Appearance of interelectrode arcs and electric fluctuations in an MHD channel

The conditions for the appearance of Hall (interelectrode) arcs in the MHD channels of the U-25 device are investigated by recording and analyzing the fluctuations in the electrode potentials. The experiments were performed in induced fields. High-frequency noise of the order of $100$ kHz arises in the fluctuation spectrum of the interelectrode voltage when Hall arcs appear. The appearance of interelectrode Hall breakdown is shown as a function of the product of the current to the electrode times the magnetic field induction. It is suggested that interelectrode Hall arcs are generated by electrodes operating in the arc mode for drawing the Faraday current.