Center for Laser Applications

Plasma Opening Switch Research

A research project is being sponsored by Arnold Engineering Development Center (AEDC) to support DECADE, the country's largest nuclear weapons simulator facility. The DECADE facility is a very large X-ray machine, similar in concept to those used for medical diagnostics, but producing many times more energy. The performance-limiting device in the system is the plasma opening switch (POS). This switch is required to carry more than one million amperes and then switch this current to the X-ray diode in less than one microsecond. The plasma flow in this switch is very complex, and similar in many ways to the plasma flow in railguns. Expertise developed in the railgun project has been applied to develop computer simulation codes which are being used to understand the complex plasma flows in the DECADE POS.

Initial simulation results were encouraging, but the switch failed to open in the simulations. This defect was traced to the neglect of the Hall effect which becomes important at low plasma density and large magnetic field strength, conditions which appear during the switch operation. The problem was that no successful algorithm had been developed for inclusion of the Hall effect in a general two-dimensional MHD plasma code. The development of a suitable algorithm was undertaken and has been moderately successful, although the accuracy and efficiency is difficult to assess. Simulations including the Hall effect have been found to open as observed in experiments. Simulations of the full scale DECADE POS are now underway, but the calculations are extensive and will require the use of the new Power Challenge L Silicon Graphics computer to provide practical computer simulations.