The paper presents the first photographic evidence of the delayed implosion of the Z-pinch in nitrogen at pressures in excess of 375 μ Hg. Two implosions are observed before the discharge column is compressed to its minimum diameter. The time interval between the two implosions is found to increase linearly with pressure.The radius of the discharge column as a function of time is measured with a framing camera and is also calculated from the electrical characteristics of the discharge. By comparing the computed and measured values of the radius of the discharge column at given pressures, it has been shown that the second implosion does not arise from a transfer of the discharge current into material near the walls of the discharge vessel, in contrast to results commonly observed in very energetic discharges.
Development of a visible framing camera diagnostic for the study of current initiation in z-pinch plasmas