The structure of magnetic field lines in a tokamak with reversed magnetic shear is investigated by means of analytically derived area-preserving non-twist Poincaré maps. The basic configuration is the magnetic field produced by an ergodic limiter, superimposed to the tokamak equilibrium field in suitable coordinates. We consider the cases of one and two resonant modes, focusing on magnetic isla...

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The particle and energy transport was analyzed for different regions and regimes of the plasma in tokamak with special attention for ITER. For the particle transport in the tokamak edge plasma was obtained results useful for the qualitative cross-check of the numerical models of the first principle simulations, including ITER, as well as in the elaboration of the simplified, reduced models of t...

In this research we measured the plasma boundary shift using array of magnetic pick-up coils on the IR-T1 tokamak. Also we approximated the magnetic surfaces by an equilibrium calculation. Firstly, four magnetic probes were designed, constructed, and installed on outer surface of the IR-T1 tokamak chamber and then plasma boundary displacement measured from them. On the other hand, magnetic surf...

We analyse the effect of an Ergodic Magnetic Limiter on the magnetic field line dynamics in the edge of a large aspect-ratio Tokamak. We model the limiter action as an impulsive perturbation and use a peaked-current model for the Tokamak equilibrium field. The theoretical analysis is made through the use of invariant flux functions describing magnetic surfaces. Results are compared with a numer...

A region of zero current density in the plasma center has been observed in the advanced tokamak scenarios with off-axis lower-hybrid current drive in the JET and JT-60U tokamak experiments. Significantly, the central current density does not become negative, although this is expected based on conventional current diffusion. In this paper, it is shown that the zero central current density and th...

Qualitatively novel results on nonlocality phenomena in perturbative transport experiments are reported. Here, nonlocality means a rapid response in the core follows an edge perturbation on a time scale far shorter than any standard approximation to the global, diffusive model confinement time. Sequential firing of SMBI on the HL-2A tokamak sustained the increase in the core temperature in resp...

Nonlinear magnetohydrodynamic (MHD) simulations on relaxation phenomena in a spherical tokamak and a helical plasma, including three-dimensional (3D) equilibrium computations, are executed in full toroidal geometries. For a spherical tokamak, two-step evolution of the medium-n ballooning instabilities and a successive excitation of an internal n=1 crash has been observed. A similar process has ...

Probe measurements in the scrape-off layer of tokamak plasmas show that the ion saturation current signal is dominated by large amplitude bursts. Analysis of data time series from tokamak á configuration variable of unprecedented duration reveals that both burst amplitudes and waiting times are exponentially distributed. The average burst wave form has an exponential shape with a characteristic...

Edge-localized modes (ELMs) are cyclic disturbances in the outer region of tokamak plasmas that are influential in determining present and future tokamak performance. In this Letter, we outline an approach to modeling ELMs in which we envisage toroidal peeling modes initiating a Taylor relaxation [Phys. Rev. Lett. 33, 1139 (1974)10.1103/PhysRevLett.33.1139] of a tokamak outer region plasma. Rel...