Vol 82, No 7 (2019)

A new concept in the development of plasma rocket engines is discussed. The development based on the results of many years of research on nuclear fusion and physics of hot plasma is implementing a concept with magnetic insulation of the plasma flow and electrodeless high-frequency methods for introducing energy into the plasma. The scheme is far superior to the traditional concepts of electrojet rocket engines in terms of its capabilities and prospects for the development.

Steady-state operation of a fusion neutron source (FNS) requires plasma heating and current drive by means of additional power delivered by neutral beams. Six neutral beam injectors (NBI) will provide the DEMO-FNS machine with additional heating power up to 30 MW, with neutral particle energy of 500 keV. NBI systems developed for ITER can serve as the prototype for DEMO-FNS, as both systems have similar ion source current, with accelerated beam power in ITER NBI (1MeV) being twice as large as in DEMOFNS. The paper describes the NBI system with account of its integration into DEMO-FNS tokamak complex.

This review is focused on the effect of doping with various elements on retention in tungsten. Although tungsten is one of the most promising plasma-facing materials (PFMs), it still has a number of drawbacks. Doping is proposed as a way to make tungsten more suitable for PFM applications. A considerable number of tungsten alloys have already been developed in the course of fusion research. Doping may alter the parameters of hydrogen retention in tungsten, and this should be taken into account in selecting the materials for fusion facilities.

Vanadium alloys are considered as candidate structural materials for thermonuclear fusion reactors (FR) and fast neutron reactors. Some properties of vanadium alloys are especially attractive for FR: fast decay of induced activity, durability in liquid lithium, high temperature strength. At the same time vanadium alloys absorb and dissolve hydrogen isotopes, and hydrogen fluxes through them are quite high. Hydrogen affects on plasticity of vanadium alloys and significantly decreases it at high concentrations. This should be taken into account considering the possibility of vanadium alloys usage as the material of fusion and fission reactors, especially if these materials are assumed to be in contact with radioactive tritium. In this work deuterium permeation through V-4Cr-4Ti alloy with deposited AlN coatings on an adhesion sublayer of Al on it was investigated. Deposition of insulating coatings on blanket structural materials allows to reduce the influence of strong magnetic fields of the tokamak on liquid metal coolant (e.g., lithium flow). It has been demonstrated that the coatings also reduce deuterium permeating fluxes by several times in comparison with V-4Cr-4Ti covered with natural oxide film and about 3–4 orders of magnitude in comparison with literature data for vanadium and its alloys with oxide-free surfaces. Taking into account thermomechanical and insulating properties, moderate swelling under neutron irradiation, thermal conductivity an order of magnitude higher than that of oxide coatings AlN coatings seem to be attractive for application in FR both as insulating and as a coating for hydrogen permeability suppression.

The pulsed power supply equipment belongs to the basic technological systems intended for implementing the required scenarios of changing currents in magnetic coils. The accuracy of implementing these scenarios directly determines the possibility of attaining the plasma breakdown and the required ultimate plasma parameters. Given the uniqueness of each facility under construction in the world and the installed capacity of the electrotechnical equipment applied in the power supply configuration, one can state with confidence that the construction of similar power supply complexes and their control systems, the optimization of their electrotechnical parameters, and the subsequent accident-free operation are vital tasks in mastering controlled thermonuclear fusion technologies. This paper describes the pulsed power supply system of the KTM tokamak (Kazakhstan) designed for material testing, the digital control system for its power conversion equipment, electrotechnical solutions adopted in the design of the KTM tokamak pulsed power supply system, and findings of tests of some items of equipment and their components. The tests have demonstrated sufficient efficiency of the adopted electrotechnical solutions and the possibility of applying them to implement the pulsed power supply systems for small and medium sized tokamaks.

In 2015, the development of the conceptual design of IGNITOR, a Russian–Italian experimental thermonuclear tokamak, was completed, and the parameters of all the systems, including the fuel system, were determined. In this work, an integrated design of arrangement of all the tritium-containing gas and secondary water streams expected in the operation of the IGNITOR tokamak was proposed on the basis of analyzing the designs of the fuel cycles of the large thermonuclear facilities JET, TFTR, and ITER. This design includes the storage of deuterium and tritium in a system of gas cylinders at a pressure of 0.4 MPa, the purification of the exhaust gas mixture from the plasma chamber using a “hot getter,” the separation of the deuterium–tritium isotope mixture by displacement gas chromatography, the purification of the process gas and air streams in a wet scrubber, and the detritiation of the water streams by chemical isotope exchange of hydrogen with water. The main technical parameters of equipment in the proposed design were estimated.

The high sensitivity of traditional diagnostic methods hinders their application in inertial confinement fusion with the pulsed radiation power of target plasma being as high as 1013–1014 W. Different methods of attenuating the incident radiation flux either alter its characteristics or are too complicated. The results of tests of a new detector, where quartz glass is used as a sensing element, at the Angara-5-1 facility are presented. It is demonstrated experimentally that the detector sensitivity is ~2 V/(MW cm²) and the time resolution is ~1 ns. The mechanism of formation of the response signal, where the temperature of electrons produced under irradiation plays a significant part, is discussed.