No abstract available

No abstract available

No abstract available

[en] The propagation of a tenuous electron beam in the z-direction through a helical wiggler magnetic field is studied by using the linear vlasov theory. The dispersion relation and the resonance condition are derived. It is shown that there exists some difference between the relativistic resonance condition in momentum space and that in velocity space. For right-circularly polarized electromagnetic wave, the instability is analyzed using Wu-Lee criterion. It is revealed that Wu-Lee criterion can be applied to qualitatively analysing the free electron laser instability and the result in momentum space is the same as that in velocity space

[en] A simple model, rotation-inducing local cooling, for the mechanism on the formation of thermal transport barrier and the increase in rotation velocity is presented. It is shown that the sheared rotation can make electron temperature profile T_e(γ) steepen near the rotation layer and ΔT_e > 0 on some location inside it, in agreement with the experimental observations in tokamaks, such a JT-60U with (poloidal or toroidal) sheared rotation and HL-1M with a biased electrode. Such temperature profile can remarkably improve the energy confinement in tokamaks

[en] The eikonal approximation is applied to study the kinetic problem of Alfven wave heating of low β tokamak plasma. Comparing with the method proposed by Ross et al., the presented method is computationally simpler and more distinct. The results are in agreement with their ones. The method developed in this paper can also be employed to kinetic problems of other types of RF heating

[en] Numerous experiments in both single wire and in wire arrays have attracted much attention. For the wire array Z-pinch implosions the plasma formation in the metallic wire Z pinches is a key question. By means of analyzing a number of single-wire and multi-wire experiments, two models to describe the behavior of a wire array Z-pinch in initial phase are suggested. In this phase each wire carries a rising current and behaves independently in a way similar to that found in single wire Z-pinch experiments in which a comparable current in one wire is employed. Based on one- or/and two-dimensional magnetohydrodynamics (MHD) theory, one model is used to simulate the electrical explosion stage of the metallic wire, another is used to simulate the wire-plasma formation stage

[en] The current drive due to Alfven wave in tokamak reversed shear plasmas is studied. In cylindrical geometry, an expression for driving current density J_z is given by means of the single-fluid magnetohydrodynamic (MHD) model taking plasma rotation and magnetic shear into account. The current drive due to the compressional Alfven wave and the shear Alfven wave is considered, respectively. It is found that the efficiency of the Alfven wave current drive without the magnetic shear is independent of rotating plasma density. Moreover, it is shown that a higher efficiency can be obtained in the presence of rotation. For the shear Alfven wave, the magnetic shear has a more distinct effect on the current drive than one for the compressional Alfven wave. The effect of the negative magnetic shear on the Alfven wave current drive is opposite to the effect of the positive, and the negative shear enhances the driven current density J_z. These results show that the Alfven waves may be an excellent current drive candidate for tokamak fusion reactors

[en] A kind of singular boundary value problems for second order systems with a singularity at the origin and a non-normal singularity at the resonance layer are solved by means of the three-point difference method. Comparing with the method proposed by Ross et al., the present method is not only computationally simpler and more distinct but also can save much computer time. The numerical results are in agreement with the other results

[en] A linear analysis of the ideal magnetohydrodynamic (MHD) stability of the Z-pinch is presented in which plasma flows are included in the equilibrium. Compressibility is introduced into MHD equations via the acoustic velocity of the plasma. It is found that, compressibility can stabilize the magneto-Rayleigh-Taylor/Kelvin-Helmholtz (MRT/KH) instability, and this allows the sheared axial flow mitigate MRT instability far more effectively. Therefore, on the early stage of the implosion, because the temperature of the plasma is not high, the compressible model is much more suitable than the incompressible one. Different flow profiles have also been investigated, and it shows that the mitigation effect of the axial flow only depends on the magnitude of the velocity shear where the perturbations concentrate. (authors)