Studies on impurity seeding and transport in edge and SOL of tokamak plasma

We present numerical simulation studies on impurity seeding using Nitrogen, Neon, and Argon gases. These impurity gases are ionized by the electron impact ionization. These ions can be at multiply ionized states, recombine again with the plasma electrons, and radiate energy. The radiation losses are estimated using a non-coronal equilibrium model. A set of 2D model equations to describe their self-consistent evolution are derived using interchange plasma turbulence in the edge and SOL regions and solved using BOUT++. It is found that impurity ions (with single or double-positive charges) move in the inward direction with a velocity ∼ 0.02cs so that these fluxes are negative. These fluxes are analyzed for different strengths of an effective gravity that help to understand the impurity ion dynamics. Increased gravity shows an accumulation of certain charged species in the edge region. The radiation loss is seen to have a fluctuation in time with frequency 5-20 kHz that closely follows the behavior of the interchange plasma turbulence. The simulation results on the radiated power and its frequency spectrum compare favourably with observations on the Aditya-U tokamak. The negative fluxes of the impurity ions, their dynamics in the edge region, and the fluctuating nature of the radiation loss are the most important results of this work.

RADIATION LOSS DETERMINATION AT COLLISION OF ELECTRONS WITH LECTRONEGATIVE ATOMS AND IONS IN PLASMA CURRENT SWITCH DISCHARGES. PART II

Specific radiation-loss power values have been determined for a variety of electronegative elements (C, O, F, Cl) as functions of electron temperature and impurity particle concentration. The maximum radiation-loss power level has been registered for chlorine (≤770 W/cm3) at an electron/impurity density of 1014 cm-3. The minimum radiation-loss power level for the other three elements lies in the range from 0.4 to 2 W/cm3. Considerable radiation losses due to the presence of electronegative elements in the interelectrode discharge may lead to its destabilization, to the change in the plasma parameters (ne, Te), and eventually, to degradation of the current-voltage characteristic of the plasma current switch.

Nonradiating sources for efficient wireless power transfer

Nonradiating sources of energy realized under a wave scattering on high-index dielectric nanoparticles have attracted a lot of attention in nano-optics and nanophotonics. They do not emit energy to the far-field, but simultaneously provides strong near-field energy confinement. Near-field wireless power transfer technologies suffer from low efficiency and short operation distance. The key factor to improve efficiency is to reduce the radiation loss of the resonators included in the transmitter and receiver. In this paper, we develop a wireless power transfer system based on nonradiating sources implemented using colossal permittivity dielectric disk resonator and a subwavelength metal loop. We demonstrate that this nonradiating nature is due to the hybrid anapole state originated by destructive interference of the fields generated by multipole moments of different parts of the nonradiating source, without a contribution of toroidal moments. We experimentally investigate a wireless power transfer system prototype and demonstrate that higher efficiency can be achieved when operating on the nonradiating hybrid anapole state compared to the systems operating on magnetic dipole and magnetic quadrupole modes due to the radiation loss suppression.

Research of Insertion Loss of Polycrystalline CVD Diamond within Range of 40...80 GHz

Insertion loss of polycrystalline CVD diamond within range of40...80 GHz is investigated by free space method. A diamond disk with diameter 56,6 mm and thickness 366 um was provided by GPI RAS. The disk was found to be radio transparent. Usage of diamond lid to seal LTCC package with T/R MMIC inside resulted in radiation loss by 2,9 dB at 60,5 GHz.

Manipulation of thermal radiation by using photonic crystals

This paper focuses on manipulating thermal emission and radiation loss of heat energy in a heat waveguide. A One-Dimensional Photonic Crystal is used as a waveguide clad to prohibit the thermal emission from escaping. The model may reduce the radiation loss of heat energy in the waveguide core, and heat energy can be confined to propagate along the waveguide’s longitude axis. The waveguide clad comprises alternative layers of high and low refractive index materials containing sufficient electromagnetic stop bands to trap the thermal emission from escaping out of the waveguide. The numerical simulation of the model shows that the forbidden bandgap of photonic crystal structures with alternative layers of silica and silicon has width enough to make heat energy be confined within the waveguide core so that efficient heat energy transmission can be achieved along the longitude axis of the waveguide.