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A new cathode design is investigated using the finite element method, in an attempt to improve the energy efficiency of a cell and reduce the premature wear of the cathode due to a non-uniform current distribution. This new design relies on cylindrical collector bars including copper inserts and eliminates the need of a cast iron interface in order to improve contact between the carbon blocks and the collector bars. The thermo-electro-mechanical model developed includes contact interfaces to simulate the contact between the different materials and is employed to determine the optimal configuration. Various geometry and design parameters are explored and their effect on both voltage drop and current distribution are highlighted. Simulation results indicate that a substantial voltage drop reduction and more uniform current distribution could be achieved.

Shot planning and analysis tools (SPLAT) integrate components necessary to help achieve a high over-all operational efficiency of the National Ignition Facility (NIF) by combining near and long-term shot planning, final optics demand and supply loops, target diagnostics planning, and target fabrication requirements. Currently, the SPLAT project is comprised of two primary tool suites for shot planning and optics demand. The shot planning component provides a web-based interface to selecting and building a sequence of proposed shots for the NIF. These shot sequences, or “lanes” as they are referred to by shot planners, provide for planning both near-term shots in the Facility and long-term “campaigns” in the months and years to come. The shot planning capabilities integrate with the Campaign Management Tool (CMT) for experiment details and the NIF calendar for availability. Future enhancements will additionally integrate with target diagnostics planning and target fabrication requirements tools. The optics demand component is built upon predictive modeling of maintenance requirements on the final optics as a result of the proposed shots assembled during shot planning. The predictive models integrate energetics from a Laser Performance Operations Model (LPOM), the status of the deployed optics as provided by the online Final Optics Inspection system, and physics-based mathematical “rules” that predict optic flaw growth and new flaw initiations. These models are then run on an analytical cluster comprised of forty-eight Linux-based compute nodes. Results from the predictive models are used to produce decision-support reports in the areas of optics inspection planning, optics maintenance exchanges, and optics beam blocker placement advisories. Over time, the SPLAT project will evolve to provide a variety of decision-support and operation optimization tools.

The National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is the world's most energetic laser, providing a scientific research center to study inertial confinement fusion and matter at extreme energy densities and pressures. A target shot involves over 30 specialized diagnostics measuring critical x-ray, optical and nuclear phenomena to quantify ignition results for comparison with computational models. The Shot Analysis and Visualization System (SAVI) acquires and analyzes target diagnostic data for display within a time-budget of 30 min. Laser and target diagnostic data are automatically loaded into the NIF archive database through clustered software data collection agents. The SAVI Analysis Engine distributes signal and image processing tasks to a Linux cluster where computation is performed. Intermediate results are archived at each step of the analysis pipeline. Data is archived with metadata and pedigree. Experiment results are visualized through a web-based user interface in interactive dashboards tailored to single or multiple shot perspectives. The SAVI system integrates open-source software, commercial workflow tools, relational database and messaging technologies into a service-oriented and distributed software architecture that is highly parallel, scalable, and flexible. The architecture and functionality of the SAVI system will be presented along with examples.

Prolonged changes in electrical input to aluminum reduction cells are generally undesirable, but may be imposed, either intentionally or otherwise. In either case the smelter personnel must react so as to minimize disruption to the process. One concern with respect to such changes is maintaining the protective frozen ledge on the cell walls. The depth of the molten metal pad is one process variable commonly used as a countermeasure or enabler for electrical changes. Limited changes to power input can often be accommodated by increasing or decreasing metal depth, while keeping bath depth constant. This changes the wet area for heat transfer to the ledge around the interior periphery of the cell cavity. This paper presents simple analytical expressions for maintaining ledge by changing metal height to balance changes in cell power.

Contact resistance between the collector bar and cathode block has been previously estimated at 10 Ωmm2contributing roughly 100 mV to cell voltage. This paper proposes four mechanisms as contributors to high contact resistance through low contact pressure and large scale intermittent contact. These mechanisms are: temporary bowing of the bar during solidification of cast iron joints, shrinkage of the bar during the phase change from ferrite to austenite, mismatch of iron and carbon surface texture due to axial thermal expansion, and reduced contact pressure due to creep in the steel bar.

The study of the deformation behaviour of the collector bar at conditions experienced within the aluminium reduction cell is of great importance to optimizing the efficiency and increasing the life span of the cell. This paper communicates the results of an experimental program carried out on the steel collector bar material (AISI 1006) to investigate its behaviour in relation to its thermal, mechanical and the creep properties. Tests were carried out in compression at low stresses, 0.5 to 2 MPa and high temperature, 900 °C. Different behaviour was observed at low stresses below 2 MPa, which can be characterised by time and applied stress level. For the test at 2 MPa, a conventional creep curve with dominating secondary creep region was obtained. Oxidation and corrosion were factors considered due to the aggressive environment of the test condition. Metallographic inspection showed effect of oxides on tested sample.

A finite element model of a cathode assembly including a copper insert inside the collector bar was developed. This thermo-electro-mechanical model includes interfaces to simulate the contact between different materials. In order to optimize this model, the authors propose an economic analysis based on the electrical operating cost, the relining cost and the life expectancy of a cell. The geometry of the model is subsequently varied in order to generate a multidimensional response surface based on these economic criteria. Results indicate that substantial economies could be achieved by reducing the resistivity of the collector bar and improving contact at the interface. Also, this model provides some insight in the contact between the different materials of the cathode assembly and its effect on cell performance.

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