Thermodynamic property measurement near the (sup 3)He liquid-gas critical point
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critical phenomena liquid-gas critical point↗
Engineering topics
Barmatz, M. B.
Publications and source records attributed to Barmatz, M. B..
MISTE flight experiment status
The MISTE flight experiment has made significant scientific and technical progress in preparing for a future microgravity flight. We are collaborating with several theoretical modeling groups that have developed crossover (equation-of-state) models for predicting thermodynamic behavior near the liquid-gas critical point. Several of these models have already been used to test experimental measurements of the heat capacity at constant volume, isothermal susceptibility, and coexistence curve in the crossover region near the 3He liquid-gas critical point. A brief description of these models and a representative fit to experimental data will be presented. In collaboration with Mission Research Corporation, MISTE has been testing a new small pneumatic valve for use at low temperatures. The results of recent successful low temperature actuation tests will also be discussed.
critical phenomena liquid-gas critical point↗
MISTE/LTMPEF International Space Station mission
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critical phenomena liquid-gas critical point Inter↗
Test of sigma(sup 4) model predictions near the (sup 3)He liquid-gas critical point
NASA is supporting the development of an experiment called MISTE (Microgravity Scaling Theory Experiment) for a future International Space Station mission.
critical phenomena liquid-gas critical point↗
Determining Equilibrium Position For Acoustical Levitation
Equilibrium position and orientation of acoustically-levitated weightless object determined by calibration technique on Earth. From calibration data, possible to calculate equilibrium position and orientation in presence of Earth gravitation. Sample not levitated acoustically during calibration. Technique relies on Boltzmann-Ehrenfest adiabatic-invariance principle. One converts resonant-frequency-shift data into data on normalized acoustical potential energy. Minimum of energy occurs at equilibrium point. From gradients of acoustical potential energy, one calculates acoustical restoring force or torque on objects as function of deviation from equilibrium position or orientation.
Barmatz, M. B.↗
Simplified Rotation In Acoustic Levitation
New technique based on old discovery used to control orientation of object levitated acoustically in axisymmetric chamber. Method does not require expensive equipment like additional acoustic drivers of precisely adjustable amplitude, phase, and frequency. Reflecting object acts as second source of sound. If reflecting object large enough, close enough to levitated object, or focuses reflected sound sufficiently, Rayleigh torque exerted on levitated object by reflected sound controls orientation of object.
Barmatz, M. B.↗
Vibrations Would Induce Flow In Molten Silicon
Flow patterns and velocities controlled to improve cystals. According to proposal, intense sound used to induce flow in molten silicon to increase quality of crystals grown in shallow-melt Czochralski process.
Barmatz, M. B.↗
Rotation Control In A Cylindrical Acoustic Levitator
Second driver introduces net circulation around levitated sample. Two transducers produce two sets of equal counterrotating acoustic fields. By appropriate adjustment of amplitudes and phases in two transducers, total acoustic field made to consist of two unequal counterrotating fields, producing net torque on levitated sample.
Barmatz, M. B.↗
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.↗
Acoustic Translation of an Acoustically Levitated Sample
Acoustic-levitation apparatus uses only one acoustic mode to move sample from one region of chamber to another. Sample heated and cooled quickly by translation between hot and cold regions of levitation chamber. Levitated sample is raised into furnace region by raising plunger. Frequency of sound produced by transducers adjusted by feedback system to maintain (102) resonant mode, which levitates sample midway between transducers and plunger regardless of plunger position.
Barmatz, M. B.↗
Acoustic Levitator Maintains Resonance
Transducer loading characteristics allow resonance tracked at high temperature. Acoustic-levitation chamber length automatically adjusted to maintain resonance at constant acoustic frequency as temperature changes. Developed for containerless processing of materials at high temperatures, system does not rely on microphones as resonance sensors, since microphones are difficult to fabricate for use at temperatures above 500 degrees C. Instead, system uses acoustic transducer itself as sensor.
Barmatz, M. B.↗
Vibrating-chamber levitation systems
Systems are described for the acoustic levitation of objects, which enable the use of a sealed rigid chamber to avoid contamination of the levitated object. The apparatus includes a housing forming a substantially closed chamber, and means for vibrating the entire housing at a frequency that produces an acoustic standing wave pattern within the chamber.
Barmatz, M. B.↗
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.↗
Acoustic particle separation
A method is described which uses acoustic energy to separate particles of different sizes, densities, or the like. The method includes applying acoustic energy resonant to a chamber containing a liquid of gaseous medium to set up a standing wave pattern that includes a force potential well wherein particles within the well are urged towards the center, or position of minimum force potential. A group of particles to be separated is placed in the chamber, while a non-acoustic force such as gravity is applied, so that the particles separate with the larger or denser particles moving away from the center of the well to a position near its edge and progressively smaller lighter particles moving progressively closer to the center of the well. Particles are removed from different positions within the well, so that particles are separated according to the positions they occupy in the well.
Barmatz, M. B.↗
Gravity enhanced acoustic levitation method and apparatus
An acoustic levitation system is provided for acoustically levitating an object by applying a single frequency from a transducer into a resonant chamber surrounding the object. The chamber includes a stabilizer location along its height, where the side walls of the chamber are angled so they converge in an upward direction. When an acoustic standing wave pattern is applied between the top and bottom of the chamber, a levitation surface within the stabilizer does not lie on a horizontal plane, but instead is curved with a lowermost portion near the vertical axis of the chamber. As a result, an acoustically levitated object is urged by gravity towards the lowermost location on the levitation surface, so the object is kept away from the side walls of the chamber.
Barmatz, M. B.↗
Matching Impedances and Modes in Acoustic Levitation
Temperature differences accommodated with tunable coupler. Report discusses schemes for coupling sound efficiently from cool outside atmosphere into hot acoustic-levitation chamber. Theoretical studies have practical implications for material-processing systems that employ acoustic levitation.
Barmatz, M. B.↗
Phase Modulation Stops Levitated Sample Rotation
Rotation of sample in acoustic levitator prevented by relatively simple phase-modulation scheme. Technique differs from older methods; no feedback control or observation of sample required, nor necessary to carefully tune or detune two oscillators to precise frequency differences from resonance.
Barmatz, M. B.↗
Acoustic-Levitation Chamber
Uncontaminated environments for highly-pure material processing provided within completely sealed levitation chamber that suspends particles by acoustic excitation. Technique ideally suited for material processing in low gravity environment of space.
Barmatz, M. B.↗