Factors related to mineral separation in a vacuum
Very high vacuum terrestrial mineral beneficiation methods transferred to vacuum ambient of lunar surface
Fraas, F.↗
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Measurement of electrode erosion during high- voltage vacuum breakdown
Electrode erosion during high voltage vacuum breakdown measured by neutron activation analysis and gamma ray spectrometry, noting plasma formation from electrode material
Fagen, W. F.↗
Selective coatings for vacuum-stable high- temperature solar absorbers
Coating for vacuum-stable high temperature solar absorbers
VACUUM↗
High Insulating Vacuum Pump Cart Analysis
To maintain superconductive and cryogenic temperature, it is necessary to utilize high vacuum to eliminate convective heat transfer. To reach the desirable pressure of 10^-6 Torr at a reasonable time, the vacuum pumps and vessel geometry are evaluated for compatibility. Based on the analysis, a list of dry scroll pumps and turbomolecular pumps are recommended.
Chicas, Kelly [Illinois U., Urbana]↗
Air lock mechanism speeds specimen testing in high-temperature vacuum furnaces
Mechanism, made of 347 stainless steel, is attached to furnace port by bolted flange. Unit incorporates quick opening, high vacuum valve and associated fittings which provide connections to air lock evacuation and to inert gas supply for quenching specimen after it is withdrawn from furnace into air lock.
Whitehead, C.↗
Emission tester for high-power vacuum tubes
A simple emission-testing circuit for high power vacuum tubes to check their output stability is described. With modification it may be useful in testing mercury-arc rectifiers.
Lundy, C.↗
Getters for Reliable Hermetic Packages
A variety of sealed-off devices such as cathode ray tubes (CRT's) electron tubes, plasma displays, particle accelarators and colliders vacuum thermal insulation, ultra-high vacuum (UHV), extreme high vacuum (XHV) systems for semiconductor processing, X-ray tubes, lamps, field-emission displays (FEDs) flat panel displays (FPDs), some microelectromechanical systems (MEMS) and science instruments for space applications, nuclear systems require a vacuum for their successful operation.
getters hermetic packaging electronic↗
A search for experiments to exploit the space shuttle environment, volume 1
A search for worthwhile experiments in pure and applied physics and chemistry which might take advantage of conditions achievable aboard the space shuttle is documented. Of particular interest were the very large pumping speeds at high or ultra high vacuum, the highly nonequilibrium composition of the ambient atmosphere, and the relative absence of gravitational effects. Ideas and suggestions were solicated in the course of visits to 31 research establishments in Western Europe, India, and Japan; conversations with over 90 scientists; and presentations at 3 international meetings. Intriguing possibilities emerged in the following arenas: (1) spectroscopy of the transition state in chemical reactions; (2) flame structure and analysis; (3) solid propellant combustion; (4) analysis of atmospheric composition; (5) turbulence effects on aerosol coagulation.
Fenn, J. B.↗
Space Station - The base for tomorrow's electronic industry
The potential value of space material processing on the Space Station for the electronics industry is examined. The primary advantages of the space environment for producing high-purity semiconductors and electrooptical materials are identified as the virtual absence of gravity (suppressing buoyancy-driven convection in melts and density segregation of alloys) and the availabilty of high vacuum (with high pumping speed and heat rejection). The recent history of material development and processing technology in the electronics industry is reviewed, and the principal features of early space experiments are outlined.
Naumann, Robert J.↗
Particle adhesion to surfaces under vacuum
The release of glass beads and standard dust from aluminum and glass substrates under centrifugation (simulating atmospheric pressure, low vacuum, and high vacuum conditions) was measured, with application to the estimation of contaminant particle release during spacecraft launch. For particles in the 10-100 micron range, dust was found to adhere more strongly than glass beads in all the cases considered. For most of the cases, dust and glass beads adhered more strongly to glass than to aluminum at all pressures. The adhesion force for dust on glass at 10 torr was shown to be as small as the value for dust on aluminum.
Barengoltz, Jack B.↗
Wide gap, permanent magnet biased magnetic bearing system
The unique features and applications of the presented electrical permanent magnetic bearing system essentially result from three facts: (1) the only bearing rotor components are nonlaminated ferromagnetic steel collars or cylinders; (2) all radial and axial forces are transmitted via radial gaps; and (3) large radial bearing gaps can be provided with minimum electric power consumption. The large gaps allow for effective encapsulation and shielding of the rotors at elevated or low temperatures, corrosive or ultra clean atmosphere or vacuum or high pressure environment. Two significant applications are described: (1) a magnetically suspended x ray rotary anode was operated under high vacuum conditions at 100 KV anode potential, 600 C temperature at the rotor collars and speed 18000 rpm with 13 mm radial bearing gap; and (2) an improved Czochralski type crystal growth apparatus using the hot wall method for pulling GaAs single crystals of low dislocation density. Both crystal and crucible are carried and transported by magnetically suspended shafts inside a hermetically sealed housing at 800 C shaft and wall temperature. The radial magnetic bearing gap measures 24 mm.
Boden, Karl↗
Containerless Liquid to Solid Nucleation Pathways in Two Representative Grades of Commercially Available Zirconium
Experimental measurements were conducted to determine the solid metal nucleation pathways of radiatively cooling, molten zirconium spheres of two different commercially available purity grades in a high-vacuum, high-temperature electrostatic levitator. The ensemble distribution of maximum undercooling temperatures was interpreted using Poisson statistics to determine the temperature dependence of the solid metal nucleation rate. For a sample of nominally 99.95% pure zirconium, the results are consistent with heterogeneous solid metal nucleation either on static catalyst particles at least approx. 30 nm diameter or on a surface coating. For a sample of nominally 99% pure zirconium, however, it appears that heterogeneous solid metal nucleation occurred either on a polydispersion of approx. 10 nm (mean diameter) static catalyst particles or on dynamic catalyst particles that precipitated from a solution that became supersaturated as the melt cooled.
Rulison, A. J.↗
Precise Frequency Measurements Using a Superconducting Cavity Stabilized Oscillator
Many physics experiments call on improved resolution to better define the experimental results, thus improving tests of theories. Modern microwave technology combined with high-Q resonators can achieve frequency readout and control with resolutions up to a part in 10(exp 18). When the physical quantity in question in the experiment can be converted to a frequency or a change in frequency, a high-stability microwave oscillator can be applied to obtain state-of-the-art precision. In this work we describe the overall physical concepts and the required experimental procedures for optimizing a high-resolution frequency measurement system that employs a high-Q superconducting microwave cavity and a low-noise frequency synthesizer. The basic approach is to resolve the resonant frequencies of a high-Q (Q > 10(exp 10)) cavity to extremely high precision (one part in 10(exp 17)- 10(exp 18)). Techniques for locking the synthesizer frequency to a resonant frequency of the superconducting cavity to form an ultra-stable oscillator are described. We have recently set up an ultra-high-vacuum high-temperature annealing system to process superconducting niobium cavities, and have been able to consistently achieve Q > 10(exp 9). We have integrated high-Q superconducting cavities with a low-noise microwave synthesizer in a phase-locked-loop to verify the frequency stability of the system. Effects that disturb the cavity resonant frequency (such as the temperature fluctuations and mechanical vibrations) and methods to mitigate those effects are also considered. Applicability of these techniques to experiments will be discussed, and our latest experimental progress in achieving high-resolution frequency measurements using the superconducting-cavity-stabilized-oscillator will be presented.
Strayer, D. M.↗
Containerless Liquid to Solid Nucleation Pathways in Two Representative Grades of Commercially Available Zirconium
Experimental measurements were conducted to determine the solid metal nucleation pathways of radiatively cooling, molten zirconium spheres of two different commercially available purity grades in a high-vacuum, high-temperature electrostatic levitator. The ensemble distribution of maximum undercooling temperatures was interpreted using Poisson statistics to determine the temperature dependence of the solid metal nucleation rate. For a sample of nominally 99.95% pure zirconium, the results are consistent with heterogeneous solid metal nucleation either on static catalyst particles at least ~30 nm diameter or on a surface coating. For a sample of nominally 99% pure zirconium, however, it appears that heterogeneous solid metal nucleation occurred either on a polydispersion of ~10 nm (mean diameter) static catalyst particles or on dynamic catalyst particles which precipitated from a solution which became supersaturated as the melt cooled. A quantitative analysis of the compositions of both samples suggests that the catalysts probably consisted of one or more of the following elements: niobium, molybdenum, hafnium, and oxygen.
containerless, nucleation, zirconium↗
A Novel Instrument and Methodology for the In-Situ Measurement of the Stress in Thin Films
We introduce a novel methodology for the in-situ measurement of mechanical stress during thin film growth utilizing a highly sensitive non-contact variation of the classic spherometer. By exploiting the known spherical deformation of the substrate the value of the stress induced curvature is inferred by measurement of only one point on the substrate's surface-the sagittal. From the known curvature the stress can be calculated using the well-known Stoney equation. Based on this methodology, a stress sensor has been designed which is simple, highly sensitive, compact, and low cost. As a result of its compact nature, the sensor can be mounted in any orientation to accommodate a given deposition geometry without the need for extensive modification to an already existing deposition system. The technique employs the use of a double side polished substrate that offers good specular reflectivity and is isotropic in its mechanical properties, such as <111> oriented crystalline silicon or amorphous soda lime glass, for example. The measurement of the displacement of the uncoated side during deposition is performed with a high resolution (i.e. 5nm), commercially available, inexpensive, fiber optic sensor which can be used in both high vacuum and high temperature environments (i.e. 10(exp-7) Torr and 480oC, respectively). A key attribute of this instrument lies in its potential to achieve sensitivity that rivals other measurement techniques such as the micro cantilever method but, due to the comparatively larger substrate area, offers a more robust and practical alternative for subsequent measurement of additional characteristics of the film that can might be correlated to film stress. We present measurement results of nickel films deposited by magnetron sputtering which show good qualitative agreement to the know behavior of polycrystalline films previously reported by Hoffman.
Broadway, David M.↗
Apparatus for inserting and removing specimens from high temperature vacuum furnaces
The apparatus comprises a high speed gate valve for isolating the interior of the furnance from an air lock chamber on the opposite side of the gate valve. The air lock chamber is provided with valve ports connected to a vacuum source, a source of inert quenching gas, and the atmosphere, respectively. Attached to the end of the air lock chamber away from the furnace is a cylindrical tube having disposed within it a rod carrying specimen pan at the end towards the furnace and having mounted at its top end an annular magnet having a diameter slightly less than the interior diameter of the tube. The top end of the tube is closed by a removeable cap. Encircling the tube in the vicinity of the magnet is a carbon steel ring which when axially moved along the tube causes the magnet to follow it and thereby controls the position of the rod and specimen pan within the tube.
Whitehead, C. W.↗
Robust Multilayer Insulation for Cryogenic Systems
New requirements for thermal insulation include robust Multilayer insulation (MU) systems that work for a range of environments from high vacuum to no vacuum. Improved MLI systems must be simple to install and maintain while meeting the life-cycle cost and thermal performance objectives. Performance of actual MLI systems has been previously shown to be much worse than ideal MLI. Spacecraft that must contain cryogens for both lunar service (high vacuum) and ground launch operations (no vacuum) are planned. Future cryogenic spacecraft for the soft vacuum environment of Mars are also envisioned. Industry products using robust MLI can benefit from improved cost-efficiency and system safety. Novel materials have been developed to operate as excellent thermal insulators at vacuum levels that are much less stringent than the absolute high vacuum requirement of current MLI systems. One such robust system, Layered Composite Insulation (LCI), has been developed by the Cryogenics Test Laboratory at NASA Kennedy Space Center. The experimental testing and development of LCI is the focus of this paper. LCI thermal performance under cryogenic conditions is shown to be six times better than MLI at soft vacuum and similar to MLI at high vacuum. The experimental apparent thermal conductivity (k-value) and heat flux data for LCI systems are compared with other MLI systems.
Fesmire, J. E.↗
Electrostatic Studies for the 2008 Hubble Service Repair Mission
High vacuum triboelectric testing of space materials was required to identify possible Electrostatic Discharge (ESD) concerns for the astronauts in space during electronics board replacement on the Hubble Space Telescope. Testing under high vacuum conditions with common materials resulted in some interesting results. Many materials were able to charge to high levels which did not dissipate quickly even when grounded. Certain materials were able to charge up in contact with grounded metals while others were not. An interesting result was that like materials did not exchange electrostatic charge under high vacuum conditions. The most surprising experimental result is the lack of brush discharges from charged insulators under high vacuum conditions.
Buhler, C. R.↗