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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Improving Qubit Coherence Time Through Detailed Materials Analysis

This study investigates the defects, imperfections, and variations in Nb thin films deposited on sapphire substrates. Two samples, W114 and W118, were fabricated using DC Magnetron Sputtering and Electron Cyclotron Resonance (ECR), respectively. Each sample was analyzed at five distinct spots to compare elemental homogeneity and variations in oxide layers. Scanning Electron Microscopy (SEM) was employed to examine surface morphology, while Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS) provided elemental and chemical state analyses. SEM revealed distinct structures in W114 and a uniform surface in W118. EDS showed higher aluminum signals in W118, indicating a thinner film in comparison to W114. XPS detected a higher Nb₂O₅ signal in W118, in comparison to W114, which can be attributed to the presence of a thicker Nb₂O₅ layer in W118. These findings highlight the critical role of precise material characterization in advancing quantum computing technologies.

Rosado Bonilla, Cristy M.↗
DOE OSTI2024

Performance of the Fermilab Linac Injector

The Fermilab Linac injection line consists of a 35 keV magnetron-type H- ion source, two-solenoid Low Energy Beam Transport (LEBT), 201 MHz 4-rod 750 keV Radio Frequency Quadrupole (RFQ), and a Medium Energy Transport (MEBT) containing 4 quadrupoles and a bunching cavity. The injector delivers 25 mA, 48 s pulses to drift-tube Linac at a repetition rate of 15Hz. The transmission efficiency has been lower than expected since commissioning. Recent beam current measurements suggest that the beam is primarily lost upstream of the RFQ exit. Numerical simulations indicate that ions passing through the non-linear field region of the solenoids could produce a beam with an increased emittance resulting in up to 50 % of the LEBT beam current failing to meet the RFQ acceptance. An aperture restriction was installed upstream of the first solenoid to remove these ions. This report describes the results of measurements and simulations as well as the LEBT tuning.

Jones, Daniel C.↗
DOE OSTI2024

Performance of the Fermilab Linac Injector

The Fermilab Linac injection line consists of a 35 keV magnetron-type H\textsuperscript{-} ion source, two-solenoid Low Energy Beam Transport (LEBT), 201 MHz 4-rod 750 keV Radio Frequency Quadrupole (RFQ), and a Medium Energy Transport (MEBT) containing 4 quadrupoles and a bunching cavity. The injector delivers 25 mA, 48 µs pulses to the drift-tube Linac at a repetition rate of 15Hz. The transmission efficiency of the injector has been lower than expected since commissioning. Recent beam current measurements suggest that the beam is primarily lost upstream of the RFQ exit. Numerical simulations indicate that ions passing through the non-linear field region of the solenoids could produce a beam with an increased emittance resulting in up to 50\% of the LEBT beam current failing to meet the RFQ acceptance. An aperture restriction was installed upstream of the first solenoid to remove these ions. This report describes the results of measurements and simulations as well as the LEBT tuning.

43 PARTICLE ACCELERATORS↗
DOE OSTI2025

NOVEL METHODS FOR IN SITU HIGH DENSITY SURFACE CLEANING SCRUBBING OF ULTRAHIGH VAC LONG NARROW TUBES TO REDUCE SECONDARY ELECTRON YIELD AND OUT GASSING

This project developed new methods for cleaning the inside surfaces of very long, narrow vacuum tubes used in particle accelerators. Traditional cleaning approaches are expensive, slow, or difficult to implement in accelerator tunnels. We designed and tested a portable plasma discharge cleaning system that uses lower-cost microwave and magnetron technologies to reduce outgassing and secondary electron emission from stainless steel and copper surfaces. The system, called the Plasma Discharge Test System (PDTS), allows accelerator components to be scrubbed more efficiently, which can improve performance and reduce maintenance costs for research and industrial applications.

POOLE, JOE HENRY [PRESIDENT]↗
DOE OSTI2025

Development and Testing of a new Current-Regulated Arc Modulator for the LINAC

In this study, the performance of a current-regulated arc modulator was investigated with a focus on its role in initiating and sustaining plasma discharge within the Magnetron Body of the LINAC system. The analysis centered on how switching components, circuit topology, and feedback loop architecture influence critical factors such as energy efficiency, discharge stability, and long-term plasma containment. Particular attention was given to variations in pulse termination behavior, as observed through oscilloscope traces, which revealed inconsistencies affecting the duty factor and cathode temperature. These fluctuations have downstream effects on the cesium-coated cathode surface, thereby impacting H⁻ ion production and beam reliability. Simulation-based testing in LTspice was used to evaluate noise suppression techniques and arc current regulation schemes, revealing how optimized snubber networks, improved pulse shaping, and feedback stability can mitigate modulator-induced noise. The results identified hardware level parameters that significantly enhance discharge repeatability and improve overall plasma performance under operational conditions.

Campos, Nathan [Unlisted, US; Fermilab]↗
DOE OSTI2026

Nb3Sn Superconducting Radiofrequency Cavity Fabricated by Sputter Deposition from a Stoichiometric Target

Nb$_3$Sn is a promising coating material for superconducting radiofrequency cavities in next-generation accelerators due to its higher superconducting transition temperature (~18.3 K) and superheating field (~400 mT), offering the potential to surpass the intrinsic performance limits of bulk niobium. We developed a sputter coating technique employing a stoichiometric target to fabricate Nb$_3$Sn films on the inner surfaces of niobium cavities. A Nb$_3$Sn tube target, prepared by growing a >20 m thick Nb$_3$Sn coating on the surface of a Nb tube via a Sn vapor diffusion process, was used in a DC cylindrical magnetron sputtering system. Approximately 170 nm thick Nb-Sn films were sputter-coated onto flat Nb substrates positioned to replicate the beam tube and equator regions of a 2.6 GHz cavity, followed by annealing at 950 °C for 3 hours to form Nb$_3$Sn. The composition, morphology, and structure of the annealed Nb$_3$Sn films were examined. Then, a ~1.2 m-thick film was sputter-coated onto the interior of a 2.6 GHz Nb cavity following the procedure developed for the flat samples. The cavity was subsequently annealed under the same conditions used for the flat samples. Cryogenic RF testing of the sputter-coated cavity demonstrated a T$_c$ of approximately 17.8 K, consistent with Nb$_3$Sn layer. Subsequently, the cavity underwent a light Sn recoating followed by a vapor diffusion Nb$_3$Sn coating process, achieving a quality factor of approximately 8.5 × 10$^9$ and an accelerating gradient of up to 11.3 MV/m at 4.2 K.

Shakel, Md Sharifuzzaman [Old Dominion U.; Jeffers↗
DOE OSTI2018

Effect of RF Power on Structural, Magnetic, and Optical Properties of CoFe{sub 2}O{sub 4} Thin Films

The thin films of CoFe{sub 2}O{sub 4} were deposited on glass substrates by radio-frequency (RF) sputtering. The effect of RF power variation from 60–120 W on the structure, magnetic, and optical properties of the as-deposited films and films annealed at 500 °C was studied. The magnetic parameters of the film, i.e., in-plane coercivity (H{sub c}), saturation magnetization (M{sub s}), and remanence (M{sub r}) increase as RF power is increased from 60 to 80 W followed by a decreasing trend with further increase in RF power to 120 W. Annealing of the film significantly improves the magnetic properties. The largest grain size and the best crystallinity of the film are obtained for the film deposited at 80 W of RF power. The thin films exhibited 70–80% optical transmittance. Optical band gap (E{sub g}) depends on the RF power and grain size, and it varies between 2.08 and 2.16 eV for the as-deposited films and between 2.16 and 2.30 eV for the annealed films. The study shows that RF power used for depositing the film has strong effect on the microstructure and properties of the film.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Bacterial Ferrihydrite Nanoparticles: Preparation, Magnetic Properties, and Application in Medicine

Nanoparticles of antiferromagnetically ordered materials acquire the uncompensated magnetic moment caused by defects and surface effects. A bright example of such a nano-antiferromagnet is nanoferrihydrite consisting of particles 2–5 nm in size, the magnetic moment of which amounts to hundreds of Bohr magnetons per particle. We present a brief review of the studies on magnetic properties of ferrihydrite produced by bacteria. Special attention is focused on the aspects of possible biomedical applications of this material, i.e., the particle elimination, toxicity, and possible use for targeted drug delivery.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2017

Fourier Transform Ion Cyclotron Resonance Mass Spectrometry at the Cyclotron Frequency

The phenomenon of ion cyclotron resonance allows for determining mass-to-charge ratio, m/z, of an ensemble of ions by means of measurements of their cyclotron frequency, ω{sub c}. In Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), the ω{sub c} quantity is usually unavailable for direct measurements: the resonant state is located close to the reduced cyclotron frequency (ω{sub +}), whereas the ω{sub c} and the corresponding m/z values may be calculated via theoretical derivation from an experimental estimate of the ω{sub +} quantity. Here, we describe an experimental observation of a new resonant state, which is located close to the ω{sub c} frequency and is established because of azimuthally-dependent trapping electric fields of the recently developed ICR cells with narrow aperture detection electrodes. We show that in mass spectra, peaks close to ω{sub +} frequencies can be reduced to negligible levels relative to peaks close to ω{sub c} frequencies. Due to reduced errors with which the ω{sub c} quantity is obtained, the new resonance provides a means of cyclotron frequency measurements with precision greater than that achieved when ω{sub +} frequency peaks are employed. The described phenomenon may be considered for a development into an FT-ICR MS technology with increased mass accuracy for applications in basic research, life, and environmental sciences. .

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

X-ray photoelectron spectroscopy and rotating disk electrode measurements of smooth sputtered Fe-N-C films

Electrocatalysts for the oxygen reduction reaction (ORR) based on complexes of iron and nitrogen in a carbon matrix (Fe-N-C) are a promising alternative to platinum group metal (PGM) based catalysts in polymer electrolyte membrane (PEM) fuel cells. Further improvements of Fe-N-C catalysts would benefit from model thin film studies of activity and stability of catalytic sites, but synthesis of Fe-N-C model thin films is challenging. Here we report on synthesis and characterization of Fe-N-C thin films produced by co-sputtering iron and carbon in a reactive nitrogen atmosphere onto removable glassy carbon rotating disk electrode (RDE) tips. Scanning electron microscopy (SEM) measurements indicate that the Fe-N-C films deposited at high temperature are smoother than the films annealed at high temperature. Electrocatalytic activity measured on the thin Fe-N-C films is greater for both high-temperature samples than for the room-temperature sample. From the analysis of X-ray photoelectron spectroscopy (XPS) data, exposure of the films to high temperatures results in increased graphitization of the carbon with the Fe-N-C films, and increased relative amount of graphitic and hydrogenated nitrogen species. Overall the results of this study demonstrate the feasibility of a thin film model system approach for studying active sites in PGM-free catalysts.

14 SOLAR ENERGY↗
DOE OSTI2017

Vertically oriented ZrO 2 –TiO 2 –Nb 2 O 5 –Al 2 O 3 mixed nanopatterned bioceramics on Ti6Al7Nb implant assessed by laser spallation technique

Recently, reports on the fabrication of nonstructural configuration have generated scientific interest due to increased awareness of the oxide nanotubes in the biomedical implant field and other industrial approaches. In this paper, highly ordered ZrO 2 –TiO 2 –Nb 2 O 5 –Al 2 O 3 nanotube arrays were grown by physical vapor deposition (PVD) of a zirconium layer on titanium-niobium alloy implant (IMPTi67) and succeeding anodic oxidation at a constant voltage (60 V) with exposure times ranging from 30 to 300 min. To crystallize the resulting mixed oxide nanotubes, heat treatment was also applied. The nanotubes were placed in an atmospheric furnace at temperatures ranging from 450 to 800 °C for 2 h. This treatment provided a morphological evolution was strongly influenced by the anodization time, where highly aligned bamboo-shaped oxide nanotubes (161 ± 44 nm in inside diameter and ~1 μm in length) were formed after 300 min of anodization. After annealing at temperature below 500 °C, the nano-array configuration remained stable and the average inner diameter decreased to around 40 nm. The effects of anodically fabrication time on the adhesion strength of four-phase multilayered mixed oxide nanotubes on anodized Zr/IMPTi67 surfaces assed by microscratch analysis. From the results, increasing the annealing temperature further to 800 °C fully destroyed the nanotubes and consequently the tubular arrangement was converted to a coarse grain structure. It was revealed that annealing at 450 °C for 2 h was the optimum conditions for stable nanotubular array generation, where the highest adhesion strength (shifted from 2595.59 to 2640.12 mN), microhardness (372 HV) and hydrophilicity (15 ± 1°) were recorded. It is notify that the adhesion strength of highly ordered mixed nanotubes was remarkably decreased after thermal treatment at 800 °C (1817.51 mN). Through the laser spallation analysis, the intrinsic adhesion strength of the Zr/IMPTi67 interface was found to be at 63 MPa, while the first stages of failure occurred at a stress state of 35 MPa. The adhesion of the film with the tubular structure proved to have a significantly larger adhesion strength of 246 MPa for the complete failure and 203 MPa for incipient stages of spallation. Finally, the considered surface modification can be an effective step in determining the interface strength between biomedical implants and the nanostructured coatings.

36 MATERIALS SCIENCE↗
DOE OSTI2025

The physical origin of heterogeneous solute clustering and nanoprecipitation at grain boundaries in ultrafine-grained immiscible alloys

Here, grain-boundary segregation effects on heterogeneous solute clustering and nanoprecipitation at low solute concentrations were investigated in sputter-deposited ultrafine-grained Ag-Cu alloy films. X-ray diffraction and scanning transmission electron microscopy revealed extended solubility of Cu in Ag matrix, accompanied by the formation of Cu-rich nanoprecipitates and solute clusters at grain boundaries and their junctions. Atomistic simulations further demonstrated that Cu solutes heterogeneously segregate to Ag GBs and form small clusters that grow into nuclei for Cu nanoprecipitates. These findings provide critical insights into the role of heterogeneous grain-boundary segregation in governing the phase separation pathways of immiscible nanocrystalline and ultrafine-grained alloys.

Heterogeneous segregation↗
DOE OSTI2023

Fabrication of superconducting Nb 3 Sn film by Co-sputtering

High-efficiency SRF cavities are the key technology to construct cost-effective CW SRF accelerators. Improvements in the efficiency of SRF cavities are realized by using novel materials, such as niobium-tin. Advances in niobium-tin coatings on the inner surface of SRF cavities showed the potential for this material to increase the operating temperature of the SRF cavity to above 4 K, leading to significant reduction of the capital and operating cost of SRF accelerators. Among the techniques used to apply the niobium-tin coating to the surface of the SRF cavity is sputtering. Old Dominion University, Jefferson Lab, and Fermilab are collaborating on developing an optimized niobium-tin coating of the inside surface of niobium SRF cavities using a recently-developed cylindrical sputtering system. This research will result in optimized sputtering coating techniques leading to high efficiency SRF structures.

42 ENGINEERING↗
DOE OSTI2025

Sputter deposition of ultrathick Bi coatings onto rotating substrates for inertial confinement fusion

Sputter-deposited Bi is a potential candidate material for the production of inertial confinement fusion (ICF) hohlraums, which are sphero-cylindrical canisters that serve as the housing for hydrogen-fuel-filled capsules in ICF implosions. The fabrication of hohlraums involves deposition onto rotating sphero-cylindrical substrates and, hence, requires an understanding of oblique angle deposition phenomena. Here, we systematically study the effect of dynamic substrate tilt on properties of Bi films deposited onto rotating planar substrates. Results show that film morphology, porosity, and electrical resistivity depend on substrate tilt. In comparison with films deposited onto substrates adhered to a stationary sample holder, films deposited on rotating substrates have more uniform microstructure with fewer void defects. Based on Monte Carlo simulations, these changes in film morphology and microstructure are attributed to averaging and geometric effects related to sample position and rotation. In conclusion, the fabrication of an ∼ 50-µm-thick Bi film on a rotating sphero-cylindrical mandrel demonstrates a significant step toward the production of Bi hohlraums.

Bismuth↗
DOE OSTI2019

Synthesis of Ni-Rich Thin-Film Cathode as Model System for Lithium Ion Batteries

We demonstrate a process to prepare model electrodes of the Ni-rich layered compound LiNi 0.6 Mn 0.2 Co 0.2 O 2 . These thin-film cathodes are compared with the composite materials to demonstrate the system is a viable platform for isolating interfacial phenomena between the electrolyte and active material without the influence of binders and conductive additives. The appropriate choice of heterolayers was found to influence the preferential orientation of the (101) and (104) planes relative to the (003) plane of the layered R-3m crystal structure, enhancing Li + diffusion and improving electrochemical performance. The addition of a Co interlayer between the Pt current collecting layer and alumina substrate increased the (101) and (104) texturing of the 500 nm Ni-rich film and allowed cells to deliver greater than 50% of their theoretical capacity. This work provides an architecture for isolating complex mechanisms of active materials that suffer from surface reconstruction and degradation in electrochemical cells.

25 ENERGY STORAGE↗
DOE OSTI2025

Ultrathin VO 2 Films on Functional Substrates

The metal–insulator transition (MIT) in vanadium dioxide (VO 2 ) thin films is strongly affected by grain size, thickness, and interfacial properties. Typically, a minimum thickness around 50 nm is required for VO 2 to exhibit a significant MIT when functional substrates like sapphire and silicon are used. Several works have shown that thin films below 20 nm, with up to 2–3 decades of change in the resistance across the MIT, can be achieved but require complex pre- or postprocessing of the samples. We show that predeposition substrate condition control facilitates the direct growth of VO 2 ultrathin 15 nm films, exhibiting a resistance change between 3 and 4 decades across the MIT. Our findings indicate that the interface between the film and the substrate is crucial in determining the initial growth layers and the structural evolution. With appropriate substrate surface treatment, the desired VO 2 MIT can be enhanced regardless of the substrate crystallographic orientation. Moreover, we propose a novel approach to obtain large resistance changes across the MIT in ultrathin VO 2 films by incorporating a predeposited 1.5 nm vanadium oxide buffer layer, thereby eliminating the need to use different materials or complex pre- or postprocessing of the samples. Here we also demonstrate that this method improves the transition of 25–50 nm VO 2 thin films on silicon substrates. Our study reveals a simple approach for direct growth of ultrathin VO 2 films exhibiting a significant MIT, which is commonly accepted unattainable over substrates of technological importance, such as sapphire and silicon.

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

Enhancement of the ultraviolet photoluminescence of ZnO films: Coatings, annealing, and environmental exposure studies

To realize the many potential applications of ZnO films, it is vital to produce films with high optical quality that exhibit strong UV luminescence. By combining annealing at an optimal temperature followed by the deposition of a coating, one can achieve a significant enhancement of photoluminescence (PL). The effectiveness of the coating over time is a crucial point to be considered. Three types of coating materials were investigated: MgO, SiO 2 , and Al 2 O 3 . Due to its strong bond energy, MgO was found to be the most effective coating material for passivation of the surfaces of the ZnO films; SiO 2 was the second best. The UV-PL intensity of MgO coated ZnO was found to increase by a factor of 52 relative to an uncoated film. The effectiveness of the coatings exhibited a linear correlation with their bond energies and is discussed in terms of competing mechanisms to surface passivation such as the adsorption of OH-groups; these can act as surface traps and diminish the UV-PL intensity. Annealing at 900 °C prior to the deposition of the coating was found to be an important step in realizing the optimal performance of the coating due to the reduction of Zn interstitials accompanied by improved crystallinity. Exposure to the environment, up to 294 days, results in the degradation of the UV-PL of the MgO coated film; this effect was not observed for the film coated with SiO 2 . This effect is discussed in terms of the strong reactivity of MgO with environmental contaminants from the OH-groups.

36 MATERIALS SCIENCE↗