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Gallium oxide (G a 2 O 3 ) is a promising ultra-wide bandgap material offering a large bandgap (> --> 4.7 eV) and high critical electric fields. The increasing demand for electronic devices for high-power applications in electric automobiles, high-performance computing, green energy technologies, etc., requires higher voltages and currents with enhanced efficiency. Vertical transistors, such as fin-shaped field-effect transistors (FinFETs) have emerged to meet the growing need with improved current handling capabilities, reduced resistance, and enhanced thermal performance. However, to fully exploit the Ga 2 O 3 power transistors, precise and reliable physics-driven models are crucial. Therefore, a comprehensive surface potential model has been developed in this work for a vertical Ga 2 O 3 FinFET. The electric potential across the channel is explained by analyzing the two-dimensional (2D) Poisson equation employing parabolic approximation. Such a surface potential model is instrumental in determining the performance of the Ga 2 O 3 FinFET as it affects the threshold voltage, the drain current, and fringing capacitance. Exploiting the surface potentials, a fringing capacitance model is derived which is crucial in analyzing the speed of the device in compact integrated circuits. In addition, statistical analysis of the Ga 2 O 3 FinFET using the Monte Carlo simulation technique is performed to determine the leakage current fluctuation due to doping variations. The validation of the analytical model with experimental results confirms the effectiveness and prospects of the developed models in the rapid development and characterization of next-generation high-performance vertical Ga 2 O 3 power transistors. [ABSTRACT FROM AUTHOR]

An available supply of high-specific-activity radioisotopes was identified by the U.S. Department of Energy as a critical priority in the development and eventual deployment of next-generation medical diagnostic and cancer therapy tools. A radioisotope mass separator, located at the Missouri University Research Reactor Center, was developed to provide radioactive ion beams for the separation and production of high-specific-activity lanthanides used in radiopharmacology. Experiments characterizing the ionization efficiency of a thermal ion source supporting the production of high-specific-activity 153Sm are reported. With the goal of maximizing ion current while maintaining beam stability, experiments with the test ion source expand upon previously reported data from a titanium prototype ion source. Experimental results of various factors affecting ion source performance, such as diameter of the extraction orifice, ionizer geometry, ionizer temperature, and sample evaporation rate, are presented. [ABSTRACT FROM AUTHOR]

An available supply of high-specific-activity radioisotopes was identified by the U.S. Department of Energy as a critical priority to the development and eventual deployment of next-generation medical diagnostic and cancer therapy tools. Work at the University of Missouri Research Reactor Center has been undertaken to develop an electromagnetic isotope separation technique that will leverage the production capabilities of the 10-MW reactor to provide radiolanthanides in quantities suitable for use in preclinical trials. A high-throughput concept design based on a solid tantalum hot surface ion source and an insertable titanium crucible will be described. Significant aspects of the electrical and thermal design of the ion source will be presented. Novel heating and cooling strategies were employed to concentrate heating where it is most needed while attempting to reduce thermal stress where heating is not required. Thermal testing from the commissioning process will be presented to demonstrate the temperature at several key locations in and around the ion source. [ABSTRACT FROM AUTHOR]

Circuit modeling is ubiquitous throughout the pulsed power discipline. Both plasma processes and systems can be modeled with circuits of varying complexities. Sometimes, circuit models need to be generated to match experimental waveforms. Particle swarm optimization (PSO) is a technique which can be utilized to automatically generate a circuit model to match experimental data. This paper details the PSO algorithm as well as two case studies of the implementation. Index Terms--Circuit modeling, closing switches, Marx banks, optimization, particle swarm, pulsed power.

The University of Missouri has completed a new facility, named Tiger, for pulsed-power experimentation. Tiger consists of a 2.8-MV 450-kJ Marx bank that charges up to four 7-nF intermediate storage capacitors (I-stores) in parallel. When charged, the storage capacitors are switched into a resistive load through an SF6-filled laser-triggered gas switch. This switch has been designed to study the factors affecting runtime and jitter of spark-gap switches. All experiments presented in this paper were performed with a single I-store. The test switch was operated from about 500 kV up to 1.25 MV, at switch pressures from 10 to 50 psig. A 30-mJ 266-nm Nd:YAG laser was focused between the switch electrodes to initiate breakdown in the switch. The University of Missouri has examined laser energy, percentage of serf-break, and focal length to determine their relation to runtime and jitter. A short discussion of the Tiger facility is presented with experimental results of jitter and runtime tests. The end goal of this paper is to understand the factors contributing to increased jitter and runtime and, thereby, provide paths to improved switch performance. Index Terms--Jitter, light-triggered switches, Marx generators, runtime.

Many accelerators at Sandia National Laboratories utilize the Rimfire gas switch for high-voltage, high-power switching. Future accelerators will have increased performance requirements for switching elements. When designing improved versions of the Rimfire switch, there is a need for quick and accurate simulation of the electrical effects of geometry changes. This paper presents an advanced circuit model of the Rimfire switch that can be used for these simulations. The development of the model is shown along with comparisons to past models and experimental results. Index Terms--Gas switching, multichannel gaps, PSpice modeling, rimfire, spark gaps.

In the performance of intense electromagnetic transient, gaseous breakdown experiments, one parameter of interest is the effective electric field. A method of calculating the effective electric field for an arbitrary electromagnetic pulse is presented. This method is based upon the Laplace transform of the Lorentz force equation. Results from previous efforts are reproduced via this method and compared. Examples are calculated for various electromagnetic transients, most of which have never been calculated before. These examples of effective electric fields are used to generate theoretical Paschen curves, which are compared to experimental results. Index Terms - Effective electric field, electromagnetic transient.

Tokamak disruption simulation experiments have been conducted at the University of New Mexico using the PLADIS I plasma gun system. Earlier work had characterized the plasma-surface interaction in terms of parameters such as incident energy from bucket calorimeter measurements and rough measurements of beam area from flat damage targets. A variety of new plasma diagnostics have been used to further investigate the characteristics of the incident plasma beam and vapor shield plasma in a simulated tokamak disruption. These diagnostics have included laser interferometry, two-color pyrometry, emission spectroscopy, and other methods to quantify the characteristics of the incident and vapor shield plasmas of a simulated tokamak disruption. The synthesis of different beam area measurement techniques is used to determine the radial structure of the plasma beam. Vacuum ultra violet spectroscopy is used to determine the thickness and internal structure of the vapor shield plasma. Results from two-color optical pyrometry and surface pressure measurements are used to determine the dynamics of vapor shield formation. Index Terms - Ablation, cooperative tokamak disruption simulation experiments, dense vapor shield, disruption-like heat flux, energy fluxes, graphite erosion, graphites, heat load material, impurity content, ITER program, PLADIS plasma gun simulator, plasma diagnostics, plasma facing components, plasma facing component materials, plasma flow, plasma stream impact, plasma wall interactions, tokamak disruption, tokamak disruption simulation experiments, tokamak disruption simulations, transmission grating, vacuum ultraviolet spectrographs.