Control of thermonuclear burning in tokamaks with a strong magnetic field

Translated from Atomnaya Énergiya, Vol. 67, No. 6, pp. 400–403, December, 1989.     

Radial motion of plasma filament in tokamak thermonuclear machine

Conclusions The present paper gives the results of the elaboration of a mathematical model of the radial motion of the plasma filament in tokamak thermonuclear machines with account for its ohmic resistance as well as the total flux linkage of the circuit formed in the plasma filament. At the same time, no account was taken of the effect of the metallic structures of the machine on the radial motion of the plasma filament. A significant limitation on the applicability of this model is the requirement of a small slope for the plasma filament (a/r1). Under these conditions it has been shown that the motion of the plasma filament from one equilibrium position to another under a change in the vertical magnetic field is of a complex nature. The parameters of the elements of the motion depend markedly on the initial characteristics of the plasma filament.Analysis of the plasma-filament model for stability led to easily interpreted conditions, one, of which had been known earlier. For present-day tokamak machines whose plasma filament has a high slope (a/r1/3) the results of the study can be rather of a qualitative than a quantitative character. In the case of experimental confirmation of the properties, however, it is desirable to use the present model in designing systems for stabilizing the parameters of the plasma filament and in modern tokamak thermonuclear machines.Translated from Atomnaya Énergiya, Vol. 47, No. 2, pp. 119–122, August, 1979.     

Chemical effects of thermonuclear plasma interactions with insulator and metal surfaces

The interactions of chemically reactive ions with insulator and metal surfaces result in specific chemical effects which must be considered in sputtering, blistering, trapping and re-emission processes involving these projectiles. Chemical sputtering and chemical trapping of ion beam flux are examples of chemical interaction effects which are discussed. Bombardment of a niobium surface by oxygen and nitrogen ions results in the formation of sputtered niobium oxide and nitride molecules. The molecular species are identified and characterized by means of their vibrational spectra using isotopic substitution and matrix isolation techniques. Results using matrix isolation spectroscopy for both physical and chemical sputtering studies on materials of CTR interest are presented. Chemical trapping is evaluated as a method of chemically pumping the major fraction of ion beam flux in the divertor of next generation tokamaks.     

The absorption of deuterium by carbon-based facing materials on components in contact with the plasma in a thermonuclear reactor

Conclusions The conditions have been proposed for performing modeling experiments making it possible to predict the accumulation of hydrogen isotopes in carbon materials which are in contact with a tokamak plasma acting as a source of particles having a flux density of between 3×10¹⁶ and 3×10¹⁹ cm⁻²·sec⁻¹. By analyzing the reemission fluxes formed in the stopping zone of the particles implanted from the plasma it is suggested that the action of the plasma as regards the sorption of hydrogen is identical to that of annealing the material in an atmosphere of hydrogen isotopes at a pressure of 1–10³ Pa and a temperature of 1200–1700 K. The quantity of absorbed deuterium in POCO, UAM, RGT-B, and USB increases as the temperature is lowered and the pressure is raised (1500 K, 0.66 Pa→1200 K, 133 Pa). As regards their sorption of deuterium, POCO, UAM, and RGT behave similarly. There is a tendency for the sorption capacity of materials doped with boron to be reduced. In a class of itself is the isotropic material USB, whose sorption capacity is a factor of 10–100 lower than that of undoped graphite. The introduction into these materials of radiation-induced defects (T=300 K) by means of ion irradiation in the range 0.1–1 dpa results in a continuous rise in the deuterium sorption capacity by a factor of 10–100 (up to 10⁻² atomic fraction). The USB graphite demonstrates record low increments in the sorption capacity. In the fluence range identical to 1–10 dpa the sorption capacity of carbon materials for hydrogen is almost constant. The process of the sorption of hydrogen isotopes can be described as the filling of two ensembles of traps, deep traps which are difficult to access and readily accessible Langmuir traps. In the RGT-B materials containing 0.1% of boron, the traps introduced by irradiation with 300-keV neon ions vanish on annealing in a vacuum (T=1800 K, t=1 min). Institute of Physical Chemistry, Russian Academy of Sciences. SINTEZ Scientific and Technical Center, Scientific-Research Institute of Electrophysical Apparatus. Graphite Scientific-Research Institute. National Scientific Center, Kharkov Physicotechnical Institute. Translated from Atomnaya énergiya, Vol. 82, No. 6, pp. 448–464, June, 1997.     

Determination of magnetic forces in tokamaks during axisymmetric plasma disruptions

Methods are developed to infer estimates of plasma parameters from measurements of the dynamic response (e.g. displacements and support forces at critical locations) of the structure of a tokamak undergoing plasma disruptions. Simplified lumped-parameter models, based upon dynamic finite element (FE) calculations, are used to describe the mechanical response of the structure of the JET tokamak to transient forces generated during axisymmetric disruptions. These are then used in dynamic simulations, driven by parametrically-represented magnetic forces, where parameters include amplitude, duration and point of application. Estimates for these parameters are then obtained by finding values, which give the best fit, in a statistical sense, between the model's predictions of dynamic response to the measured response of the structure. These methods can then be used to help guide mechanical design of new machines so that structural loadings remain tolerable throughout the operational envelope.     

Estimation of the conductivity of a low-temperature (U-F) plasma of high density

The electron and ion electrical conductivity of a low-temperature plasma are estimated in the temperature range 0.4 to 3 eV, under conditions of thermodynamic equilibrium. The calculation shows that a decisive part is played by non-Coulomb electron collisions in the plasma. The electrical conductivity may therefore differ from the Spitzer value by several orders of magnitude.Translated from Atomnaya Énergiya, Vol. 22, No. 4, pp. 265–271, April, 1967.     

Effect of implanted helium on nickel stability in simulation of plasma disruption in a thermonuclear reactor

Moscow Engineering Physics Institute. TRINITI. Translated from Atomnaya Énergiya, Vol. 72, No. 6, pp. 565-570, June, 1992.     

Concerning the possibility of a self-sustaining thermonuclear reaction in a mirror machine

An investigation is made of the energy balance in thermonuclear reactors of various types employing magnetic mirror trapping. Only the energy loss due to the escape of particles through the mirrors is taken into account. It is very likely that a self-sustaining thermonuclear reaction cannot be produced in such devices.Translated from Atomnaya Énergiya, Vol. 19, No. 6, pp. 510–517, December, 1965.Report read by G. I. Budker at the International Conference on High-Energy Accelerators (Frascati, Italy).     

Experience and technical issues of liquid lithium application as plasma facing material in tokamaks

The following critical issues of liquid lithium used in tokamak conditions are considered: major physical properties of lithium, physico-chemical aspects of lithium interaction and compatibility with structural materials of fusion reactors. Lithium capillary-porous system (CPS) is considered as advanced plasma facing material for power fusion reactor and its main properties are presented. Review of plasma facing element (PFE) structures based on lithium CPS and tests results in T-11M, T-10 and FTU tokamaks are included. Brief review of projects of lithium limiter of FTU with active system for thermal stabilization and module of lithium divertor for KTM tokamak with liquid metal (Na-K) cooling system based on the lithium CPS use are presented.     

Experimental studies on the propagation of whistler-mode waves in a magnetized plasma structure with a non-uniform density

Propagation of whistler-mode waves in a magnetized plasma structure is investigated in the Keda linear magnetized plasma device. The magnetized plasma structure has its density peak in the center, and the background magnetic field is homogeneous along the axial direction. A whistlermode wave with a frequency of 0.3 times of electron cyclotron frequency( fce) is launched into the plasma structure. The wave normal angle(WNA) is about 25°, and the wavefront exhibits a wedge structure. During propag...     

Screening effect of plasma flow on the resonant magnetic perturbation penetration in tokamaks based on two-fluid model

Numerical simulation on the resonant magnetic perturbation penetration is carried out by the newly-updated initial value code MDC(MHD@Dalian Code). Based on a set of two-fluid fourfield equations, the bootstrap current, parallel, and perpendicular transport effects are included appropriately. Taking into account the bootstrap current, a mode penetration-like phenomenon is found, which is essentially different from the classical tearing mode model. To reveal the influence of the plasma flow on th...