High Density Plasma Opening Switch Experiments on Hawk
Abstract
Previously, plasma opening switch (POS) experiments on Hawk have shown fast opening (< 100 ns) into electron-beam diode loads, generating 1-2 MV after 0.5-1 microsecond conduction time. The plasma density measured in these experiments was in the 10 to the 15th power- 10 to the 16th power cm-3 range. Plasma thinning by J x B forces during conduction reduces this density, ultimately leading to gap formation in the low density region. The Hawk experiments described here were designed to investigate this switching phenomenon with higher initial densities, in the 10 to the 17th power cm-3 range, to determine whether fast switching and high voltage could be sustained. This scaling is important for POS applications on future, higher energy generators. Experiments were performed with a relatively small center conductor radius (1.27 cm) and small plasma length (3 cm or 8 cm). Either 36 or 12 cable gun plasma sources were used to inject plasma into the coaxial switch region. The anode structure was varied to investigate techniques to increase the voltage when the switch opens. High voltage (1.5 MV) switching was observed at ~ 0.9 microsecond conduction time when the radial gap between the inner and outer conductors in the switch region was reduced from 7 cm to 2 cm. Two techniques that improved switching on the DPMl experiment at conduction times < 600 ns were investigated on Hawk: (1) removing the physical connection on the anode through the switch plasma, and (2) varying the radius of the anode conductor on the load side of the switch. These changes had no noticeable effect on the switch voltage for the longer conduction time scale of Hawk. The number of plasma sources had little effect on the voltage. These experiments demonstrate that, at least for some geometrical configurations, POS operation at 10 to the 17 power cm-3 density is similar to operation at one or two orders-of-magnitude lower density.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jul 01, 1995
- Accession Number
- ADA638323
Entities
People
- Bruce V. Weber
- P. J. Goodrich
- R. A. Riley Jr.
- Robert J. Commisso
Organizations
- United States Naval Research Laboratory