Thickness and volume dependence of dielectric strength in advanced nanodielectric materials allowing for further size reduction of ultrahigh voltage capacitor prototypes.

We have developed a high dielectric, nanocomposite material, MU100, for use in pulsed power applications that include dielectric loaded antennas and ultra-high voltage capacitors. This paper presents the electrical properties of the first full-scale capacitor prototype along with sub-element modules. Additionally, refinements in the development process have sparked interest in a third-generation capacitor that would use similar dimensions as the initial small-scale samples that recorded breakdown fields of 225 kV/cm on average with peak breakdown fields of 328 kV/cm. The dielectric constant of these large-scale capacitors was 160. These capacitor prototypes have demonstrated voltage hold off of 500 kV. Similarly, thin samples that operated at 35-40 kV had lifetimes without failure in excess of 800 000 discharges at 80% of their maximum rated field strength.

Analysis of non-destructive current simulators of flux compression generators.

Development and evaluation of power conditioning systems and high power microwave components often used with flux compression generators (FCGs) requires repeated testing and characterization. In an effort to minimize the cost and time required for testing with explosive generators, non-destructive simulators of an FCG's output current have been developed. Flux compression generators and simulators of FCGs are unique pulsed power sources in that the current waveform exhibits a quasi-exponential increasing rate at which the current rises. Accurately reproducing the quasi-exponential current waveform of a FCG can be important in designing electroexplosive opening switches and other power conditioning components that are dependent on the integral of current action and the rate of energy dissipation. Three versions of FCG simulators have been developed that include an inductive network with decreasing impedance in time. A primary difference between these simulators is the voltage source driving them. It is shown that a capacitor-inductor-capacitor network driving a constant or decreasing inductive load can produce the desired high-order derivatives of the load current to replicate a quasi-exponential waveform. The operation of the FCG simulators is reviewed and described mathematically for the first time to aid in the design of new simulators. Experimental and calculated results of two recent simulators are reported with recommendations for future designs.

Novel high-frequency, high-power, pulsed oscillator based on a transmission line transformer.

Recent analysis and experiments have demonstrated the potential for transmission line transformers to be employed as compact, high-frequency, high-power, pulsed oscillators with variable rise time, high output impedance, and high operating efficiency. A prototype system was fabricated and tested that generates a damped sinusoidal wave form at a center frequency of 4 MHz into a 200 Omega load, with operating efficiency above 90% and peak power on the order of 10 MW. The initial rise time of the pulse is variable and two experiments were conducted to demonstrate initial rise times of 12 and 3 ns, corresponding to a spectral content from 4-30 and from 4-100 MHz, respectively. A SPICE model has been developed to accurately predict the circuit behavior and scaling laws have been identified to allow for circuit design at higher frequencies and higher peak power. The applications, circuit analysis, test stand, experimental results, circuit modeling, and design of future systems are all discussed.

Short communication: effects of X-rays on growth and germinal tissue of calves.

A study was carried out to measure the growth and germinal tissue responses of young bull calf whose testicles were exposed to different levels of high energy, pulsed beams (X rays). Treatments (absorbed doses) were 0, 1530, 1980, 3060, or 6300 rads. Body weights were measured monthly for 10 mo; testosterone concentrations were measured in mo 2 and 5. At the end of the study, scrotal circumferences were measured, and testes were removed and weighed. Sections of testes were taken, processed, and evaluated for effects on germinal epithelium. Treatments did not affect body weights or weight gains. Testosterone concentrations at mo 5 generally decreased with increased energy dose. Testicular weights were not different among treatments; generally, scrotal circumferences decreased and germinal tissue degeneration increased as the absorbed dose was increased.

Influence of adjuvants on physicochemical properties, droplet size spectra and deposit patterns: relevance in pesticide applications.

The influence of adjuvants on physicochemical properties, droplet size spectra and deposit patterns of five aqueous spray mixtures was studied under laboratory conditions, using two surfactants, Atlox 3409F and Triton X-114; two humectants, propylene glycol and glycerol; and one polymeric adjuvant, Agrisol FL-100F. For the sake of comparison, two fenitrothion formulations containing polymeric adjuvants, and water were also included in the study. Spray was applied at 25 degrees C and 75 +/- 5% relative humidity, in an enclosure using a twin fluid atomizer. Deposits were collected on Kromekote card/glass plate units. Physicochemical properties studied were: relative viscosity, surface tension, apparent viscosity-shear rate relationship, volatility, pH and conductance. The first four of these properties played significant roles on the droplet and deposit patterns on sampling units. However, the chemical nature of the adjuvants also played some role. Between the two surfactants tested, Triton X-114 provided a pseudoplastic medium, but both surfactant solutions provided similar droplet size spectra and deposit patterns. Between the two humectants, glycerol proved to be more advantageous than propylene glycol. The polymeric adjuvant provided droplet sizes similar to those of the two surfactants, although the recovery of the applied spray volume was higher. Among the two fenitrothion formulations, the one containing lower amounts of polymeric adjuvants showed some advantages, although deposits on the actual biological target should be examined before any definite conclusions can be drawn on the optimum adjuvant concentrations in end-use formulations.