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NASA NTRSDate not supplied

Long Term Performance Stability of TES Detectors

We are developing superconducting transition-edge sensor (TES) microcalorimeter arrays for a variety of applications such as ground-based laboratory astrophysics experiments and next generation space-based X-ray missions. These detectors can provide X-ray spectral information with an unprecedent resolution of ~2 eV at 6 keV and have been selected for the X-ray Integral Field Unit (X-IFU) instrument of ESA’s large flagship mission Athena. To maintain detector performance over the lifetime of the mission, it is important to understand whether environmental conditions that the detector may be exposed to will affect its properties over time. This “aging” begins right after the array leaves the fabrication environment, with potential exposure to humidity, oxygen, or elevated temperatures which may affect the detector performance. In a few prior arrays we have observed increased fall times in the pulse shape and/or the introduction of anomalous low energy tails on the X-ray spectrum. This is thought to be an indication of “aging” on chips exposed to such conditions, causing e.g. changes in the absorber properties. In this contribution, we report on a systematic characterization of TES properties, before and after exposing the chip to various controlled temperature and humidity levels and assess the changes in the measured transition and pulse shapes, energy resolution, and spectral redistribution.

S Beaumont↗
NASA NTRS1993

Superconducting terahertz mixer using a transition-edge microbolometer

We present a new device concept for a mixer element for THz frequencies. This uses a superconducting transition-edge microbridge biased at the center of its superconducting transition near 4.2 K. It is fed from an antenna or waveguide structure. Power from a local oscillator and an RF signal produce a temperature and resulting resistance variation at the difference frequency. The new aspect is the use of a very short bridge in which rapid (less than 0.1 ns) outdiffusion of hot electrons occurs. This gives large intermediate frequency (IF) response. The mixer offers about 4 GHz IF bandwidth, about 80 ohm RF resistive impedance, good match to the IF amplifier, and requires only 1-20 nW of local oscillator power. The upper RF frequency is determined by antenna or waveguide properties. Predicted mixer conversion efficiency is 1/8, and predicted double-sideband receiver noise temperatures are 260 and 90 K for transition widths of 0.1 and 0.5 Tc, respectively.

Prober, D. E.↗
NASA NTRS1995

Oxide perovskite crystals for HTSC film substrates microwave applications

The research focused upon generating new substrate materials for the deposition of superconducting yttrium barium cuprate (YBCO) has yielded several new hosts in complex perovskites, modified perovskites, and other structure families. New substrate candidates such as Sr(Al(1/2)Ta(1/2))O3 and Sr(Al(1/2)Nb(1/2))O3, Ba(Mg(1/3)Ta(2/3))O3 in complex oxide perovskite structure family and their solid solutions with ternary perovskite LaAlO3 and NdGaO3 are reported. Conventional ceramic processing techniques were used to fabricate dense ceramic samples. A laser heated molten zone growth system was utilized for the test-growth of these candidate materials in single crystal fiber form to determine crystallographic structure, melting point, thermal, and dielectric properties as well as to make positive identification of twin free systems. Some of those candidate materials present an excellent combination of properties suitable for microwave HTSC substrate applications.

Bhalla, A. S.↗
NASA NTRS1996

Preparation and Properties of High-T(sub c) Bi-Pb-Sr-Ca-Cu-O Thick Film Superconductors on YSZ Substrates

An evaluation of four firing profiles was performed to determine the optimum processing conditions for producing high-T(sub c) Bi-Pb-Sr-Ca-Cu-O thick films on yttria-stabilized zirconia substrates. Using these four profiles, the effects of sintering temperatures of 830-850 C and soak times of 0.5 to 12 hours were examined. In this study, T-c, zero values of 100 K were obtained using a firing profile in which the films were sintered for 1.5 to 2 hours at 840 to 845 C and then quenched to room temperature. X-ray diffraction analyses of these specimens confirmed the presence of the high-T(sub c) phase. Films which were similarly fired and furnace cooled from the peak processing temperature exhibited a two-step superconductive transition to zero resistance, with T-c,zero values ranging from 85 to 92 K. The other firing profiles evaluated in this investigation yielded specimens which either exhibited critical transition temperatures below 90 K or did not exhibit a superconductive transition above 77 K.

Hooker, Matthew W.↗
NASA NTRS1988

Electronic materials high-T(sub c) superconductivity polymers and composites structural materials surface science and catalysts industry participation

The fifth year of the Center for Advanced Materials was marked primarily by the significant scientific accomplishments of the research programs. The Electronics Materials program continued its work on the growth and characterization of gallium arsenide crystals, and the development of theories to understand the nature and distribution of defects in the crystals. The High Tc Superconductivity Program continued to make significant contributions to the field in theoretical and experimental work on both bulk materials and thin films and devices. The Ceramic Processing group developed a new technique for cladding YBCO superconductors for high current applications in work with the Electric Power Research Institute. The Polymers and Composites program published a number of important studies involving atomistic simulations of polymer surfaces with excellent correlations to experimental results. The new Enzymatic Synthesis of Materials project produced its first fluorinated polymers and successfully began engineering enzymes designed for materials synthesis. The structural Materials Program continued work on novel alloys, development of processing methods for advanced ceramics, and characterization of mechanical properties of these materials, including the newly documented characterization of cyclic fatigue crack propagation behavior in toughened ceramics. Finally, the Surface Science and Catalysis program made significant contributions to the understanding of microporous catalysts and the nature of surface structures and interface compounds.

Source record↗
NASA NTRS1999

Microgravity Processing of Oxide Superconductors

Considerable effort has been concentrated on the synthesis and characterization of high T(sub c) oxide superconducting materials. The YBaCuO system has received the most intense study, as this material has shown promise for the application of both thin film and bulk materials. There are many problems with the application of bulk materials- weak links, poor connectivity, small coherence length, oxygen content and control, environmental reactivity, phase stability, incongruent melting behavior, grain boundary contamination, brittle mechanical behavior, and flux creep. The extent to which these problems are intrinsic or associated with processing is the subject of controversy. This study seeks to understand solidification processing of these materials, and to use this knowledge for alternative processing strategies, which, at the very least, will improve the understanding of bulk material properties and deficiencies. In general, the phase diagram studies of the YBaCuO system have concentrated on solid state reactions and on the Y2BaCuO(x) + liquid yields YBa2Cu3O(7-delta) peritectic reaction. Little information is available on the complete melting relations, undercooling, and solidification behavior of these materials. In addition, rare earth substitutions such as Nd and Gd affect the liquidus and phase relations. These materials have promising applications, but lack of information on the high temperature phase relations has hampered research. In general, the understanding of undercooling and solidification of high temperature oxide systems lags behind the science of these phenomena in metallic systems. Therefore, this research investigates the fundamental melting relations, undercooling, and solidification behavior of oxide superconductors with an emphasis on improving ground based synthesis of these materials.

Olive, James R.↗
NASA NTRS2001

Reduced T(sub c) Niobium Superconducting HEB Mixers

A reduction in the mixer noise is expected when using superconductors with a lower transition temperature (T(sub c)) since the thermal noise components of the mixer noise should scale with T(sub c). Also, the local oscillator (LO) power required for a diffusion-cooled device should decrease as T(sub c) when T(sub bath) << T(sub c). We previously studied mixing in aluminum based hot-electron bolometers (HEBs) at microwave frequencies (approximately 30 GHz), and observed a significant improvement in noise performance, and a reduction in LO power as predicted. However, the bias voltage range over which good mixer performance was observed was approximately 5 - 10 microV. These devices are thus susceptible to saturation effects, in particular output saturation. In the present work, we have investigated Nb HEBs whose T(sub c) is lowered by applying a magnetic field. The goal is to study a case intermediate between Nb and Al, and hopefully to find properties that will allow use in practical receivers. A 15 kOe perpendicular magnetic field was applied to a Nb HEB (L = 0.16 micrometers, W = 0.08 micrometers, R(sub N) = 90 ohms) to reduce T(sub c) from 5.2 K to 2.4 K. The mixer noise, as inferred from the output noise and the conversion efficiency, decreased from 390 K, DSB to 171 K, DSB. The LO power required for near optimum mixer conversion efficiency (eta(sub mixer) = -9 dB in this device) was 8 nW in zero field, and approximately 2 nW when T(sub c) was reduced to 2.4 K. T(sub bath) = 0.22 K. The conversion bandwidth was previously measured to be 2.4 GHz and the same bandwidth was observed in the presence of a magnetic field. By lowering T(sub c), the voltage range over which good mixing was observed also decreased. However, even with T(sub c) reduced to 2.4 K, the conversion efficiency dropped by 3 dB from its maximum value only when the bias voltage was changed by approximately 90 microV. Saturation effects should thus be much less of a concern in these devices than in Al HEBS. In situations where the application of a large magnetic field is not feasible, we suggest using Ta based HEBS. Ta HEBs should have T(sub c) = 3 - 3.5 K and material properties very similar to Nb.

Siddiqi, I.↗
NASA NTRS1993

An experimental investigation of high temperature superconducting microstrip antennas at K- and Ka-band frequencies

The recent discovery of high temperature superconductors (HTS) has generated a substantial amount of interest in microstrip antenna applications. However, the high permittivity of substrates compatible with HTS results in narrow bandwidths and high patch edge impedances of such antennas. To investigate the performance of superconducting microstrip antennas, three antenna architectures at K and Ka-band frequencies are examined. Superconducting microstrip antennas that are directly coupled, gap coupled, and electromagnetically coupled to a microstrip transmission line were designed and fabricated on lanthanum aluminate substrates using YBa2Cu3O7 superconducting thin films. For each architecture, a single patch antenna and a four element array were fabricated. Measurements from these antennas, including input impedance, bandwidth, patterns, efficiency, and gain are presented. The measured results show usable antennas can be constructed using any of the architectures. All architectures show excellent gain characteristics, with less than 2 dB of total loss in the four element arrays. Although the direct and gap coupled antennas are the simplest antennas to design and fabricate, they suffer from narrow bandwidths. The electromagnetically coupled antenna, on the other hand, allows the flexibility of using a low permittivity substrate for the patch radiator, while using HTS for the feed network, thus increasing the bandwidth while effectively utilizing the low loss properties of HTS. Each antenna investigated in this research is the first of its kind reported.

Richard, Mark A.↗
NASA NTRS1990

Ellipsometric study of YBa2Cu3O(7-x) laser ablated and co-evaporated films

High temperature superconducting films of YBa2Cu3O(7-x) (YBCO were grown on SrTiO3, LaA1O3, and YSZ substrates using two techniques: excimer laser ablation with in situ annealing and co-evaporation of Y, Cu, and BaF2 with ex-situ annealing. Film thicknesses were typically 5000 A, with predominant c-axis alignment perpendicular to the substrate. Critical temperatures up to Tc(R=O)=90 K were achieved by both techniques. Ellipsometric measurements were taken in the range 1.6 to 4.3 eV using a variable angle spectroscopic ellipsometer. The complex dielectric function of the laser ablated films was reproducible from run to run, and was found to be within 10 percent of that previously reported for (001) oriented single crystals. A dielectric overlayer was observed in these films, with an index of refraction of approximately 1.55 and nearly zero absorption. For the laser ablated films the optical properties were essentially independent of substrate material. The magnitude of the dielectric function obtained for the co-evaported films was much lower than the value reported for single crystals, and was sample dependent.

Alterovitz, S. A.↗
NASA NTRS1990

Ellipsometric study of YBa2Cu3O(7-x) laser ablated and co-evaporated films

High temperature superconducting films of YBa2Cu3O(7-x) (YBCO) were grown on SrTiO3, LaAl03, and YSZ substrates using two techniques: excimer laser ablation with in situ annealing and co-evaporation of Y, Cu, and BaF2 with ex-situ annealing. Film thicknesses were typically 5000 A, with predominant c-axis alignment perpendicular to the substrate. Critical temperatures up to Tc(R = 0) = 90 K were achieved by both techniques. Ellipsometric measurements were taken in the range 1.6 to 4.3 eV using a variable angle spectroscopic ellipsometer. The complex dielectric function of the laser ablated films was reproducible from run to run, and was found to be within 10 percent of that previously reported for (001) oriented single crystals. A dielectric overlayer was observed in these films, with an index of refraction of approximately 1.55 and nearly zero absorption. For the laser ablated films the optical properties were essentially independent of substrate material. The magnitude of the dielectric function obtained for the co-evaporated films was much lower than the value reported for single crystals, and was sample dependent.

Alterovitz, S. A.↗
NASA NTRS1997

Dynamics of Superfluid Helium in Low-Gravity

This report summarizes the work performed under a contract entitled 'Dynamics of Superfluid Helium in Low Gravity'. This project performed verification tests, over a wide range of accelerations of two Computational Fluid Dynamics (CFD) codes of which one incorporates the two-fluid model of superfluid helium (SFHe). Helium was first liquefied in 1908 and not until the 1930s were the properties of helium below 2.2 K observed sufficiently to realize that it did not obey the ordinary physical laws of physics as applied to ordinary liquids. The term superfluidity became associated with these unique observations. The low temperature of SFHe and it's temperature unifonrmity have made it a significant cryogenic coolant for use in space applications in astronomical observations with infrared sensors and in low temperature physics. Superfluid helium has been used in instruments such as the Shuttle Infrared Astronomy Telescope (IRT), the Infrared Astronomy Satellite (IRAS), the Cosmic Background Observatory (COBE), and the Infrared Satellite Observatory (ISO). It is also used in the Space Infrared Telescope (SIRTF), Relativity Mission Satellite formally called Gravity Probe-B (GP-B), and the Test of the Equivalence Principle (STEP) presently under development. For GP-B and STEP, the use of SFHE is used to cool Superconducting Quantum Interference Detectors (SQUIDS) among other parts of the instruments. The Superfluid Helium On-Orbit Transfer (SHOOT) experiment flown in the Shuttle studied the behavior of SFHE. This experiment attempted to get low-gravity slosh data, however, the main emphasis was to study the low-gravity transfer of SFHE from tank to tank. These instruments carried tanks of SFHE of a few hundred liters to 2500 liters. The capability of modeling the behavior of SFHE is important to spacecraft control engineers who must design systems that can overcome disturbances created by the movement of the fluid. In addition instruments such as GP-B and STEP are very sensitive to quasi-steady changes in the mass distribution of the liquid. The CFD codes were used to model the fluid's dynamic motion. Tests in one-g were performed with the main emphasis on being able to compute the actual damping of the fluid. A series of flights on the NASA Lewis reduced gravity DC-9 aircraft were performed with the Jet Propulsion Laboratory (JPL) Low Temperature Flight Facility and a superfluid Test Cell. The data at approximately 0.04g, lg and 2g were used to determine if correct fundamental frequencies can be predicted based on the acceleration field. Tests in zero gravity were performed to evaluate zero gravity motion.

Frank, David J.↗
NASA NTRSDate not supplied

Preparing Quantum Many-Body Scar States on Quantum Computers

Quantum many-body scar states are highly excited eigenstates of many-body systems that exhibit atypical entanglement and correlation properties relative to other eigenstates at the same energy density. Scar states also give rise to infinitely long-lived coherent dynamics when the system is prepared in a special initial state having finite overlap with them. Many models with exact scar states have been constructed, but the fate of scarred eigenstates and dynamics when these models are perturbed is difficult to study with classical computational techniques. In this work, we propose state preparation protocols for individual scar states in a particular model, as well as superpositions of them that give rise to coherent dynamics. For superpositions of scar states, we propose both a linear depth unitary and a finite-depth nonunitary state preparation protocol, the latter of which uses measurement and postselection to reduce the circuit depth. For individual scarred eigenstates, we propose a circuit architecture with polynomial depth. We also provide proof of principle implementations of these protocols on superconducting quantum hardware.

Quantum Computing↗
NASA NTRS1992

Superconductivity devices: Commercial use of space

High T sub C superconducting thick film were prepared by a screen printing process. Y-based (YBa2Cu3O(7-x) superconducting thick film were printed on 211/Al2O3, SNT/Al2O3, and YSZ substrates. Because of poor adhesion of the superconductor thick films to 211/Al2O3 and SNT/Al2O3 substrates, relatively low T sub C and J sub C values were obtained from the films printed on these substrates. Critical temperatures (T sub C) of YBa2Cu3O(7-x) thick films deposited on 211/Al2O3 and SNT/Al2O3 substrates were about 80 K. The critical current densities (J sub C) of these films were less than 2 A/sq cm. Higher T sub C and J sub C YBa2Cu3O(7-x) thick films were printed on YSZ substrates. A YBa2Cu3O(7-x) thick film with T sub C=86.4 and J sub C= 50.4 A/sq cm was prepared by printing the film on YSZ substrate and firing at 990 C for 10 minutes. Multiple-lead samples were also prepared on the YSZ substrates. The multiple-lead samples showed lower T sub C and/or J sub C values than those of the plain samples. The electrical properties of YBa2Cu3O(7-x) thick films were determined by the microstructures of the films. The YBa2Cu3O(7-x) thick films printed on the YSZ substrates, which had the best properties among the films printed on the three different kinds of substrates, had the highest density and the best particle interconnection. The YBa2Cu3O(7-x) thick films with preferred orientation in (001) direction were obtained on the YSZ substrates. Cracks, which retard the properties of the films, were found from the films deposited on the YSZ substrates. Currently, a MSZ (Magnesium Stabilized Zirconia) substrate, which had higher thermal expansion coefficient than the YSZ substrate, is used as substrate for the YBa2Cu3O(7-x) thick film in order to eliminate the cracks on the film. Bi-based superconductor thick films were printed on polycrystalline MgO and YSZ substrates. Interactions between BSCCO thick films and the YSZ substrates were observed. Various buffer layer materials were applied onto the substrates in order to avoid the interactions between the BSCCO thick films and the ZrO2-based substrates. So far, a BSCCO printed on MgO substrate with T Sub C=89K was obtained. The J sub C of the film was lower than 0.1 A/sq cm by reason of poor interconnectivity of the BSCCO particles.

Haertling, Gene↗
NASA NTRS2003

Flightweight Carbon Nanotube Magnet Technology

Virtually all plasma-based systems for advanced airborne/spaceborne propulsion and power depend upon the future availability of flightweight magnet technology. Unfortunately, current technology for resistive and superconducting magnets yields system weights that tend to counteract the performance advantages normally associated with advanced plasma-based concepts. The ongoing nanotechnology revolution and the continuing development of carbon nanotubes (CNT), however, may ultimately relieve this limitation in the near future. Projections based on recent research indicate that CNTs may achieve current densities at least three orders of magnitude larger than known superconductors and mechanical strength two orders of magnitude larger than steel. In fact, some published work suggests that CNTs are superconductors. Such attributes imply a dramatic increase in magnet performance-to-weight ratio and offer real hope for the construction of true flightweight magnets. This Technical Publication reviews the technology status of CNTs with respect to potential magnet applications and discusses potential techniques for using CNT wires and ropes as a winding material and as an integral component of the containment structure. The technology shortfalls are identified and a research and technology strategy is described that addresses the following major issues: (1) Investigation and verification of mechanical and electrical properties, (2) development of tools for manipulation and fabrication on the nanoscale, (3) continuum/molecular dynamics analysis of nanotube behavior when exposed to practical bending and twisting loads, and (4) exploration of innovative magnet fabrication techniques that exploit the natural attributes of CNTs.

Chapman, J. N.↗
NASA NTRS2009

NASA Tech Briefs, July 2009

Topics covered include: Dual Cryogenic Capacitive Density Sensor; Hail Monitor Sensor; Miniature Six-Axis Load Sensor for Robotic Fingertip; Improved Blackbody Temperature Sensors for a Vacuum Furnace; Wrap-Around Out-the-Window Sensor Fusion System; Wide-Range Temperature Sensors with High-Level Pulse Train Output; Terminal Descent Sensor Simulation; A Robust Mechanical Sensing System for Unmanned Sea Surface Vehicles; Additive for Low-Temperature Operation of Li-(CF)n Cells; Li/CFx Cells Optimized for Low-Temperature Operation; Number Codes Readable by Magnetic-Field-Response Recorders; Determining Locations by Use of Networks of Passive Beacons; Superconducting Hot-Electron Submillimeter-Wave Detector; Large-Aperture Membrane Active Phased-Array Antennas; Optical Injection Locking of a VCSEL in an OEO; Measuring Multiple Resistances Using Single-Point Excitation; Improved-Bandwidth Transimpedance Amplifier; Inter-Symbol Guard Time for Synchronizing Optical PPM; Novel Materials Containing Single-Wall Carbon Nanotubes Wrapped in Polymer Molecules; Light-Curing Adhesive Repair Tapes; Thin-Film Solid Oxide Fuel Cells; Zinc Alloys for the Fabrication of Semiconductor Devices; Small, Lightweight, Collapsible Glove Box; Radial Halbach Magnetic Bearings; Aerial Deployment and Inflation System for Mars Helium Balloons; Steel Primer Chamber Assemblies for Dual Initiated Pyrovalves; Voice Coil Percussive Mechanism Concept for Hammer Drill; Inherently Ducted Propfans and Bi-Props; Silicon Nanowire Growth at Chosen Positions and Orientations; Detecting Airborne Mercury by Use of Gold Nanowires; Detecting Airborne Mercury by Use of Palladium Chloride; Micro Electron MicroProbe and Sample Analyzer; Nanowire Electron Scattering Spectroscopy; Electron-Spin Filters Would Offer Spin Polarization Greater than 1; Subcritical-Water Extraction of Organics from Solid Matrices; A Model for Predicting Thermoelectric Properties of Bi2Te3; Integrated Miniature Arrays of Optical Biomolecule Detectors; A Software Rejuvenation Framework for Distributed Computing; Kurtosis Approach to Solution of a Nonlinear ICA Problem; Robust Software Architecture for Robots; R4SA for Controlling Robots; Bio-Inspired Neural Model for Learning Dynamic Models; Evolutionary Computing Methods for Spectral Retrieval; Monitoring Disasters by Use of Instrumented Robotic Aircraft; Complexity for Survival of Living Systems; Using Drained Spacecraft Propellant Tanks for Habitation; Connecting Node; and Electrolytes for Low-Temperature Operation of Li-CFx Cells.

Source record↗
NASA NTRS1994

Permanent superconducting magnets for space applications

Work has been done to develop superconducting trapped field magnets (TFM's) and to apply them to a bumper-tether device for magnetic docking of spacecraft. The quality parameters for TFM's are J(c), the critical current of the superconductor, and d, the diameter of the superconducting tile. During this year we have doubled d, for production models, from 1 cm to 2 cm. This was done by means of seeding, an improved temperature profile in processing, and the addition of 1 percent Pt to the superconductor chemistry. Using these tiles we have set increasing records for the fields' permanent magnets. Magnets fabricated from old 1 cm tiles trapped 1.52 Tesla at 77K, 4.0T at 65K and 7.0T at 55K. The second of these fields broke a 17 year old record set at Stanford. The third field broke our own record. More recently using 2 cm tiles, we have trapped 2.3T at 77K, and 5.3T at 65K. We expect to trap lOT at 55K in this magnet in the near future. We have also achieved increases in J(c) using a method we developed for seeding U-235, and subsequently bombarding with neutrons. This method doubles J(c). We have not yet fabricated magnets from these tiles. During this year we have increased production yields from 15 percent to 95 percent. We have explored the properties of a magnetic bumper-tether for spacecraft. We have measured the bumper forces, and their dependence on time, distance, and the field of the ordinary ferromagnet (used together with a TFM). We have accounted for 85 percent of the collision energy, and its transformation to magnetic energy and heat energy. We have learned to control the relative bumper and tether forces by controlling TFM and ferromagnetic field strengths.

Weinstein, Roy↗