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At least 109 records · Page 6

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NASA NTRS2021

Benchmarking Surface Tension Measurement Method using two Oscillation Modes in Levitated Liquid Metals

The Faraday forcing method in levitated liquid droplets has recently been introduced as a method for measuring surface tension using resonance. By subjecting an electrostatically-levitated liquid metal droplet to a continuous, oscillatory, electric field, at a frequency nearing that of the droplet’s first principal mode of oscillation (known as mode 2), the method was previously shown to determine surface tension of materials that would be particularly difficult to process by other means, e.g. liquid metals and alloys. It also offers distinct advantages in future work involving high viscosity samples because of the continuous forcing approach. This work presents 1) a benchmarking experimental method to measure surface tension by excitation of the second principal mode of oscillation (known as mode 3) in a levitated liquid droplet and 2) a more rigorous quantification of droplet excitation using a projection method. Surface tension measurements compare favorably to literature values for Zirconium, Inconel 625, and Rhodium, using both modes 2 and 3. Thus, this new method serves as a credible, self-consistent benchmarking technique for the measurement of surface tension

Levitation↗

DOE OSTI2019

Temperature gradients for thermophysical and thermochemical property measurements to 3000 °C for an aerodynamically levitated spheroid

This study examines thermal gradients in ceramic oxide spheroids being aerodynamically levitated in a conical nozzle levitator (CNL) system equipped with a CO 2 laser (10.6 μm wavelength). The CNL system is a versatile piece of equipment that can easily be coupled with advanced thermophysical and thermochemical measuring devices, such as diffraction/scattering (X-ray and neutron), nuclear magnetic resonance, and calorimetry, for the analysis of bulk spheroidal solids and liquids. The thermal gradients of a series of single crystal, polycrystalline solids, and liquid spheroids have been measured spatially in the CNL system, by means of a disappearing filament pyrometer (800-3000 °C) and by X-ray diffraction with reference to an internal standard (Pt: 800-1600 °C). The thermal gradient in a levitated sample being heated by a laser from the top can be minimized by: (i) maximizing the sphericity, (ii) maximizing the density, and (iii) minimizing microstructural features. A spheroid with these properties can be manufactured via machining a perfect sphere from a highly dense, chemically and phase pure pellet. These properties promote rotation of the sample about multiple axes in the air stream, enabling homogeneous heating. This homogeneous heating is the dominant factor in reducing thermal gradients in solid state samples. It was found that the thermal gradient in an similar to 3 mm diameter solid sample could be reduced from 1000 °C to 30 °C, by having a perfectly spherical shape that could rotate on multiple axes in a high velocity gas stream (similar to 1500-2000 cm 3 /min). As a result, these findings will allow accurate thermophysical and thermochemical property measurements of solids in situ at high temperatures, using the CNL system.

47 OTHER INSTRUMENTATION↗

DOE OSTI2024

Ultralight dark matter detection with levitated ferromagnets

Levitated ferromagnets act as ultraprecise magnetometers, which can exhibit high quality factors due to their excellent isolation from the environment. These instruments can be utilized in searches for ultralight dark matter candidates, such as axionlike dark matter or dark-photon dark matter. In addition to being sensitive to an axion-photon coupling or kinetic mixing, which produce physical magnetic fields, ferromagnets are also sensitive to the effective magnetic field (or “axion wind”) produced by an axion-electron coupling. While the dynamics of a levitated ferromagnet in response to a dc magnetic field have been well studied, all of these couplings would produce ac fields. In this work, we study the response of a ferromagnet to an applied ac magnetic field and use these results to project their sensitivity to axion and dark-photon dark matter. We pay special attention to the direction of motion induced by an applied ac field, in particular, whether it precesses around the applied field (similar to an electron spin) or librates in the plane of the field (similar to a compass needle). We show that existing levitated ferromagnet setups can already have comparable sensitivity to an axion-electron coupling as comagnetometer or torsion balance experiments. In addition, future setups can become sensitive probes of axion-electron coupling, dark-photon kinetic mixing, and axion-photon coupling, for ultralight dark matter masses m DM ≲ feV . Published by the American Physical Society 2024

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

DOE OSTI2018

Developing Quantum Levitation of ICF Capsules Coated with MgB 2 Thin Films

Current inertial confinement fusion (ICF) capsule support technologies create implosion perturbations which reduce fusion yield, driving the search for new support paradigms. Quantum levitation of the capsule will eliminate the requirement of a physical support structure, increasing fusion yield. The application of an external magnetic field to a capsule coated with a superconducting film can provide the necessary conditions for levitation. Magnesium diboride (MgB 2 ) is an attractive option for ICF applications as it has a high reported superconducting transition temperature of 39 K and is a low Z compound. This project is part of an ongoing effort which seeks to coat ICF capsules with a thin layer of superconducting MgB 2 . This project studied the synthesis of MgB 2 and diffusion/reaction kinetics of B/Mg/B m ultilayer thin films. These films were sputter deposited on flat glassy carbon substrates. Films were annealed in a tube furnace at temperatures between 400 °C and 650 °C for a total of 29 hours with film characterization done at predetermined intervals. At each interval, superconducting properties of the samples were evaluated with superconducting quantum interference device (SQUID) magnetometry, while Rutherford backscattering (RBS) with 2 MeV 4 He + ions was done to determine the composition and depth profile of the films. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) were used to characterize surface morphology. Superconducting behavior was observed in thin films annealed at and above 450 °C. Formation of superconducting MgB 2 at 450 °C h as not been previously reported below 500 °C. The surface of the samples annealed at 500 °C and below was smooth with a measured roughness of ~3 nm. After 29 hours of annealing time, the 450 °C sample had a transition temperature of 27.3 K. The highest transition temperature measured was 30.9 K and was associated with a sample annealed for 29 hours at 650 °C. Transition temperatures were weakly positively correlated with annealing temperature and showed dependence on initial structural quality and oxygen contamination. Current research is attempting to synthesize superconducting MgB 2 coatings on spherical Si beads with the findings of this study. Future efforts are focused on the construction and testing of a levitation apparatus.

36 MATERIALS SCIENCE↗

DOE OSTI2022

SRF Levitation and Trapping of Nanoparticles Experiment

The levitation and trapping of micro particles using lasers is not a new accomplishment and has been applied in containerless processing and spectroscopy of microparticles. Recent developments in the field of optomechanics have achieved levitating nanoparticles such that quantum phenomena was observed which would have relevance in quantum science and technology. This two-year project sought to levitate and trap mesoscopic particles using radio frequency (RF) fields in a resonating superconducting RF (SRF) cavity. By exploiting the intrinsic characteristics of an SRF resonating cavity, the project was to explore overcoming a major limit faced by current laser trapping techniques. The goal was to establish a foundation to enable the observation of quantum phenomena of an isolated mechanical oscillator interacting with microwave fields. If successful the experiment could establish its ground-breaking relevance to quantum information science and technology.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗

NASA NTRS1969

Levitation-melting technique for metals and alloys

Experimentation resulted in an improved levitation-melting technique for metals and alloys which quickly produces a completly homogeneous melt. Also developed were two levitation coils that permit a wide variety of metals to be levitated in the molten state and a helium quenching method which minimizes contamination and segregation.

Downey, J. W.↗

NASA NTRS1975

Electromagnetic levitation facility incorporating electron beam

An electromagnetic levitation apparatus incorporating an electron beam for auxiliary heating and melting has been developed for experiments on containerless vacuum purification and undercooled solidification of high melting materials. Stable levitation of 10-g specimens of molten tungsten has been achieved and a variety of containerless solidification experiments is being performed, including pure polycrystalline castings and single tungsten crystals grown from the undercooled levitated melts.

Wouch, G.↗

NASA NTRS1983

Variable-Position Acoustic Levitation

Method of acoustic levitation supports objects at positions other than acoustic nodes. Acoustic force is varied so it balances gravitational (or other) force, thereby maintaining object at any position within equilibrium range. Levitation method applicable to containerless processing. Such objects as table-tennis balls, hollow plastic spheres, and balsa-wood spheres levitated in laboratory by new method.

Barmatz, M. B.↗

NASA NTRS1983

Controlling the Rotation of Levitated Samples

In proposed acoustic levitation system, separate excitation of different acoustic modes independently levitate and control rotation of sample. Three independent axes of rotation are available, leading to rotation of levitated object about any other selected axis.

Barmatz, M. B.↗

NASA NTRS1983

Electrostatic Levitator With Feedback Control

Sample position automatically maintained. Object levitated by electrostatic field between two electrodes. Because of particular curved electrode shape, levitation field has stable horizontal position on vertical axis of symmetry. Vertical position of object sensed and compared with preset value. When position error is detected, amplitude of levitating field is increased or decreased to restore zero error. System offers options well to containerless processing.

Rhim, W. K.↗

NASA NTRS1982

Atomic fluorescence study of high temperature aerodynamic levitation

Ultraviolet laser induced atomic fluorescence has been used to characterize supersonic jet aerodynamic levitation experiments. The levitated specimen was a 0.4 cm sapphire sphere that was separately heated at temperatures up to 2327 K by an infrared laser. The supersonic jet expansion and thermal gradients in the specimen wake were studied by measuring spatial variations in the concentration of atomic Hg added to the levitating argon gas stream. Further applications of atomic fluorescence in containerless experiments, such as ideal gas fluorescence thermometry and containerless process control are discussed.

Nordine, P. C.↗

NASA NTRS1982

Theory and applications of electromagnetic levitation

A simple treatment of the electromagnetic levitation problem is presented, with emphasis placed on approximate formulas useful in planning and interpreting laboratory measurements. Consideration is also given to numerical solutions for fields, eddy currents, and Lorentz forces for rapidly varying applied fields, with particular reference made to traveling wave levitation experiments. Applications of levitation processing are briefly reviewed, including thermophysical property measurements, undercooling studies, containerless crystal growth, and continuous casting of cylinders.

Frost, R. T.↗

NASA NTRS1982

Development of electrostatic levitator at JPL

Preliminary results on the design and operation of electrostatic levitators developed at JPL are reported. Particular attention is given to the single-axis levitators for ground-based operation and for operation in the reduced gravity environment. Descriptions are given of the design principles and the performance of final products. A levitator designed for zero-g environment is shown. It is a single-axis system, so there is no active lateral damping. Two ring and two disk electrodes are included. The ring electrodes always maintain a constant voltage difference with respect to the central disk electrodes. This is to ensure that there is always a centering force that does not depend on the voltage difference between the top and bottom electrodes. As the ring-to-disk voltage increases, there is a proportionate increase in the centering force.

Rhim, W.-K.↗

NASA NTRS1982

Air jet levitation furnace system for observing glass microspheres during heating and melting

A collimated hole structure air jet levitation system has been developed which can be used to levitate hollow glass microspheres used in inertial confinement fusion studies. An ellipsoidal furnace has been added to the system to provide a heating source. A video camera and a 16 mm movie camera connected to a microsphere system provide real time observation as well as permanent documentation of the experiments. Microspheres have been levitated at temperatures over 1400 C for over 10 minutes at a time.

Ethridge, E. C.↗

NASA NTRS1983

Electromagnetic levitation coil fabrication technique for MSFC containerless processing facilities

A technique is described for more reproducible fabrication of electromagnetic levitation coils. A split mandrel was developed upon which the coil is wound. After fabrication the mandrel can be disassembled to remove it from the coil. Previously, a full day was required to fabricate a levitation coil and the success rate for a functional coil was only 50 percent. About eight coils may be completed in one day using the technique developed and 95 percent of them are good levitation coils.

Ethridge, E. C.↗

NASA NTRS1985

Controlling Sample Rotation in Acoustic Levitation

Rotation of acoustically levitated object stopped or controlled according to phase-shift monitoring and control concept. Principle applies to square-cross-section levitation chamber with two perpendicular acoustic drivers operating at same frequency. Phase difference between X and Y acoustic excitation measured at one corner by measuring variation of acoustic amplitude sensed by microphone. Phase of driver adjusted to value that produces no rotation or controlled rotation of levitated object.

Barmatz, M. B.↗

NASA NTRS1986

Levitation With a Single Acoustic Driver

Pair of reports describes acoustic-levitation systems in which only one acoustic resonance mode excited, and only one driver needed. Systems employ levitation chambers of rectangular and cylindrical geometries. Reports first describe single mode concept and indicate which modes used to levitate sample without rotation. Reports then describe systems in which controlled rotation of sample introduced.

Barmatz, M. B.↗

NASA NTRS1987

Measuring Shapes of Acoustically Levitated Drops

Instrument records shadows of drops in acoustic field. Shapes of acoustically levitated liquid drops and gas bubbles examined by shadow projector. Although acoustic radiation pressure counterbalances gravitational force acting on levitated drops and bubbles, pressure usually not uniform over surfaces and causes them to assume nonspherical shapes. Shape of drop or bubble gives useful information about acoustic field and levitated material. Held aloft in laser beam by acoustic field, liquid drop casts shadow on photographic film. Changing shape of drop recorded in sequence of exposures.

Trinh, E. H.↗