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108 results on '"Weidman D"'

1. From R&D to Mass Production of Micromorph Thin Film Silicon PV

Author

Meier, J., Kroll, U., Benagli, S., Fesquet, L., Steinhauser, J., Borello, D., Orhan, J.-B., Djeridane, Y., Vallat-Sauvain, E., Fecioru-Morariu, M., Mereu, B., Kalas, J., Hoetzel, J., Losio, P., Kupich, M., Kluth, O., Eisenhammer, T., Weidman, D., Marjanovic, S., and Kohnke, G.

Published
2012
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3. Radius tailoring of an electron beam using a fast rise-time focusing coil: Experiment and simulation.

Author

Weidman, D. J., Nguyen, K. T., Rhee, M. J., Schneider, R. F., and Stark, R. A.

Subjects
*ELECTRON beams, *ELECTRIC coils, *DIODES, *SCINTILLATORS
Abstract

Reports on the results from an experiment that demonstrates a technique for producing a radius-tailored electron beam using a fast rise-time focusing coil. Configuration of the experiment showing the diode, the beam rise-time sharpener, the fast focusing coil and the scintillator plate; Electron beam used in the experiment.

Published
1994
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4. Use of an active wire Bθ cell for electron beam conditioning.

Author

Murphy, D. P., Myers, M. C., Weidman, D. J., Antoniades, J. A., Fernsler, R. F., and Meger, R. A.

Subjects
ELECTRON beams, ELECTRON bombardment conductivity, ASTRONOMICAL perturbation
Abstract

Presents information on a study that demonstrated that an active-wire Β ø is an effective tool for reducing the initial perturbations that feed the growth of the resistive hose instability during the propagation of intense, relativistic electron beams in air. Design issues associated with the cell; Discussion on the conversion of radius tailoring to emittance tailoring; Explanation on matching the beam from the cell into the air; Conclusions.

Published
1996
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7. Recent Developments of High-Efficiency Micromorph Tandem Solar Cells in KAI-M/ Plasmabox PECVD Reactors

Author

Kroll, U., Meier, J., Fesquet, L., Steinhauser, J., Benagli, S., Orhan, J.B, Wolf, B., Borrello, D., Castens, L., Djeridane, Y., Multone, X., Choong, G., Domine, D., Boucher, J.-F., Madliger, P.-A., Marmelo, M., Monteduro, G., Dehbozorgi, B., Romang, D., Omnes, E., Chevalley, M., Charitat, G., Pomey, A., Vallat, E., Marjanovic, S., Kohnke, G., Koch, K., Liu, J., Modavis, R., Thelen, D., Vallon, S., Zakharian, A., and Weidman, D.

Subjects
Thin Film Solar Cells, Amorphous and Microcrystalline Silicon Solar Cells
Abstract

26th European Photovoltaic Solar Energy Conference and Exhibition; 2340-2343, The use of textured glass substrates in the fabrication of Micromorph tandem thin film silicon cells is shown to improve light-trapping, as evidenced by increased bottom cell EQE, and this results in cell efficiency improvements superior to those previously reported. This work utilizes LPCVD ZnO coated textured glass substrates having very high haze values of around 80%, most notably in the wavelength range where the microcrystalline cell possesses a strong spectral response. A 1000 hour light-soaked stable efficiency of 12.16% has been demonstrated and an efficiency of 12.34% after 700 hours of light-soaking has also been measured. In addition, initial efficiencies as high as 14.4% were recently achieved. These results were obtained using substrates that result in a 7.3% bottom cell current gain relative to cells fabricated with flat glass substrates. Textures enabling still higher bottom cell current gains of up to 13.9% as compared to non-textured glass have been identified.

Published
2011
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8. Recent Developments of High-Efficiency Micromorph® Tandem Solar Cells in KAI-M PECVD Reactors

Author

Bailat, J., Fesquet, L., Orhan, J.-B, Djeridane, Y., Wolf, B., Madliger, P., Steinhauser, J., Benagli, S., Borrello, D., Castens, L., Monteduro, G., Marmelo, M., Dehbozorgi, B., Vallat, E., Multone, X., Romang, D., Boucher, J.-F., Meier, J., Kroll, U., Despeisse, M., Bugnon, G., Ballif, C., Marjanovic, S., Kohnke, G., Borrelli, N., Koch, K., Liu, J., Modavis, R., Thelen, D., Vallon, S., Zakharian, A., and Weidman, D.

Subjects
Thin Film Solar Cells, Amorphous and Microcrystalline Silicon Solar Cells
Abstract

25th European Photovoltaic Solar Energy Conference and Exhibition / 5th World Conference on Photovoltaic Energy Conversion, 6-10 September 2010, Valencia, Spain; 2720-2723, This paper addresses three independent approaches to improving the performance of Micromorph® tandem solar cells: 1. Thinner cells for higher throughput in mass-production, 2. Optimum cell design and processes yielding stable efficiencies of 11.5% on as-grown ZnO front contact, and finally 3. The introduction of novel textured glass substrates prepared by Corning Incorporated to improve light-management. As a result of the joint research between Oerlikon Solar- Lab and Corning Incorporated, a Micromorph® tandem cell with no anti-reflection coating demonstrated a stable efficiency of 11.9% as independently measured by NREL. This third result represents a new milestone for thin film silicon solar cell technology which is 8% higher than one year ago. Combinations of these improvements are expected to enable cell efficiencies of 12.5% and beyond.

Published
2010
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9. Assessment of dynamic analyses for deploying space truss structures

Author

Weidman, D and Housner, J

Subjects
Structural Mechanics
Abstract

A selected list of references on the analysis of the deployment concepts for large space truss structures are reviewed. The stability of the deployment process is discussed, and stable methods of deployment mentioned. Analytical and experimental needs to assess feasibility and performance of proposed deployment concepts are outlined.

Published
1984

10. NASTRAN status and plans

Author

Weidman, D. J

Subjects
Structural Mechanics
Abstract

Current status and future NASA plans for the NASTRAN program are presented and discussed. Information is also presented to indicate the extent of NASTRAN use throughout the world.

Published
1975

11. The NASA NASTRAN structural analysis computer program - New content

Author

Weidman, D. J

Subjects
Computer Programming And Software
Abstract

Capabilities of a NASA-developed structural analysis computer program, NASTRAN, are evaluated with reference to finite-element modelling. Applications include the automotive industry as well as aerospace. It is noted that the range of sub-programs within NASTRAN has expanded, while keeping user cost low.

Published
1978

12. NASTRAN: Status, plans, and performance

Author

Weidman, D. J

Subjects
Structural Mechanics
Abstract

Plans for NASTRAN, a program developed and improved over the past 13 years, were outlined in reference to a new capability of level 17. The target release date is given as December 1977 and domestic release will be through COSMIC. As an example of the improved efficiency of NASTRAN level 16, a table of CPU run time comparisons is shown.

Published
1977

13. Nonlinear panel flutter - A finite-element approach

Author

Mei, C and Weidman, D. J

Subjects
Structural Mechanics
Abstract

A finite-element approach has been developed for computing nonlinear flutter characteristics of rectangular isotropic panels with stream-alined side edges, based on aerodynamic forces from supersonic two-dimensional quasi-steady aerodynamic theory. Stress distributions and panel oscillation frequencies were determined from the analysis. The finite-element formulation, solution procedure, and convergence characteristics are presented. Comparisons are made with linear flutter and large-amplitude vibration results and demonstrate that good accuracy is obtained. Non-linear flutter results are presented for effects of aerodynamic damping, length-width ratio, initial in-plane forces and boundary-support conditions. Comparisons with experimental results are also presented.

Published
1977

14. NASA's plans for future NASTRAN capability

Author

Weidman, D. J

Subjects
Structural Mechanics
Abstract

Improvements in the NASTRAN systems management office are presented. Among the improvements are the following items: (1) the FEER eigenmethod and its extension to complete eigenvalue problems; (2) the addition of a supersonic flutter package which allows gust response calculations and active control effects as membrane In addition to capabilities mentioned, an error correction information system is also introduced.

Published
1976

21. High intensity heat and light unit Patent

Author

Griffith, G. E, Kordes, E. E, Trussell, D. H, and Weidman, D. J

Subjects
Electronic Equipment
Abstract

High intensity heat and light unit containing quartz lamp elements protectively positioned to withstand severe environmental stress

Published
1961

22. Future NSMO plans for maintenance of NASTRAN

Author

Weidman, D. J

Subjects
Structural Mechanics
Abstract

The objectives of the NASTRAN computer program system are discussed. Specific reference is made to the use of NASTRAN in the space shuttle program. The use of NASTRAN by agencies other than NASA is reported. The subjects presented are: (1) planned developments, (2) capability improvements, (3) efficiency improvements, and (4) new error correction procedure.

Published
1973

23. NASTRAN: A progress report

Author

Raney, J. P and Weidman, D. J

Subjects
Structural Mechanics
Abstract

Significant NASTRAN-related events since September, 1971 are reviewed. The present operation of the NASTRAN systems management office is described, as well as new capabilities and improvements incorporated in Level 15 of NASTRAN, and priorities for future levels of NASTRAN.

Published
1972

24. Plasma Wakefield Effects On High-Current Relativistic Electron Beam Transport In The Ion-Focused Regime

Author

NAVAL SURFACE WEAPONS CENTER WHITE OAK LAB SILVER SPRING MD, Miller, J. D., Schneider, R. F., Weidman, D. J., Uhm, H. S., Nguyen, K. T., NAVAL SURFACE WEAPONS CENTER WHITE OAK LAB SILVER SPRING MD, Miller, J. D., Schneider, R. F., Weidman, D. J., Uhm, H. S., and Nguyen, K. T.

Abstract

Modulation of the beam current has been observed during ion focused regime (IFR) transport of a high power relativistic electron beam propagating through a low-density background plasma. Injecting a high current, high energy electron beam into an IFR channel immersed in a background plasma induces plasma oscillations. These background plasma oscillations, induced by the risetime portion of the beam ejecting plasma electrons from the vicinity of the beam into the background plasma, give rise to a modulated axial electric field. This field travels with the beam leading to beam energy and current oscillations. In the experiment, a 1.7-MeV, 1-kA, risetime-sharpened electron beam is propagated on a KrF excimer laser produced IFR channel in TMA gas, which is immersed in a low density plasma filled transport tube. We present experimental measurements and computer simulations demonstrating modulation of this high current relativistic electron beam near the low density background plasma frequency., Prepared in collaboration with Mission Research Corp., Newington, VA

Published
1992

25. Study of Intense Relativistic Electron Beam Modulation by Wakefield Effects

Author

NAVAL SURFACE WARFARE CENTER SILVER SPRING MD, Miller, J. D., Schneider, R. F., Nguyen, K. T., Stark, R. A., Weidman, D. J., NAVAL SURFACE WARFARE CENTER SILVER SPRING MD, Miller, J. D., Schneider, R. F., Nguyen, K. T., Stark, R. A., and Weidman, D. J.

Abstract

An experimental study has been undertaken in order to investigate plasma wakefield effects produced in intense electron beam propagation in a background plasma. A 2 MeV, 1 kA, electron beam is used for this experiment. A 50 cm diam., 3.6 m long drift tube is filled with a background gas, typically trimethylamine (TMA). This gas is ionized by electrons emitted from heated tungsten filaments which are biased at approximately -100 Volts. The resultant plasma density is fairly uniform and is adjustable in the range 10 to the 8th power to 5 x 10 to the 9th power per cubic cm. A higher density Ion Focused Regime (IFR) channel for electron beam propagation is generated by KrF-laser (248 nm) ionization of the background TMA gas. The intense electron beam propagating on an IFR channel in this background plasma experiences wakefield effects due to the natural oscillations of the background plasma which are excited by the beam current risetime. The Ez component of the induced field is responsible for producing beam current modulation near the background plasma frequency. The results scale with plasma density as expected and current modulation is nearly complete for a certain parameter range. This technique may be amenable to a high power microwave generation technique analogous to the relativistic klystron. Detailed experimental results of beam modulation will be presented., Prepared in collaboration with Maryland Univ. and Mission Research Corp.

Published
1991

31. Intense electron beam radius-tailoring experiment for propagation studies.

Author

Weidman, D. J., Miller, J. D., Nguyen, K. T., Rhee, M. J., Schneider, R. F., and Stark, R. A.

Abstract

We have generated a "radius-tailored" electron beam, a beam that is tapered with a larger head and a smaller tail, using a Fast rise-time magnetic Focusing Coil (FFC) around a vacuum drift tube placed downstream of the electron beam diode. The electron beam is injected during the rise time of the FFC magnetic field so that the beam head expands, while the beam body and tail are confined by the axial magnetic field of the FFC. The electron beam for this experiment is 1.7 MeV, 1 kA, and 13 ns flattop. Time-resolved beam radius measurements, from a scintillator viewed by a streak camera, indicate the beam radius as a function of time. Intense relativistic electron beams propagating through a gas exhibit the resistive hose instability. The growth rate of the hose instability can be reduced by "tailoring" the beam radius from a large head to a small tail. The next step of the experiment would be to study the propagation characteristics of the radius-tailored beam in neutral gas. This beam could be injected into a gas-filled drift tube to compare the propagation characteristics to those of an untailored beam. Diagnostics could include B probes to measure the beam centroid and an open-shutter camera. [ABSTRACT FROM PUBLISHER]

Published
1992

38. Simple time-resolving Thomson spectrometer.

Author

Rhee, M. J., Schneider, R. F., and Weidman, D. J.

Subjects
SPECTROMETERS, TIME-resolved spectroscopy, SCIENTIFIC apparatus & instruments
Abstract

We describe a simple time-resolving Thomson spectrometer system which can provide the temporal information of ions produced by a pulsed source, in addition to the time-integrated information. The electric field in a conventional spectrometer is modulated by a time-varying field. It is shown that from the resulting spectrogram, the time-resolved quantities associated with the ions can be deduced. Experimental results with plasma focus produced ions are given as an example. [ABSTRACT FROM AUTHOR]

Published
1987
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39. Temporal evolution of ion energy in a plasma focus.

Author

Rhee, M. J. and Weidman, D. J.

Subjects
*ION flow dynamics, *FLUID dynamics, *TIME-resolved spectroscopy
Abstract

For the first time, the temporal structure of ion energy in a plasma focus is revealed using a time-resolving Thomson spectrometer. The velocities and arrival times of ions are determined from the spectrogram. The resulting distribution of ions in velocity–time space at the source is found to be a line distribution, as if the ions were accelerated in a diode by a pulsed voltage. [ABSTRACT FROM AUTHOR]

Published
1988
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40. Nonlinear optical susceptibilities of high-index glasses.

Author

Hall, D. W., Newhouse, M. A., Borrelli, N. F., Dumbaugh, W. H., and Weidman, D. L.

Subjects
NONLINEAR optics, OPTICAL measurements, OPTICAL glass, OXIDES, ARSENIC sulfide
Abstract

We report results of degenerate four-wave mixing measurements of nonresonant nonlinearities in a variety of high-index lead and bismuth containing oxide glasses and the chalcogenide As2S3. The third-order nonlinear susceptibilities of the oxide glasses are found to scale with the heavy metal content. A lead-bismuth-gallate glass was identified with a nonresonant χ3 equal to 42±7×10-14 esu, which is approximately three times larger than that of any glass previously reported. [ABSTRACT FROM AUTHOR]

Published
1989
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41. Recent Developments of High Efficiency Micromorph tandem solar cells in KAI-M PECVD reactors

Author

Bailat, Julien, Fesquet, Luc, Orhan, Jean-Baptiste, Wolf, B., Madliger, P., Steinhauser, J., Benagli, Stefano, Borrello, D., Castens, Lucie, Monteduro, G., Marmelo, M., Dehbozorghi, B., Vallat-Sauvain, E., Multone, X., Romang, D., Boucher, J.-F., Meier, J., Kroll, U., Despeisse, Matthieu, Bugnon, Grégory, Ballif, Christophe, Marjanovic, S., Kohnke, G., Borrelli, N., Koch, K., Liu, J., Modavis, R., Thelen, D., Vallon, S., Zakharian, A., and Weidman, D.

Abstract

This paper addresses three independent approaches to improving the performance of Micromorph® tandem solar cells: 1. Thinner cells for higher throughput in mass-production, 2. Optimum cell design and processes yielding stable efficiencies of 11.5% on as-grown ZnO front contact, and finally 3. The introduction of novel textured glass substrates prepared by Corning Incorporated to improve light-management. As a result of the joint research between Oerlikon Solar- Lab and Corning Incorporated, a Micromorph® tandem cell with no anti-reflection coating demonstrated a stable efficiency of 11.9% as independently measured by NREL. This third result represents a new milestone for thin film silicon solar cell technology which is 8% higher than one year ago. Combinations of these improvements are expected to enable cell efficiencies of 12.5% and beyond

47. 185

Author

Weidman, D. A., primary, Tesch, J. C., additional, Castek, J. E., additional, Wilson, P. K., additional, and Buckenmeyer, P. J., additional

Published
1987
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