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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 1,081 records · Page 60
All sourcesNASA NTRSDOE OSTI
NASA NTRS1998

Effects of Microheterogeneity in Hen Egg-White Lysozyme Crystallization

In earlier sodium dodecylsulfate polyacylamide gel electrophoresis (SDS-PAGE) studies it has been found that commonly utilized commercial hen egg-white lysozyme (HEWL) preparations contained 0.2-0.4 mol% covalently bound dimers. Here it is shown, using high-performance capillary electrophoresis (HPCE), that HEWL contains, in addition, two differently charged monomers in comparable amounts. To explore the origin of these microheterogeneous contaminants, purified HEWL (PHEWL) has been oxidized with hydrogen peroxide (0.0026-0.88 M) at various pH levels between 4.5 and 12.0. Optical densitometry of oxidized PHEWL (OHEWL) bands in SDS PAGE gels shows that hydrogen peroxide at 0.88 M in acetate buffer pH 4.5 increased the amount of dimers about sixfold over that in commercial HEWL. OHEWL had, in addition to one of the two monomer forms found in HEWL and PHEWL, three other differently charged monomer forms, each of them representing about 25% of the preparation. SDS-PAGE analysis of OHEWL yielded two closely spaced dimer bands with M(sub r) = 28 000 and 27 500. In addition, larger HEWL oligomers with M, = 1.7 million and 320 000 were detected by gel-filtration fast protein liquid chromatography with multiangle laser light scattering detection. Non-dissociating PAGE in large pore size gels at pH 4.5 confirmed the presence of these large oligomers in HEWL and OHEWL. Increased microheterogeneity resulted in substantial effects on crystal growth and nucleation rate. On addition of 10 microgram(exp -1) mg ml(exp -1) OHEWL to 32 mg ml(exp -1) HEWL crystallizing solutions, both the number and size of forming crystals decreased roughly proportionally to the concentration of the added microheterogeneity. The same effect was observed in HEWL solutions on addition of 0.03-9,3 M Hydrogen peroxide. Repartioning of the dimer during crystallzation aat various temperatures between 277 and 293 K was analyzed by SDS-PAGE. The crystals contained <= 25 % weight by volume of the oligomers in the solution, with no apparent temperature dependence of the repartioning.

Thomas, B. R.↗
DOE OSTI2025

Encapsulation of Monolayer 2D Materials Using Kinetic Energy-Controlled Pulsed Laser Deposition

The integration of monolayer (ML) two-dimensional (2D) materials into next-generation microelectronics, optoelectronics, and sensors is hindered by their sensitivity to environmental exposure. Deposition of additional layers for encapsulation or growth on ML 2D materials by versatile but energetic plasma techniques such as pulsed laser deposition (PLD) has not been considered at the monolayer level because of potential damage caused by hyperthermal species with kinetic energies (KEs) exceeding the threshold displacement energy (TDE) of the ML. Here, we describe a general strategy to understand and mitigate damage during PLD by reducing the incident KE of ablated species below the TDE of the 2D monolayer using background gas collisions. Ion flux diagnostics, combined with in situ Raman spectroscopy of monolayer graphene during PLD of amorphous boron nitride (a-BN) as a dielectric encapsulation layer, show that damage is primarily correlated with fast ions that penetrate the background gas in accordance with Beer’s Law and are often overlooked in ICCD imaging due to the dominance of the bright, delayed plasma luminescence. Significantly, if fast ions are eliminated and a ∼2 nm-thick a-BN layer is “soft landed”, the monolayer graphene is effectively protected from damage by high KE species in the boron nitride plasma plume. Deposited a-BN films display a characteristic dielectric constant of 3.6 at 100 kHz and tunable charge injection properties. Our results enable PLD as a viable option for encapsulation and thin film growth onto ML 2D materials, with implications for both fundamental research and device integration.

2D materials↗
DOE OSTI2022

Full-potential KKR within the removed-sphere method: A practical and accurate solution to the Poisson equation

Here an efficient and accurate generalization of the removed-sphere method (RSM) to solve the Poisson equation for total charge density in a solid with space-filling convex Voronoi polyhedra (VPs) and any symmetry is presented. The generalized RSM avoids the use of multipoles and VP shape functions for cellular integrals, which have associated ill-convergent large, double-internal L sums in spherical-harmonic expansions, so that fast convergence in single-L sums is reached. Our RSM adopts full Ewald formulation to work for all configurations or when symmetry breaking occurs, such as for atomic displacements or elastic constant calculations. The structure-dependent coefficients A L that define RSM can be calculated once for a fixed structure and speed up the whole self-consistent-field procedure. The accuracy and rapid convergence properties are confirmed using two analytic models, including the Coulomb potential and energy. We then implement the full-potential RSM using the Green's function Korringa-Kohn-Rostoker (KKR) method for real applications and compare the results with other first-principle methods and experimental data, showing that they are equally as accurate.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
NASA NTRS2016

The IOAG Recommendations on Spacecraft Emergency Cross Support

In 2014, the Inter-agency Operations Advisory Group (IOAG) chartered a multi-agency team effort to study how to best handle spacecraft emergency as part of cross support among network assets. The original intent is to put in place for the first time a process and guidelines to make emergency support as part of a permanent cross-support capability between space agencies. From the perspective of space communications service providers, a few key issues, common to all agencies, concerning the Spacecraft Emergency Cross Support (SECS) have been explored. They are: context of emergency support, provision of emergency support under a cross-support agreement, provision of emergency support with no cross-support agreement, legal and liability issues, response time, support priority, services provided, sustaining emergency support capabilities, and charge for the support. The positions of the various participating agencies with respect to these issues have been collected, analyzed, and finally harmonized to form the recommended IOAG positions. A central challenge most communications service providers are facing is that since the spacecraft emergency is an unplanned critical event, it typically requires fast response to the emergency call, hence lacking an international standard process for the operational interfaces seems to exacerbate the difficulty in providing SECS. For reducing the response time, i.e. from the time of accepting a request for SECS to the readiness for support, it is recommended that a “cross-support emergency system” be established by IOAG member agencies. Along with it, the IOAG core services, just-in-time ground communications line, cross support service management (CSSM), and standard operations procedures (SOP) for operational interfaces form the basic foundation of the “cross support emergency system”. Of the above, new to the cross support conducted thus far in the IOAG community is the concept of the SOP specifically for the interfaces between the service provider and service user during the SECS. Use cases, salient features, and definition of the key operational activities/tasks relevant to the interfaces are addressed by the effort. Underpinning such a system is the availability of the RF license granted by the local authority, at national and/or regional level, for a given ground station to communicate with and track the spacecraft in emergency mode at the uplink and downlink frequencies assigned to that spacecraft. That means it is critical for the IOAG member agencies to obtain a priori all-band licenses (for the entire X-band or S-band) for some, if not all, of their ground stations that are most capable of or likely to provide SECS. It is also recommended that certain prior arrangements be made with the relevant local licensing authorities for a process that will allow expedited authorization to transmit/receive signals to/from the declared spacecraft over the declared ground stations specifically and solely for the emergency case. Our analysis of the SECS has also uncovered a few fundamental programmatic issues. Recognizing any IOAG positions reached on these issues do not necessarily lead to any binding authority, it is recommended that they, along with those key attributes of the cross support emergency system, be explicitly stated as multi-agency guidelines to guide the implementation and provision of the SECS. The paper will present the results of the working group on Spacecraft Emergency Cross Support and, in particular, its findings, products and recommendations. It will also identify the next steps of this work that may include the production of some international standards as an extension of this work, or the process to make this emergency system usable by other spacecraft operators beyond the space agencies.

Tai, Wallace S.↗
NASA NTRS2016

The IOAG Recommendations on Spacecraft Emergency Cross Support

In 2014, the Inter-agency Operations Advisory Group (IOAG) chartered a multi-agency team effort to study how to best handle spacecraft emergency as part of cross support among network assets. The original intent is to put in place for the first time a process and guidelines to make emergency support as part of a permanent cross-support capability between space agencies. From the perspective of space communications service providers, a few key issues, common to all agencies, concerning the Spacecraft Emergency Cross Support (SECS) have been explored. They are: context of emergency support, provision of emergency support under a cross-support agreement, provision of emergency support with no cross-support agreement, legal and liability issues, response time, support priority, services provided, sustaining emergency support capabilities, and charge for the support. The positions of the various participating agencies with respect to these issues have been collected, analyzed, and finally harmonized to form the recommended IOAG positions. A central challenge most communications service providers are facing is that since the spacecraft emergency is an unplanned critical event, it typically requires fast response to the emergency call, hence lacking an international standard process for the operational interfaces seems to exacerbate the difficulty in providing SECS. For reducing the response time, i.e. from the time of accepting a request for SECS to the readiness for support, it is recommended that a “cross-support emergency system” be established by IOAG member agencies. Along with it, the IOAG core services, just-in-time ground communications line, cross support service management (CSSM), and standard operations procedures (SOP) for operational interfaces form the basic foundation of the “cross support emergency system”. Of the above, new to the cross support conducted thus far in the IOAG community is the concept of the SOP specifically for the interfaces between the service provider and service user during the SECS. Use cases, salient features, and definition of the key operational activities/tasks relevant to the interfaces are addressed by the effort. Underpinning such a system is the availability of the RF license granted by the local authority, at national and/or regional level, for a given ground station to communicate with and track the spacecraft in emergency mode at the uplink and downlink frequencies assigned to that spacecraft. That means it is critical for the IOAG member agencies to obtain a priori all-band licenses (for the entire X-band or S-band) for some, if not all, of their ground stations that are most capable of or likely to provide SECS. It is also recommended that certain prior arrangements be made with the relevant local licensing authorities for a process that will allow expedited authorization to transmit/receive signals to/from the declared spacecraft over the declared ground stations specifically and solely for the emergency case. Our analysis of the SECS has also uncovered a few fundamental programmatic issues. Recognizing any IOAG positions reached on these issues do not necessarily lead to any binding authority, it is recommended that they, along with those key attributes of the cross support emergency system, be explicitly stated as multi-agency guidelines to guide the implementation and provision of the SECS. The paper will present the results of the working group on Spacecraft Emergency Cross Support and, in particular, its findings, products and recommendations. It will also identify the next steps of this work that may include the production of some international standards as an extension of this work, or the process to make this emergency system usable by other spacecraft operators beyond the space agencies.

Tai, Wallace S.↗
DOE OSTI2025

Status of the Mu2e experiment

The Mu2e experiment at Fermilab searches for the coherent, neutrino-less conversion of a μ − to e − in the Coulomb field of Al nuclei, that represents one of the cleanest Charged Lepton Flavor Violating (CLFV) processes for exploring Beyond the Standard Model (BSM) physics. Mu2e aims to improve previous sensitivity by four orders of magnitude, with a distinctive signature provided by identifying mono-energetic electrons with energy slightly below the muon rest mass. To reach this goal, the experiment will use the highest intensity pulsed muon beam in the world, with up to 6 × 1 0 9 stopped muons/sec. This is achieved using the Fermilab proton beam and the design and realization of a unique 25 m long superconducting solenoidal system. The high beam intensity relies upon minimizing beam losses in the slow extraction region, indicating an opportunity of using bent crystals for shadowing. A high-resolution straw tracker and a fast CsI crystal calorimeter identify the conversion electron. Both detectors are inserted behind the Stopping Target in the last solenoid section. A Cosmic Ray Veto covers a large part of the solenoids to suppress background produced by cosmic rays. In this paper, we report the details of the experimental layout, the construction status of the magnetic system and detectors, and a short description of the simulation and realization of the bent crystals. Performing crystal channeling in front of the first slow extraction septa will allow beam shadowing and largely reduce beam losses. •Charge Lepton Flavor Violation processes: μ − → e − conversion.•Large Superconducting Solenoid system.•High-Intensity beams•High precision detectors.•Crystal channeling.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

All-Solid-State Lithium–Sulfur Batteries Enhanced by Redox Mediators

We report redox mediators (RMs) play a vital role in some liquid electrolyte-based electrochemical energy storage systems. However, the concept of redox mediator in solid-state batteries remains unexplored. Here, we selected a group of RM candidates and investigated their behaviors and roles in all-solid-state lithium-sulfur batteries (ASSLSBs). The soluble-type quinone-based RM (AQT) shows the most favorable redox potential and the best redox reversibility that functions well for lithium sulfide (Li 2 S) oxidation in solid polymer electrolytes. Accordingly, Li 2 S cathodes with AQT RMs present a significantly reduced energy barrier (average oxidation potential of 2.4 V) during initial charging at 0.1 C at 60 °C and the following discharge capacity of 1133 mAh g s -1 . Using operando sulfur K-edge X-ray absorption spectroscopy, we directly tracked the sulfur speciation in ASSLSBs and proved that the solid-polysulfide-solid reaction of Li 2 S cathodes with RMs facilitated Li 2 S oxidation. In contrast, for bare Li 2 S cathodes, the solid-solid Li 2 S-sulfur direct conversion in the first charge cycle results in a high energy barrier for activation (charge to ~4 V) and low sulfur utilization. The Li 2 S@AQT cell demonstrates superior cycling stability (average Coulombic efficiency 98.9% for 150 cycles) and rate capability owing to the effective AQT-enhanced Li-S reaction kinetics. This work reveals the evolution of sulfur species in ASSLSBs and realizes the fast Li-S reaction kinetics by designing an effective sulfur speciation pathway

25 ENERGY STORAGE↗
DOE OSTI2025

Revealing the electronic structure of the current-induced metastable state in 1T-TaS 2

Among the key features for next-generation memory devices is the need for high-contrast switching between metallic and insulating states with fast switching speed and long lifetime. However, materials exhibiting such properties are rare, and their electronic structure is often poorly understood. Here, by combining state-of-the-art devices with angle-resolved photoemission spectroscopy, we study the emergence of a metastable metallic state from the insulating ground state in the charge-density wave (CDW) material 1T-TaS 2 after applying short current pulses. Analysis of the electronic structure suggests a picture in which 1T-TaS 2 transforms from a band insulator in the commensurate CDW ground state to a correlated metal in the metastable state. Moreover, the optically induced metastable state reveals a strong similarity to the current-induced one. This work provides an extensive characterization of metastable order in 1T-TaS 2 and proves how studying electronic properties under in-operando conditions is a critical step for next-generation devices.

Huber, Maximilian [Lawrence Berkeley National Labo↗
DOE OSTI2022

Mechanism for the Efficient Homogeneous Nucleation of Ice in a Weakly Ionized, Ultracold Plasma

Abstract It is proposed that the rapid observed homogeneous nucleation of ice dust in a cold, weakly ionized plasma depends on the formation of hydroxide (OH − ) by fast electrons impacting water molecules. These OH − ions attract neutral water molecules because of the high dipole moment of the water molecules and so hydrates of the form (OH) − (H 2 O) n are formed. The hydrates continuously grow in the cold environment to become macroscopic ice grains. These ice grains are negatively charged as a result of electron impact and so continue to attract water molecules. Because hydroxide is a negative ion, unlike positive ions, it does not suffer recombination loss from collision with plasma electrons. Recombination with positive ions is minimal because positive ions are few in number (weak ionization) and slow-moving as result of being in thermal equilibrium with the cold background gas.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

Photorefractive materials for optical storage and display

Real-time data storage and processing using optical techniques have been considered in recent years. Of particular interest are photosensitive electro-optic crystals which permit volume storage in the form of phase holograms, by means of a charge transfer process. A survey of the state of the art of such holographic memories is presented. The physical mechanism responsible for the formation of phase holograms in such crystals is discussed. Attention is focused on various aspects of materials characterization, development and utilization. Experimental reversible holographic read-write memory systems with fast random access and high storage capacity employing this new class of photosensitive materials have already been demonstrated.

Shah, R. R.↗
NASA NTRS2018

Electrodynamic Dust Shield (EDS) Preparation for MISSE-11 Launch

The dusty surfaces of the Moon, Mars, and various asteroids present a significant challenge to NASA’s manned and unmanned space exploration efforts. The fine, electrostatically charged dust is difficult to remove and has resulted in vision obscuration, false instrument readings, contamination, elevated temperatures, performance reduction, and equipment failure. To alleviate these problems, NASA KSC’s Electrostatics and Surface Physics Laboratory (ESPL) is developing active dust mitigation systems for solar system exploration and in situ resource utilization (ISRU). Part of KSC’s Swamp Works system, the lab emphasizes fast-paced, hands-on, cost-effective, and collaborative innovation. The Electrodynamic Dust Shield (EDS) is an ESPL technology being developed to prevent dust accumulation on space components. It consists of a dielectric substrate embedded with parallel electrodes which, when applied with high voltage out-of-phase waveforms, produce a traveling electric field wave that scatters dust particles from its surface via dielectrophoretic and electrostatic forces. The EDS is currently fully functional and has been tested for scalability and endurance in reduced gravity/pressure flight. Next, it will be part of the May 2019 Materials International Space Station Experiment-11 (MISSE-11) payload, which will test small shield samples for performance durability with exposure to the harsh space environment. The summer objective was to test EDS functionality before active and passive dust shield samples launch on MISSE-11, in order to screen for good flight/control samples as well as to compare pre-flight and post-flight clearing efficiencies. I imaged glass and Kapton shields of 2-phase and 3-phase electrode configurations with the Keyence VHX-5000 digital microscope to check for damage before and after all testing for a qualitative pre-flight baseline; helped with vacuum testing of high-voltage shield breakdown; assembled shields and wires using Electrobond 004 silver epoxy; and helped with vacuum and cryogenic dust clearance testing of assembled EDS systems. I learned CAD (computer-aided design) and 3D printing skills to create parts for a shaker table/motor assembly, which will allow for repeatable experiments by evening out EDS dust distribution in a consistent manner prior to dust scattering testing. I will also be improving the interfacing with Alpha Space’s prototype Data Communications Unit (DCU), a payload component to control power to the EDS and store data, by mapping the DCU structure upon power-up and writing shell scripts to improve various processes. Finally, I also CADed and 3D-printed plastic supports for three different geometries of the Electrostatic Precipitator (ESP), a project that aims to use high voltage electrodes to charge and filter out dust from the Martian atmosphere drawn for ISRU devices. This work on dust mitigation technologies will help to support future robotic and human space exploration missions, including NASA’s Journey to Mars; the EDS has especially significant applications to spacecraft solar panels, thermal radiators, viewports, and astronaut visors. This opportunity has also allowed me to become more familiar with various lab equipment and hardware testing, develop key modeling skills in SolidWorks, explore past and present components critical to America’s space program, work with inspiring peers and mentors, and ascertain my dream of working permanently for NASA.

space↗
DOE OSTI2020

Fast and stable deep-learning predictions of material properties for solid solution alloys

We present a novel deep learning (DL) approach to produce highly accurate predictions of macroscopic physical properties of solid solution binary alloys and magnetic systems. The major idea is to make use of the correlations between different physical properties in alloy systems to improve the prediction accuracy of neural network (NN) models. We use multitasking NN models to simultaneously predict the total energy, charge density and magnetic moment. These physical properties mutually serve as constraints during the training of the multitasking NN, resulting in more reliable DL models because multiple physics properties are correctly learned by a single model. Two binary alloys, copper–gold (CuAu) and iron–platinum (FePt), were studied. Our results show that once the multitasking NN's are trained, they can estimate the material properties for a specific configuration hundreds of times faster than first-principles density functional theory calculations while retaining comparable accuracy. We used a simple measure based on the root-mean-squared errors to quantify the quality of the NN models, and found that the inclusion of charge density and magnetic moment as physical constraints leads to more stable models that exhibit improved accuracy and reduced uncertainty for the energy predictions.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2022

MZA: A Data Conversion Tool to Facilitate Software Development and Artificial Intelligence Research in Multidimensional Mass Spectrometry

Modern mass spectrometry-based workflows employing hybrid instrumentation and orthogonal separations collect multidimensional data, potentially allowing deeper understanding in omics studies through adoption of artificial intelligence methods. However, the large volume of these rich data challenges existing data storage and access technologies, therefore precluding informatics advancements. Here we present MZA™ (pronounced m-za), the mass-to-charge (m/z) generic data storage and access tool designed to facilitate software development and artificial intelligence research in multidimensional mass spectrometry measurements. Composed by a data conversion tool and a simple file structure based on the HDF5 format, MZA provides easy, cross-platform and efficient programmatic access to raw MS-data, enabling fast development of new tools in data science programming languages such as Python and R. The software executable and example Python and R scripts are freely available at https://github.com/PNNL-m-q/mza.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2022

Control of Structural Hydrophobicity and Cation Solvation on Interlayer Water Transport during Clay Dehydration

Swelling clay hydration/dehydration is important to many environmental and industrial processes. Experimental studies usually probe equilibrium hydration states in an averaged manner and thus cannot capture the fast water transport and structural change in interlayers during hydration/dehydration. Using molecular simulations and thermogravimetric analyses, we observe a two-stage dehydration process. The first stage is controlled by evaporation at the edges: water molecules near hydrophobic sites and the first few water molecules of the hydration shell of cations move fast to particle edges for evaporation. The second stage is controlled by slow desorption of the last 1–2 water molecules from the cations and slow transport through the interlayers. The two-stage dehydration is strongly coupled with interlayer collapse and the coordination number changes of cations, all of which depend on layer charge distribution. Furthermore, this mechanistic interpretation of clay dehydration can be key to the coupled chemomechanical behavior in natural/engineered barriers.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Construction status of the Mu2e crystal calorimeter

The Mu2e experiment at Fermilab will search for the charged-lepton flavor violating neutrino-less conversion of a negative muon into an electron in the field of an aluminum nucleus. The Mu2e detector is composed of a tracker, an electromagnetic calorimeter and an external veto for cosmic rays. The calorimeter plays an important role in providing excellent particle identification capabilities and a fast online trigger filter, while aiding the track reconstruction capabilities. Calorimeter requirements are to provide a large acceptance for 0~10 MeV electrons and reach: i) a time resolution better than 0.5 ns; ii) an energy resolution better than 10%; and iii) a position resolution of 1 cm. The calorimeter consists of two disks, each one made of 674 pure CsI crystals. Each crystal is readout by two large area 2×3 arrays of UV-extended SiPMs of 6×6 mm2 dimensions. A large scale prototype (Module-0) has been tested at an electron beam. We report here the tests done to finalize the calorimeter design, the results obtained with Module-0 and the status of production. At this time, the performance characteristics of 85% of the crystals and all of the SiPMs have been measured. The calorimeter engineering drawings have been completed and the large mechanical components are under fabrication. Analog and digital electronics have been prototyped and tested with irradiation dose. Their serial production is being organized. The calorimeter assembly phase is planned for mid-2020.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Secured Reserve Scheduling of Pumped-Storage Hydropower Plants in ISO Day-ahead Market

Due to the fast response ability and high ramping rates, pumped-storage hydropower (PSH) plants are playing an increasingly critical role in mitigating power generation fluctuations induced by the growing proliferation of renewable energy resources. However, because they are energy-limited resources, actual reserve deployment from PSHs would cause the deviation of state-of-charge (SOC) from the scheduled value, which, once accumulated over time, could induce potential violations on SOC limits and cause non-dispatchability of PSHs. In recognizing this potential issue, it can become important to securing the reserve schedule of PSHs and other energy limited resources preventively in the day-ahead market clearing. To ensure reserve dispatchability of PSHs despite SOC deviations, this paper proposes the reserve secure constraints, which are cast as a distributionally robust chance-constrained formulation by judiciously introducing random parameters to describe deployment ratios of scheduled regulation reserve from PSHs. Furthermore, these constraints are converted into tractable second-order cone constraints, and further approximated as linear constraints to be compatible with the current ISO day-ahead market clearing model. A modified IEEE 118-bus system with multiple PSHs is adopted to verify the proposed approach.

13 HYDRO ENERGY↗
NASA NTRS2001

Novel High Efficient Organic Photovoltaic Materials

In man's mission to the outer space or a remote site, the most abundant, renewable, nonpolluting, and unlimited external energy source is light. Photovoltaic (PV) materials can convert light into electrical power. In order to generate appreciable electrical power in space or on the Earth, it is necessary to collect sunlight from large areas due to the low density of sunlight, and this would be very costly using current commercially available inorganic solar cells. Future organic or polymer based solar cells seemed very attractive due to several reasons. These include lightweight, flexible shape, ultra-fast optoelectronic response time (this also makes organic PV materials attractive for developing ultra-fast photo detectors), tunability of energy band-gaps via molecular design, versatile materials synthesis and device fabrication schemes, and much lower cost on large-scale industrial production. It has been predicted that nano-phase separated block copolymer systems containing electron rich donor blocks and electron deficient acceptor blocks will facilitate the charge separation and migration due to improved electronic ultrastructure and morphology in comparison to current polymer composite photovoltaic system. This presentation will describe our recent progress in the design, synthesis and characterization of a novel donor-bridge-acceptor block copolymer system for potential high-efficient organic optoelectronic applications. Specifically, the donor block contains an electron donating alkyloxy derivatized polyphenylenevinylene, the acceptor block contains an electron withdrawing alkyl-sulfone derivatized polyphenylenevinylene, and the bridge block contains an electronically neutral non-conjugated aliphatic hydrocarbon chain. The key synthetic strategy includes the synthesis of each individual block first, then couple the blocks together. While the donor block stabilizes the holes, the acceptor block stabilizes the electrons. The bridge block is designed to hinder the electron-hole recombination. Thus, improved charge separation is expected. In addition, charge migration will also be facilitated due to the expected nano-phase separated and highly ordered block copolymer ultrastructural. The combination of all these factors will result in significant overall enhancement of photovoltaic power conversion efficiency.

Sun, Sam↗
NASA NTRS2018

Production of Negative Hydrogen Ions Within the MMS Fast Plasma Investigation Due to Solar Wind Bombardment

The particle data delivered by the Fast Plasma Investigation instrument aboard National Aeronautics and Space Administration's Magnetospheric Multiscale (MMS) mission allow for exceptionally high-resolution examination of the electron and ion phase space in the near-Earth plasma environment. It is necessary to identify populations which originate from instrumental effects. Using Fast Plasma Investigation's Dual Electron Spectrometers, we isolate a high-energy (approximately kiloelectron volt) beam, present while the spacecraft are in the solar wind, which exhibits an azimuthal drift with period associated with the spacecraft spin. We show that this population is consistent with negative hydrogen ions H− generated by a double charge exchange interaction between the incident solar wind H+ ions and the metallic surfaces within the instrument. This interaction is likely to occur at the deflector plates close to the instrument aperture. The H− density is shown to be approximately 0.2-0.4% of the solar wind ion density, and the energy of the negative ion population is shown to be 70% of the incident solar wind energy. These negative ions may introduce errors in electron velocity moments on the order of 0.2-0.4% of the solar wind velocity and significantly higher errors in the electron temperature.

Magnetospheric Multiscale↗