Numerical studies were carried out to show that a regime implied as the standard or basic regime in the l = 2 torsatrons and heliotrons with no additional longitudinal magnetic field coils can be realized in the l = 2 torsatron with the aforementioned coils. The regime is characterized by a shift in the closed magnetic surface configuration inwards in the torus, by the transformation of the spatial magnetic axis into the planar axis and by close to minimum values of the field ripple at the magnetic surfaces. For the simulation model used, the main parameters of the magnetic surface are given at several values of the additional longitudinal magnetic field.

The development of a stellarator-mirror fission-fusion hybrid concept is reviewed. The hybrid comprises of a fusion neutron source and a powerful sub-critical fast fission reactor core. The aim is the transmutation of spent nuclear fuel and safe fission energy production. In its fusion part, neutrons are generated in deuterium-tritium (D-T) plasma, confined magnetically in a stellarator-type system with an embedded magnetic mirror. Based on kinetic calculations, the energy balance for such a system is analyzed. Neutron calculations have been performed with the MCNPX code, and the principal design of the reactor part is developed. Neutron outflux at different outer parts of the reactor is calculated. Numerical simulations have been performed on the structure of a magnetic field in a model of the stellarator-mirror device, and that is achieved by switching off one or two coils of toroidal field in the Uragan-2M torsatron. The calculations predict the existence of closed magnetic surfaces under certain conditions. The confinement of fast particles in such a magnetic trap is analyzed.

Numerical studies were undertaken to elucidate the field ripple behavior on the magnetic axis, g ax , and on the last closed magnetic surface, g lc , as a function of the transverse magnetic field B z in helical magnetic system models with l ¼ 2,3 polarity. The models are similar to some heliotrons/torsatrons now in operation such as LHD and U-3M that have no additional longitudinal magnetic field coils. In the investigated B z range, the existence of closed magnetic surface configuration in the regime B z ¼ B zm with a minimal field ripple has been revealed. The main features of these configurations are the zero value of the minor radius of the magnetic axis (plane magnetic axis) in the l ¼ 2 system and the minimal minor radius of the bifurcation line of inner separatrix of the maximum developed inner island structure in the l ¼ 3 system. At B z range boundaries, the g lc values begin to decrease and the g ax values continue to increase.

No abstract

Проведено изучение свойств магнитных поверхностей в модели двухзаходного (l = 2) торсатрона с катушками дополнительного тороидального магнитного поля (торсатрон типа У-2М) в зависимости от величины тороидального угла полного и частичного расщепления его винтовых обмоток на две равные части. Показано, что в рассматриваемой модели l = 2 винтовой магнитной системы так же, как и в модели l = 2 винтовой магнитной системы без катушек дополнительного тороидального магнитного поля (гелиотрон типа LHD), частичное расщепление винтовых обмоток является эффективным методом управления положением конфигурации магнитных поверхностей относительно поверхности опорного тора. Применение метода может способствовать созданию увеличенного зазора между плазмой и 1-й стенкой в термоядерном реакторе на основе магнитной системы стеллараторного типа. Расчёты также показали, что при углах расщепления больше некоторой предельной величины появляются признаки деградации магнитных поверхностей, свойственные торсатронам/гелиотронам с повышенной заходностью винтовых обмоток (l > 2). Ключевые слова: l = 2 торсатрон, гелиотрон, винтовые обмотки, расщепление, магнитные поверхности, численный расчёт. THE INFLUENCE OF A HELICAL COIL SPLITTING ON MAGNETIC CONFIGURATION OF THE l = 2 TORSATRON WITH AN ADDITIONAL TOROIDAL MAGNETIC FIELD. V.G. KOTENKO, D.V. KURILO, Ju.F. SERGEJEV, E.L. SOROKOVOJ, Ye.D. VOLKOV. Numerical studies were undertaken to elucidate the magnetic surface behavior in the model of the l = 2 U-2M torsatron type with additional toroidal magnetic field coils as a function of the toroidal angle of the total and partial helical coil splitting into two equal parts. It is shown that in the l = 2 torsatron helical magnetic system considered similar to the l = 2 helical magnetic system without additional toroidal magnetic field coils (the LHD heliotron type), a partial splitting of the helical coil is an effective method to control the magnetic surface configuration position relative to the surface of the supporting torus. The application of the method can facilitate creation of the enlarged plasma-1st wall clearance in a fusion reactor based on stellarator-type magnetic systems. Also, the calculations show the signs of the magnetic surface degradation inherent in the torsatrons/heliotrons with polarity l > 2, if the toroidal angle of the helical coil splitting becomes larger than some boundary value.