Previous experiments with the electric explosion of conductors in a strong (50 T) longitudinal magnetic field showed the formation of a relatively low-density plasma around the central part of the explosion channel, which exhibited expansion at a velocity on the order of 10–20 km/s [1, 2]. Expansion of the plasma was accompanied by displacement of the magnetic field from the explosion channel, which was manifested by a diamagnetic signal. An analysis of the plasma energy balance is hindered by the lack of reliable data about radiative energy losses. Here, we report the first experimental results on the radiation pulse kinetics and the first estimates of the radiation energy.