Measurement of the current in water discharge using magneto-optical Faraday effect

The observation of magnetooptical Faraday effects in water in experiments with electrical breakdown is presented. After high-voltage breakdown, the ionized channel with ∼4kA current was generated. The magnetic field from the current channel induces a circular birefringence which results in rotation of the polarization plane of a probing laser (200ps, 532nm). In spite of fast opposite radius drop of the magnetic field in radial direction, the Faraday rotation effect drops very slowly. The rotation of the polarization plane was ∼0.65°±5%. The optical measurements are in good agreement within ∼7% with the electrical measurements of the current.