The Pulsed Power Sciences Center at Sandia National Laboratories operates the Z-machine for a variety of national security missions. Options are being evaluated for developing a new pulsed power driver capable of much higher peak current and power delivery to the load, with four options presented here. We provide an overview of technology maturation efforts that will reduce the technology risk associated with design and construction of any of these architectures.

Vulcan is a new pulsed power system at Sandia National Laboratories based on fast Marx technology. Vulcan will serve as an intermediate scale demonstration of a fast Marx system and as a testbed for vacuum insulator testing. Vulcan uses multiple parallel fast Marxes, in a layout we call a Fast Marx Array (FMA), and a pulse forming line (PFL) to generate pulses up to 5 MV with effective pulse lengths for vacuum insulator testing that are relevant to larger facilities like Z. Vulcan consists of two parallel 25 stage Marxes with a total stored energy of up to 20 kJ. Vulcan applies up to 5 MV to a vacuum insulator stack load, thereby enabling testing of large area insulator stacks with areas on the order of 1000 cm 2 . The PFL design includes an oil output switch to adjust the voltage stress duration applied to the vacuum insulator. We will discuss Vulcan’s design, including the FMA, Marx trigger generator, energy diverter, PFL, oil output switch, and results of initial commissioning experiments.

We present experimental results from the first systematic study of performance scaling with drive parameters for a magnetoinertial fusion concept. In magnetized liner inertial fusion experiments, the burn-averaged ion temperature doubles to 3.1 keV and the primary deuterium-deuterium neutron yield increases by more than an order of magnitude to 1.1×10^{13} (2 kJ deuterium-tritium equivalent) through a simultaneous increase in the applied magnetic field (from 10.4 to 15.9 T), laser preheat energy (from 0.46 to 1.2 kJ), and current coupling (from 16 to 20 MA). Individual parametric scans of the initial magnetic field and laser preheat energy show the expected trends, demonstrating the importance of magnetic insulation and the impact of the Nernst effect for this concept. A drive-current scan shows that present experiments operate close to the point where implosion stability is a limiting factor in performance, demonstrating the need to raise fuel pressure as drive current is increased. Simulations that capture these experimental trends indicate that another order of magnitude increase in yield on the Z facility is possible with additional increases of input parameters.

Pulsed power accelerators compress electrical energy in space and time to provide versatile experimental platforms for high energy density and inertial confinement fusion science. The 80-TW "Z" pulsed power facility at Sandia National Laboratories is the largest pulsed power device in the world today. Z discharges up to 22MJ of energy stored in its capacitor banks into a current pulse that rises in 100ns and peaks at a current as high as 30 MA in low-inductance cylindrical targets. Considerable progress has been made over the past 15years in the use of pulsed power as a precision scientific tool. This paper reviews developments at Sandia in inertial confinement fusion, dynamic materials science, x-ray radiation science, and pulsed power engineering, with an emphasis on progress since a previous review of research on Z in Physics of Plasmas in 2005.

Herein we describe the design, simulation and performance of a 118-GW linear transformer driver (LTD) cavity at Sandia National Laboratories. The cavity consists of 20 to 24 “Bricks”. Each brick is comprised of two 80 nF, 100 kV capacitors connected electrically in series with a custom, 200 kV, three-electrode, field-distortion gas switch. The brick capacitors are bi-polar charged to a total of 200 kV. Typical brick circuit parameters are 40 nF (two 80 nF capacitors in series) and 160 nH inductance. Over the course of over 10,000 shots the cavity generated a peak electrical current and power of 1.19 MA and 118 GW.

The Saturn X-ray generator is a 2.5 megavolt, 10 megampere electrical driver at Sandia National Laboratories. Saturn has been in operation for more than 30 years. Work is underway to identify key areas of the machine, improvement of which would benefit operational efficiency and reproducibility of the system. Saturn is used to create high-dose, short-pulse intense ionizing radiation environments for testing electronic and mechanical systems. Saturn has 36 identical modules driving a common electron beam bremsstrahlung load. Each module utilizes a microsecond Marx generator, a megavolt gas switch, and untriggered water switches in a largely conventional pulse-forming system. Achieving predictable and reliable radiation exposure is critical for users of the facility. Saturn has endured decades of continual use with minimal opportunities for research, improvements, or significant preventive maintenance. Because of degradation in components and limited attention to electrical performance, the facility has declined both in the number of useful tests per year and their repeatability. The Saturn system resides in a cylindrical tank 33m in diameter, and stores 5.6 MJ at the nominal operating Marx charge voltage. The system today is essentially identical to that described by Bloomquist in 1987. [1] Advances in technology for large pulsed power systems affords opportunities to improve the performance and more efficiently utilize the energy stored. Increased efficiency can improve reliability and reduce maintenance. The goals for the Saturn improvement work are increased shot rate, reduced X-ray dose shot-to-shot dose fluctuation, and reduced required maintenance. Major redesign with alternate pulsed power technology is considered outside the scope of this effort. More X-ray dose, larger exposure area, and lower X-ray endpoint energy are also important considerations but also deemed outside the scope of the present project due to schedule and resource constraints. The first considerations, described here, are improving the present design with better components.