Vanishing magnetic shear and electron transport barriers in the RFX-mod reversed field pinch

We define the safety factor q for the helical plasmas of the experiment RFX-mod by accounting for the actual three-dimensional nature of the magnetic flux surfaces. Such a profile is not monotonic but goes through a maximum located in the vicinity of the electron transport barriers measured by a high resolution Thomson scattering diagnostic. Helical states with a single axis obtained in viscoresistive magnetohydrodynamic numerical simulations exhibit similar nonmonotonic q profiles provided that the final states are preceded by a magnetic island phase, like in the experiment.     

Radial magnetic field in magnetic confinement device

The intrinsic radial magnetic field(B r) in a tokamak is explored by the solution of the Grad–Shafranov equation in axisymmetric configurations through an expansion of the four terms of the magnetic surfaces. It can be inferred from the simulation results that at the core of the device, the tokamak should possess a three-dimensional magnetic field configuration, which could be reduced to a two-dimensional one when the radial position is greater than 0.6a. The radial magnetic field and the amzimuthal magnetic field have the same order of magnitude at the core of the device. These results can offer a reference for the analysis of the plasma instability, the property of the core plasma, and the magnetic field measurement.     

Electric confinement and magnetic superconductors

Reinterpretation of the pioneering work of Nielsen and Olesen and others on magnetic confinement in (electric) superconductors leads to simple models which exhibit electric confinement of the type hoped for in quantum chromodynamics. “Electric” flux tubes joining “quarks” arise at a semi-classical level as a result of the existence of (pseudo) particles. The theory can be described in terms of a classical action principle only upon suitable modification of the action; this modification has profound topological significance as it is intimately related to the quantization condition for (pseudo) particles.     

Interfaces in driven Ising models: shear enhances confinement

We use a phase-separated driven two-dimensional Ising lattice gas to study fluid interfaces exposed to shear flow parallel to the interface. The interface is stabilized by two parallel walls with opposing surface fields, and a driving field parallel to the walls is applied which (i) either acts locally at the walls or (ii) varies linearly with distance across the strip. Using computer simulations with Kawasaki dynamics, we find that the system reaches a steady state in which the magnetization profile is the same as that in equilibrium, but with a rescaled length implying a reduction of the interfacial width. An analogous effect was recently observed in sheared phase-separated colloidal dispersions. Pair correlation functions along the interface decay more rapidly with distance under drive than in equilibrium and for cases of weak drive, can be rescaled to the equilibrium result.     

托卡马克高约束运行模式和磁约束受控核聚变

磁约束受控核聚变是最终解决人类能源问题的有希望的途径之一.托卡马克的高约束运行模式可以大大降低下一代磁约束聚变实验装置和将来的聚变示范反应堆的规模和造价.文章简要介绍了托卡马克高约束模式的特征,实现条件及亟待研究解决的科学技术问题,包括触发高约束模式的物理机理,功率阈值与等离子体参数的关系等,以及在高约束运行模式下观察到的边缘局域模的驱动机制、控制或缓解技术等.     

托卡马克高约束运行模式和磁约束受控核聚变

磁约束受控核聚变是最终解决人类能源问题的有希望的途径之一.托卡马克的高约束运行模式可以大大降低下一代磁约束聚变实验装置和将来的聚变示范反应堆的规模和造价.文章简要介绍了托卡马克高约束模式的特征,实现条件及亟待研究解决的科学技术问题,包括触发高约束模式的物理机理,功率阈值与等离子体参数的关系等,以及在高约束运行模式下观察到的边缘局域模的驱动机制、控制或缓解技术等.     

Improved model of optical phonon confinement in silicon nanocrystals

We develop a model for calculating the Raman scattering spectra from phonons confined in for silicon nanocrystals, which is based on the familiar approach taking into account the uncertainty in the quasi-momentum of phonons localized in the nanocrystals. The model is considerably improved by taking into account dispersion of phonons not only in the magnitude of the quasi-momentum, but also in its direction. A significant refinement of the model is also due to the fact that phonon dispersion is calculated using the widely approved Keating model instead of being approximated by empirical expressions as was done in earlier approaches. The calculations based on this model make it possible to determine the sizes of silicon nanocrystals more precisely from analysis of the experimental Raman spectra.     

Plasma confinement by a magnetic shell configuration

The confinement properties of a new magnetic shell configuration have been investigated experimentally. The diffusion coefficient D has been determined.     

MHD shear flows with non-constant transverse magnetic field

Viscous conducting flows parallel to a fixed plate are studied. In contrast with the Hartmann setting, the problem is not linearized near a fixed transverse magnetic field, although the field tends to be transversal far from the wall. While general solutions may be formally obtained for all cases, their behavior is far more clear when the magnetic Prandtl number equals one. We consider two different instances: a fixed magnetic field at the wall, or an insulating sheet. The evolution of the flow and the magnetic field both near the plate and far from it are detailed, analyzing the possibility of reverse flow and instability of the solutions.     

Roles of electric field on toroidal magnetic confinement

Theoretical research on the influence of electric field on toroidal magnetic confinement is surveyed. The static electric field is first described. A physical picture of the radial electric field generation and its influence on confinement are shown. Neoclassical effects as well as the non-classical processes are discussed. Emphasis is made on the connection with improved confinement. Convective cells with a nonuniform potential on the magnetic surface are also discussed. The roles of the fluctuating electric field are then reviewed. Recent progress in anomalous transport theory is addressed. Through these surveys, the impact of experiments using the heavy ion beam probes on modern plasma physics is illustrated