Deflection of Streamer Channels in High Magnetic Field

Streamer propagation on a dielectric film under transverse magnetic field produced by a superconducting magnet is investigated by using the Lichtenberg figure technique. The positive and negative streamer channels are deflected in the same direction due to the Lorentz force, which acts on electrons in the streamer head. The deflection angle of negative streamer is larger than that of the positive one and increases with the propagation in the radial direction. On the other hand, the deflection angle of positive streamer is almost constant along the path. A streamer propagation model is proposed taking account of the electric field in the space charge region left behind the streamer channel and the field enhancement effect at the streamer tip. Through comparison of the experimental results of the streamer deflection characteristics with the theoretical prediction, the electric field in the space charge region is supposed to reach a value of 2 to 3 kV/cm. The internal field causes voltage drop across the space charge region, while the electric field is enhanced in the concentrated positive streamer head. On the other hand, the negative steamer spreads uniformly and the field concentration effect at the tip is weak.