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Beam dynamics studies in a high-brightness photo-injector

Description: A high-brightness photo-injector has been developed at Fermilab in collaboration with the TTF project at DESY. Two systems have been commissioned, one at DESY and one at Fermilab. The injector [1] consists of a 1.625-cell cavity RF gun, a superconducting niobium cavity (both 1.3 GHz), and a magnetic chicane. The gun is designed for an electric field of up to 50 MV/m on the cathode. Emittance compensation solenoids surround the gun to correct the linear space charge emittance growth. A high quan… more
Date: October 25, 1999
Creator: Carneiro, Jean-Paul
Partner: UNT Libraries Government Documents Department
open access

Test on 2,000 photomultipliers for the CDF endplug calorimeter upgrade

Description: A systematic test of various characteristics, such as gain, dark current, maximum peak current, stability and relative quantum efficiency, has been made to evaluate about 2,000 photomultiplier tubes for the upgraded CDF Endplug calorimeters. The phototubes are Hamamatsu R4125,19mm diameter with green-extended photocathode. In this report we discuss the distribution of the major characteristics measured and the failure mode. Comparisons between independent measurements made on some of the charac… more
Date: December 1, 1997
Creator: Fiori, I.
Partner: UNT Libraries Government Documents Department
open access

The effect of hydrogen-plasma and PECVD-nitride deposition on bulk and surface passivation in string-ribbon silicon solar cells

Description: We have investigated whether an in-situ hydrogen or ammonia rf-plasma treatment prior to a PECVD-nitride deposition would promote bulk defect passivation independently of surface effects. We also studied whether the predeposition of a thin silicon-nitride protective layer vbefore performing the plasma treatment would serve to minimize surface damage. We found that for the limited set of deposition conditions in of cells processed using the used five different deposition strategies and compared … more
Date: December 1, 1995
Creator: Ruby, D. S.; Wilbanks, W. L.; Fleddermann, C. B. & Hanoka, J. I.
Partner: UNT Libraries Government Documents Department
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Phosphorus and aluminum gettering - investigation of synergistic effects in single-crystal and multicrystalline silicon

Description: Synergistic effects from simultaneous phosphorus-diffusion/aluminium alloy gettering are investigated in three different crystalline- silicon substrates. The silicon materials, experimental design, characterization, and analysis are presented. Some evidence for synergism is observed in the finished cells on all three substrates types. These results are combined with complementary observations of the effects of oxidation on bulk properties of previously gettered substrates to suggest a high volu… more
Date: June 1, 1996
Creator: Schubert, W. K. & Gee, J. M.
Partner: UNT Libraries Government Documents Department
open access

Experience at Fermilab with high quantum efficiency photo-cathodes for rf electron guns

Description: As part of the A0 Photo-injector collaboration at Fermi-lab [1, 2] and the TeSLA collaboration [3], a high bright-ness, low emittance electron source has been developed. In the process, a system was constructed for coating molybde-num cathodes with a layer of cæsium telluride (Cs2 Te), a photo-emissive material of high quantum efficiency (QE). The use of Cs2 Te was first investigated at CERN [4] and LANL [5]. The development of the systems for the TeSLA Test Facility Linac and the Fermilab Phot… more
Date: October 1998
Creator: Fry, A.; Hahn, E.; Hartung, W.; Kuchnir, M.; Michelato, P. & Sertore, D.
Partner: UNT Libraries Government Documents Department
open access

Multi-kiloampere, electron-beam generation using metal photo-cathodes driven by ArF and KrF lasers

Description: An electron-beam-pumped laser operating at ArF (193 nm) or KrF (248 nm) producing 35 MW (3.5 J in 100 ns) has been used to illuminate a micro-machined aluminum cathode. The cathode was pulsed to 2.75 MV at fields of 185 kV/cm (15-cm AK gap) using REX[1,2](a 4-MV, 5-kA,85-ns) pulsed-diode machine. The extracted current versus incident laser power, and therefore, quantum efficiency was measured for KrF at 5x10{sup -5}; ArF was significantly higher at 1x10{sup -3}. Current densities of 100 A/cm{su… more
Date: June 1996
Creator: Carlson, R. L.; Moya, S. A.; Ridlon, R. N.; Seitz, G. J. & Shurter, R. P.
Partner: UNT Libraries Government Documents Department
open access

Mirror reflectivity and doping considerations for high performance oxide-confined vertical cavity lasers

Description: We report the effects of mirror doping and reflectivity in 850 and 780 nm oxide-confined vertical cavity surface emitting lasers. Decreased doping throughout the n-type mirror produces significantly higher quantum efficiency, while the optimum reflectivity is dependent upon the gain material.
Date: January 1, 1996
Creator: Geib, K.M.; Choquette, K. D.; Chui, H. .; Hou, H. Q. & Hammons, B. E.
Partner: UNT Libraries Government Documents Department
open access

Optimization of plasma deposition and etching processes for commercial multicrystalline silicon solar cells

Description: The authors conducted an investigation of plasma deposition and etching processes on full-size multicrystalline (mc-Si) cells processed in commercial production lines, so that any improvements obtained will be immediately relevant to the PV industry. In one case, the authors performed a statistically designed multiparameter experiment to determine the optimum PECVD-nitride deposition conditions specific to EFG silicon from ASE Americas, Inc. In a related effort, they studied whether plasma-etch… more
Date: June 1, 1996
Creator: Ruby, D. S.; Wilbanks, W. L.; Fleddermann, C. B.; Rosenblum, M. D.; Roncin, S. & Narayanan, S.
Partner: UNT Libraries Government Documents Department
open access

High-efficiency cell structures and processes applied to photovoltaic-grade Czochralski silicon

Description: The authors performed a detailed study to examine the limiting performance available using photovoltaic-grade Cz silicon. Photovoltaic-grade silicon refers to silicon produced by the photovoltaic industry, which may differ from the silicon used in the semiconductor device industry in impurity and defect concentrations.The study included optimization of fabrication processes, development of advanced device structures, and detailed model calculations to project future performance improvements. Pr… more
Date: December 1, 1996
Creator: Gee, J. M.; King, R. R. & Mitchell, K. W.
Partner: UNT Libraries Government Documents Department
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Interfacial recombination in In(Al)GaAsSb/GaSb thermophotovoltaic cells

Description: The authors have studied efficient p-on-n homo- (InGaAsSb/GaSb) and heterojunction (InGaAsSb/AlGaAsSb/GaSb) thermophotovoltaic (TPV) cells with respect to the recombination velocity at the cap-layer/emitter interface, S. In both cell types the open-circuit voltage, V{sub oc}, and the short-circuit current, J{sub ac}, have about the same sensitivity to S. The dark current, J{sub 0}, is the most sensitive of all. An examination of the essential factors in the one-dimensional minority-carrier diff… more
Date: October 1, 1998
Creator: Khalfin, V. B.; Garbuzov, D. Z.; Lee, H.; Taylor, G. C.; Morris, N.; Martinelli, R. U. et al.
Partner: UNT Libraries Government Documents Department
open access

Recent progress in InGaAsSb/GaSb TPV devices

Description: AstroPower is developing InGaAsSb thermophotovoltaic (TPV) devices. This photovoltaic cell is a two-layer epitaxial InGaAsSb structure formed by liquid-phase epitaxy on a GaSb substrate. The (direct) bandgap of the In{sub 1{minus}x}Ga{sub x}As{sub 1{minus}y}Sb{sub y} alloy is 0.50 to 0.55 eV, depending on its exact alloy composition (x,y); and is closely lattice-matched to the GaSb substrate. The use of the quaternary alloy, as opposed to a ternary alloy--such as, for example InGaAs/InP--permit… more
Date: May 1, 1996
Creator: Shellenbarger, Z. A.; Mauk, M. G.; DiNetta, L. C. & Charache, G. W.
Partner: UNT Libraries Government Documents Department
open access

Performance status of 0.55 eV InGaAs thermophotovoltaic cells

Description: Data on {approximately} 0.55 eV In{sub 0.72}Ga{sub 0.28}As cells with an average open-circuit voltage (Voc) of 298 mV (standard deviation 7 mV) at an average short-circuit current density of 1.16 A/cm{sup 2} (sdev. 0.1 A/cm{sup 2}) and an average fill-factor of 61.6% (sdev. 2.8%) is reported. The absorption coefficient of In{sub 0.72}Ga{sub 0.28}As was measured by a differential transmission technique. The authors use a numerical integration of the absorption data to determine the radiative rec… more
Date: October 1, 1998
Creator: Wojtczuk, S.; Colter, P.; Charache, G. & DePoy, D.
Partner: UNT Libraries Government Documents Department
open access

Substrate misorientation effects on epitaxial GaInAsSb

Description: The effect of substrate misorientation on the growth of GaInAsSb was studied for epilayers grown lattice-matched to GaSb substrates by low-pressure organometallic vapor phase epitaxy. The substrates were (100) misoriented 2 or 6{degree} toward (110), (111)A, or (111)B. The surface is mirror-like and featureless for layers grown with a 6{degree} toward (111)B misorientation, while, a slight texture was observed for layers grown on all other misorientations. The optical quality of layers, as dete… more
Date: December 1, 1997
Creator: Wang, C. A.; Choi, H. K.; Oakley, D. C. & Charache, G. W.
Partner: UNT Libraries Government Documents Department
open access

Measurements of barium photocathode quantum yields at four excimer laser wavelengths

Description: The electron quantum yields from barium cathodes excited by excimer laser radiation at 193, 248, 308, and 351 nm have been determined. Experiments with different cathode surface preparation techniques reveal that deposition of barium film a few microns thick on a clean copper surface under moderate vacuum conditions achieves relatively high quantum efficiencies. Quantum yields measured from surfaces prepared in this manner are 2.3 x 10{sup -3} at 193 nm, 7.6 x 10{sup - 4} at 248 nm, 6.1 x 10{su… more
Date: June 1992
Creator: Van Loy, M. D.; Young, A. T. & Leung, K. N.
Partner: UNT Libraries Government Documents Department
open access

Production data on 0.55 eV InGaAs thermophotovoltaic cells

Description: Low bandgap 0.55 eV (2.25 {micro}m cutoff wavelength) indium gallium arsenide (In{sub 0.72}Ga{sub 0.28}As) thermophotovoltaic (TPV) cells use much more of the long wavelength energy emitted from low temperature (< 1,200 C) thermal sources than either Si or GaSb cells. Data are presented on a statistically significant number (2,500) of these TPV cells, indicating the performance obtainable in large numbers of cells. This data should be useful in the design and modeling of TPV system performance.… more
Date: May 1, 1996
Creator: Wojtzuk, S.; Colter, P.; Charache, G. & Campbell, B.
Partner: UNT Libraries Government Documents Department
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Single fiber beta detector for stereotactic biopsy and intraoperative lumpectomy of breast cancer

Description: We have developed an intraoperative probe for use in early detection of breast cancer and aiding lumpectomy. The probe consists of a small plastic scintillator, 0.8mm dia and 3mm long, coupled to a single clear optical-fiber strand, and solid state photomultiplier. Due to the small size of the probe, it can be placed inside of a small gauge biopsy needle. The scintillator is very efficient in detecting betas and positrons while being very in efficient to energetic gammas due to small size and l… more
Date: October 1, 1996
Creator: Atac, M.; Nalcioglu, O. & Roeck, W.W.
Partner: UNT Libraries Government Documents Department
open access

Measurement techniques for single junction thermophotovoltaic cells

Description: Several measurement systems and techniques for the electrical and thermal characterization of thermophotovoltaic (TPV) cells are discussed. One computer controlled system measures the quantum efficiency of cells from 0.8 to 2.6 microns. A probe resistor is used to account for cells with low shunt resistances. In the second system, a production-style robot provides automated measurements of I-V characteristics under dark, blackbody, and flashed illumination conditions. The system measures the le… more
Date: October 1, 1998
Creator: Danielson, L. R.; Parrington, J. R.; Charache, G. W.; Nichols, G. J. & DePoy, D. M.
Partner: UNT Libraries Government Documents Department
open access

Current status of low-temperature radiator thermophotovoltaic devices

Description: The current performance status of low-temperature radiator (< 1,000 C) thermophotovoltaic (TPV) devices is presented. For low-temperature radiators, both power density and efficiency are equally important in designing an effective TPV system. Comparisons of 1 cm x 1 cm, 0.55 eV InGaAs and InGaAsSb voltaic devices are presented. Currently, InGaAs lattice-mismatched devices offer superior performance in comparison to InGaAsSb lattice-matched devices, due to the former`s long-term development for … more
Date: May 1, 1996
Creator: Charache, G. W.; Egley, J. L.; Danielson, L. R.; DePoy, D. M.; Baldasaro, P. F.; Campbell, B. C. et al.
Partner: UNT Libraries Government Documents Department
open access

A novel approach for the improvement of open circuit voltage and fill factor of InGaAsSb/GaSb thermophotovoltaic cells

Description: Heterojunction n-Al{sub 0.25}Ga{sub 0.75}As{sub 0.02}Sb{sub 098}/p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96} thermophotovoltaic (TPV) cells were grown by molecular-beam epitaxy on n-GaSb-substrates. In the spectral range from 1 {micro}m to 2.1 {micro}m these cells, as well as homojunction n-p-In{sub 0.16}Ga{sub 0.84}As{sub 0.04}Sb{sub 0.96} cells, have demonstrated internal quantum efficiencies exceeding 80%, despite about a 200 meV barrier in the conduction band at the heterointerface. … more
Date: October 1, 1997
Creator: Garbuzov, D. Z.; Martinelli, R. U.; Khalfin, V.; Lee, H.; Morris, N. A.; Taylor, G. C. et al.
Partner: UNT Libraries Government Documents Department
open access

Extending the cutoff wavelength of lattice-matched GaInAsSb/GaSb thermophotovoltaics devices

Description: This paper reports the growth, materials characterization, and device performance of lattice-matched GaInAsSb/GaSb thermophotovoltaic (TPV) devices with cutoff wavelength as long as 2.5 {micro}m. GaInAsSb epilayers were grown lattice matched to GaSb substrates by organometallic vapor phase epitaxy (OMVPE) using all organometallic precursors including triethylgallium, trimethylindium, tertiarybutylarsine, and trimethylantimony with diethyltellurium and dimethylzinc as the n- and p-type dopants, … more
Date: October 1, 1998
Creator: Wang, C. A.; Choi, H. K.; Oakley, D. C. & Charache, G. W.
Partner: UNT Libraries Government Documents Department
open access

Studies of photoredox reactions on nanosize semiconductors

Description: Light induced electron transfer (ET) from nanosize semiconductors Of MoS{sub 2} to organic electron acceptors such as 2,2`-bipyridine (bpy) and methyl substituted 4,4`,5,5`-tetramethyl- 2,2`-bipyridine (tmb) was studied by static and time resolved photoluminescence spectroscopy. The kinetics of ET were varied by changing the nanocluster size (the band gap), the electron acceptor, and the polarity of the solvent. MoS{sub 2} is an especially interesting semiconductor material as it is an indirect… more
Date: February 1, 1997
Creator: Wilcoxon, J. P.; Parsapour, F. & Kelly, D. F.
Partner: UNT Libraries Government Documents Department
open access

Commissioning results of the next generation photoinjector

Description: The Next Generation Photoinjector (NGP) developed by the BNL SLAC / UCLA collaboration was installed at the Brookhaven National Laboratories Accelerator Test Facility (ATF). The commissioning results and performance of the photocathode injector are present. The Next Generation Photoinjector consists of the symmetrized BNL/SLAC/UCLA 1.6 cell S-band Photocathode RF gun and a single solenoidal magnet for transverse emittance compensation. The highest acceleration field achieved on the cathode is 1… more
Date: December 1, 1996
Creator: Palmer, D. T.; Miller, R. H.; Pellegrini, C.; Winick, H.; Wang, X. J.; Babzien, M. et al.
Partner: UNT Libraries Government Documents Department
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Development and Characterization of Diamond Film and Compound Metal Surface High Current Photocathodes

Description: High current photocathodes operating in vacuum environments as high as 8xE-5 torr are being developed at Los Alamos for use in a new generation of linear induction accelerators. We report quantum efficiencies in wide bandgap semiconductors, pure metals, and compound metal surfaces photocathode materials illuminated by ultraviolet laser radiation.
Date: September 1, 1997
Creator: Shurter, R. P.; Moir, D. C.; Devlin, D. J.; Springer, R. W. & Archuleta, T. A.
Partner: UNT Libraries Government Documents Department
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