PBFA-Z vacuum section design using TLCODE simulations

Circuit code simulations were used to predict the performance of and to assess design trade-offs for the vacuum section of PBFA-Z. PBFA-Z was designed to drive a plasma radiation source (PRS) within the PBFA-II facility by replacing its central water and vacuum sections. The insulator stack and vacuum feeds were patterned after those of the SATURN PRS configuration which has 4 separate sources combined in vacuum by a relatively small diameter double post hole convolute (DPHC). The design method for choosing the PBFA-Z MITL impedance profiles is described and represents a departure from the method used for PROTO-II and SATURN and was motivated by analysis of SATURN experimental data. Other trade studies included the effect of MITL impedance profile on anode dose along the MITL due to partial magnetic insulation at early times and during the load run-in, and the choice of load diameter and mass on the choice of MITL profiles. These simulations predicted peak load currents ranging from 16 to 23 MA and kinetic energies from 1 to 1.6 MJ for plasma radiation sources (PRS) with implosion times from 100 to 150 ns. PBFA-Z experimental data is compared with an "as built" circuit model for a wire array load with good agreement up to the time of peak load current. A significant disagreement between the data and the model then starts and increases until the time of implosion.