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  • 1
    Electronic Resource
    Electronic Resource
    Microwave surface resistance of YBa2Cu3O7 thin films on LaAlO3 substrates (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 2514-2516 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The surface resistance Rs of YBa2Cu3O7 (YBCO) thin films (0.6±0.1 μm) deposited onto 2.5-cm diam (100) LaAlO3 substrates has been measured at 22 GHz using both Cu and Nb cavities. The surface resistance falls precipitously at the superconducting transition (Tc =90 K) from a normal state value of approximately 2 Ω to a 77 K value of 13.7±1 mΩ, which is 1.6 times lower than Cu. At 4 K the surface resistance is 1±0.1 mΩ, as measured in a Nb superconducting cavity, which is an order of magnitude lower than Cu. The critical current density at 77 K is 4.5×104 A/cm2. Pole figure analyses show the ratio of c-axis to a-axis-oriented material in the film is 2.4:1. YBCO films deposited onto either LaGaO3 or LaAlO3 substrates with varying c/a ratios yield surface resistance values at 77 K that are crudely correlated with Rs. Therefore, the principal effect of orienting the material is to improve the sharpness of the high-frequency superconducting transition, consistent with the notion that the sharpness is associated with intergranular rather than intragranular properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.346493
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  • 2
    Electronic Resource
    Electronic Resource
    Microwave power absorption by thallium-based superconductors on metallic substrates (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 1329-1331 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Tl-based superconducting thick films deposited on large-area (11.4 cm2) Ag alloy (Consil 995) substrates have been characterized by surface resistance measurements yielding values of 4 and 14 mΩ at 4 and 77 K, respectively, as measured in an 18 GHz Cu cavity; corresponding Cu values are 8 and 21 mΩ. Utilizing a Nb cavity, the dependence of surface resistance on microwave power was also measured. The surface resistance begins to rise in microwave magnetic fields of 1–10 Oe and saturates in 20–60 Oe, the exact values depending on the degree of c-axis texturing of the polycrystalline films. Enhanced texturing sharpens the high-frequency transition into the superconducting state and also weakens the dependence of surface resistance on microwave magnetic field. These results are significant for high temperature superconductor applications such as microwave cavities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104300
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  • 3
    Electronic Resource
    Electronic Resource
    Power and magnetic field-induced microwave absorption in Tl-based high Tc superconducting films (1991)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 58 (1991), S. 307-309 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The increase in the microwave surface resistance Rs of high Tc superconductors at elevated microwave power levels is reported for both oriented and unoriented Tl-based films as a function of rf magnetic field at 820 MHz and 18 GHz. The application of dc magnetic fields produces qualitatively similar increases in Rs and in the surface reactance Xs. The increase in Rs with dc field is shown to arise from simple decoupling of grains by intergranular magnetic flux. The increase in Rs with microwave power, on the other hand, is a consequence of hysteretic intergranular processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.104670
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  • 4
    Electronic Resource
    Electronic Resource
    Neutron-induced microwave loss in ceramic YBa2Cu3O7−δ (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2462-2464 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: An increase by over three orders of magnitude from 0.58 mΩ to 1.17 Ω was observed at 4.0 K in the 3 GHz microwave surface resistance of ceramic YBa2Cu3O7−δ following exposure to neutrons. The transport resistivity of an unirradiated pellet was linear in temperature down to Tc with a room-temperature value of 2.13 mΩ cm and a resistivity extrapolated to 4.0 K of 0.53 mΩ cm. Following irradiation, the resistivity rose with decreasing temperature from a room-temperature value of 1.5 Ω cm to a maximum at around 45 K with little change evident at Tc . These results, in conjunction with eddy current, susceptibility, iodometric titration, and thermally stimulated luminescence measurements on irradiated and unirradiated samples, collectively suggest that the effect of neutron irradiation has been to decrease intergranular coupling without the development of an insulating phase.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.103256
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  • 5
    Electronic Resource
    Electronic Resource
    Microwave surface resistance of magnetron-sputtered Tl-Ba-Ca-Cu-O films on silver substrates (1990)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 56 (1990), S. 2147-2149 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface resistance measurements on Tl-Ba-Ca-Cu-O thick films (∼15 μm) magnetron sputtered onto BaF2-buffered, silver-based (Consil 995) substrates have been made at a microwave frequency of 22 GHz. The relatively large-area films (∼5 cm2) are characterized by surface resistance values of 6.9±2 mΩ at 11.3 K and 30.2±1 mΩ at 77 K; the corresponding values for Cu are 10 and 22 mΩ, respectively. These results demonstrate that Tl-Ba-Ca-Cu-O can be deposited onto large-area, metallic substrates with characteristic surface resistance values lower than Cu at 4 K. Orientation of the film should improve the surface resistance at 77 K, thereby making the fabrication of microwave cavities that are superior to Cu possible.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.102954
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  • 6
    Electronic Resource
    Electronic Resource
    Sacrococcygeal teratoma: A case of mistaken identity (1994)
    Springer
    Pediatric radiology 24 (1994), S. 52-53 
    Details
    ISSN: 1432-1998
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract We report a case in which prenatal diagnosis of fetal myelomeningocele led to termination of the pregnancy at 17 weeks. The diagnosis was made on the basis of prenatal ultrasound scand and raised maternal α-fetoprotein. Although the large cystic lesion arising in the sacral region appeared to confirm the diagnosis, autopsy examination revealed that this was a cystic sacrococcygeal teratoma. This case illustrates the importance of submitting all fetuses for full autopsy.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02017663
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  • 7
    Electronic Resource
    Electronic Resource
    RF properties of high-temperature superconductors: Cavity methods (1990)
    Springer
    Journal of superconductivity 3 (1990), S. 297-304 
    Details
    ISSN: 1572-9605
    Keywords: High-temperature superconductivity ; microwave cavities ; sample surface impedance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A description of cavities used in the study of the microwave properties of the high-temperature superconductors is followed by a lumped-circuit analysis of the coupling of transmission lines and resonators. The frequency dependence of the reflected and transmitted microwave power and the character of transient cavity response are analyzed. Techniques are discussed for the introduction of samples of the high-temperature superconductors into microwave cavities. Following a discussion of sample surface impedance and sample geometry factor, the connection between surface resistance and cavityQ is examined as well as the connection between cavity frequency shift and surface reactance. Measurement techniques that utilize reflected or transmitted power or transient response are described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625271
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  • 8
    Electronic Resource
    Electronic Resource
    Microwave surface resistance and power dependence of thallium-based films deposited onto large-area silver substrates (1990)
    Springer
    Journal of superconductivity 3 (1990), S. 261-267 
    Details
    ISSN: 1572-9605
    Keywords: High-temperature superconductivity ; microwave surface impedance ; Tl-based superconducting films ; metallic substrates ; field dependence of surface resistance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract Microwave surface resistance (R s ) measurements on large-area (11.4 cm2) Tl-based films deposited onto Ag (Consil 995) substrates have been made at a frequency of 18 GHz as a function of temperature. Deposition onto unoriented Ag substrates yields unoriented films characterized byR s values of 8.2 and 33.6 mΩ at 10.6 and 77 K, respectively. In contrast, similar deposition onto oriented Ag substrates yields oriented films with values of 12.6 and 14.6 mΩ at 11.2 and 77 K, respectively; corresponding Cu values are 9 and 21 mΩ. Additionally, it is found that the dependence ofR s on microwave surface magnetic fieldH s is weaker for the oriented films. These results suggest that the effect of orienting thec-axis in Tl films is twofold: (1) the high-frequency superconducting transition is made considerably sharper, resulting in a lowerR s value at 77 K, and (2) the rate of increase inR s with appliedH s is reduced. Both effects have significant ramifications for the potential application of these materials to high-frequency accelerating cavities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00625266
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  • 9
    Electronic Resource
    Electronic Resource
    A Tl-based high-temperature superconducting X-band cavity (1992)
    Springer
    Journal of superconductivity 5 (1992), S. 431-435 
    Details
    ISSN: 1572-9605
    Keywords: High-temperature superconductivity ; X-band cavity ; Tl-based superconducting films ; metallic substrates
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A nonplanar X-band cavity amenable to coating with high-temperature superconducting films by conventional physical vapor deposition processes has been designed, fabricated, and tested. The cavity geometry resembles a symmetric clamshell configuration. It consists of two truncated cones joined at their bases. The specific dimensions of the cavity were calculated using the SUPERFISH computer code. Cavities were constructed using a silver-based alloy, Consil 995. The separate cavity sections were coated with Tl-based high-temperature superconducting material using a two-step deposition and annealing process. The unloaded Q values for this coated clamshell cavity are 66,000 and 105,000 at 77 and 20 K, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00618144
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  • 10
    Electronic Resource
    Electronic Resource
    George Gray (1993)
    Springer
    Journal of neurocytology 22 (1993), S. 684-688 
    Details
    ISSN: 1573-7381
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01181313
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