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We have conducted a series of experiments designed to measure the flashover strength of various azimuthally symmetric 45 vacuum-insulator configurations. The principal objective of the experiments was to identify a configuration with a flashover strength greater than that of the standard design, which consists of a 45 polymethyl-methacrylate (PMMA) insulator between flat electrodes. The thickness d and circumference C of the insulators tested were held constant at 4.318 and 95.74 cm, respectively. The peak voltage applied to the insulators ranged from 0.8 to 2.2 MV. The rise time of the voltage pulse was 40 -60 ns; the effective pulse width [as defined in Phys. Rev. ST Accel. Beams 7, 070401 (2004)] was on the order of 10 ns. Experiments conducted with flat aluminum electrodes demonstrate that the flashover strength of a crosslinked polystyrene (Rexolite) insulator is 18 7% higher than that of PMMA. Experiments conducted with a Rexolite insulator and an anode plug, i.e., an extension of the anode into the insulator, demonstrate that a plug can increase the flashover strength by an additional 44 11%. The results are consistent with the Anderson model of anode-initiated flashover, and confirm previous measurements. It appears that a Rexolite insulator with an anode plug can, in principle, increase the peak electromagnetic power that can be transmitted across a vacuum interface by a factor of 1:18 1:44 2 2:9 over that which can be achieved with the standard design.

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The Z pulsed power driver at Sandia National Laboratories is used to develop high energy density z-pinch x-ray sources for inertial confinement fusion research and radiation effects testing, and drive megabar pressures in material samples for equation of state studies. The pulsed power system is in the process of being replaced, improving reliability and increasing energy delivered to the load.The upgraded pulsed power system will deliver more than nine megajoules of forward wave energy in the first one hundred nanoseconds of its pulse. The system is comprised of thirty-six nominally identical modules, each producing a 3.3-terawatt pulse in 6Q water-insulated transmission lines. The peak forward-going voltage is about 5 MV. The pulse rise time is -75 ns; the full width at half maximum is -190 ns. The thirty-six modules are combined in parallel and drive twenty to twenty-five MA into the single load. In such a system, reliable insulation and precise switching are primary concerns. We will show key components of the system and results from a test module. We will also show performance results from the energy storage, triggering, and pulse-forming systems. We will also show the differing constraints of power flow from the 175 kA from each Marx generator, to currents in excess of 24 MA in the final feed to the load.

This h a preprint of apaper intended for publication in a journal orproceerIing9. Since changes may be nude before publidion, this preprint is made available with the andexstanding that it will not be cited or reproduced without the permission of the author. Fast, low jitter command triggered switching is key to the successful implementation of the dielectric wall accelerator (DWA). We are studying a W induced vacuum surface flashover switch for this purpose. We present our initial data Using a NdYAG laser incident onto a high gradient insulator d a c e at lo, 20,30, and 40. Best la jitter was <1 ns with no degradation of the switch after 500 shots.