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2,939 Matching Results
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MOS-Gated Thyristors (MCTs) for Repetitive High Power Switching
Certain applications for pulse power require narrow, high current pulses for their implementation. This work was performed to determine if MCTS (MOS Controlled Thyristors) could be used for these applications. The MCTS were tested as discharge switches in a low inductance circuit delivering 1 {micro}s pulses at currents between roughly 3 kA and 11 kA, single shot and repetitively at 1, 10 and 50 Hz. Although up to 9000 switching events could be obtained, all the devices failed at some combination of current and repetition rate. Failure was attributed to temperature increases caused by average power dissipated in the thyristor during the switching sequence. A simulation was performed to confirm that the temperature rise was sufficient to account for failure. Considerable heat sinking, and perhaps a better thermal package, would be required before the MCT could be considered for pulse power applications.
Date:
January 13, 2000
Creator:
Bayne, S. B.; Portnoy, W. M.; Rohwein, G. J. & Hefner, A. R.
Object Type:
Article
System:
The UNT Digital Library
The Use of Thyristors for Repetitive Narrow Pulse, High Power Switching
Inverter type thyristors were switched repetitively to failure with 1 {micro}s pulses at repetition rates of 10, 50 and 100 pps and at peak currents up to 12 kA. Millions of pulses could be obtained before failure if the peak current were held at around 6 kA.
Date:
January 13, 2000
Creator:
Bayne, S. B.; Portnoy, W. M. & Rohwein, G. J.
Object Type:
Article
System:
The UNT Digital Library
Theory of Nanocluster Size Distributions from Ion Beam Synthesis
Ion beam synthesis of nanoclusters is studied via both kinetic Monte Carlo simulations and the self-consistent mean-field solution to a set of coupled rate equations. Both approaches predict the existence of a steady state shape for the cluster size distribution that depends only on a characteristic length determined by the ratio of the effective diffusion coefficient to the ion flux. The average cluster size in the steady state regime is determined by the implanted species/matrix interface energy.
Date:
June 13, 2008
Creator:
Yuan, C. W.; Yi, D. O.; Sharp, I. D.; Shin, S. J.; Liao, C. Y.; Guzman, J. et al.
Object Type:
Article
System:
The UNT Digital Library
Effect of pressure on the luminescence emissions in CuGaSe2
We present the results of a pressure-dependent photoluminescence (PL) study on CuGaSe{sub 2} films grown on GaAs substrate by metalorganic vapor phase epitaxy. The low-temperature PL spectra of the CuGaSe{sub 2} samples measured at atmospheric pressure are dominated by one near band-edge exciton luminescence line and two strong and relatively broad emissions associated with donor acceptor pairs (DAP). All the observed luminescence emission lines shift toward higher energy with increasing pressure at almost the same rate. The nearly identical pressure coefficients of the two DAP emissions as compared to that of the exciton emission confirm the suggestion that the recombination processes associated with the DAPs involve one shallow donor and two different acceptor species with different binding energies and related to two different native defects.
Date:
July 13, 2004
Creator:
Shan, W.; Walukiewicz, W.; Wu, J.; Yu, K. M.; Ager, J. W., III; Siebentritt, S. et al.
Object Type:
Article
System:
The UNT Digital Library
Pressure-dependent photoluminescence study of ZnO nanowires
The pressure dependence of the photoluminescence (PL) transition associated with the fundamental band gap of ZnO nanowires has been studied at pressures up to 15 GPa. ZnO nanowires are found to have a higher structural phase transition pressure around 12 GPa as compared to 9.0 GPa for bulk ZnO. The pressure-induced energy shift of the near band-edge luminescence emission yields a linear pressure coefficient of 29.6 meV/GPa with a small sublinear term of -0.43 meV/GPa{sup 2}. An effective hydrostatic deformation potential -3.97 eV for the direct band gap of the ZnO nanowires is derived from the result.
Date:
September 13, 2004
Creator:
Shan, W.; Walukiewicz, W.; Ager, J. W., III; Yu, K. M.; Zhang, Y.; Mao, S. S. et al.
Object Type:
Article
System:
The UNT Digital Library
Fuel Retrieval Sub (FRS) Project Decapping Station Performance Test Data Report
This document is to provide the test data report for Decapping Station Performance Testing. These performance tests were full scale and viewed as a continuation of development testing performed earlier (SNF-2710). A prototype decapping station confinement box was tested, along with some special tools required for the process, providing assurance that the fuel handling equipment will operate as designed, allowing for release of the FRS equipment for installation.
Date:
January 13, 2000
Creator:
Thielges, J. R.
Object Type:
Report
System:
The UNT Digital Library
New Results with the superconducting ECR ion source VENUS
During the last year, the VENUS ECR ion source was commissioned at 18 GHz and preparations for 28 GHz operation, which is set to begin early in 2004, are now underway. The goal of the VENUS ECR ion source project as the RIA R&D injector is the production of 240emA of U30+, a high current medium charge state beam. On the other hand, as an injector ion source for the 88-Inch Cyclotron the design objective is the production of 5emA of U48+, a low current, very high charge state beam. During the commissioning phase with 18 GHz, tests with various gases and recently metals have been performed with up to 2000 W RF power and the performance is very promising. For example, 1100 e mu A of O6+,180 e mu A of Ar12+, 150 emA of Xe20+ and 100 emA of Bi24+ were produced in the early commissioning phase, ranking VENUS among the currently highest performance 18 GHz ECR ion sources. The emittance of the beams produced at 18 GHz was measured with a two axis emittance scanner. In FY04 a 10 kW, 28 GHz gyrotron system will be added, which will enable VENUS to reach full performance. The performance …
Date:
May 13, 2004
Creator:
Lyneis, C. M.; Leitner, D.; Abbott, S. R.; Dwinell, R. D.; Leitner, M.; Silver, C. S. et al.
Object Type:
Article
System:
The UNT Digital Library
U.S. Food and Agricultural Imports: Safeguards and Selected Issues
None
Date:
February 13, 2008
Creator:
Becker, Geoffrey S.
Object Type:
Report
System:
The UNT Digital Library
Iran: Current Developments and U.S. Policy
This report discusses the developments in Iranian foreign policy, their involvement with terrorist organizations, the developments made with respect to weapons of mass destruction, and human rights concerns. It also details the Bush Administration's efforts to maintain the sanctions put in place by the Clinton Administration.
Date:
March 13, 2003
Creator:
Katzman, Kenneth
Object Type:
Report
System:
The UNT Digital Library
H.R. 3108: The Pension Funding Equity Act
None
Date:
July 13, 2004
Creator:
Purcell, Patrick & Graney, Paul
Object Type:
Report
System:
The UNT Digital Library
Biological and Chemical Weapons: Criminal Sanctions and Federal Regulations
Various federal regulations and criminal sanctions apply to biological and chemical weapons. Some of the provisions are broadly drafted, covering biological and chemical weapons as well as other controlled material and technology. Some focus on biological and chemical weapons as such. Recent anti-terrorism legislation, Public Law 107-56, amended many of these provisions, broadening the scope criminal sanctions relating to the use of biological and chemical weapons and materials. This report outlines provisions criminalizing certain uses of biological and chemical weapons, and references other relevant domestic and international material.
Date:
September 13, 2001
Creator:
Jennings, Christopher Alan
Object Type:
Report
System:
The UNT Digital Library