Particle acceleration by a large-amplitude wave associated with an ion beam in a magnetized plasma

Large-amplitude waves associated with a relativistic ion beam in a magnetized plasma are investigated by means of relativistic electromagnetic particle simulations. In the simulations, it is shown that electromagnetic fields are induced by an ion bunch which has Gaussian density distribution and that their profiles are similar to those of magnetosonic solitons. Further, when an ion beam propagates obliquely to the external magnetic field, it is found that an induced electric field has a parallel component along the magnetic field. Then, as the next step, giving another positron bunch, it is observed that some particles in a positron bunch are accelerated by the parallel electric field

Microscopic Effect on Filamentary Coherent Structure Dynamics in Boundary Layer Plasmas

This study has demonstrated kinetic behaviors on the plasma filament propagation with the three-dimensional (3D) Particle-in-Cell (PIC) simulation. When the ion-to-electron temperature ratio Ti/Te is higher, the poloidal symmetry breaking in the filament propagation occurs. The poloidal symmetry breaking is thought to be induced by the unbalanced potential structure that arises from the effect of the gyro motion of plasma particles

Impurity Ion Transport by Filamentary Plasma Structures

We have studied the impurity ion transport by a filamentary plasma structure with the three-dimensional electrostatic particle-in-cell simulation. The effective diffusivity of the impurity ions transported by a filamentary plasma structure has been calculated from the simulation result. The sequence of simulations has revealed that the effective diffusivity of impurity ions has a positive correlation with the poloidal size of a filament and a slight inverse correlation with the ion temperature, and that the effective diffusivity becomes quite small in theheavy impurity ion mass case

Study of Self-Consistent Particle Flows in a Plasma Blob with Particle-in-Cell Simulations

The self-consistent particle flows in a filamentary coherent structure along the magnetic field line in scrape-off layer (SOL) plasma (plasma blob) have been investigated by means of a three-dimensional electrostatic particle-in-cell simulation code. The presence of the spiral current system composed of the diamagnetic and parallel currents in a blob is confirmed by the particle simulation without any assumed sheath boundary models. Furthermore, the observation of the electron and ion parallel velocity distributions in a blob shows that those distributions are far from Maxwellian due to modification with the sheath formation and that the electron temperature on the higher potential side in a blob is higher than that on the lower potential side. Also, it is found that the ions on the higher potential side are accelerated more intensively along the magnetic field line than those on the lower potential side near the edge. This study indicates that particle simulations are able to provide an exact current closure to analysis of blob dynamics and will bring more accurate prediction of plasma transport in the SOL without any empirical assumptions

Impurity Transport Caused by Blob and Hole Propagations

It is for the first time demonstrated by means of the three-dimensional electrostatic particle-in-cell simulation that the impurity ion transport caused by blob and hole propagations might not be negligible as compared with other types of transport. The simulations have shown that the impurity ion density profile in the blob/hole structure becomes a dipolar profile and the dipolarprofile of the impurity ion density propagates with the blob/hole. Furthermore, the simulations in which the initial impurity ion density has a radial gradient have revealed that the estimated effective radial diffusion coefficient for impurity ions by a single blob/hole is comparable to the Bohm diffusion coefficient

Three-dimensional Effect of Particle Motion on Plasma Filament Dynamics

It is shown for the first time with the three-dimensional (3D) electrostatic particle-in-cell simulation that the plasma particle motion influences plasma filament dynamics three-dimensionally. If we assume that the filament size on the cross section is a few times as large as ρe√mi/me and that the ion temperature is higher than the electron temperature, the poloidal symmetry of filament propagation is broken and the propagation velocity has the non-negligible poloidal component, where ρe is the electron Larmor radius. Then, it is observed that such propagation dynamics depend on the position on the magnetic field line, i.e., in the toroidal direction. As the ion temperature increases beyond the electron temperature, the perpendicular electric field in a filament varies greatly according to the toroidal position. Such a variation might arise from the presheath potential drop on the potential hill side in a filament. Thus, the toroidal dependence of the propagation dynamics appears

シリコン単一電子素子の特性評価とその応用に関する研究

University of Tokyo (東京大学

Observation of the Strong Temperature Gradient in Detached Plasma by PIC Simulation with Monte Carlo Collision

In this work, the 1D-3V particle simulation with Monte Carlo collision and cumulative scattering angle Coulomb collision was developed to study the kinetic behavior of the detached plasma. The constant pressure and temperature of the neutral gas box in front of the divertor target were used in the simulation. The simulation was performed with a fixed upstream plasma density nu ∼ 3 × 1018 m−3 and a modified large Coulomb collision frequency. When the neutral gas pressure is increased, there is a strong decrease in the electron temperature inside the neutral gas box. The electron temperature in front of the divertor target also decreases to below 1 eV, which is one of the conditions for detached plasma