A. V. Timofeev

The EPSILON experimental pseudo-symmetric trap

Within the framework of the Adaptive Plasma Experiment (APEX) conceptual project, a trap with closed magnetic field lines, the Experimental Pseudo-Symmetric Closed Trap (EPSILON), is examined. The APEX project is aimed at theoretical and experimental development of the physical foundations for a steady state thermonuclear reactor designed on the basis of an alternative magnetic trap with tokamak-like large β plasma confinement. A discussion is given of the fundamental principle of pseudo-symmetry, which a magnetic configuration with tokamak-like plasma confinement should satisfy. Examples are given of calculations in the paraxial approximation of pseudo-symmetric curvilinear elements with a poloidal modulus B isoline. The EPSILON trap, consisting of two direct axisymmetric mirrors linked by two curvilinear pseudo-symmetric elements, is considered. To increase the equilibrium β, the plasma currents are short-circuited within curvilinear equilibrium elements. An untraditional scheme of MHD stabilization for a trap with closed field lines by use of axisymmetric mirrors with a divertor is analysed. The experimental installation EPSILON-One Mirror Element (OME), which is under construction for experimental investigation of stabilization by divertor, is discussed. The opportunity for applying the ECR method of plasma production in EPSILON-OME in conditions of high density and low magnetic field is examined.

Plasma method for processing spent nuclear fuel

Plasma methods for processing spent nuclear fuel are analyzed. It is shown that, by ICR heating in a nonuniform magnetic field, the energy of the heated ash ions can be increased substantially, while nuclear fuel ions can be kept cold. Two methods for extracting heated ash ions from a cold plasma flow are considered, specifically, that by increasing the ion gyroradius and that due to ion drift in a curved magnetic field. It is found that the required degree of separation of ash and fuel ions can be achieved in systems with quite moderate parameters.

Ion sepation by a curved magnetic field in a multicomponent plasma

It is shown that a curved magnetic field can be used to separate ions in a multicomponent plasma. Without selective ion preheating, the separation over one cycle is inefficient: the separated ion fractions will only be enriched with ions of the corresponding isotopes. Selective ion cyclotron resonance heating makes it possible to achieve essentially a complete separation of the ions.

Evolution of the electron Langmuir oscillations in an inhomogeneous magnetized plasma

The conditions under which the energy of the electron Langmuir oscillations can escape from the plasma into vacuum are determined in the simplest model of a plane slab of an inhomogeneous cold magnetized plasma in a uniform magnetic field.

Combined ICR heating antenna for ion separation systems

A combination of one- and two-wave antennas (one and two turns of conductors around a plasma cylinder, respectively) is proposed. This combined antenna localizes an RF field within itself. It is shown that spent nuclear fuel processing systems based on ICR heating of nuclear ash by such a combined antenna have high productivity. A theory of the RF field excitation in ICR ion separation systems is presented in a simple and compact form.

Plasma processing of spent nuclear fuel by two-frequency ion cyclotron resonance heating

A previously developed method for analyzing the plasma processing of spent nuclear fuel is generalized to a plasma containing multicharged fuel ions. In such a plasma, ion cyclotron resonance heating of nuclear ash ions should be carried out in two monochromatic RF fields of different frequencies, provided that the fraction of ξ multicharged ions is small, ξ ≤ 0.1, a condition that substantially restricts the productivity of systems for processing spent nuclear fuel. Ways of overcoming this difficulty are discussed.

ECR heating of a dense plasma by helicon waves

Eigenmodes of an axisymmetric plasma column that is uniform along the magnetic field are investigated. It is shown that, as the plasma density increases, eigenmodes with frequencies close to the electron gyrofrequency tend to localize at the plasma periphery. This effect is likely to restrict the electron density at which the plasma can be heated by means of such modes. A theory is developed for the excitation of the eigenmodes of a plasma column in a weakly nonuniform magnetic field by an external antenna.

On the influence of Alfvén resonance on ion cyclotron resonance heating

Physical processes determining the excitation of RF electromagnetic fields in a plasma column in a magnetic field are analyzed. The Alfvén resonance plays an important role at frequencies close to the ion cyclotron frequency. It leads to the enhancement of the RF electric field and transformation of Alfvén oscillations with a predominantly transverse polarization of the electric field into lower hybrid ones, which have a significant longitudinal component of the electric field. Lower hybrid oscillations efficiently interact with electrons causing their heating. Difficulties in the implementation of ion cyclotron resonance heating by the magnetic beach method are outlined. The processes considered in this work can be important for the VASIMR plasma engine.

Flow of a plasma of multielectron elements along a magnetic field

An analysis is made of a flow of Ar plasma imitating plasma flows in ion separation systems such as systems for processing spent nuclear fuel or ion cyclotron resonance isotope separation systems. It is found that the electron temperature is equalized along the flow by electron heat conduction. When the electron temperature is not too low (Te ≥ Eion/10, where Eion is the ionization energy), multicharged ions are intensely produced along the entire flow. It is shown that this process is accompanied by the flow acceleration. Difficulties in describing a supersonic flow by hydrodynamic equations are pointed out.

Electromagnetic oscillations near the critical surface in a plasma: Methodological note

Agreement between different approaches to studying the propagation of electromagnetic oscillations near the critical surface is elucidated. The propagation of plane waves, electromagnetic rays, and wave beams are analyzed. The results obtained are valid when the angles between the magnetic field and the plasma density gradient are not too small.