Performance of a ten-stage electrostatic depressed collector for klystrons
Klystron power conversion efficiency augmentation by electrostatic depressed collector design, presenting performance prediction calculation method
Mihran, T. G.↗
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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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Experimental investigations of a uranium plasma pertinent to a self-sustaining plasma source
The research is pertinent to the realization of a self-sustained fissioning plasma for applications such as nuclear propulsion, closed cycle MHD power generation using a plasma core reactor, and heat engines such as the nuclear piston engine, as well as the direct conversion of fission energy into optical radiation (nuclear pumped lasers). Diagnostic measurement methods and experimental devices simulating plasma core reactor conditions are discussed. Studies on the following topics are considered: (1) ballistic piston compressor (U-235); (2) high pressure uranium plasma (natural uranium); (3) sliding spark discharge (natural uranium); (4) fission fragment interaction (He-3 and U-235); and (5) nuclear pumped lasers (He-3 and U-235).
Schneider, R. T.↗
Study of the Staebler-Wronski degradation effect in a-Si:H based p-i-n solar cell
Conversion of solar energy into electricity using environmentally safe and clean photovoltaic methods to supplement the ever increasing energy needs has been a cherished goal of many scientists and engineers around the world. Photovoltaic solar cells on the other hand, have been the power source for satellites ever since their introduction in the early sixties. For widespread terrestrial applications, however, the cost of photovoltaic systems must be reduced considerably. Much progress has been made in the recent past towards developing economically viable terrestrial systems, and the future looks highly promising. Thin film solar cells offer cost reductions mainly from their low processing cost, low material cost, and choice of low cost substrates. These are also very attractive for space applications because of their high power densities (power produced per kilogram of solar cell pay load) and high radiation resistance. Amorphous silicon based solar cells are amongst the top candidates for economically viable terrestrial and space based power generation. Despite very low federal funding during the eighties, amorphous silicon solar cell efficiencies have continually been improved - from a low 3 percent to over 13 percent now. Further improvements have been made by the use of multi-junction tandem solar cells. Efficiencies close to 15 percent have been achieved in several labs. In order to be competitive with fossil fuel generated electricity, it is believed that module efficiency of 15 percent or cell efficiency of 20 percent is required. Thus, further improvements in cell performance is imperative. One major problem that was discovered almost 15 years ago in amorphous silicon devices is the well known Staebler-Wronski Effect. Efficiency of amorphous silicon solar cells was found to degrade upon exposure to sunlight. Until now their is no consensus among the scientists on the mechanism for this degradation. Efficiency may degrade anywhere from 10 percent to almost 50 percent within the first few months of operation. In order to improve solar cell efficiencies, it is clear that the cause or causes of such degradation must be found and the processing conditions altered to minimize the loss in efficiency. This project was initiated in 1987 to investigate a possible link between metallic impurities, in particular, Ag, and this degradation. Such a link was established by one of the NASA scientists for the light induced degradation of n+/p crystalline silicon solar cells.
Naseem, H. A.↗
Local Measurement of Tropospheric HO(x)
In March of 1992 a workshop sponsored by NASA and NSF was held at SRI International to assess the current ability to measure atmospheric OH and HO2. The measurement techniques reviewed during the workshop for detection of OH included five laser-induced fluorescence schemes, five laser-based adsorption techniques, and four non-laser methods. Six instruments or instrument concepts for HO2 detection, including chemical amplification, conversion to OH with subsequent OH detection, or direct spectroscopic detection of the HO2 were also discussed. The conclusions from the workshop identify several measurement techniques for OH and HO2 that are ready for field tests. These have the ability to measure the radicals with sufficient sensitivity and accuracy to form meaningful comparison with atmospheric model predictions. The workshop conclusions also include recommendations for informal and formal intercomparison protocols.
Crosley, David R.↗
The HP 85192B EEFet3 GaAs FET Nonlinear Model Used in the High Efficiency Microwave Power Amplifier (HEMPA)
Most nonlinear circuit analysis programs that exist today were designed primarily for transient analysis. By incorporating more accurate models in simulation programs, accurate predictions of GaAs field effect transistors (FET) behavior can be accomplished. However, should the designer need to simulate GaAs FETs that operate at high DC-to-RF conversion efficiencies, a more sophisticated model is needed. A relevant and appropriate method is called harmonic-balance, as described by Quere et al.
Sims, William Herbert, III↗
Recent Progress in x3-Related Optical Process Experimental Technique. Raman Lasing
We describe theoretically and verify experimentally a simple technique for analyzing conversion efficiency and threshold of ail-resonant intracavity Raman lasers. The method is based on a dependence of the ring-down time of the pump cavity mode on the energy, accumulated in the cavity.
optical resonator↗
Advanced Concepts: Aneutronic Fusion Power and Propulsion
Aneutronic Fusion for In-Space thrust, power. Clean energy & potential nuclear gains. Fusion plant concepts, potential to use advanced fuels. Methods to harness ionic momentum for high Isp thrust plus direct power conversion into electricity will be presented.
Chapman, John J.↗
Sonification of Kepler Field SU UMa Cataclysmic Variable Stars V344 Lyr and V1504 Cyg
Sonification is the conversion of quantitative data into sound. In this work we explain the methods used in the sonification of light curves provided by the Kepler instrument from Q2 through Q6 for the cataclysmic variable systems V344 Lyr and V1504 Cyg . Both systems are SU UMa stars showing dwarf nova outbursts and superoutbursts as well as positive and negative superhumps. Focused sonifications were done from average pulse shapes of each superhump, and separate sonifications of the full, residual light curves were done for both stars. The audio of these data reflected distinct patterns within the evolutions of supercycles and superhumps that matched pervious observations and proved to be effective aids in data analysis.
Tutchton, Roxanne M.↗
Metabolomic and Genomic Markers of Atherosclerosis as Related to Oxidative Stress, Inflammation, and Vascular Function in Twin Astronauts
Background: Future human space travel will consist primarily of long-duration missions onboard the International Space Station (ISS) or exploration-class missions to Mars, its moons, or nearby asteroids. Astronauts participating in long-duration missions may be at an increased risk of oxidative stress and inflammatory damage due to radiation, psychological stress, altered physical activity, nutritional insufficiency, and hyperoxia during extravehicular activity. By studying one identical twin during his 1-year ISS mission and one ground-based twin, this work extends a current NASA-funded investigation to determine whether these spaceflight factors contribute to an accelerated progression of atherosclerosis. This study of twins affords a unique opportunity to examine the spaceflight-related atherosclerosis risk independent of the confounding factors associated with different genotypes. Purpose: The purpose of this investigation is to determine whether biomarkers of oxidative and inflammatory stress are elevated during and after long-duration spaceflight and determine if a relation exists between levels of these biomarkers and structural and functional indices of atherosclerotic risk measured in the carotid and brachial arteries. These physiological and biochemical data will be extended by using an exploratory approach to investigate the relationship between intermediate phenotypes and risk factors for atherosclerosis and the metabolomic signature from plasma and urine samples. Since metabolites are often the indirect products of gene expression, we will simultaneously assess gene expression and DNA methylation in leukocytes. Hypothesis: We predict that the space-flown twin will experience elevated biomarkers of oxidative stress and inflammatory damage, altered arterial structure and function, accelerated telomere shortening, dysregulation of genes associated with oxidative stress and inflammation, and a metabolic profile shift that is associated with elevated atherosclerosis risk factors. Conversely, these will not be observed in the ground-based twin. Methods: We will measure blood and urine biomarkers of oxidative stress and inflammation as well as arterial structure and function (carotid intima-medial thickness and brachial artery flow-mediated dilation) in one twin astronaut before, during, and after long-duration spaceflight and in his twin serving as a ground-based control. Furthermore, we will measure metabolomics (targeted and untargeted approaches) and genomic markers (DNA methylation, mRNA gene expression, telomere length) to elucidate the molecular mechanisms involved. A panel of biomarkers of oxidative and inflammatory stress will be measured in venous blood samples and 24-hour (in-flight) and 48-hour (pre- and post-flight) urine pools twice before flight, early (flight days 15 and 60) and late (2 weeks before landing) during the mission, and early in the post-flight recovery phase (approximately 3-5 days after landing). Arterial structure, assessed from measures of intima-media thickness, will be measured at the same times. Arterial function will be assessed using brachial flow-mediated dilation, a well-validated measure used to assess endothelium-dependent vasodilation and a sensitive predictor of atherosclerotic risk, only before and after spaceflight. Discussion: Pre- and in-flight data collection is in progress for the space-flown twin, and similar data have been obtained from the ground-based twin. Blood and urine samples will be batch processed when received from ISS after the conclusion of the 1-year mission. Results from these individual subjects will be compared to the larger complement of subjects participating in the companion study currently ongoing in ISS astronauts.
Lee, Stuart M. C.↗
Space-based UV Spectropolarimetry for Chromospheric Magnetic Field Measurements
High-resolution observations with space-and ground-based telescopes, along with advanced numerical modeling, have highlighted the intricate coupling between the chromosphere, transition region, and corona, and the critical role the chromosphere plays in the mass and energy balance of the outer solar atmosphere. Despite these recent advances, a major impediment to better understanding the solar atmosphere is our lack of empirical knowledge regarding the direction and strength of the magnetic field in the upper chromosphere (Decadal Survey, 2012). Such measurements are crucial to address several major unresolved issues in solar physics: for example, to constrain the energy flux carried by the Alfvén waves propagating through the chromosphere, and to determine the height at which the plasma β = 1 transition occurs, which has important consequences for the braiding of magnetic fields, for propagation and mode conversion of waves and for non-linear force-free extrapolation methods that are key to determining what drives instabilities such as flares or coronal mass ejections. Probing the magnetic nature of the Sun’s atmosphere requires measurement of the Stokes I, Q, U and V profiles of relevant spectral lines (of which Q, U and V encode the magnetic field information). Many of the magnetically sensitive lines formed in the chromosphere and transition region are in the ultraviolet spectrum, necessitating observations above the absorbing terrestrial atmosphere. The Chromospheric Layer Spectro-Polarimeter (“CLASP2”) sounding rocket was flown successfully in April 2019, as a follow-on to the successful flight in September 2015 of the Chromospheric Lyman-Alpha Spectro-Polarimeter (“CLASP1”). In October of 2021, we re-flew the CLASP2 experiment with a modified observing program to further demonstrate the maturity of the UV spectropolarimetry techniques, and readiness for development into a satellite observatory. During the reflight, called “CLASP2.1”, the spectrograph slit was scanned across an active region plage to acquire a two-dimensional map of Stokes V/I, to demonstrate the ability of UV spectropolarimetry to yield chromospheric magnetic fields over a large area.
David E McKenzie↗
Electrochemical reductive amination of furfural-based molecules
Electrochemical cells for the reductive amination of furfural-based molecules are provided. Also provided are methods of using the electrochemical cells to carry out the electrochemical reductive amination reactions. Using the cells and methods, furfural-based molecules can be converted into amines via the conversion of their formyl groups to amine groups.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Catalytic conversion of ethanol to 1-/2-butenes
Simple and economical conversion of aqueous ethanol feed streams into butenes by a single step method using transition metal oxides on a silica supports under preselected processing conditions. By directly producing a C4-rich olefin mixture from an ethanol containing stream various advantages are presented including, but not limited to, significant cost reduction in capital expenses and operational expenses.
Dagle, Vanessa M.↗
The Effects of Ground and Space Processing on the Properties of Organic, Polymeric, and Colloidal Materials
In recent years, a great deal of interest has been directed toward the use of organic materials in the development of high-efficiency optoelectronic and phototonic devices. There is a myriad of possibilities among organic materials which allow flexibility in the design of unique structures with a variety of functional groups. The use of nonlinear optical (NLO) organic materials as thin film wave-guides allows full exploitation of their desirable qualifies by permitting long interaction lengths and large susceptibilities allowing modest power input. There are several methods in use to prepare thin films such as Langmuir-Blodgett (LB) and self-assembly techniques, vapor deposition, growth from sheared solution or melt, and melt growth between glass plates. Organic-based materials have many features that make them desirable for use in optical devices, such as high second-and third-order nonlinearity, flexibility of molecular design, and damage resistance to optical radiation. However, their use in devices has been hindered by processing difficulties for crystals and thin films. We discuss the potential role of microgravity processing of a few organic and polymeric materials. It is of interest to note how materials with second-and third-order NLO behavior may be improved in a diffusion-limited environment and ways in which convection may be detrimental to these materials. We focus our discussion on third-order materials for all-optical switching, and second-order materials for frequency conversion and electrooptics. The goal of minimizing optical loss obviously depends on processing methods. For solution-based processes, such as solution crystal growth and solution photopolymerization, it is well known that thermal and solutal density gradients can initiate buoyancy-driven convection. Resultant fluid flows can affect transport of material to and from growth interfaces and become manifest in the morphology and homogeneity of the growing film or crystal. Likewise, buoyancy-driven convection can hinder production of defect-free, high-quality crystals or films during crystal and film growth by vapor deposition.
Frazier, Donald O.↗
Extracting meaningful standard enthalpies and entropies of activation for surface reactions from kinetic rates
While analyses based on the Arrhenius kinetic model have been successfully applied since its introduction, the Arrhenius model neglects to describe pre-exponential factor in a scientifically meaningful fashion. Since the 1930s, transition-state theory (TST), has met with success in interpreting the pre-exponential factor’s value, allowing a standard entropy of activation to be estimated. However, analyses based on TST’s assumptions have been applied inconsistently in the literature, particularly in corrosion science, leading to difficulty in comparison of standard entropy of activations from different studies. In this work, the foundational principles of TST and standard states are discussed and a standard method to apply TST in analyzing rates of surface reactions is recommended. When full details are not available, reacting species’ concentrations should be normalized to the concentration of active surface sites. For corrosion reactions, conversion relationships are given to convert from units of corrosion rate to surface reaction rate, consistent with TST. This method is dubbed a surface reactant equi-density approximation. Application of this standard to reported data results in adjustments of the standard entropy of activation between - 65 and +50 J/mol K and brings reported entropies into a narrower range of values.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Nondestructive measurement of intensity of optical fields using spontaneous parametric down conversion
Results of nondestructive measurements of intensity (photons per mode) of light from different sources are discussed. The procedure of measurement does not destroy the state of the optical field. The method is based on using the second order nonlinearity of crystal media lacking a center of symmetry and the nonclassical properties of the process of Spontaneous Parametric Down Conversion (SPDC).
Penin, A. N.↗
Scalable Two–Step Production of High–Efficiency Perovskite Solar Cells and Modules
Perovskite solar cells (PSCs) fabricated in laboratories have already achieved power conversion efficiency (PCE) comparable to market-dominant crystalline silicon solar cells. However, this promising photovoltaic technology suffers from severe loss of PCE during scaling up, limiting its progress toward commercialization. One critical question is to develop scalable, low-cost, high throughput, and well-controlled production methods to deposit high-quality perovskite films. Among various approaches, two-step sequential deposition methods have their unique advantages but have been long overlooked. This review provides an overview of two-step methods for fabricating efficient and stable perovskite solar modules (PSMs). We first discuss the mechanisms of two-step perovskite conversion and advanced engineering approaches to modulate the perovskite formation process. We survey the progress of efficient PSCs prepared by different two-step methods and compare the advantages and disadvantages of each method for scalable production of PSMs. Particularly, we highlight that the vapor-based two-step methods are promising for high-throughput in-line production of PSMs. Finally, we provide insights into the challenges and outlook of the industrialization of two-step processes for producing PSMs.
14 SOLAR ENERGY↗
Refinement and Modeling of a Blackbody-Based Calibration Method in the InfraBREAD Detector
The Broadband Reflector Experiment for Axion Detection (BREAD) is an ongoing collaboration searching for the conversion of yet undiscovered axion-like dark matter particles to photons in the presence of a magnetic field. InfraBREAD, an experiment of BREAD, uses a superconducting nanowire single photon detector (SNSPD), a high-efficiency and low-noise device, to specifically detect infrared-range photons produced by $\mathcal{O}$(eV) axion-like particles. The unique BREAD reflector setup allows for the focusing of converted signal photons to a 1mm $\times$ 1mm SNSPD. However, when the detector is cooled to cryogenic temperatures during operation, uneven thermal contraction of reflector components may lead to a small shift in the location of the focal spot. A novel calibration method using blackbody radiation is proposed to locate the true focal spot of the detector \textit{in situ}. Through ray tracing simulations done in FRED Optical Engineering Software, this method is demonstrated to locate the focus to within $\SI{50}{\micro\metre}$ in the $z$ dimension.
Rao, Shardul↗
Decomposing Cloud Radiative Feedbacks by Cloud-Top Phase
Changes in cloud scattering properties and emissivity that arise from atmospheric warming cause substantial radiative feedbacks in model projections of anthropogenic climate change, and the relative importance of the underlying mechanisms is poorly understood. One leading hypothesis is that ice-to-liquid conversions cause clouds to optically thicken, producing a major negative feedback. We test this hypothesis by developing a method to decompose cloud radiative feedbacks by cloud-top phase. The method is applied to an ensemble of six state-of-the-art global climate models run with prescribed sea surface temperature. In these simulations, the global mean of the net cloud scattering and emissivity feedback from cloud-phase conversions ranges from −0.17 to −0.01 W m −2 K −1 , while the overall net cloud feedback ranges from 0.02 to 0.91 W m −2 K −1 . The multimodel mean of the cloud scattering and emissivity feedback from cloud-phase conversions is approximately 19% of the magnitude of the multimodel mean of the overall cloud feedback (−0.10 vs 0.52 W m −2 K −1 ). These results indicate that cloud-phase conversions cause a robust negative feedback by changing cloud scattering and emissivity, but this mechanism makes a modest contribution to the overall cloud feedback at the global scale.
Climate change↗