 13.5 to 9.0 Wm−1 K−1 without degradation of the electrical conductivity and the Seebeck coefficient. Furthermore, a relatively high power factor (maximum: 14 μW cm−1 K−2 at room temperature) was also achieved for the Ge1−x−y Si x Sn y layers, almost the same as the Si1−x Ge x ones (maximum: 12 μW cm−1 K−2 at room temperature) grown with the same conditions. This result opens up the possibility of developing Sn-incorporated group-IV thermoelectric devices.

A novel nonlinear functional relation of turbulence potential intensity, zonal flow potential intensity, and ion thermal diffusivity that accurately reproduces nonlinear gyrokinetic simulations of toroidal ion temperature gradient (ITG) driven turbulence is proposed. Applying mathematical optimization techniques to find extremal solutions in high-dimensional parameter space, the optimal regression parameters in the functional form are determined to be valid for both near- and far-marginal regime of the ITG stability including the Dimits-shift. Then, the regression error of ∼5% is accomplished. In addition, it is clarified that the intensity ratio of the zonal flow and turbulence potential intensity is a crucial factor to determine the reproduction accuracy.

In recent deuterium experiments on the large helical device (LHD), we succeeded in expanding the temperature domain to higher regions for both electron and ion temperatures. Suppression of the energetic particle driven resistive interchange mode (EIC) by a moderate electron temperature increase is a key technique to extend the high temperature domain of LHD plasmas. We found a clear isotope effect in the formation of the internal transport barrier in high temperature plasmas. A new technique to measure the hydrogen isotope fraction was developed in the LHD in order to investigate the behavior of the isotope mixing state. The technique revealed that the non-mixing and the mixing states of hydrogen isotopes can be realized in plasmas. In deuterium plasmas, we also succeeded in simultaneously realizing the formation of the edge transport barrier (ETB) and the divertor detachment. It is found that resonant magnetic perturbation plays an important role in the simultaneous formation of the ETB and the detachment. Contributions to fusion reactor development from the engineering point of view, i.e. negative-ion based neutral beam injector research and the mass balance study of tritium, are also discussed.

Time-resolved X-ray tomography (4D-CT) and three-dimensional X-ray diffraction (3DXRD) were performed to investigate semisolid deformation in Al–10mass%Cu alloy. The configurations of solid grains were observed in-situ by 4D-CT and the crystallographic orientations of grains were also measured by 3DXRD. Translation and rotation of the solid grains in the semisolid are quantitatively analysed by the reconstructed 3D images and the diffraction spots. Based on the in-situ observation, we discuss about the motion of the solid grains and the formation of the shear band during the semisolid deformation., MCWASP XV: International Conference on Modelling of Casting, Welding and Advanced Solidification Processes 22-23 June 2020, Jönköping, Sweden.

A quasi-axisymmetric stellarator, the CFQS, has been designed as a joint project of the National Institute for Fusion Science and Southwest Jiaotong University to prove intrinsic advantages of quasi-axisymmetry. Principal parameters of the CFQS are as follows: the major radius is 1 m, the magnetic field strength is 1 T, the aspect ratio is 4, and the toroidal periodic number is 2. The magnetic field configuration is designed based on that of the CHS-qa. Enhanced confinement properties within the context of neoclassical theory are achieved by its quasi-axisymmetric configuration. In the entire radial range, the magnetic well is retained to keep favourable stability features in the magnetohydrodynamic equilibrium. A magnetic field coil system was designed for the CFQS, which consists of 16 modular coils, 12 toroidal field coils, and 4 poloidal field coils. The supporting structure is designed to withstand strong electromagnetic force under 1 T operation, maintaining enough space for heating and diagnostic systems. The mock-up modular coil with the most complicated shape was constructed by Hefei Keye Electro Physical Equipment Manufacturing Co., Ltd. to check manufacturability and the achieved accuracy. A heat-run test was performed to check the temperature rise of conductors, and the capability of 1 T operation was confirmed. After various tests for the mock-up coil, construction of actual modular coils and the vacuum vessel has begun.

In this paper, the background physics of the isotope effects in the ion internal transport barrier (ITB) are discussed in detail. An heuristic criterion for the ITB strength is defined based on the nonlinear dependence of the ion thermal diffusivity on the local ion temperature in the L-mode phase. Comparing deuterium plasmas and hydrogen plasmas, two isotope effects on the ion ITB are clarified: stronger ITBs formed in the deuterium plasmas and an ITB concomitant edge confinement degradation in the hydrogen plasmas. Principal component analysis reveals that the ion ITB becomes strong when a high input power normalized by the line averaged electron density is applied and electron density profile is peaked. A gyrokinetic simulation suggests that the ITB profile is determined by the ion temperature gradient driven turbulence, while the way the profile saturates in L-mode plasmas is unknown. In the electron density turbulence behavior, a branch transition is observed, where the increasing trend in turbulence amplitude against the ITB strength is flipped to a decreasing trend across the ITB formation. The radial electric field structure is measured by the charge exchange recombination spectroscopy system. It is found that the radial electric field shear plays a minor role in determining the ITB strength.

A novel quasilinear turbulent transport model DeKANIS has been constructed founded on the gyrokinetic analysis of JT-60U plasmas. DeKANIS predicts particle and heat fluxes fast with a neural network (NN) based approach and distinguishes diffusive and non-diffusive transport processes. The original model only considered particle transport, but its capability has been extended to cover multi-channel turbulent transport. To solve a set of particle and heat transport equations stably in integrated codes with DeKANIS, the NN model embedded in DeKANIS has been modified. DeKANIS originally determined turbulent saturation levels semi-empirically based on JT-60U experimental data, but now it can also estimate them using a theory-based saturation rule. The new saturation model is still partly connected to experimental data, but it offers the potential for applying DeKANIS independently of the device.

A novel quasilinear turbulent transport model DeKANIS has been constructed founded on the gyrokinetic analysis of JT-60U plasmas. DeKANIS predicts particle and heat fluxes fast with a neural network (NN) based approach and distinguishes diffusive and non-diffusive transport processes. The original model only considered particle transport, but its capability has been extended to cover multi-channel turbulent transport. To solve a set of particle and heat transport equations stably in integrated codes with DeKANIS, the NN model embedded in DeKANIS has been modified. DeKANIS originally determined turbulent saturation levels semi-empirically based on JT-60U experimental data, but now it can also estimate them using a theory-based saturation rule. The new saturation model is still partly connected to experimental data, but it offers the potential for applying DeKANIS independently of the device.