A first report on electromigration studies at a model copper-aluminum railgun contact

10A) was necessary to produce the large current densities typically found in railguns, and was able to simulate the skin effect on both the Cu rails and Al armature under static, long-term testing conditions. In this method, the effects of electromigration were discerned clearly, in dissociation from various movement related damage phenomena. The aluminum from the armature quickly reached its melting point via Joule heating due to high contact resistance at the armature-rail contact. Once liquid aluminum was formed, it rapidly migrated along the copper rail towards the negative terminal. This transport of liquid aluminum along the copper rails was attributed to electromigration of the liquid under the influence of the direct electric field. Once the aluminum began to be transported along the rail towards the cathode terminal, it alloyed with the copper rails and the resistance steadily increased in the circuit. Electromigration is shown to be a contributing factor to the degradation of aluminum armatures performance and copper rails lifespan in the railgun.http://archive.org/details/afirstreportonel109452511Approved for public release; distribution is unlimited

A preliminary analysis of the data from experiment 77-13 and final report on glass fining experiments in zero gravity

Thermal fining, thermal migration of bubbles under reduced gravity conditions, and data to verify current theoretical models of bubble location and temperatures as a function of time are discussed. A sample, sodium borate glass, was tested during 5 to 6 minutes of zero gravity during rocket flight. The test cell contained a heater strip; thermocouples were in the sample. At present quantitative data are insufficient to confirm results of theoretical calculations

Photo sensor array technology development

The development of an improved capability photo sensor array imager for use in a Viking '75 type facsimile camera is presented. This imager consists of silicon photodiodes and lead sulfide detectors to cover a spectral range from 0.4 to 2.7 microns. An optical design specifying filter configurations and convergence angles is described. Three electronics design approaches: AC-chopped light, DC-dual detector, and DC-single detector, are investigated. Experimental and calculated results are compared whenever possible using breadboard testing and tolerance analysis techniques. Results show that any design used must be forgiving of the relative instability of lead sulfide detectors. A final design using lead sulfide detectors and associated electronics is implemented by fabrication of a hybrid prototype device. Test results of this device show a good agreement with calculated values

Novel wasteforms for caesium-containing spent adsorbents from Fukushima Daiichi: a study of volatilisation and low-temperature glass processing

Remediation activities at Fukushima Daiichi have produced large volumes of highly radioactive adsorbents. These require immobilisation but are contaminated with Cs which volatilises at the temperatures typical for common methods like vitrification. Here a low temperature immobilisation process was developed. Cs volatilisation studies were conducted for three commercial adsorbents: A-51 JHP, IE-911 and IE-96. These were loaded with 8 wt.% Cs, and heated in air to establish the highest temperature that avoided volatilisation. Any Cs evolved was measured using atomic absorption spectroscopy, in the range 600-1000 C. Volatilisation started at 700ºC in all samples, with a relative volatilisation of 1.67% ±0.15% and 0.097% ±0.0080 for A-51 JHP and IE-96 respectively at 1000 C and 7.71% ± 0.66% at 900 C for IE-911 (which degraded at high temperature preventing examination at higher temperatures). This established a maximum process temperature of 600 C. Glass-Composite Material (GCM) waste forms were designed within this processing envelope. Lead borosilicate (PBS) and a lead borate (PB) compositions were chosen due to their low working temperatures. These were used to encapsulate Cs exchanged chabazite and IE-96 by low temperature sintering. A 15 wt.% mass loss, observed at 350 C, was confirmed, using evolved gas analysis mass spectroscopy, to be due to adsorbed water. Its release led to trapped gases during sintering, resulting in closed porosity in the final waste forms. A thermal treatment was developed to reduce closed porosity in the final waste form with pre-treatment (600 C) of the adsorbent prior to mixing, followed by degasification (350 C), sintering (either 400 C or 500 C) and annealing (350 C and 450 C) produced dense waste forms for both PB and PBS respectively. Wasteloadings of 50 wt.% (72.6 vol.%) in PBS GCM and 40 wt.% (65.2 vol.%) in PB GCM were achieved. No influence of Cs on the sintering behaviour was found as Cs remained sequestered in the adsorbent during sintering.Open Acces

Solid state image sensor research Final technical report

Fifty-element linear arrays of InAs photodiode

High temperature sensor/microphone development for active noise control

The industrial and scientific communities have shown genuine interest in electronic systems which can operate at high temperatures, among which are sensors to monitor noise, vibration, and acoustic emissions. Acoustic sensing can be accomplished by a wide variety of commercially available devices, including: simple piezoelectric sensors, accelerometers, strain gauges, proximity sensors, and fiber optics. Of the several sensing mechanisms investigated, piezoelectrics were found to be the most prevalent, because of their simplicity of design and application and, because of their high sensitivity over broad ranges of frequencies and temperature. Numerous piezoelectric materials are used in acoustic sensors today; but maximum use temperatures are imposed by their transition temperatures (T(sub c)) and by their resistivity. Lithium niobate, in single crystal form, has the highest operating temperature of any commercially available material, 650 C; but that is not high enough for future requirements. Only two piezoelectric materials show potential for use at 1000 C; AlN thin film reported to be piezoactive at 1150 C, and perovskite layer structure (PLS) materials, which possess among the highest T(sub c) (greater than 1500 C) reported for ferroelectrics. A ceramic PLS composition was chosen. The solid solution composition, 80% strontium niobate (SN) and 20% strontium tantalate (STa), with a T(sub c) approximately 1160 C, was hot forged, a process which concurrently sinters and renders the plate-like grains into a highly oriented configuration to enhance piezo properties. Poled samples of this composition showed coupling (k33) approximately 6 and piezoelectric strain constant (d33) approximately 3. Piezoactivity was seen at 1125 C, the highest temperature measurement reported for a ferroelectric ceramic. The high temperature piezoelectric responses of this, and similar PLS materials, opens the possibility of their use in electronic devices operating at temperatures up to 1000 C. Concurrent with the materials study was an effort to define issues involved in the development of a microphone capable of operation at temperatures up to 1000 C; important since microphones capable of operation above 260 C are not generally available. The distinguishing feature of a microphone is its diaphragm which receives sound from the atmosphere: whereas, most other acoustic sensors receive sound through the solid structure on which they are installed. In order to gain an understanding of the potential problems involved in designing and testing a high temperature microphone, a prototype was constructed using a commercially available lithium niobate piezoelectric element in a stainless steel structure. The prototype showed excellent frequency response at room temperature, and responded to acoustic stimulation at 670 C, above which temperature the voltage output rapidly diminished because of decreased resistivity in the element. Samples of the PLS material were also evaluated in a simulated microphone configuration, but their voltage output was found to be a few mV compared to the 10 output of the prototype

Nonterrestrial utilization of materials: Automated space manufacturing facility

Four areas related to the nonterrestrial use of materials are included: (1) material resources needed for feedstock in an orbital manufacturing facility, (2) required initial components of a nonterrestrial manufacturing facility, (3) growth and productive capability of such a facility, and (4) automation and robotics requirements of the facility

Crystal growth furnace safety system validation

The findings are reported regarding the safe operation of the NASA crystal growth furnace (CGF) and potential methods for detecting containment failures of the furnace. The main conclusions are summarized by ampoule leak detection, cartridge leak detection, and detection of hazardous species in the experiment apparatus container (EAC)

The Crystal Growth of Cesium Cerium Chloride Scintillator for X-Ray and Gamma-Ray Spectroscopy Applications

The detection and identification of sources of nuclear radiation is an integral tool in defending our nation from threats of nuclear terrorism as well as enforcement of nuclear non-proliferation agreements around the globe. To improve the capabilities in this application, new detection materials surpassing the performance of existing technology utilizing sodium iodide [NaI:Tl] scintillator crystals must be developed and their production cost lowered to meet the demand for the large volumes required. A recently discovered intrinsic scintillation material in the form of crystalline cesium cerium chloride (CsCe2Cl7) has demonstrated promising performance in the detection of X-ray and gamma ray radiation. In order to assess the potential of this material to be developed into larger scale growth of crystals greater than one cubic inch in volume, research into optimizing the growth processes at smaller volumes is necessary. Single crystalline boules of CsCe2Cl7 were grown from the melt in sealed fused silica ampoules using the Bridgman method of crystal growth. A transparent growth furnace along with continuous observation apparatus were developed to aid in the investigation of the growth processes. A comparison of growth and cracking behavior under varied conditions was produced and growth protocols identified which improve crystal boule quality. Crystal quality benefits from controlling the self-seeding process through manipulation and control of critical freezing point isotherms during growth. Cracking appears to originate from aggressive detachment of the crystal from the fused silica ampoule wall while inclusions formed during growth by constitutional supercooling of the melt introduce additional crack nucleation sites through action as stress intensifiers within the bulk matrix. Reducing ampoule volume has a minor effect on cracking severity while additions of excess cesium chloride to the initial mixture produce a greater reduction in cracking. The anisotropic coefficients of thermal expansion as well as the refined crystal structure of cesium cerium chloride have been determined through single crystal Laue and temperature dependent powder X-ray diffraction pattern analyses respectively

Advanced high temperature static strain sensor development

An examination was made into various techniques to be used to measure static strain in gas turbine liners at temperatures up to 1150 K (1600 F). The methods evaluated included thin film and wire resistive devices, optical fibers, surface acoustic waves, the laser speckle technique with a heterodyne readout, optical surface image and reflective approaches and capacitive devices. A preliminary experimental program to develop a thin film capacitive device was dropped because calculations showed that it would be too sensitive to thermal gradients. In a final evaluation program, the laser speckle technique appeared to work well up to 1150 K when it was used through a relatively stagnant air path. The surface guided acoustic wave approach appeared to be interesting but to require too much development effort for the funds available. Efforts to develop a FeCrAl resistive strain gage system were only partially successful and this part of the effort was finally reduced to a characterization study of the properties of the 25 micron diameter FeCrAl (Kanthal A-1) wire. It was concluded that this particular alloy was not suitable for use as the resistive element in a strain gage above about 1000 K