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Power and phase monitoring system for the lower hybrid phased array heating system on ATC machine

Description: A four waveguide phased array slow wave structure has been constructed to couple microwave energy into plasma in the ATC Tokamac at Princeton. Theory has indicated that the coupling of power into the plasma column is a strong function of the imposed fourier spectrum at the antenna aperture. To optimize heating, and to verify theoretical results, a precision amplitude and phase monitoring system has been designed and constructed. The system data output is routed to an IBM 1800 computer where the… more
Date: January 1, 1975
Creator: Reed, B.W.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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The Structure of the Cubic Coincident Site Lattice Rotation Group

Description: This work is intended to be a mathematical underpinning for the field of grain boundary engineering and its relatives. The interrelationships within the set of rotations producing coincident site lattices in cubic crystals are examined in detail. Besides combining previously established but widely scattered results into a unified context, the present work details newly developed representations of the group structure in terms of strings of generators (based on quaternionic number theory, and in… more
Date: January 13, 2004
Creator: Reed, B W; Minich, R W; Rudd, R E & Kumar, M
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Prospects for Electron Imaging with Ultrafast Time Resolution

Description: Many pivotal aspects of material science, biomechanics, and chemistry would benefit from nanometer imaging with ultrafast time resolution. Here we demonstrate the feasibility of short-pulse electron imaging with t10 nanometer/10 picosecond spatio-temporal resolution, sufficient to characterize phenomena that propagate at the speed of sound in materials (1-10 kilometer/second) without smearing. We outline resolution-degrading effects that occur at high current density followed by strategies to m… more
Date: January 26, 2007
Creator: Armstrong, M R; Reed, B W; Torralva, B R & Browning, N D
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
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Rapid Laser Induced Crystallization of Amorphous NiTi Films Observed by Nanosecond Dynamic Transmission Electron Microscopy (DTEM)

Description: The crystallization processes of the as-deposited, amorphous NiTi thin films have been studied in detail using techniques such as differential scanning calorimetry and, in-situ TEM. The kinetic data have been analyzed in terms of Johnson-Mehl-Avrami-Kolomogrov (JMAK) semi-empirical formula. The kinetic parameters determined from this analysis have been useful in defining process control parameters for tailoring microstructural features and shape memory properties. Due to the commercial push to … more
Date: March 1, 2010
Creator: LaGrange, T; Campbell, G H; Browning, N D; Reed, B W & Grummon, D S
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Directly Imaging Fast Reaction Fronts

Description: Direct observation of fast intermetallic phase formation in Reactive Multilayer Foils (RMLFs) has been achieved. Snap-shots of the reaction appear to show development of mass-thickness contrast of the unmixed Al and Ni layers and an intermetallic phase. Electron imaging of these RMLF reaction fronts have never been attained in the past. The reaction front travels at {approx}10 meters per second as the nanoscale layers mix in an exothermic chain reaction, thus making traditional in situ electron… more
Date: February 21, 2007
Creator: Kim, J. S.; LaGrange, T. B.; Reed, B. W.; Campbell, G. H. & Browning, N. D.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Time Resolved Annular Dark Field Imaging of Catalyst Nanoparticles

Description: Dynamic transmission electron microscopy (DTEM) has the potential to provide insight into nanoparticle catalyst dynamics by obtaining direct images with high spatial and temporal resolution. To date, the limited signal to noise ratios attainable for dispersed nanoparticle samples have made such studies difficult to perform at the highest resolution. These limitations have been overcome by the fabrication of an annular objective lens aperture that permits images to be obtained with a 5 fold incr… more
Date: August 4, 2009
Creator: Masiel, D J; Reed, B W; LaGrange, T B; Campbell, G H; Guo, T & Browning, N D
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Solving the Accelerator-Condenser Coupling Problem in a Nanosecond Dynamic Transmission Electron Microscope

Description: We describe a modification to a transmission electron microscope (TEM) that allows it to briefly (using a pulsed-laser-driven photocathode) operate at currents in excess of 10 mA while keeping the effects of condenser lens aberrations to a minimum. This modification allows real-space imaging of material microstructure with a resolution of order 10 nm over regions several {micro}m across with an exposure time of 15 ns. This is more than 6 orders of magnitude faster than typical video-rate TEM im… more
Date: December 29, 2009
Creator: Reed, B W; LaGrange, T; Shuttlesworth, R M; Gibson, D J; Campbell, G H & Browning, N D
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Activation Energy for Grain Growth in Bismuth Coatings

Description: The knowledge of both activation energy and diffusion coefficient is needed for a predictive processing of grain size in coatings. However, for metals as Bismuth there is insufficient information available in the literature for these parameters. To determine these values, a method is adopted wherein an examination of the grain size is conducted for coatings deposited isothermally. The exponent for grain growth with time is determined, thereby enabling quantification of the activation energy and… more
Date: September 9, 2005
Creator: Jankowski, Alan Frederic; Hayes, Jeffrey P.; Smith, R. F.; Reed, B. W.; Kumar, M. & Colvin, J. D.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

In-situ Studies of the Martensitic Transformation in Ti Thin Films using the Dynamic Transmission Microscope (DTEM)

Description: The {alpha} to {beta} transition in pure Ti occurs mainly by a 'martensitic type' phase transformation. In such transformations, growth rates and interface velocities tend to be very large, on the order of 10{sup 3} m/s, making it difficult to observe the transformation experimentally. With thin films, it becomes even more difficult to observe, since the large surface augments the nucleation and transformation rates to levels that require nanosecond temporal resolution for experimental observat… more
Date: November 21, 2005
Creator: LaGrange, T. B.; Campbell, G. H.; Colvin, J. D.; King, W. E.; Browning, N. D.; Armstrong, M. R. et al.
Item Type: Refine your search to only Article
Partner: UNT Libraries Government Documents Department
open access

Fundamental Mechanisms Driving the Amorphous to Crystalline Phase Transformation

Description: Phase transformations are ubiquitous, fundamental phenomena that lie at the heart of many structural, optical and electronic properties in condensed matter physics and materials science. Many transformations, especially those occurring under extreme conditions such as rapid changes in the thermodynamic state, are controlled by poorly understood processes involving the nucleation and quenching of metastable phases. Typically these processes occur on time and length scales invisible to most exper… more
Date: January 4, 2011
Creator: Reed, B W; Browning, N D; Santala, M K; LaGrange, T; Gilmer, G H; Masiel, D J et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
open access

Time Resolved Phase Transitions via Dynamic Transmission Electron Microscopy

Description: The Dynamic Transmission Electron Microscope (DTEM) project is developing an in situ electron microscope with nanometer- and nanosecond-scale resolution for the study of rapid laser-driven processes in materials. We report on the results obtained in a year-long LDRD-supported effort to develop DTEM techniques and results for phase transitions in molecular crystals, reactive multilayer foils, and melting and resolidification of bismuth. We report the first in situ TEM observation of the HMX {bet… more
Date: February 22, 2007
Creator: Reed, B. W.; Armstrong, M. R.; Blobaum, K. J.; Browning, N. D.; Burnham, A. K.; Campbell, G. H. et al.
Item Type: Refine your search to only Report
Partner: UNT Libraries Government Documents Department
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