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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

A CFD Study Assisted with Experimental Confirmation for Liquid Shape Control of Electromagnetically Levitated Bulk Materials

Two types of optimized electromagnetic levitators were designed to achieve the free surface shape control of metallic melts as the combined results of the Lorentz force, sample gravity, and surface tension. The levitation behavior of bulk melts was investigated using computational fluid dynamics (CFD) modeling coupled with high-frequency electromagnetic field analysis and the arbitrary Lagrangian–Eulerian (ALE) method. The difference in the oscillation behavior between the solid and molten samples was explained by the damping of the electromagnetic induction and liquid viscosity. The motion of the mass center, melt shape, flow pattern, and Lorentz force in the levitated melt were determined within a wide excitation current range. With the increase in the applied current, the melt’s centroid position rose sharply in the area with low current but displayed a slow increase in the area with high current. Meanwhile, the stable shape of the bulk melt showed the typical transition from a long taper through a short taper and then into a rhombus. The internal flow pattern transformed from a simple double-loop structure to a complex configuration with three or four loops. The dependence of the deformation on the Bond number was analyzed in the two types of levitators. In addition, the stable shape and swing process of the bulk Al melt within the two types of electromagnetic levitation (EML) systems were quantitatively studied under protective inert gas conditions. The melt contour could be well described by the 10th Legendre polynomial function with a deviation of less than 0.5 pct.

36 MATERIALS SCIENCE↗
DOE OSTI2014

Experimental determination of the dynamics of an acoustically levitated sphere

Levitation of solids and liquids by ultrasonic standing waves is a promising technique to manipulate materials without contact. When a small particle is introduced in certain areas of a standing wave field, the acoustic radiation force pushes the particle to the pressure node. This movement is followed by oscillations of the levitated particle. Aiming to investigate the particle oscillations in acoustic levitation, this paper presents the experimental and numerical characterization of the dynamic behavior of a levitated sphere. To obtain the experimental response, a small sphere is lifted by the acoustic radiation force. After the sphere lift, it presents a damped oscillatory behavior, which is recorded by a high speed camera. To model this behavior, a mass-spring-damper system is proposed. In this model, the acoustic radiation force that acts on the sphere is theoretically predicted by the Gor'kov theory and the viscous forces are modeled by two damping terms, one term proportional to the square of the velocity and another term proportional to the particle velocity. The proposed model was experimentally verified by using different values of sound pressure amplitude. The comparison between numerical and experimental results shows that the model can accurately describe the oscillatory behavior of the sphere in an acoustic levitator.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Particle manipulation by a non-resonant acoustic levitator

We present the analysis of a non-resonant acoustic levitator, formed by an ultrasonic transducer and a concave reflector. In contrast to traditional levitators, the geometry presented herein does not require the separation distance between the transducer and the reflector to be a multiple of half wavelength. The levitator behavior is numerically predicted by applying a numerical model to calculate the acoustic pressure distribution and the Gor'kov theory to obtain the potential of the acoustic radiation force that acts on a levitated particle. We also demonstrate that levitating particles can be manipulated by controlling the reflector position while maintaining the transducer in a fixed position.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2024

Quantum control and Berry phase of electron spins in rotating levitated diamonds in high vacuum

Levitated diamond particles in high vacuum with internal spin qubits have been proposed for exploring macroscopic quantum mechanics, quantum gravity, and precision measurements. The coupling between spins and particle rotation can be utilized to study quantum geometric phase, create gyroscopes and rotational matter-wave interferometers. However, previous efforts in levitated diamonds struggled with vacuum level or spin state readouts. To address these gaps, we fabricate an integrated surface ion trap with multiple stabilization electrodes. This facilitates on-chip levitation and, for the first time, optically detected magnetic resonance measurements of a nanodiamond levitated in high vacuum. The internal temperature of our levitated nanodiamond remains moderate at pressures below 10 -5 Torr. We have driven a nanodiamond to rotate up to 20 MHz (1.2 × 10 9 rpm), surpassing typical nitrogen-vacancy (NV) center electron spin dephasing rates. Using these NV spins, we observe the effect of the Berry phase arising from particle rotation. In addition, we demonstrate quantum control of spins in a rotating nanodiamond. These results mark an important development in interfacing mechanical rotation with spin qubits, expanding our capacity to study quantum phenomena.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2019

Enhanced Magnetic Levitation and Guidance Force in MgB{sub 2} Bulks by Synthetic Engine Oil Immersion

We have used ‘Synthetic engine oil’ as a rich easily accessible carbon source and investigated the effect of engine oil on the microstructure, critical current density (J{sub c}), vertical levitation force (F{sub z}) and guidance force (F{sub x}) properties of MgB{sub 2} superconductor. The polycrystalline disk-shaped MgB{sub 2} bulk samples have been prepared using two-step solid-state reaction process. After the first heating process, MgB{sub 2} bulk samples immersed in the engine oil for different durations (30, 120, 300 and 1440 min). XRD analysis indicated the decreasing of lattice parameters of samples and confirmed C substitution in boron sites. Vertical levitation and guidance force measurements were carried out with both Field-cooling (FC) and zero-field-cooling (ZFC) regimes at different temperatures of 20, 24 and 28 K. It was found that engine oil addition slightly increases the levitation and guidance force properties. The F{sub z} values were obtained as 11.17 and 11.58 N for pure and MgB{sub 2} sample immersed for 30 min at 20 K in ZFC regime. In addition, the MgB{sub 2} sample immersed for 300 min in engine oil showed the highest J{sub c} value of 5.3×10{sup 4} A cm{sup − 2} at 15 K and self-field and showed the highest guidance force value of 4.14 N at 20 K. These finding suggest that synthetic engine oil is a cost-effective and promising method to improve the levitation and guidance force performance as well as the critical current density of MgB{sub 2} bulk superconductor.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Trapped Field and Levitation Performance of a YBCO Superconductor Magnetized in Different External Magnetic Fields

In order to find a relative preferable method to improve the trapped magnetic field (B{sub trap}) of a YBCO superconductor, the influences of field-cooling height (FCH), magnetization intensity, and magnetization process on the trapped fields of the high temperature superconductor (HTS) magnetized in the magnetic fields of the permanent magnet guideway (PMG) and the superconducting magnet (SM) were both studied. In addition, the levitation forces of the bulk magnetized in the two different magnetic fields were also investigated in this paper. The experimental results showed that the maximum trapped field ratio (δ{sub trap}) of the bulk magnetized above the PMG attained the largest value, when the initial FCH was 30 mm. The remagnetization process was a preferable method to increase the B{sub trap}, in the case that the FCH was higher than 30 mm. When the exciting current (I{sub e}) of the SM was smaller than 15 A, the remagnetization process was an effective method to improve the B{sub trap}. The remagnetization performance of the bulk attained the saturation, under the condition that the I{sub e} was larger than 15 A. In the aspect of the levitation performance, it can be found that the decreasing amplitude of the force with the B{sub trap} became larger, when the levitation gap was lower. The force acted on the bulk increased with increasing the magnetic fields of the SM. Moreover, the results also indicated that the initial B{sub trap} was larger; the maximum levitation force (F{sub lmax}) became smaller. The magnetic hysteresis of the bulk was found to decrease with increasing the B{sub trap.}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2011

A highly modular beamline electrostatic levitation facility, optimized for in situ high-energy x-ray scattering studies of equilibrium and supercooled liquids

High-energy x-ray diffraction studies of metallic liquids provide valuable information about structural evolution on the atomic length scale, leading to insights into the origin of the nucleation barrier and the processes of supercooling and glass formation. The containerless processing of the beamline electrostatic levitation (BESL) facility allows coordinated thermophysical and structural studies of equilibrium and supercooled liquids to be made in a contamination-free, high-vacuum ({approx}10{sup -8} Torr) environment. To date, the incorporation of electrostatic levitation facilities into synchrotron beamlines has been difficult due to the large footprint of the apparatus and the difficulties associated with its transportation and implementation. Here, we describe a modular levitation facility that is optimized for diffraction studies of high-temperature liquids at high-energy synchrotron beamlines. The modular approach used in the apparatus design allows it to be easily transported and quickly setup. Unlike most previous electrostatic levitation facilities, BESL can be operated by a single user instead of a user team.

47 OTHER INSTRUMENTATION↗
DOE OSTI2015

An in-vacuo optical levitation trap for high-intensity laser interaction experiments with isolated microtargets

We report on the design, construction, and characterisation of a new class of in-vacuo optical levitation trap optimised for use in high-intensity, high-energy laser interaction experiments. The system uses a focused, vertically propagating continuous wave laser beam to capture and manipulate micro-targets by photon momentum transfer at much longer working distances than commonly used by optical tweezer systems. A high speed (10 kHz) optical imaging and signal acquisition system was implemented for tracking the levitated droplets position and dynamic behaviour under atmospheric and vacuum conditions, with ±5 μm spatial resolution. Optical trapping of 10 ± 4 μm oil droplets in vacuum was demonstrated, over timescales of >1 h at extended distances of ∼40 mm from the final focusing optic. The stability of the levitated droplet was such that it would stay in alignment with a ∼7 μm irradiating beam focal spot for up to 5 min without the need for re-adjustment. The performance of the trap was assessed in a series of high-intensity (10{sup 17} W cm{sup −2}) laser experiments that measured the X-ray source size and inferred free-electron temperature of a single isolated droplet target, along with a measurement of the emitted radio-frequency pulse. These initial tests demonstrated the use of optically levitated microdroplets as a robust target platform for further high-intensity laser interaction and point source studies.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2011

Levitated crystals and quasicrystals of metamaterials

New scientific and technological opportunities exist by marrying dusty plasma research with metamaterials. Specifically, by balancing control and self-assembly, certain laboratory plasmas can become a generic levitation platform for novel structure formation and nanomaterial synthesis. We propose to experimentally investigate two dimensional (2D) and three dimensional (3D) levitated structures of metamaterials and their properties. Such structures can self assemble in laboratory plasmas, similar to levitated dust crystals which were discovered in the mid 1990's. Laboratory plasma platform for metamaterial formation eliminates substrates upon which most metamaterials have to be supported. Three types of experiments, with similar setups, are discussed here. Levitated crystal structures of metamaterials using anisotropic microparticles are the most basic of the three. The second experiment examines whether quasicrystals of metamaterials are possible. Quasicrystals, discovered in the 1980's, possess so-called forbidden symmetries according to the conventional crystallography. The proposed experiment could answer many fundamental questions about structural, thermal and dynamical properties of quasicrystals. And finally, how to use nanoparticle coated microparticles to synthesize very long carbon nanotubes is also described. All of the experiments can fit inside a standard International Space Station locker with dimensions of 8-inch x 17-inch X 18-inch. Microgravity environment is deemed essential in particular for large 3D structures and very long carbon nanotube synthesis.

36 MATERIALS SCIENCE↗
DOE OSTI2013

Final Report: Levitated Dipole Experiment

Since the very first experiments with the LDX, research progress was rapid and significant. Initial experiments were conducted with the high-field superconducting coil suspended by three thin rods. These experiments produced long-pulse, quasi-steady-state microwave discharges, lasting more than 10 s, having peak beta values of 20% [Garnier et al., Physics of Plasmas, 13 (2006) 056111]. High- beta, near steady-state discharges have been maintained in LDX for more than 20 seconds, and this capability made LDX the longest pulse fusion confinement experiment operating in the U.S. fusion program. A significant measure of progress in the LDX research program was the routine investigation of plasma confinement with a magnetically-levitated dipole and the resulting observations of confinement improvement. In both supported and levitated configurations, detailed measurements were made of discharge evolution, plasma dynamics and instability, and the roles of gas fueling, microwave power deposition profiles, and plasma boundary shape. High-temperature plasma was created by multi frequency electron cyclotron resonance heating at 2.45 GHz, 6.4 GHz, 10.5 GHz and 28 GHz allowing control of heating profiles. Depending upon neutral fueling rates, the LDX discharges contain a fraction of energetic electrons, with mean energies above 50 keV. Depending on whether or not the superconducting dipole was levitated or supported, the peak thermal electron temperature was estimated to exceed 500 eV and peak densities to approach 1e18 m -3 . We have found that levitation causes a strong inwards density pinch [Boxer et al., Nature Physics, 6 (2010) 207] and we have observed the central plasma density increase dramatically indicating a significant improvement in the confinement of a thermal plasma species.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2017

Thermal Conductivity Measurement of Molten Cu-Co Alloy Using an Electromagnetic Levitator Superimposed with a Static Magnetic Field

The thermal conductivity of molten Cu-Co alloy with different compositions around the liquidus line temperature was measured by the periodic laser-heating method using an electromagnetic levitator superimposed with a static magnetic field to suppress convection in a levitated droplet sample. During the measurement, a static magnetic field of 10 T was applied to the levitated droplet. To confirm that the strength of the static magnetic field was sufficient to suppress convection in the droplet, numerical simulations were performed for the flow and thermal fields in an electromagnetically levitated droplet under a static magnetic field, and moreover, for the periodic laser-heating method to determine the thermal conductivity. It was found that the thermal conductivity of molten Cu-Co alloy increased gradually with increasing Cu composition up to 80 at. pct, beyond which it increased markedly and reached that of pure Cu. In addition, it was found that the composition dependence of the thermal conductivity can be explainable by the Wiedemann–Franz law.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Extreme Levitation of Colloidal Particles in Response to Oscillatory Electric Fields

Micron-scale colloidal particles suspended in electrolyte solutions have been shown to exhibit a distinct bifurcation in their average height above the electrode in response to oscillatory electric fields. Recent work by Hashemi Amrei et al. (Phys. Rev. Lett.,2018,121, 185504) revealed that a steady, long-range asymmetric rectified electric field (AREF) is formed when an oscillatory potential is applied to an electrolyte with unequal ionic mobilities. In this work, we use confocal microscopy to test the hypothesis that a force balance between gravity and an AREF-induced electrophoretic force is responsible for the particle height bifurcation observed in some electrolytes. We demonstrate that at sufficiently low frequencies, particles suspended in electrolytes with large ionic mobility mismatches exhibit extreme levitation away from the electrode surface (up to 50 particle diameters). This levitation height scales approximately as the inverse square root of the frequency for both NaOH and KOH solutions. Moreover, larger particles levitate smaller distances, while the magnitude of the applied field has little effect above a threshold voltage. A force balance between the AREF-induced electrophoresis and gravity reveals saddle node bifurcations in the levitation height with respect to the frequency, voltage, and particle size, yielding stable fixed points above the electrode that accord with the experimental observations. These results point toward a low-energy, non-fouling method for concentrating colloids at specific locations far from the electrodes.

74 ATOMIC AND MOLECULAR PHYSICS↗
DOE OSTI2026

Ion Cyclotron Heating in a Levitated Dipole Fusion Reactor

OpenStar Technologies is pursuing the levitated dipole (LD) as a highly modular, loosely-coupled system that leverages their expertise in high temperature superconductor (HTS) technology. The next generation experiment at OpenStar, Tahi (Ma¯ori for “first”), will demonstrate the generation and confinement of fast ions in a levitated dipole for the first time. Ion cyclotron range of frequency (ICRF) heating is a leading candidate for energetic ion formation in Tahi. A frequency in the 10 MHz range will be used for H minority heating or D majority heating with waves launched from an antenna located above the floating coil. Unlike a tokamak, where the targeted cyclotron resonance is typically a vertical path through the center of the plasma, in a dipole the resonance location follows a C-shaped path from the separatrix to the center of the plasma. The value of B also varies significantly within the confined plasma resulting in a large number of cyclotron harmonics present in the low field region. Furthermore, levitated dipoles contain a “first closed flux surface” surrounding the floating coil, in addition to the traditional separatrix /last closed flux surface. Simulation e ff orts using full-wave ICRF codes show that ICRF heating of a levitated dipole reactor is feasible using a pair of toroidal current straps phased to launch the appropriate parallel ( i.e. poloidal) refractive index.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2010

Effect of the levitating microparticle cloud on radiofrequency argon plasma

The effect of a levitating cloud of microparticles on the parameters of a radiofrequency (RF) plasma has been studied by means of two experimental techniques. Axial distributions of 1s excited states of argon were measured by a self-absorption method. A correction of a standard self-absorption method for the extinction of the light by the levitating microparticles is proposed. In addition the electron temperature was estimated using the optical emission spectroscopy. Measurements at the same discharge conditions in a microparticle-free discharge and discharge, containing a cloud of levitating microparticles, revealed the non-local influence of the microparticle cloud on the discharge plasma. The most probable cause of this influence is the disturbance of the ionization balance by the levitating microparticles.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2021

On-chip optical levitation with a metalens in vacuum

Optical levitation of dielectric particles in vacuum is a powerful technique for precision measurements, testing fundamental physics, and quantum information science. Conventional optical tweezers require bulky optical components for trapping and detection. Here, we design and fabricate an ultrathin dielectric metalens with a high numerical aperture of 0.88 at 1064 nm in vacuum. It consists of 500-nm-thick silicon nano-antennas, which are compatible with an ultrahigh vacuum. We demonstrate optical levitation of nanoparticles in vacuum with a single metalens. The trapping frequency can be tuned by changing the laser power and polarization. We also transfer a levitated nanoparticle between two separated optical tweezers. Optical levitation with an ultrathin metalens in vacuum provides opportunities for a wide range of applications including on-chip sensing. Such metalenses will also be useful for trapping ultracold atoms and molecules.

Shen, Kunhong↗
DOE OSTI2013

Bifunction in Er{sup 3+}/Yb{sup 3+} co-doped BaTi{sub 2}O{sub 5}–Gd{sub 2}O{sub 3} glasses prepared by aerodynamic levitation method

Graphical abstract: - Highlights: • Novel BaTi{sub 2}O{sub 5}–Gd{sub 2}O{sub 3} based glasses have been prepared by aerodynamic levitation. • The obtained glasses show high thermal stability with T{sub g} = 763.3 °C. • Er{sup 3+}/Yb{sup 3+} co-doped glasses show strong upconversion based on a two-photon process. • Red emission is stronger than green emissions for EBT by high Yb{sup 3+} concentration. • Magnetic ions are paramagnetic and the distribution is homogeneous in the glasses. - Abstract: Novel Er{sup 3+}/Yb{sup 3+} co-doped BaTi{sub 2}O{sub 5}–Gd{sub 2}O{sub 3} spherical glasses have been fabricated by aerodynamic levitation method. The thermal stability, upconversion luminescence, and magnetic properties of the present glass have been studied. The glasses show high thermal stability with 763.3 °C of the onset temperature of the glass transition. Red and green emissions centered at 671 nm, 548 nm and 535 nm are obtained at 980 nm excitation. The upconversion is based on a two-photon process by energy transfer, excited-state absorption, and energy back transfer. Yb{sup 3+} ions are more than Er{sup 3+} ions in the glass, resulting in efficient energy back transfer from Er{sup 3+} to Yb{sup 3+}. So the red emission is stronger than the green emissions. Magnetization curves indicate that magnetic rare earth ions are paramagnetic and the distribution is homogeneous and random in the glass matrix. Aerodynamic levitation method is an efficient way to prepare glasses with homogeneous rare earth ions.

36 MATERIALS SCIENCE↗
DOE OSTI2012

Determination of the levitation limits of dust particles within the sheath in complex plasma experiments

Experiments are performed in which dust particles are levitated at varying heights above the powered electrode in a radio frequency plasma discharge by changing the discharge power. The trajectories of particles dropped from the top of the discharge chamber are used to reconstruct the vertical electric force acting on the particles. The resulting data, together with the results from a self-consistent fluid model, are used to determine the lower levitation limit for dust particles in the discharge and the approximate height above the lower electrode where quasineutrality is attained, locating the sheath edge. These results are then compared with current sheath models. It is also shown that particles levitated within a few electron Debye lengths of the sheath edge are located outside the linearly increasing portion of the electric field.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2016

Acoustic levitation of a large solid sphere

We demonstrate that acoustic levitation can levitate spherical objects much larger than the acoustic wavelength in air. The acoustic levitation of an expanded polystyrene sphere of 50 mm in diameter, corresponding to 3.6 times the wavelength, is achieved by using three 25 kHz ultrasonic transducers arranged in a tripod fashion. In this configuration, a standing wave is created between the transducers and the sphere. The axial acoustic radiation force generated by each transducer on the sphere was modeled numerically as a function of the distance between the sphere and the transducer. The theoretical acoustic radiation force was verified experimentally in a setup consisting of an electronic scale and an ultrasonic transducer mounted on a motorized linear stage. The comparison between the numerical and experimental acoustic radiation forces presents a good agreement.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗