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.

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.

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In the l = 3 Uragan-3M torsatron with RF-produced and heated plasmas (ω ω ci ), a two-temperature ion distribution with a suprathermal tail is formed. Faster ions (FIs) can be the characteristic of reactor-size stellarators in the long mean free path regime. The presence of the helical divertor offers new opportunities for studying FI loss by measuring ion fluxes and energies in the divertor plasma.Ion energy distributions were measured in divertor flows in two symmetric poloidal cross-sections in several field periods. It is shown that FI flows out to the divertor mainly on the ion B × ∇B drift side in accordance with the assumptions of a determinative FI contribution to the plasma divertor flow vertical asymmetry inherent to torsatrons/heliotrons.Strong toroidal non-uniformities in flows and energies of ions outflowing into the divertor are observed. The island structure of the U-3M magnetic configuration and locality of RF power injection are considered as possible reasons for these non-uniformities.