Magnetic field structure near separatrix in a toroidal stellarator

A system of equations permitting to determine specific points of the separatrix proceeding solely from the magnetic field, assigned in the components and omitting the stage of numerical calculation of the sepratrix as a magnetic surface, is obtained from the analysis of magnetic structure of a toroidal stellarator (torsotron) near the separatrix. Knowledge of specific points of the sepratrix permits to determine the limiting aperture of the plasma filament and to estimate possible thickness of a deverter (preseparatorix) layer