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Surface passivation of Fe{sub 3}O{sub 4} nanoparticles with Al{sub 2}O{sub 3} via atomic layer deposition in a rotating fluidized bed reactor
Iron(II,III) oxide (Fe{sub 3}O{sub 4}) nanoparticles have shown great promise in many magnetic-related applications such as magnetic resonance imaging, hyperthermia treatment, and targeted drug delivery. Nevertheless, these nanoparticles are vulnerable to oxidation and magnetization loss under ambient conditions, and passivation is usually required for practical applications. In this work, a home-built rotating fluidized bed (RFB) atomic layer deposition (ALD) reactor was employed to form dense and uniform nanoscale Al{sub 2}O{sub 3} passivation layers on Fe{sub 3}O{sub 4} nanoparticles. The RFB reactor facilitated the precursor diffusion in the particle bed and intensified the dynamic dismantling of soft agglomerates, exposing every surface reactive site to precursor gases. With the aid of in situ mass spectroscopy, it was found that a thicker fluidization bed formed by larger amount of particles increased the residence time of precursors. The prolonged residence time allowed more thorough interactions between the particle surfaces and the precursor gas, resulting in an improvement of the precursor utilization from 78% to nearly 100%, even under a high precursor feeding rate. Uniform passivation layers around the magnetic cores were demonstrated by both transmission electron microscopy and the statistical analysis of Al mass concentrations. Individual particles were coated instead of the soft agglomerates, as was validated by the specific surface area analysis and particle size distribution. The results of thermogravimetric analysis suggested that 5 nm-thick ultrathin Al{sub 2}O{sub 3} coatings could effectively protect the Fe{sub 3}O{sub 4} nanoparticles from oxidation. The x-ray diffraction patterns also showed that the magnetic core crystallinity of such passivated nanoparticles could be well preserved under accelerated oxidation conditions. The precise thickness control via ALD maintained the saturation magnetization at 66.7 emu/g with a 5 nm-thick Al{sub 2}O{sub 3} passivation layer. This good preservation of the magnetic properties with superior oxidation resistance will be beneficial for practical magnetic-based applications.
Slipping and tangential discontinuity instabilities in quasi-one-dimensional planar and cylindrical flows
An analytical linear theory of instability of an electron beam with a nonuniform directional velocity (slipping instability) against perturbations with wavelengths exceeding the transverse beam size is offered. An analogy with hydrodynamic instabilities of tangential discontinuity of an incompressible liquid flow is drawn. The instability growth rates are calculated for particular cases and in a general form in planar and cylindrical geometries. The stabilizing effect of the external magnetic field is analyzed.
The European ERL Roadmap
Following the European Strategy process in 2019, five Roadmap Panels were set up to prepare the technologies needed for future accelerators and colliders: high-field magnets, SRF, muon colliders, plasma wakefield accelera-tors and Energy Recovery Linacs (ERLs). The ERL Roadmap Panel, consisting of ERL experts from around the world, first developed an overview of current and future ERLs. From this it was possible to carry out a gap analysis to see what R&D would be needed, from which the roadmap could be developed. The European ERL Roadmap [1] focused on three main aspects: 1) the con-tinuation and development of facility programs for which no additional funds are needed, S-DALINAC in Darm-stadt and MESA in Mainz; 2) technology development for room-temperature HOM damping and twin-axis SRF cavities; 3) the timely upgrade of bERLinPro for 100 mA current and the construction of PERLE at Orsay as a dedi-cated 10 MW power multi-turn facility. The roadmap entails a vision of a future energy frontier electron-positron and electron-hadron collider and describes a high-quality ERL program for 4.4K SRF technology at high Q0.
Sextupole misalignment and defect identification and remediation in IOTA
The nonlinear integrable optics studies at the integrable optics test accelerator (IOTA) demand fine control of the chromaticity using sextupole magnets. During the last experimental run undesirable misalignments and multipole composition in some sextupole magnets impacted operations. This report outlines the beam-based methods used to identify the nature of the misalignments and defects, and the subsequent magnetic measurements and remediation of the magnets for future runs.
Pulsed Joining Of Body-In-White Components
The objective of this project was to develop cost efficient high quality pulsed welding (PW) technology for joining 6xxx Aluminum and High Strength Steel (with tensile strength above 580MPa) components enabling broad usage of hydroformed parts and leading to substantial weight reduction of cars and trucks to reduce US demand on petroleum, lower carbon emissions and energy expenditures. In general, pulsed welding is a form of impact welding where two dissimilar metal pieces are joined by accelerating one to velocities exceeding 300m/s at which point the first piece strikes the second and forms a weld. In this work, two methods were used to accelerate the flyer material: Electro-Magnetic (EM) pulse and Electro-Hydraulic (EH) pulse launching. The advantage of pulsed welding techniques is that welds can be formed between two materials that cannot otherwise be welded: high strength aluminum and high strength steel. The technical objectives of the project included: 1) developing cost affordable production feasible tooling design for PW of 6xxx aluminum to High Strength steel with strengths above 580MPa; 2) demonstrating that fabricated joints can exceed the required service load strength initially at the coupon level and then at the component level; 3) developing fundamental understanding of the mechanisms of joint formation and conditions leading to formation of high quality PW joint; and 4) creating a numerical model predicting the tooling and electric discharge parameters necessary for the joint formation and that satisfy the targeted strength parameters. The project successfully developed: 1) EM and EH pulsed welds between high strength aluminum with tensile strengths exceeding 240MPa and steels exceeding 580MPa; 2) pulsed welds of extrusions with strengths exceeding project requirements; 3) EM and EH flyer launch models and 4) weld interface formation models. However, the grant holder, Ford Motor Company, could see no path to commercialization and the work was discontinued at the end of the first budget period.
An Adaptive Gap Prototype IVU from the X9 MGU Mechanics
In consideration of affordable options to construct a prototype of an Adaptive-Gap Undulator (AGU), in which different segments along the structure may have different gaps and periods, we investigate the possible use of an existing undulator structure and mechanics from former NSLSI. An AGU is intended to allow for conforming gap clearance to the vertical "envelope" within a straight section of the NSLS-II accelerator, allowing precise tuning of its magnet array segments to the same fundamental photon energy while still satisfying impedance constraints. Placing together undulator segments with different periods and gaps portends possible undesirable effects, such as "kicks" to electron trajectories and perturbations to undulator radiation phase at the segment junctions, as well as increased impedance.
Kinetic characterization of 3D magnetic reconnection: A transformative step (Final Report)
We investigated magnetic reconnection in the Earth’s magnetopause, magnetotail, and the bow shock, by means of fully kinetic simulations and analysis of space data obtained by NASA’s Magnetospheric Multiscale mission. We elucidated signatures of particle energization in particle distribution functions in the vicinity of reconnection X-line, properties of reconnection in shock-driven turbulence, and wave excitations and nonlinear structures. We advanced the understanding of magnetic reconnection from the viewpoint of particle kinetics in the diffusion region.
Optimizing Material Selection and Operational Conditions for XHV Systems: Lessons from AISI 1020 and 316L Comparative Studies
In this study, AISI 1020 low-carbon steel is investigated as a cost-effective alternative to SS316 stainless steel for reaching extreme high vacuum (XHV) conditions. After being baked at 400°C, a vacuum chamber made of the low-carbon steel material exhibited an outgassing rate approximately 2000 times smaller than a similar chamber made of stainless steel. Its activation energy for hydrogen diffusion (27 kJ/mol) is less than half that of stainless steel (60.3 kJ/mol), indicating more efficient hydrogen removal during bakeout. MolFlow+ simulations supported the experimental data and demonstrated the importance of system geometry optimization and minimizing stainless steel content for achieving optimal vacuum performance. AISI 1020's magnetic properties, typically considered disadvantageous for accelerator applications, could benefit spin-polarized electron sources by shielding photocathodes from stray fields while simultaneously providing improved vacuum through reduced outgassing. To optimize AISI 1020's performance in XHV systems, practical considerations include pre-baking protocols and careful system design to minimize stainless steel components.
The Impact of Naphthenic Acids on Dynamic Fluid–Fluid Interactions: Implication for Enhanced Oil Recovery
Previous coreflooding results and wettability analyses in our group show that injection of naphthenic-acid-enriched water can improve oil recovery over traditional waterflooding. This observation is still a subject of research efforts without a definitive explanation. Naphthenic acids (NA) have been reported to drive wettability alteration and increase the water–oil interface elasticity. These alterations depend on the NA carbon number and aqueous-phase salinity, among other conditions, as reported in the literature. Smart-water flooding (SWF) research often links recovery to the initial wettability condition, being higher for initially oil-wet rock. SWF refers to a technique in which the aqueous-phase ion composition or/and salinity are changed to maximize oil recovery. Given NAs’ complex solution behavior, selecting acid combinations that prompt oil recovery is a difficult objective. The aim of this research is to determine the effects of select naphthenic acids on the oil–water interfacial rheology and wettability alteration and how these interfacial effects are associated with oil recovery under spontaneous imbibition. NAs were selected based on their carbon number, molecular structure, and solubility in the saline solution used in this research. We aimed at exploring which NAs should be used to regulate interfacial properties so as to either increase oil recovery or accelerate production. Time-domain nuclear magnetic resonance, interfacial dilatational rheology, and liquid-bridge experiments, i.e., proxy of snap-off, were conducted. A baseline was established using results obtained with a previously tested sulfate-rich aqueous phase, shown to be effective in recovering oil. Results show that NA14 and N18 increase the water–oil interfacial viscoelasticity and induce interfacial healing but led to different recovery factors. N10, while effective at inducing water wetness in oil-wet rock, is ineffective at increasing the recovery factor. We concluded that wettability and oil–water interfacial rheology are not exclusive, and instead they can synergistically favor EOR benefits. Moreover, oil recovery benefits under spontaneous imbibition are shown to depend strongly on the initial wettability conditions.
Three Regimes and Four Modes for the Resonant Saturation of Parallel Ion-beam Instabilities
Motivated by recent advances in laboratory experiments on parallel ion-beam instabilities, we present a theoretical framework for—and simulations of—their evolution toward shock formation and Fermi acceleration. Here, after reviewing the linear theory of beam instabilities, with an emphasis on how magnetic helicity and polarization depend on properties of the beam, we compare the evolution and saturation of three distinct parameter regimes: (I) the left-handed "non-resonant" regime; (II) the right-handed beam-gyroresonant regime; (III) the balanced, mixed-turbulence regime.
Flux Ropes, Turbulence, and Collisionless Perpendicular Shock Waves: High Plasma Beta Case
With the onset of solar maximum and the expected increased prevalence of interplanetary shock waves, Parker Solar Probe is likely to observe numerous shocks in the next few years. An outstanding question that has received surprisingly little attention has been how turbulence interacts with collisionless shock waves. Turbulence in the supersonic solar wind is described frequently as a superposition of a majority 2D and a minority slab component. Here we formulate a collisional perpendicular shock-turbulence transmission problem in a way that enables investigation of the interaction and transmission of quasi-perpendicular fluctuations such as magnetic flux ropes/islands and vortices as well as entropy and acoustic modes in the large plasma beta regime. We focus on the transmission of an upstream spectrum of these modes, finding that the downstream spectral amplitude is typically increased significantly (a factor of 10 or more), and that the upstream spectral index of the inertial range, and indeed the general spectral shape, is unchanged for the downstream magnetic variance, kinetic energy, and density variance. A comparison of the theoretically predicted downstream magnetic variance, kinetic energy, and density variance spectra with those observed at 1, 5, and 84 au by Wind, Ulysses, and Voyager 2 shows excellent agreement. The overall theoretically predicted characteristics of the transmission of turbulence across shocks observed in the solar wind appear to be largely consistent with recent observational studies by Pitňa et al. and Borovsky.
Applied Superconductivity Conference, 5th, Annapolis, Md., May 1-3, 1972, Proceedings.
Recently developed practical applications of superconductivity are described in papers dealing with transportation and propulsion, power generation, power transmission, special-purpose magnets, superconducting materials, Josephson junctions, and microwave systems. Important topics considered include tracked magnetic-cushion vehicles, electrical machines, cryogenic underground power transmission systems, magnets for fusion reactors and particle accelerators, thin-film superconductors, effects of the structural characteristics of materials on transition temperatures, frequency measurement with Josephson devices, and superconducting scientific instruments. Individual items are announced in this issue.
Performance of the new Efratom optically pumped rubidium frequency standards and their possible application in space relativity experiments
The characteristics of Efratom optically pumped rubidium frequency standards are discussed. The Efratom units were compared with cesium beam and hydrogen maser standards and showed a stability of approximately 5 times 10 to the minus 12th power over two one-week periods. Dependency of frequency upon the environmental parameters of pressure, magnetic field, temperature, supply voltage, and acceleration was measured. A package of three units with automatic phase comparison and recording was designed and constructed to allow a measurement of relativistic effects on time with high accuracy during space missions.
Anomalous composition and energy spectra of cosmic rays below 20 MeV/nucleon
The relative abundances and energy spectra of C, N, O, Ne, and Fe are investigated as a function of the interplanetary low energy proton intensity using observations obtained over a 17-month period by IMP-8. The oxygen intensity was enhanced when proton activity was at its lowest level, while all other heavy elements almost disappeared. Nuclei of less than 3 MeV/nucleon showed a strong intensity fluctuation strongly correlated with the interplanetary proton flux and displayed a velocity anisotropy along the garden-hose angle, indicating that they are of solar origin. The anomalous oxygen hump between 3 and 20 MeV is apparently not of solar origin. The observations are compatible with the model proposed by Fisk et al. (1974), in which these oxygen nuclei are considered to be interstellar neutral oxygen atoms which are ionized and accelerated to the observed energies by magnetic field irregularities in the outer solar system.
The magnetosphere of Mercury
Data on Mercury's magnetosphere and on the plasma, planetomagnetic, and energetic particle environment of the planet obtained in three encounters (Mariner 10 flybys) are compared, and tasks for future research are outlined. The Mercury bow shock and magnetopause are much closer to the planet than the earth counterparts are to the earth. The magnetotail with embedded plasma sheet-field reversal region, global deflection of the solar wind by an intrinsic dipolar magnetic field, variations in solar wind momentum flux, and absence of such features as ionosphere, plasmasphere, and radiation belts, are described. Energetic electrons are accelerated in the magnetotail, however, and the interplanetary magnetic field variations distort Mercury's magnetosphere to produce a southward field associated with substorm-like disturbances.
VLA observations of positions 42 6 centimeter burst peaks associated with hard X-ray burst spikes
Using the Very Large Array with a spatial resolution of 3 arcsec, two-dimensional, 10-second synthesis maps are produced of four 6-cm lambda bursts associated with multiply spiked hard X-ray bursts (20-300 keV). The positional, structural, and polarization characteristics are investigated. It is noted that three of the four burst sources are rather compact (less than approximately 10 arcsec). It is found that the positions of the individual peaks or spikes within a single burst are the same within plus or minus 2 arcsec. Interpreting these different peaks as separate electron acceleration events, the results suggest repeated acceleration of electrons within the same magnetic trap. The trap situation is found to be consistent with the bipolar nature of the burst sources except in one case.
Measurements of outflow from the base of solar coronal holes
New evidence is presented that EUV emission lines formed at the levels of the base of the corona and the transition region are systematically shifted to shorter wavelengths within coronal holes relative to the rest of the solar disk, and that moreover this shift increases with height in the atmosphere. Measurements were made with a rocket-borne EUV spectrometer having high spectroscopic resolution and stability flown on July 15, 1980. Repeated measurements were made along a chord of the solar disk that crossed a compact coronal hole near sun center identified on gamma 10830 He I spectroheliograms. The maximum measured shift corresponded to a velocity of 12 km/sec in gamma 625 Mg X and 7 km/sec in gamma 629 O V. If these velocities correspond to a true mass flux, they provide important data on the acceleration of coronal plasma in open magnetic field regions. These observed Doppler displacements are a strong and significant signature of coronal holes, now measured on three rocket flights.