Publications

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Low- and high-voltage Soliton waves were produced and used to demonstrate collision and compression using diode-based nonlinear transmission lines. Experiments demonstrate soliton addition and compression using homogeneous nonlinear lines. We built the nonlinear lines using commercially available diodes. These diodes are chosen after their capacitance versus voltage dependence is used in a model and the line design characteristics are calculated and simulated. Nonlinear ceramic capacitors are then used to demonstrate high-voltage pulse amplification and compression. The line is designed such that a simple capacitor discharge, input signal, develops soliton trains in as few as 12 stages. We also demonstrated output voltages in excess of 40 kV using Y5V-based commercial capacitors. The results show some key features that determine efficient production of trains of solitons in the kilovolt range.

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The ZR accelerator is a refurbishment of Sandia National Laboratories Z accelerator [1]. The ZR accelerator components were designed using electrostatic and circuit modeling tools. Transient electromagnetic modeling has played a complementary role in the analysis of ZR components [2]. In this paper we describe a 3D transient electromagnetic analysis of the ZR water convolute and stack using edge-based finite element techniques. © 2005 IEEE.

The ZR gas switch, located between the Intermediate Store capacitor (I-Store) and the Pulsed Forming Line (PFL), requires a laser pulse for its triggering. There are several routes for the beam to reach the gas switch but all of them cross over the high voltage regions. The Z laser tube crosses over the outer to inner PFL electrodes with a voltage difference no larger than 3.5 MV. The ZR gas switch was designed to be in oil, given the higher operational voltages, as a consequence the laser tube is in the oil side of the PFL interface. The ZR laser tube is required to hold in excess of 5 MV across it using high pressure SF6 gas, the ID is 2.5″ to accommodate the laser beam, mechanically should tolerate the non-axial shock loading during the water switches firing. After a couple of iterations it was decided to use Polyurethane, it provided most of the desired mechanical properties, except that it outgases ether and ether based compounds. The effect of just a few ppm of ether on SF6 is a significant reduction on the HV hold off especially surface tracking or flashover. As a consequence the final design is such that the electric field distribution on the tube is as conservative as it was possible due to space constrains. We present the basic design, the field distribution, its relationship with available SF6 breakdown data and the present performance. © 2005 IEEE.

The laser trigger switch (LTS) is a key component in ZR-type pulsed power systems. In ZR, the pulse rise time through the LTS is > 200 ns and additional stages of pulse compression are required to achieve the desired <100 ns rise time. The inductance of the LTS ({approx}500nH) in large part determines the energy transfer time through the switch and there is much to be gained in improving system performance and reducing system costs by reducing this inductance. The current path through the cascade section of the ZR LTS is at a diameter of {approx} 6-inches which is certainly not optimal from an inductance point of view. The LTS connects components of much greater diameter (typically 4-5 feet). In this LDRD the viability of switch concepts in which the diameter of cascade section is greatly increased have been investigated. The key technical question to be answered was, will the desired multi-channel behavior be maintained in a cascade section of larger diameter. This LDRD proceeded in 2 distinct phases. The original plan for the LDRD was to develop a promising switch concept and then design, build, and test a moderate scale switch which would demonstrate the key features of the concept. In phase I, a switch concept which meet all electrical design criteria and had a calculated inductance of 150 nH was developed. A 1.5 MV test switch was designed and fabrication was initiated. The LDRD was then redirected due to budgetary concerns. The fabrication of the switch was halted and the focus of the LDRD was shifted to small scale experiments designed to answer the key technical question concerning multi-channel behavior. In phase II, the Multi-channel switch test bed (MCST) was designed and constructed. The purpose of MCST was to provide a versatile, fast turn around facility for the study the multi-channel electrical breakdown behavior of a ZR type cascade switch gap in a parameter space near that of a ZR LTS. Parameter scans on source impedance, gap tilt, gap spacing and electrode diameter were conducted.

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