Tokamak DEMO-FNS: Concept of magnet system and vacuum chamber

The level of knowledge accumulated to date in the physics and technologies of controlled thermonuclear fusion (CTF) makes it possible to begin designing fusion—fission hybrid systems that would involve a fusion neutron source (FNS) and which would admit employment for the production of fissile materials and for the transmutation of spent nuclear fuel. Modern Russian strategies for CTF development plan the construction to 2023 of tokamak-based demonstration hybrid FNS for implementing steady-state plasma burning, testing hybrid blankets, and evolving nuclear technologies. Work on designing the DEMO-FNS facility is still in its infancy. The Efremov Institute began designing its magnet system and vacuum chamber, while the Kurchatov Institute developed plasma-physics design aspects and determined basic parameters of the facility. The major radius of the plasma in the DEMO-FNS facility is R = 2.75 m, while its minor radius is a = 1 m; the plasma elongation is k ₉₅ = 2. The fusion power is P _FUS = 40 MW. The toroidal magnetic field on the plasma-filament axis is B _t0 = 5 T. The plasma current is I _p = 5 MA. The application of superconductors in the magnet system permits drastically reducing the power consumed by its magnets but requires arranging a thick radiation shield between the plasma and magnet system. The central solenoid, toroidal-field coils, and poloidal-field coils are manufactured from, respectively, Nb₃Sn, NbTi and Nb₃Sn, and NbTi. The vacuum chamber is a double-wall vessel. The space between the walls manufactured from 316L austenitic steel is filled with an iron—water radiation shield (70% of stainless steel and 30% of water).     

Subthreshold sputtering at high temperatures

The sputtering of tungsten from a target at a temperature of 1470 K during irradiation by 5-eV deuterium ions in a steady-state dense plasma is discovered. The literature values of the threshold for the sputtering of tungsten by deuterium ions are 160–200 eV. The tungsten sputtering coefficient measured by the loss of weight is found to be 1.5×10^?4 atom/ion at a deuterium ion energy of 5 eV. Previously, such a sputtering coefficient was usually observed at energies of 250 eV. The sputtering is accompanied by a change in the target surface relief, i.e., by the etching of the grain boundaries and the formation of a wavy structure on the tungsten surface. The subthreshold sputtering at a high temperature is explained by the possible sputtering of adsorbed tungsten atoms that are released from the traps around the interstitial atoms and come to the target surface from the space between the grains. The wavy structure on the surface results from the merging of adsorbed atoms into ordered clusters.     

Spectroscopy of homogeneous deuterated hydrocarbon films redeposited from a T-10 tokamak plasma discharge

Homogeneous deuterated hydrocarbon films redeposited from a deuterium plasma discharge inside the T-10 tokamak vacuum chamber are studied using photoluminescence methods; EXAFS, EPR, and IR spectroscopies; and temperature measurements. The photoluminescence excitation spectra of sp ³-sp ² nanostructures of tokamak films are compared with those of sp ² nanostructures of C60 fullerite films. The effect of defect states on photoluminescence and its temperature quenching is discussed. It is concluded that the model of temperature luminescence quenching for homogeneous deuterated tokamak films is similar to that for amorphous a-C:H films.     

Current Status and Objectives of Modernizing the Engineering,Physical, and Energy Infrastructure of the SFT Facility for the Implementation of the Ignitor Project

Physics of Atomic Nuclei - The Ignitor tokamak nuclear fusion research project is one of the most ambitious initiatives undertaken under the long-term scientific cooperation program between the...     

All solid-state battery based on ceramic oxide electrolytes with perovskite and NASICON structure

The Li_0.33Lia_0.56TiO₃ and Li_1.3Ti_1.7Al_0.3(PO₄)₃ ceramics with the structures of defect-perovskite and NASICON structures with conductivity of 1–6?×?10^?6 S/cm at the room temperature are obtained. Ceramic electrolytes were developed for a solid-state battery EMF of 4.1 V and high discharge stability in time. Discharge characteristics of solid-state batteries are studied in a laboratory cell.     

Synthesis of reduced graphene oxide and its electrocatalytic properties

The method of the chemical synthesis of reduced graphene oxide was developed. Sodium hypophosphite and sulfi te were used as reducing agents. The formation of reduced graphene oxide was confi rmed by several methods. Volt-ampere characteristics of electrodes based on reduced graphene oxide were investigated in an experimental model of an oxygen fuel cell with an alkaline electrolyte. Characteristics of oxygen electrodes based on reduced graphene oxide were stable over semiannual tests. The resulting reduced graphene oxide is a promising material for oxygen electrodes of chemical current sources.     

Kinetics of electrochromic process in thin films of cathodically deposited nickel hydroxide

Ni(OH)₂ films have been obtained by cathodic deposition from 1 M Ni(NO₃)₂ on a glass with a current-conducting SnO₂ layer. The films have a porous structure and consist of chaotically joined formations of 100–150 nm in size. They contain a considerable amount of adsorbed water, because of which their refraction index was n?=?~1.5, whereas for crystalline nickel hydroxide, it was n?=?2.37. It has been shown that in the course of discoloration of films through a shift of their potential towards more negative values, an electric field is formed in the bulk of film, which accelerates the entry of cations into it (protons as [H₃O]⁺) from the electrolyte and electrons from ohmic contact. In this case, the initial dependence i(t), where i?~?t ^?1/4, is bound up with gradual increase in proton surface concentration. It is proposed to determine separately the dependence of the effective codiffusion coefficient of charge carriers (protons and electrons) on decoloration potential by the analysis of plots of current, injected charge, and luminous transmittance of films against time. This procedure involves a series of periodic stops of potential during the recording of current–potential curves for an electrochromic electrode and allows one to monitor the ratio of the film forms NiOOH and Ni(OH)₂ in the course of film reduction.     

Cluster-Type Structure of Amorphous Smooth Hydrocarbon CD<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript> Films (<Emphasis Type="Italic">x</Emphasis> ~ 0.5) from T-10 Tokamak

Structure of smooth hydrocarbon CD _x films with a high deuterium ratio x ~ 0.5 redeposited from T-10 tokamak D-plasma discharges (NRC Kurchatov Institute, Moscow) has been studied. For the first time, small and wide angle X-ray scattering technique using synchrotron radiation and neutron diffraction have been employed. A fractal structure of CD _x films is found to consist of mass-fractals with rough border, surface fractals (with rough surface), plane scatterers and linear chains forming a branched and highly cross-linked 3D carbon network. The found fractals, including sp² clusters, are of typical size ~1.60 nm. They include a C₁₃ fragment consisting of three interconnected aromatic rings forming a minimal fractal sp² aggregate 9 × C₁₃. These graphene-like sp² clusters are interconnected and form a 3D lattice which can be alternatively interpreted as a highly defective graphene layer with a large concentration of vacancies. The unsaturated chemical bonds are filled with D, H atoms, linear sp² C=C, C=O, and sp³ structural elements like C-C, C-H(D), C-D_2,3, C-O, O-H, COOH, C _x D(H) _y found earlier from the infrared spectra of CD _x films, which are binding linear elements of a carbon network. The amorphous structure of CD _x films has been confirmed by the results of earlier fractal structure modeling, as well as by researches with X-ray photoelectron spectroscopy which allow finding a definite similarity with the electron structure of their model analogues — polymeric a-C:H and a-C:D films with a disordered carbon network consisting of atoms in sp³ + sp² states.     

Air electrode of chemical power cell as oxygen sensor

The possibility of using the air electrode of a chemical power cell as an electrochemical oxygen sensor was studied.Translated from Zhurnal Prikladnoi Khimii, Vol. 77, No. 10, 2004, pp. 1663–1666.Original Russian Text Copyright © 2004 by Danilov, Kolbasov, Vyunova.