Toroidal stellarator diode: discharge features and electron transport

The radial dependences of the emission current I em of a small thermionic emitter at different anode voltages, as well as the current–voltage characteristics (CVCs) and the dependence of I em on the magnetic field B were measured to investigate the relationship between the electron transport and the E×B electric and magnetic fields in the toroidal stellarator diode system in stellarator-type magnetic traps (Uragan-3M and Uragan-2M torsatrons). It is demonstrated that the electron transport in the discharge is controlled to a large measure by an applied radial electric field, while the current jump (nonlinear dynamic behaviour) in the discharge is due to the attainment of the critical value by the radial electric field and to the occurrence of the ionization process. A phenomenological description of the CVCs showing a hysteresis behaviour is presented. A large variety of electron transport scalings (I em– B dependences) were obtained in two different torsatrons.