Design options for a pulsed-power upgrade of the Z accelerator

We are presently considering an extensive modification of the Z accelerator at the Sandia National Laboratories to both increase the current and radiative power, and to improve the facility, diagnostics, and shot rate. Record-breaking peak x-ray powers and Hohlraum temperatures achieved in z-pinch experiments on this machine motivate this effort. The electrical design goal of the upgrade is to drive a 40-mm diameter, 20-mm long wire-array z-pinch load with a peak current of 26 MA with a 100-ns implosion. Several changes to the pulsed-power design of Z are being considered. They are to increase the energy and lower the inductance of the Marx bank, increase the capacitance of the intermediate-store water capacitor, increase the voltage hold-off capability of the laser-triggered gas switch, lengthen the first section of the water pulse-forming line, remove impedance mismatches in the pulse-forming line, and adjust field grading on the water side of the insulator stack. With these changes Z will be able to provide peak currents greater than 26 MA, and x-ray energies exceeding 2.7 MJ. We plan to use the existing oil and water tanks, use the existing insulator stack and MITL's, and as much of the existing Marx-bank hardware as feasible. Circuit-code calculations for one design option are shown. The results of these simulations, when applied to standard water-breakdown criteria, are used to determine the size of the intermediate store (IS) and pulse-forming-line (PFL) components. We also indicate where further component development is needed.