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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 883 records · Page 49
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Using hole injection layers for decreased metastability and higher performance in Cu(In,Ga)Se 2 devices

In this work, modifications to the buffer structure in Cu(In,Ga)Se 2 (CIGS) solar cells are examined in terms of power conversion efficiency and metastability. Varying amounts of thin hole-injecting layers are introduced at different locations in the CIGS/Zn(O,S) device structure. It is found that such layers simultaneously increase performance and decrease metastability. The most effective variant produces devices without metastability and with higher efficiency than the CdS-only controls. The most effective location for hole injection is found to be between the Zn(O,S) buffer and the transparent conductor. At this location, passivation of the CIGS surface is not a function of the hole injection layer, and thus a variety of materials with appropriate band-edge energies should achieve the same purpose.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Linker Length-Dependent Electron-Injection Dynamics of Trimesitylporphyrins on SnO 2 Films

Electron-injection dynamics of dye-sensitized photoelectrochemical cells depend on the length of the linker connecting the molecular photosensitizer to the metal oxide electron acceptor. However, systematic studies of the effect of chromophore–oxide distance are scarce. In this work, we present the synthesis, characterization, spectroscopy, and computational modeling of electron-injection dynamics from free-base trimesitylporphyrins with varying linker lengths into tin(IV) oxide (SnO 2 ). In each system, the porphyrin core and metal oxide film remain the same while only the linker binding the porphyrin to the carboxylate anchor group is varied. A length range spanning 8.5–17.2 Å is studied by employing phenylene, biphenylene, terphenylene, and benzanilide groups as the linker. We find a clear correlation between linker length and injection rates, providing insights that will be exploited in the optimization of dye-sensitized photoelectrochemical cells.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Harmonic and Subharmonic RF Injection Locking of THz Metasurface Quantum-Cascade VECSEL

Harmonic and subharmonic RF injection locking is demonstrated in a terahertz (THz) quantum-cascade vertical-external-cavity surface-emitting laser (QC-VECSEL). By tuning the RF injection frequency around integer multiples and submultiples of the cavity round-trip frequency, different harmonic and subharmonic orders can be excited in the same device. Modulation-dependent behavior of the device has been studied with recorded lasing spectral broadening and locking bandwidths in each case. In particular, harmonic injection locking results in the observation of harmonic spectra with bandwidths over 200 GHz. A semiclassical Maxwell-density matrix formalism has been applied to interpret QC-VECSEL dynamics, which aligns well with experimental observations.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2018

On the Relationship Between Fault Permeability Increases, Induced Stress Perturbation, and the Growth of Aseismic Slip During Fluid Injection

Fluid injections into the deep subsurface can, at times, generate earthquakes, but often, they only produce aseismic deformations. Here we analyze the influence of fault hydromechanical properties on the growth of injection-induced aseismic slip. Using hydromechanical modeling, we show how permeability enhancement in addition to the background stress and frictional weakening has an important effect on the pressure diffusion and slip growth during injection. We find that the more pronounced the fault permeability enhancement, the stronger is the growth of the aseismic slip zone. The effect of enhanced permeability is more pronounced when the fault is initially close to failure. Our results show that aseismic slip grows beyond the pressurized zone when the fault permeability increases, while slip remains behind the pressurized zone when permeability does not vary from its initial preslip value. Furthermore, fault permeability increases should be considered as complementary mechanism to current models of fluid-induced aseismic slip.

58 GEOSCIENCES↗
DOE OSTI2019

Impact of Anthropogenic Emission Injection Height Uncertainty on Global Sulfur Dioxide and Aerosol Distribution

Anthropogenic sulfur compounds play an important role in acid deposition, aerosol particle formation, and subsequent radiative forcing and human fine particulate exposure. There are substantial uncertainties in processes influencing sulfate and precursor distributions, however, that have not yet been resolved through comparisons with observations. We find here an underappreciated factor that has a large impact on model results: uncertain emission height. Global aerosol-climate model simulations indicate that the assumed effective anthropogenic emission height is very important to SO 2 near-surface concentrations and vertical profile. The global range of near-surface SO 2 concentration over land (ocean) due to uncertainty in industrial (international shipping) emission injection height is 81% (76%), relative to the average concentration. This sensitivity is much larger than the uncertainty of SO 2 emission rates. Black carbon and primary organic matter concentration and profiles are also sensitive to emission heights (53% over land and 28% over oceans). The impact of emission height uncertainty is larger in winter for land-based emissions, but larger in summer over the Northern Hemisphere ocean for shipping emissions. The variation in aerosol optical depth related to shipping emission injection heights is 11% over oceans, revealing the potential importance of injection height on aerosol forcing and climatic effects. The large impact on SO 2 concentrations can confound attempts to use surface, aircraft, and satellite observations to constrain the importance of other processes that govern sulfur compound distributions in the atmosphere. In conclusion, the influence of emission height on vertical SO 2 column also will impact the accuracy of satellite retrievals.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2012

Beam injection improvement for electron cyclotron resonance charge breeders

The injection of a 1+ beam into an electron cyclotron resonance (ECR) charge breeder is classically performed through a grounded tube placed on its axis at the injection side. This tube presents various disadvantages for the operation of an ECR charge breeder. First experiments without a grounded tube show a better use of the microwave power and a better charge breeding efficiency. The optical acceptance of the charge breeder without decelerating tube allows the injection of high intensity 1+ ion beams at high energy, allowing metals sputtering inside the ion source. The use of this method for refractory metallic ion beams production is evaluated.

43 PARTICLE ACCELERATORS↗
DOE OSTI2012

Optics of ion beams for the neutral beam injection system on HL-2A Tokamak

The ion beam optics for the neutral beam injection system on HL-2A Tokomak is studied by two- dimensional numerical simulation program firstly, where the emitting surface is taken at 100 Debye lengths from the plasma electrode. The mathematical formulation, computation techniques are described. Typical ion orbits, equipotential contours, and emittance diagram are shown. For a fixed geometry electrode, the effect of plasma density, plasma potential and plasma electron temperature on ion beam optics is examined, and the calculation reliability is confirmed by experimental results. In order to improve ion beam optics, the application of a small pre-acceleration voltage ({approx}100 V) between the plasma electrode and the arc discharge anode is reasonable, and a lower plasma electron temperature is desired. The results allow optimization of the ion beam optics in the neutral beam injection system on HL-2A Tokomak and provide guidelines for designing future neutral beam injection system on HL-2M Tokomak.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2013

Generation of 500 MeV-1 GeV energy electrons from laser wakefield acceleration via ionization induced injection using CO{sub 2} mixed in He

Laser wakefield acceleration of 500 MeV to 1 GeV electron bunches has been demonstrated using ionization injection in mixtures of 4% to 10% of CO{sub 2} in He. 80 TW laser pulses were propagated through 5 mm gas jet targets at electron densities of 0.4-1.5 Multiplication-Sign 10{sup 19}cm{sup -3}. Ionization injection led to lower density thresholds, a higher total electron charge, and an increased probability of producing electrons above 500 MeV in energy compared to self-injection in He gas alone. Electrons with GeV energies were also observed on a few shots and indicative of an additional energy enhancement mechanism.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2013

Injection and transport properties of fast electrons in ultraintense laser-solid interactions

Fast electron injection and transport in solid foils irradiated by sub-picosecond-duration laser pulses with peak intensity equal to 4 Multiplication-Sign 10{sup 20} W/cm{sup 2} is investigated experimentally and via 3D simulations. The simulations are performed using a hybrid-particle-in-cell (PIC) code for a range of fast electron beam injection conditions, with and without inclusion of self-generated resistive magnetic fields. The resulting fast electron beam transport properties are used in rear-surface plasma expansion calculations to compare with measurements of proton acceleration, as a function of target thickness. An injection half-angle of {approx}50 Degree-Sign -70 Degree-Sign is inferred, which is significantly larger than that derived from previous experiments under similar conditions.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Progress toward fully noninductive discharge operation in DIII-D using off-axis neutral beam injection

The initial experiments on off-axis neutral beam injection into high noninductive current fraction (f{sub NI}), high normalized pressure (β{sub N}) discharges in DIII-D [J. L. Luxon, Fusion Sci. Technol. 48, 828 (2005)] have demonstrated changes in the plasma profiles that increase the limits to plasma pressure from ideal low-n instabilities. The current profile is broadened and the minimum value of the safety factor (q{sub min}) can be maintained above 2 where the profile of the thermal component of the plasma pressure is found to be broader. The off-axis neutral beam injection results in a broadening of the fast-ion pressure profile. Confinement of the thermal component of the plasma is consistent with the IPB98(y,2) scaling, but global confinement with q{sub min}>2 is below the ITER-89P scaling, apparently as a result of enhanced transport of fast ions. A 0-D model is used to examine the parameter space for f{sub NI}=1 operation and project the requirements for high performance steady-state discharges. Fully noninductive solutions are found with 4<β{sub N}<5 and bootstrap current fraction near 0.5 for a weak shear safety factor profile. A 1-D model is used to show that a f{sub NI}=1 discharge at the top of this range of β{sub N} that is predicted stable to n=1, 2, and 3 ideal MHD instabilities is accessible through further broadening of the current and pressure profiles with off-axis neutral beam injection and electron cyclotron current drive.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2013

Investigation of hole injection enhancement by MoO{sub 3} buffer layer in organic light emitting diodes

An MoO{sub 3} buffer layer prepared by thermal evaporation as hole injection layer was investigated in organic light emitting diodes. The MoO{sub 3} film inserted between the anode and hole transport layer decreased the operating voltage and enhanced power efficiency. Introduction of 1 nm MoO{sub 3} film, which was found to be the optimum layer thickness, resulted in 45% increase in efficiency compared with traditional ITO anode. Results from atomic force microscopy and photoemission spectroscopy showed that smooth surface morphology and suitable energy level alignment of ITO/MoO{sub 3} interface facilitated hole injection and transport. The hole injection and transport mechanism at the ITO/MoO{sub 3} interface in thin and thick buffer layers were analyzed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

A wide variety of injection molding technologies is now applicable to small series and mass production

Micro plastic parts open new fields for application, e. g., to electronics, sensor technologies, optics, and medical engineering. Before micro parts can go to mass production, there is a strong need of having the possibility for testing different designs and materials including material combinations. Hence, flexible individual technical and technological solutions for processing are necessary. To manufacture high quality micro parts, a micro injection moulding machine named formicaPlast based on a two-step plunger injection technology was developed. Resulting from its design, the residence time and the accuracy problems for managing small shot volumes with reproducible high accuracy are uncompromisingly solved. Due to their simple geometry possessing smooth transitions and non adherent inner surfaces, the plunger units allow to process 'all' thermoplastics from polyolefines to high performance polymers, optical clear polymers, thermally sensitive bioresorbables, highly filled systems (the so-called powder injection molding PIM), and liquid silicon rubber (LSR, here with a special kit). The applied platform strategy in the 1K and 2K version allows integrating automation for assembling, handling and packaging. A perpendicular arrangement allows encapsulation of inserts, also partially, and integration of this machine into process chains. Considering a wide variety of different parts consisting of different materials, the high potential of the technology is demonstrated. Based on challenging industrial parts from electronic applications (2K micro MID and bump mat, where both are highly structured parts), the technological solutions are presented in more detail.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Domain wall displacement by remote spin-current injection

We demonstrate numerically the ability to displace a magnetic domain wall (DW) by remote spin current injection. We consider a long and narrow magnetic nanostripe with a single DW. The spin-polarized current is injected perpendicularly to the film plane through a small nanocontact which is located at certain distance from the DW initial position. We show that the DW motion can be initiated not only by conventional spin-transfer torque but also by indirect spin-torque, created by remote spin-current injection and then transferred to the DW by the exchange-spring mechanism. An analytical description of this effect is proposed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Fast electron spin resonance controlled manipulation of spin injection into quantum dots

In our spin-injection light-emitting diodes, electrons are spin-polarized in a semimagnetic ZnMnSe spin aligner and then injected into InGaAs quantum dots. The resulting electron spin state can be read out by measuring the circular polarization state of the emitted light. Here, we resonantly excite the Mn 3d electron spin system with microwave pulses and perform time-resolved measurements of the spin dynamics. We find that we are able to control the spin polarization of the injected electrons on a microsecond timescale. This electron spin resonance induced spin control could be one of the ingredients required to utilize the quantum dot electrons or the Mn spins as qubits.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Electrical spin injection into InGaAs/GaAs quantum wells: A comparison between MgO tunnel barriers grown by sputtering and molecular beam epitaxy methods

An efficient electrical spin injection into an InGaAs/GaAs quantum well light emitting diode is demonstrated thanks to a CoFeB/MgO spin injector. The textured MgO tunnel barrier is fabricated by two different techniques: sputtering and molecular beam epitaxy. The maximal spin injection efficiency is comparable for both methods. Additionally, the effect of annealing is also investigated for the two types of samples. Both samples show the same trend: an increase of the electroluminescence circular polarization (P{sub c}) with the increase of annealing temperature, followed by a saturation of P{sub c} beyond 350 °C annealing. Since the increase of P{sub c} starts well below the crystallization temperature of the full CoFeB bulk layer, this trend could be mainly due to an improvement of chemical structure at the top CoFeB/MgO interface. This study reveals that the control of CoFeB/MgO interface is essential for an optimal spin injection into semiconductor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Rare-earth neutral metal injection into an electron beam ion trap plasma

We have designed and implemented a neutral metal vapor injector on the SuperEBIT high-energy electron beam ion trap at the Lawrence Livermore National Laboratory. A horizontally directed vapor of a europium metal is created using a thermal evaporation technique. The metal vapor is then spatially collimated prior to injection into the trap. The source's form and quantity constraints are significantly reduced making plasmas out of metal with vapor pressures ≤10{sup −7} Torr at ≥1000 °C more obtainable. A long pulsed or constant feed metal vapor injection method adds new flexibility by varying the timing of injection and rate of material being introduced into the trap.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2014

Efficient room temperature spin-Hall injection across an oxide barrier

Spin Hall injection is demonstrated at room temperature using Pt metal and AlO{sub x} barriers. A substantial spin accumulation, comparable to that of a magnetic spin injection, is transferred into a mesoscopic Cu wire from an adjacent Pt wire across an AlO{sub x} barrier. The Pt spin Hall angle is 0.030 ± 0.007 when assuming a Pt spin diffusion length λ{sub pt} > 6 nm and 0.09 ± 0.02 when assuming λ{sub pt} = 2 nm. Nearly (66 ± 6)% of the spin accumulation on the Pt surface is transferred into the Cu across the AlO{sub x}, enabling an efficient spin Hall injection scheme.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2014

Effect of the helicity injection rate and the Lundquist number on spheromak sustainment

The dynamics of the magnetic relaxation process during the sustainment of spheromak configurations at different helicity injection rates is studied. The three-dimensional activity is recovered using time-dependent resistive magnetohydrodynamic simulations. A cylindrical flux conserver with concentric electrodes is used to model configurations driven by a magnetized coaxial gun. Magnetic helicity is injected by tangential boundary flows. Different regimes of sustainment are identified and characterized in terms of the safety factor profile. The spatial and temporal behavior of fluctuations is described. The dynamo action is shown to be in close agreement with existing experimental data. These results are relevant to the design and operation of helicity injected devices, as well as to basic understanding of the plasma relaxation mechanism in quasi-steady state.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗