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Improved amorphous Si solar cells. Quarterly progress report, August 1-October 31, 1980

Description: A model for explaining the growth, H incorporation and bandgap data in a-Si deposited from (SiF/sub 4/ + H/sub 2/) has been developed. It is proposed that the a-Si films are subjected to reactive ion etching and ion bombardment during growth, which may lead to lower defect densities (and hence lower H content) and microcrystallinity in doped films. A morphological study of B-doped a-Si:H has also been carried out. It is found that there are certain regions of pressure, temperature and relative B/sub 2/H/sub 6/ concentrations which lead to agglomerative growth. Study of drift mobility of electrons has continued. We have obtained very high drift mobilities, (approx. 0.8 cm/sup 2//V-sec) on thick films (approx. 3 ..mu..m). Thin films (approx. 1 ..mu..m) have significantly lower mobilities. It is proposed that this phenomenon is due to the existence of a transition layer between the substrate and high quality a-Si. We have continued nip device fabrication in a-Si:H. The following parameters have been obtained individually on cells of 0.24 cm/sup 2/ area. J/sub sc/ (internal) = 12 mA/cm/sup 2/ at 100 mW/cm/sup 2/, V/sub oc/ = 820 mV, and FF = 0.56 are obtained.
Date: January 1, 1980
Creator: Dalal, V.L.
Partner: UNT Libraries Government Documents Department

Short-pulse high-current-density photoemission in high electric fields

Description: We present the experimental results of photoemission studies on thin wires of gold-coated tungsten, held at surface fields in the range of 10/sup 6/ to 3 x 10/sup 8/ V/m, and illuminated by 10 ps long, 4.66 eV photon laser pulses. The wire cathodes arranged coaxially in an anode experienced a surface-field enhancement of 10/sup 2/ to 10/sup 3/ over the applied voltage. We obtained current densities exceeding 10 kA/cm/sup 2/ from a 50 ..mu..m diameter wire, from a (50 x 400) ..mu..m/sup 2/ area, under partially space-change-limited conditions. The quantum efficiency for emission-limited cases was in the range of 10/sup -5/. For these cases results using 50 ..mu..m and 4 ..mu..m diameter wires indicated linear dependence of charge density with optical energy density. The emission also scaled linearly with the emitting area. For surface fields above 3 x 10/sup 7/ V/m, a twofold enhancement of emission was observed for a tenfold increase in the field. 7 refs., 9 figs.
Date: January 1, 1987
Creator: Fischer, J. & Srinivasan-Rao, T.
Partner: UNT Libraries Government Documents Department

InP single-junction concentrator cell. Semi-annual report, October 1, 1980-March 31, 1981

Description: The purpose of this work is to develop a glass-sealed back-contacted InP or InGaAsP solar cell for use in concentrator systems. Work to be performed in developing this cell includes growing the InP epitaxial layers needed for cells and test structures, developing a model to be used in optimizing the cell structure, measurement of InP parameters necessary for use in the model, and developing the glass-bonding and back-contacting scheme. Accomplishments in these areas are discussed.
Date: January 1, 1981
Creator: Gregory, P.E.
Partner: UNT Libraries Government Documents Department

A compact, low cost, 7 channel polychromator for Thomson scattering measurements

Description: A seven channel polychromator, utilizing high performance interference filters, has been tested for use in the multi-Nd:YAG laser Thomson scattering system for the DIII-D tokamak. Unique features of this polychromator are the combination of high throughput, easy alignment, flexibility, compact size, and low cost when compared with other alternatives. Light is introduced to the polychromator (f/1.75) via a fiber optic bundle which permits the use of small (3.0 cm dia) optics and leads to a compact design, an important design consideration for multiple polychromator systems. The light is cascaded through a series of different bandpass interference filters and relay lenses which are mounted on two precision parallel rails in such a way that alignment is trivial. The relay lenses are positioned directly in front of the filters so that light reflected from the filter passes through the lens twice. This leads to an efficient, compact design and reduces the angle of incidence (4{degree}) and the cone angle of light (4.5{degree}) seen by the filter, an important factor for narrowband (3.0 nm) filters. The transmission was optimized for 700--1100 nm by using broadband coatings throughout. The output images of each channel (2.3 mm dia) can be directly coupled to large format (3 nm dia) RCA silicon avalanche photodiode detectors, avoiding the losses caused by fiber optic coupling.
Date: October 1, 1990
Creator: Carlstrom, T.N.; DeBoo, J.C.; Evanko, R.; Greenfield, C.M.; Hsieh, C.-L.; Snider, R.T. et al.
Partner: UNT Libraries Government Documents Department

Rise time and recovery of GaAs photoconductive semiconductor switches

Description: Fast rise time applications have encouraged us to look at the rise time dependences of lock-on switching. Our tests have shown rise time and delay effects which decrease dramatically with increasing electric field across the switch and/or optical energy used in activating lock-on. Interest in high repetition rate photoconductive semiconductor switches (PCSS), which require very little trigger energy (our 1.5-cm long switches have been triggered with as little as 20 {mu}J), has also led us to investigate recovery from lock-on. Several circuits have been used to induce fast recovery, the fastest being 30 ns. The most reliable circuit produced a 4-pulse burst of +/{minus} 10-kV pulses at 7 MHz with 100-{mu}J trigger energy per pulse. 11 refs., 10 figs.
Date: January 1, 1990
Creator: Zutavern, F.J.; Loubriel, G.M.; O'Malley, M.W.; McLaughlin, D.L. & Helgeson, W.D.
Partner: UNT Libraries Government Documents Department

Pulsed 4-MeV electron injector with an excimer laser driven photocathode

Description: The Relativistic Electron-Beam Experiment injector at the Los Alamos National Laboratory is used to generate a 4-MV pulse across an anode-cathode gap. A simple metal photocathode is illuminated by a pulsed excimer laser. Time-resolved measurements of current, voltage, and current density are made. The resulting quantum efficiencies are being used to obtain the required laser power for a multikiloampere, high-brightness electron gun to be used as an injector for a linear induction accelerator. 3 refs., 5 figs.
Date: January 1, 1989
Creator: Kauppila, T.J.; Builta, L.A.; Carlson, R.L.; Moir, D.C. & Ridlon, R.N.
Partner: UNT Libraries Government Documents Department

Cadmium sulfide/copper ternary heterojunction cell research. Final report, April 1, 1980-August 25, 1982

Description: The properties of polycrystalline, thin-film CuInSe/sub 2//CdS and CuInSe/sub 2//Zn/sub x/Cd/sub 1-x/S solar cells prepared by vacuum-evaporation techniques onto metallized-alumina substrates are described. An efficiency of 10.6% for a 1 cm/sup 2/ area cell and 8.3% for an 8 cm/sup 2/ cell when tested under simulated AM1 illumination is reported. The mixed-sulfide cells are described as exhibiting increased open-circuit voltages, slightly higher short-circuit currents, and improved efficiencies. Mixed-sulfide film preparation by evaporation of CdS and ZnS powders from a single source and from two sources is discussed with preference given to the later technique. Selenide-film preparation in a planetary or rotating substrate vacuum-deposition apparatus is described. A 1 cm/sup 2/ area cell without AR-coating produced by the planetary approach is reported to demonstrate a 7.5% efficiency. The results of cell heat-treatment studies showing a strong environmental dependence are presented and indicate the desirability of an oxygen-containing atmosphere. An automatic, computer-controlled, cell-measurement system for I-V, C-V, and spectral-response analysis is described. The results of the cell-analysis and cell-modeling studies on both the plain CdS and mixed Zn/sub x/Cd/sub 1-x/S thin-film devices are presented. Finally, data obtained from constant illumination and elevated temperature life-tests on the thin-film cells showing little degradation after 9300 hours is reported.
Date: August 1, 1982
Creator: Mickelsen, R. A. & Chen, W. S.
Partner: UNT Libraries Government Documents Department

Interdigitated back contact solar cell with high-current collection

Description: Internal current-collection efficiencies greater than 90 percent and energy-conversion efficiencies of 18 percent at 30 suns have been measured on a laboratory version of the interdigitated back contact (IBC) solar cell. The quantum efficiency at 600 nm was greater than 90 percent which implies a minority carrier lifetime of greater than 350 ..mu..sec and a front surface recombination velocity of less than 30 cm/sec on the better devices. To achieve these high-current collection efficiencies, a phosphorous gettering diffusion was performed on the front surface and then etched off. Also, thermal oxides were grown on the front and back of the cell to passivate the silicon surfaces. Although the internal collection efficiencies of the cell were high, series resistance caused the fill factor (FF) to decrease at concentrations above 30 suns. Dark current measurements on cells with a new grid spacing indicate that the series resistance is much lower than in the previous cell design. This should result in higher efficiencies at high concentration.
Date: January 1, 1981
Creator: Garner, C.M.; Nasby, R.D.; Sexton, F.W.; Rodriguez, J.L. & Norwood, D.P.
Partner: UNT Libraries Government Documents Department

Polarization at the SLC

Description: The Stanford Linear collider was designed to accommodate polarized electron beams. Longitudinally polarized electrons colliding with unpolarized positrons at a center of mass energy near the Z/sup 0/ mass can be used as novel and sensitive probes of the electroweak process. A gallium arsenide based photon emission source will provide a beam of longitudinally polarized electrons of about 45 percent polarization. A system of bend magnets and a superconducting solenoid will be used to rotate the spins so that the polarization is preserved while the 1.21 GeV electrons are stored in the damping ring. Another set of bend magnets and two superconducting solenoids orient the spin vectors so that longitudinal polarization of the electrons is achieved at the collision point with the unpolarized positrons. A system to monitor the polarization based on Moller and Compton scattering will be used. Nearly all major components have been fabricated and tested. Subsystems of the source and polarimeters have been installed, and studies are in progress. The installation and commissioning of the entire system will take place during available machine shutdown periods as the commissioning of SLC progresses. 8 refs., 16 figs., 1 tab.
Date: October 1, 1988
Creator: Moffeit, K.C.
Partner: UNT Libraries Government Documents Department

Preparation and properties of evaporated CdTe films compared with single-crystal CdTe. Progress report No. 8, August 1-October 31, 1982

Description: The goal of the research is to develop efficient thin-film CdTe solar cells using the method of hot-wall vacuum evaporation for CdTe film deposition. A series of undoped CdTe film depositions was performed. Ampoules with small apertures were designed for Zone 3 and Zone 4 of the furnace (dopant zone, and Cd or Te zone) to allow the temperatures of these zones to be raised near that of the substrate and thus prevent deposition of Te in these zones during a deposition run. Weighing these ampoules also provides a convenient test of material evaporated. The first set of depositions with As impurity to produce p-type CdTe:As films was carried out. No large effect of As doping was observed in these early runs, but some system improvements have been made for the future. A CdTe homojunction with a 0.15 ..mu..m n-type CdTe:In layer on a p-type CdTe:P single crystal substrate has been analyzed. Modelling of the spectral response of the quantum efficiency suggests the presence of a thin inactive layer at the surface, possibly a depletion layer in the n-type film. Large values of the diode factor A indicate non-simple homojunction structures. A light spot scanning apparatus has been constructed using a He-Ne laser and a 4 ..mu..m optical fiber. This apparatus will be used to measure the recombination characteristics of grain boundaries covered by transparent Schottky barriers. The electrical conductivity of p-type CdTe films prepared by close-spaced vapor transport is markedly increased by heat treatment in H/sub 2/. Some recovery of the film resistivity is seen after 1 week in air.
Date: January 1, 1982
Creator: Bube, R Hl
Partner: UNT Libraries Government Documents Department

Simple laser-driven, metal photocathodes as cold, high-current electron sources

Description: Recent developments in excimer laser design have made near ultraviolet light intensities of several MW/cm/sup 2/ possible in unfocused beams. These advances and recent experiments indicate that high-current, simple-metal photoemissive electron guns are now feasible. Producing more than 50 A/cm/sup 2/ of illuminated cathode surface, the guns could operate at vacuums of 10/sup -6/ torr with no complicated system components inside the vacuum enclosure. The electron beam produced by such photoemission guns would have very low emittance and high brightness. This beam would also closely follow the temporal characteristics of the laser pulse, making fast risetime, ultrashort electron beam pulses possible.
Date: January 1, 1987
Creator: Saunders, J.D.; Ringler, T.J.; Builta, L.A.; Kauppila, T.J.; Moir, D.C. & Downey, S.W.
Partner: UNT Libraries Government Documents Department

Preparation and properties of evaporated CdTe films compared with single crystal CdTe. Progress report No. 1, October 1, 1980-January 31, 1981

Description: This program is concerned with the investigation of the materials properties of CdTe thin films deposited by hot-wall vacuum evaporation and of CdTe single crystalline material, particularly those relevant to solar cell applications in which CdTe is the absorbing member. Progress is reported on: (a) an evaluation of CdTe homojunctions formed by HWVE of CdTe by Walter Huber at the laboratory of Dr. Adolfo Lopez-Otero at the Institut fuer Physik of the University of Linz, using single crystal p-type CdTe from Stanford as a substrate; (b) the design and construction of a HWVE apparatus at Stanford; and (c) properties of grain boundaries in large grain polycrystalline CdTe.
Date: January 1, 1981
Creator: Bube, R. H.
Partner: UNT Libraries Government Documents Department

Nonphotochemical hole burning and dispersive kinetics in amorphous solids

Description: Results covering burn intensities in the nW to {mu}W/cm{sup 2} range, of dispersive hole growth kinetics are reported for Oxazine 720 in glycerol glasses and polyvinyl alcohol polymer films and their deuterated analogues. A theoretical model which employs a distribution function for the hole burning rate constant based upon a Gaussian distribution for the tunnel parameter is shown to accurately describe the kinetic data. This model incorporates the linear electron-phonon coupling. A method for calculating the nonphotochemical quantum yield is presented which utilizes the Gaussian distribution of tunnel parameters. The quantum yield calculation can be extended to determine a quantum yield as a function of hole depth. The effect of spontaneous hole filling is shown to be insignificant over the burn intensity range studied. Average relaxation rates for hole burning are {approximately}8 orders of magnitude greater than for hole filling. The dispersive kinetics of hole burning are observed to be independent over the temperature range of these experiments, 1.6 to 7.0 K. 6 refs., 20 figs., 1 tab.
Date: September 21, 1990
Creator: Kenney, M.J.
Partner: UNT Libraries Government Documents Department

UV photoemission studies of metal photocathodes for particle accelerators

Description: Photoemission from several metals was studied with 10 ps laser pulses at 266 nm. The yield was linear with energy and with area. Quantum efficiencies (/eta/) were determined (up to 10/sup /minus/3/ e/photons for samarium), and found to vary as (h..nu..-/phi/)/sup 2/. /eta/ also increased with the field. The field assisted efficiencies were calculated for some metals and confirmed by experiment for gold, up to surface fields of /approximately/3/times/10/sup 8/ V/m. High charge and current densities, close to 10/sup 5/ A/cm/sup 2/ from macroscopic areas, were measured or indicated. Results are then related to applications in accelerators. 18 refs., 15 figs., 4 tabs.
Date: September 1, 1988
Creator: Fischer, J. & Srinivasan-Rao, T.
Partner: UNT Libraries Government Documents Department

Design, performance, and calibration of the ALEXIS ultrasoft x-ray telescopes

Description: The Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment consists of six wide angle EUV/ultrasoft x-ray telescopes utilizing normal incidence multilayer mirrors, flown a miniature satellite to map out the sky in three narrow bandpasses around 66, 71, and 95 eV. The 66 and 71 eV bandpasses are centered on intense Fe emission lines which are characteristic of million degree plasmas such as the one thought to produce the soft x-ray background. The 95 eV bandpass has a higher throughput and is more sensitive to continuum sources. The mission will be launched into orbit on the Pegasus Air Launched Vehicle in mid-1991. We will present the details of the ALEXIS telescope optical design, initial characterizations of the first flight mirrors and detectors, and the current schemes for characterizing and calibrating the completed telescope assemblies. We will also discuss the details of a novel wavetrap'' feature incorporated into the multilayer mirror structure to greatly reduce the mirror's reflectivity at 304 {angstrom}, a major background contamination flux of He II emission from the geocorona. 2 refs., 13 figs.
Date: January 1, 1990
Creator: Bloch, J.J.; Ameduri, F.; Priedhorsky, W.C.; Roussel-Dupre, D.; Smith, B.W. (Los Alamos National Lab., NM (USA)); Siegmund, O.H.W. et al.
Partner: UNT Libraries Government Documents Department

Cerenkov ring imaging detector development at SLAC

Description: The imaging of Cerenkov light on to photosensitive detectors promises to be a powerful technique for identifying particles in colliding beam spectrometers. Toward this end two and three dimensional imaging photon detectors are being developed at SLAC. The present techniques involve photon conversion using easily ionized exotic chemicals like tetrakisdimethyl-amino-ethylene (TMAE) in a drift and amplifying gas mixture of methane and isobutane. Single photoelectrons from Cerenkov light are currently being drifted 20 cm and a new device under study will be used to study drifting up to 80 cm along a magnetic field. A short description of a large device currently being designed for the SLD spectrometer at the Stanford Linear Collider will be given.
Date: June 1, 1984
Creator: Williams, S.H.
Partner: UNT Libraries Government Documents Department

Design and demonstration of a spectrum-splitting photovoltaic concentrator module

Description: A spectrum splitting, concentrating photovoltaic module has been designed and fabricated that uses point focus curved facet Fresnel lenses to concentrate incident sunlight. The concentrated sunlight beam spectrum is split into a high and low energy part by a dichroic filter. The high energy part of the spectrum is transmitted to an AlGaAs solar cell and the low energy part is reflected to a Si cell. Spectrum splitting and using cells that respond best to the two parts of the spectrum splitting and using cells that respond best to the two parts of the spectrum gives a higher efficiency than the use of either cell alone. The experimental module has been tested which consists of 10 AlGaAs and 10 Si cells, and a sunlight to electricity conversion efficiency of 20% has been measured.
Date: November 1, 1982
Creator: Borden, P.G.; Gregory, P.E. & Moore, O.E.
Partner: UNT Libraries Government Documents Department

Optimized readout system for cooled optically stimulated luminescence

Description: Cooled Optically Stimulated Luminescence (COSL) in CaF{sub 2}:Mn is an ionizing radiation dosimetry method recently developed at the Pacific Northwest Laboratory (PNL). In this method CaF{sub 2}:Mn crystals irradiated by gamma radiation at room temperature are cooled to liquid nitrogen temperature (77K), stimulated by ultraviolet laser light at 326 nm, and allowed to warm to room temperature. Light emission proportional to the gamma exposure occurs as the TLD warms from liquid nitrogen temperature to room temperature. The new method is an example of a highly sensitive phototransfer technique which could form the basis for future radiation dosimetry applications. Measurements to date have shown high potential for measuring gamma exposures in the range of 10 {mu}R. The high sensitivity of the COSL technique is due in part to the larger quantum efficiency of radiative recombination at low temperatures and to the complete absence of the incandescent background associated with conventional thermoluminescent readout methods. Along with the potential for a system which is more sensitive than thermoluminescent readers, multiple COSL readouts can be performed with minimal reduction in the COSL intensity. The multiple readout capability can serve as a possible permanent dosimetry record, thus allowing the reanalysis of a questionable reading. In an attempt to optimize the sensitivity of the COSL method, a new readout system is being developed. 8 refs., 7 figs.
Date: September 1, 1990
Creator: Miller, S.D. & Eschbach, P.A.
Partner: UNT Libraries Government Documents Department

Soft x-ray resist characterization: Studies with a laser plasma x-ray source

Description: Little work has been performed to characterize the exposure sensitivity, contrast, and tone of candidate resists for photon energies between 100--300 eV, the range in which projection soft x-ray lithography will be developed. We report here the characterization of near-edge x-ray absorption fine structure (NEXAFS) spectra, exposure sensitivity, contrast, and post-exposure processing of selected polysilane resists at photon energies close to the Si L{sub 2,3} absorption edge (100 eV). We find absorption resonance features in the NEXAFS spectra which we assign to excitation into Si--Si and Si--C {sigma}* orbitals. Using monochromatized XUV exposures on the Si--Si {sigma}* resonance at 105 eV, followed by solvent dissolution development, we have measured the exposure sensitivity curves of these resists. We find sensitivities in the range of 600--3000 mJ/cm{sup 2} and contrasts in the range from 0.5--1.4, depending on the polysilane side chain. We have also performed exposure sensitivity measurements at 92 eV, below the edge. Sensitivity decreases slightly compared to 105 eV exposures and the saturation depth and contrast both increase, as expected. We find also that exposing resist films to oxygen after XUV exposure, but before development increases the sensitivity markedly. 7 figs.
Date: January 1, 1990
Creator: Kubiak, G.D.; Outka, D.A. (Sandia National Labs., Livermore, CA (USA)) & Zeigler, J.M. (Sandia National Labs., Albuquerque, NM (USA))
Partner: UNT Libraries Government Documents Department

A pulsed electron injector using a metal photocathode irradiated by an excimer laser

Description: The hot cathode of an electron gun is replaced by a metallic photocathode driven by an excimer laser. The current, current density, and emittance of the 500-kV electron beam produced by the photoelectron source are presented. In addition, the temperature of the photocathode is varied to study the possibility of a hybrid source.
Date: January 1, 1987
Creator: Kauppila, T.J.; Builta, L.A.; Crutcher, J.K.; Elliott, J.C. & Moir, D.C.
Partner: UNT Libraries Government Documents Department

Research on amorphous-silicon-based thin-film photovoltaic devices: Semiannual subcontract report, 1 July 1987--31 December 1987

Description: The objective of this work is to develop 13% (aperture area) efficient, 850-cm/sup 2/ four-terminal hybrid tandem submodules. The module design consists of a copper-indium-diselenide (CIS)-based bottom circuit and a semitransparent, thin-film silicon-hydrogen (TFS)-based top circuit. High-performance, semitransparent TFS devices and submodules were fabricated in which ZnO was used in the front and rear transparent conductors. High-performance CIS devices and submodules were also fabricated; however, the location and nature of the junction are not yet understood. Representative four-terminal hybrid tandem devices and submodules were fabricated from TFS and CIS component circuits. Optical coupling between the circuits was lower than expected, because of reflection losses at key interfaces. Efficiencies obtained for these devices and modules include 14.17% for a four-terminal, 4-cm/sup 2/ tandem cell and 12.3% for a four-terminal, tandem module. 7 refs., 90 figs.
Date: May 1, 1988
Creator: Bottenberg, W.; Mitchell, K. & Wieting, R.
Partner: UNT Libraries Government Documents Department

Silicon materials task of the Low-Cost Solar Array Project: Phase IV. Effects of impurities and processing on silicon solar cells. Twenty-first quarterly report, October-December 1980

Description: The overall objective of this program is to define the effects of impurities, various thermochemical processes, and any impurity-process interactions upon the performance of terrestrial solar cells. The results of the study form a basis for silicon producers, wafer manufacturers, and cell fabricators to develop appropriate cost-benefit relationships for the use of less pure, less costly solar grade silicon. Cr is highly mobile in silicon even at temperatures as low as 600/sup 0/C. Contrasting with earlier data for Mo, Ti, and V, Cr concentrations vary from place to place in polycrystalline silicon wafers and the electrically-active Cr concentration in the polysilicon is more than an order of magnitude smaller than would be projected from single crystal impurity data. We hypothesize that Cr diffuses during ingot cooldown after groth, preferentially segregates to grain boundaries and becomes electrically deactivated. Both Al and Au introduce deep levels when grown into silicon crystals. Accelerated aging data from Ni-contaminated silicon imply that no significant impurity-induced cell performance reduction should be expected over a twenty-year device lifetime. Combined electrical bias and thermal stressing of silicon solar cells containing Nb, Fe, Cu, Ti, Cr, and Ag, respectively produces no performance loss after 100 hour exposures up to 225/sup 0/C. Ti and V, but not Mo, can be gettered from polycrystalline silicon by POCl/sub 3/ or HCl at temperatures of 1000 and 1100/sup 0/C.
Date: January 30, 1981
Creator: Hopkins, R.H.; Hanes, M.H.; Davis, J.R.; Rohatgi, A.; Rai-Choudhury, P. & Mollenkopf, H.C.
Partner: UNT Libraries Government Documents Department

Observation of a charge limit for photocathode electron guns

Description: The Photocathode Electron Gun (PEG) at SLAC is required to produce bunch intensities of up to 10[sup 11] electrons within 2 ns (8 Amps). Operation of PEG has demonstrated a 'Charge Limit' phenomenon, whereby the charge that can be extracted from the gun with an intense laser beam saturates at significantly less than 10[sup 11] electrons (the expected Space Charge Limited' charge) when the photocathode Quantum Efficiency is low. We report studies of this Charge Limit phenomenon observed with a GaAs photocathode.
Date: December 1, 1992
Creator: Woods, M.; Clendenin, J.; Frisch, J.; Kulikov, A.; Saez, P.; Schultz, D. et al.
Partner: UNT Libraries Government Documents Department

Photoemission from Ag, Cu, and CsI

Description: Photoemission characteristics of three different cathodes, CsI, Ag film and Cu were investigated. CsI, upon irradiation by 213 nm, 10ps laser pulse yields a quantum efficiency of 4% at O.2[mu]J input energy. The saturation mechanism observed at higher input energies require further investigation. Ag film, upon irradiation by 630 nm, 300 fs laser emit prompt photoelectrons after absorbing 2 photons. There was no evidence of optical damage of the film up to 10[sup 11] W/cm[sup 2]. At low intensities, photoemission from Cu is a simple [nu]-e[sup [minus]] interaction, the nonlinearity of the process depending strongly on trace impurities. At higher intensities, there appears to be a change in the emission mechanism.
Date: June 1, 1992
Creator: Srinivasan-Rao, T.; Fischer, J. & Tsang, T.
Partner: UNT Libraries Government Documents Department