A systematic study of current flow and impedance behavior in the Z machine double post-hole convolute

Summary form only given. Large pulsed power drivers often utilize multiple self-magnetically insulated transmission lines (MITL) in parallel to reduce inductance. The MITL currents must be recombined into a single anode-cathode gap, often through a post-hole convolute. Efficient post-hole convolute operation is necessary to maximize the current delivered to the load.The Z machine utilizes 4 parallel MITLs and a double posthole convolute. The current at several radial locations in the MITLs is inferred from B-dot monitor measurements. The MITL current downstream of the convolute can be several Mega-amperes less than the sum of the currents flowing in the MITLs upstream of the convolute. The convolute current is defined as the difference in the current upstream and downstream of the convolute. The convolute impedance is defined as the voltage across the convolute divided by the convolute current. A systematic study of the convolute current and convolute impedance for several Z experiments has been conducted. Despite considerable differences in the amplitude and shape of the driving current pulse, similar convolute impedance behavior is observed for many of these experiments. Impedance variations for nominally identical experiments are significant, but follow similar trends.