Tl/sub 2/Ba/sub 2/CaCu/sub 2/O/sub 8/ films: Growth and applications in dc SQUIDs and microwave devices
Tl-2212 thin films were grown ex situ in a two step process on a variety of substrates, including ones with artificially introduced high angle steps. Grain boundary weak links were formed on LaAlO/sub 3/ substrates with steps and on bicrystal substrates and were employed in dc SQUIDs. The white noise level of the SQUIDs was 50/spl mu//spl Phi//sub 0///spl radic/(Hz) at 77 K. A 12.5 GHz HEMT oscillator stabilized with a Tl-2212 resonator gave 8-10 dB lower phase noise than using a gold resonator.
SCIENCE AND TECHNOLOGY OF HIGH-TEMPERATURE SUPERCONDUCTING FILMS1
▪ Abstract The field of high-temperature superconducting thin films is reviewed, focusing on the synthesis and properties of materials that are most promising for device applications. Current materials issues that are important for emerging device applications of oxide superconducting films are discussed, with emphasis on the growth, characterization, and use of epitaxial films. The status of specific superconducting device technologies is briefly reviewed.
Characterization of a tube-in-shell thermosyphon heat exchanger for solar water heating
Performance of a double-wall, natural convection, two-pass, tube-in-shell heat exchanger designed for use in a solar water heating system is measured. The heat exchanger is mounted along the length of a solar water storage tank. Flow of cold water on the shell side of the heat exchanger is driven solely by buoyancy forces. Hot side fluid is pumped. Flow rate, pressure drop and temperature data needed for a semi-empirical model of the heat exchanger are obtained. Performance is measured for forced convection, hot side volumetric flow rates of 0.016, 0.032 and 0.079 l/s. Temperature difference between hot and cold fluid at the inlets is varied from 0 to 75 degC. Measured values include thermosyphon and forced flow rates, temperature differences across the beat exchanger, vertical temperature distribution in the storage tank, and pressure drop due to shear on the thermosyphon side of the heat exchanger. Heat exchanger effectiveness and overall heat transfer area product (UA) are calculated. Thermosyphon mass flow rates are on the order of 0.01 kg/s. Although the low flow rates create thermal stratification of the water storage tank, they restrict energy transfer in the heat exchanger.