If fusion energy is to achieve its full potential for safety and environmental (S&E) advantages, the S&E characteristics of fusion power plant designs must be quantified and understood, and the resulting insights must be embodied in the ongoing process of development of fusion energy. As part of this task, the present work compares S&E characteristics of five inertial and two magnetic fusion power plant designs. For each design, a set of radiological hazard indices has been calculated with a system of computer codes and data libraries assembled for this purpose. These indices quantify the radiological hazards associated with the operation of fusion power plants with respect to three classes of hazard: accidents, occupational exposure, and waste disposal. The three classes of hazard have been qualitatively integrated to rank the best and worst fusion power plant designs with respect to S&E characteristics. From these rankings, the specific designs, and other S&E trends, design features that result in S&E advantages have been identified. Additionally, key areas for future fusion research have been identified. Specific experiments needed include the investigation of elemental release rates (expanded to include many more materials) and the verification of sequential charged-particle reactions. Improvements to the calculational methodology are …

This dissertation describes a numerical technique, Matrix-Free Newton Krylov, for solving a simplified Vlasov-Fokker-Planck equation. This method is both deterministic and fully implicit, and may not have been a viable option before current developments in numerical methods. Results are presented that indicate the efficiency of the Matrix-Free Newton Krylov method for these fully-coupled, nonlinear integro-differential equations. The use and requirement for advanced differencing is also shown. To this end, implementations of Chang-Cooper differencing and flux limited Quadratic Upstream Interpolation for Convective Kinematics (QUICK) are presented. Results are given for a fully kinetic ion-electron problem with a self consistent electric field calculated from the ion and electron distribution functions. This numerical method, including advanced differencing, provides accurate solutions, which quickly converge on workstation class machines. It is demonstrated that efficient steady-state solutions can be achieved to the non-linear integro-differential equation, obtaining quadratic convergence, without incurring the large memory requirements of an integral operator. Model problems are presented which simulate plasma impinging on a plate with both high and low neutral particle recycling typical of a divertor in a Tokamak device. These model problems demonstrate the performance of the new solution method.

The reliability of microelectronic systems is often limited by electromigration failure in Al-based thin-film conducting lines which interconnect devices to form an integrated circuit. Under an applied electric field Al atoms migrate with the electron flow, causing a counterflow of vacancies that accumulate into voids, eventually leading to an open circuit failure. The work reported here is concerned with clarifying the microstructural mechanism of electromigration failure, and with developing a metallurgical method to improve the electromigration resistance of Al-based interconnects. Pure Al, Al-2Cu, and Al-2Cu-1Si lines with quasi-bamboo microstructures are explored as a function of heat treatment conditions and current density. The {open_quotes}weakest{close_quotes} microstructural unit that causes failure is identified by electron microscopy; with rare exceptions, failure occurs at the upstream end of the longest polygranular segment in a given line. This microstructural characteristic of electromigration failure is even observed in lines whose maximum segment lengths are less than a few microns. The time to failure appears to increase exponentially with decreasing longest polygranular segment length. A simple constitutive equation is reported to describe the failure kinetics as a function of the polygranular segment length that leads to failure. Given correct values of the kinetic constants included in the equation, …

The hydrogenation and dehydrogenation of ethylene, propylene, and isobutene were monitored in situ during heterogeneous catalysis over Pt(111) between 10{sup -10} Torr and 1000 Torr with infrared-visible sum frequency generation (SFG). SFG is a surface specific vibrational spectroscopy capable of achieving submonolayer sensitivity under reaction conditions in the presence of hundreds of Toff of reactants and products. Olefin dehydrogenation experiments were carried out with SFG under ultra high vacuum (UHV) conditions on the (111) crystal face of platinum Ethylene chemisorbed on Pt(111) below 230 K in the di-{sigma} bonded conformation (Pt-CH{sub 2}CH{sub 2}-Pt). Upon annealing the system to form the dehydrogenation product, ethylidyne (M=CCH{sub 3}), evidence was found for an ethylidene intermediate (M=CHCH{sub 3}) from its characteristic v{sub as}(CH{sub 3}) near 2960 cm{sup -1}. Hydrogenation of ethylene was carried out between 1 Toff and 700 Torr of H{sub 2} while the vibrational spectrum of surface species was monitored with SFG. Simultaneously, gas chromatography was used to obtain the turnover rate for the catalytic reaction, which could be correlated with the adsorbed intermediate concentration to determine the reaction rate per surface intermediate. Di-{sigma} bonded ethylene, {pi}-bonded ethylene, ethyl groups and ethylidyne resided on the surface during reaction. The mechanistic pathway for …

Fe-K-edge X-ray absorption spectroscopy (XAS) has been used to investigate the electronic and geometric structure of the iron active site in non-heme iron enzymes. A new theoretical extended X-ray absorption fine structure (EXAFS) analysis approach, called GNXAS, has been tested on data for iron model complexes to evaluate the utility and reliability of this new technique, especially with respect to the effects of multiple-scattering. In addition, a detailed analysis of the 1s{yields}3d pre-edge feature has been developed as a tool for investigating the oxidation state, spin state, and geometry of iron sites. Edge and EXAFS analyses have then been applied to the study of non-heme iron enzyme active sites.