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.
The Sandia National Laboratories SPHINX accelerator is used to study the response of electronics to pulsed x-ray and electron environments. The system consists of a Marx generator and an oil-insulated pulse-forming line with self-closing oil switches. SPHINX has a peak load voltage of 2 MV and an adjustable pulse width ranging from 3 to 10 ns. The previous pulsed-power system had reliability and triggering issues with the Marx generator and subsequent undesired variations in voltage output. SPHINX was upgraded to a new Marx-generator system that has solved many of the voltage-output fluctuation and timing issues. The new Marx generator uses recently developed low-inductance 100-kV capacitors and 200-kV spark-gap switches. This paper provides an overview of SPHINX while capturing in detail the design, characterization, and comparative performance of the new Marx generator.