Engineering topics
Hyland, S.
Publications and source records attributed to Hyland, S..
S&TR April-May 2023 (Corrosion Issue)
Corrosion damages and can ultimately destroy items from household appliances and personal vehicles to aircraft parts and reinforcing steel in bridges and roadways. As the article beginning on p. 4 describes, Lawrence Livermore researchers have developed capabilities for predicting the onset of corrosion in specific materials. Of particular interest to the Laboratory and its mission are impacts to weapon components stored in potentially corrosive environments.
Science & Technology Review (January/February 2023)
The vortex on this issue’s cover represents the sense of uncertainty experienced by scientists in the initial stages of exploring a new research path. The article beginning on p. 4 introduces research projects of higher technical risk conducted under Lawrence Livermore’s Disruptive Research (DR) Program, a component of the Laboratory Directed Research and Development Program. If successful, DR projects yield order-of-magnitude rewards. If DR projects fail to meet stated goals, they offer different rewards by shaping future research and investment
Creep of web ribbons
Results are reported for work in high-temperature deformatin of dendritic web ribbons, and oxygen measurement in the material.
Power system applications of fiber optics
Power system applications of optical systems, primarily using fiber optics, are reviewed. The first section reviews fibers as components of communication systems. The second section deals with fiber sensors for power systems, reviewing the many ways light sources and fibers can be combined to make measurements. Methods of measuring electric field gradient are discussed. Optical data processing is the subject of the third section, which begins by reviewing some widely different examples and concludes by outlining some potential applications in power systems: fault location in transformers, optical switching for light fired thyristors and fault detection based on the inherent symmetry of most power apparatus. The fourth and final section is concerned with using optical fibers to transmit power to electric equipment in a high voltage situation, potentially replacing expensive high voltage low power transformers. JPL has designed small photodiodes specifically for this purpose, and fabricated and tested several samples. This work is described.
Effect of localized polycrystalline silicon properties on solar cell performance
Several forms of polycrystalline silicon, mostly from cast ingots, (including UCP, SILSO and HEM) were studied. On typical slices, localized properties were studied in two ways. Small area (about 2.5 sq mm) mesa diodes were formed, and localized photovoltaic properties were measured. Also a small area (about .015 sq mm) light spot was scanned across the cells; the light spot response was calibrated to measure local diffusion length directly. Using these methods, the effects of grain boundaries, or of intragrain imperfections were correlated with cell performance. Except for the fine grain portion of SILSO, grain boundaries played only a secondary role in determining cell performance. The major factor was intra-grain material quality and it varied with position in ingots and probably related to solidification procedure.
Correlation of solar cell electrical properties with material characteristics of silicon cast by the ubiquitous crystallization process
Solar cells were fabricated using a conservative 'baseline' process on 1-3 Omega-cm p-type silicon from ingots cast by the ubiquitous crystallization process. Conversion efficiencies of the cells were measured, as well as spectral response and minority carrier diffusion length. Adjacent slices from the same ingot were studied for their grain size, dislocation distribution, and impurity distribution. Cell performance was related to the observed structural features, as well as to the chemical structure of the ingot.
Interaction between cast silicon properties and solar cell performance
Three types of cast silicon, Silso, HEM (Heat-Exchanger Method) and UCP (Ubiquitous Crystallization Process) were studied for their use as solar cells. Optical microscopy after etching revealed a high density of uniform dislocations (approaching 1,000,000/sq cm), lines of dislocations indicating stress during crystal growth, and precipitates, some of which generate dislocations. Solar cells were fabricated by three processes. Results of solar cell processing revealed that these materials produce cells of lower efficiency than Czochralski control cells, and that the efficiencies of the three materials were quite close. Diffusion length and spectral response data are shown. Certain structural features are correlated with solar cell efficiency, diffusion length, and spectral response. Electron-beam induced current (EBIC) and light spot scanning are used to back up other measurements.
Improved performance from solar cells made from candidate sheet silicon materials
Performance of solar cells made from various candidate silicon sheets is updated and the results are presented. Solar cells were fabricated using a baseline process and other process variations, and tested under AM1 conditions. Performance of the baseline solar cells indicates that remarkable improvements in material quality have been achieved for most of the sheets, showing efficiencies close to that of the control cells made from conventional CZ silicon. Process variations (or additions), in general, have resulted in significant improvements in all performance with a degree of change dependent on the process chosen and to a certain extent the sheet quality.
Opto-electronic properties of cells made from various silicon forms
Opto-electronic properties of the various silicon forms were obtained from the solar cell performance. Performance parameters included the photovoltaic characteristics, minority carrier diffusion length, spectral response and small light spot scanning. Self consistent results were obtained from the various measurement techniques, which can provide useful information on sheet quality, as a potential for low cost terrestrial applications, and areas where the sheet formation methods can be improved.