Download or read book Thermal Conductivity and Thermal Effects in Superconducting Niobium written by Syed Mohammad Wasim and published by . This book was released on 1970 with total page 200 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Investigation of the Thermal Transport in Superconducting Niobium and Tantalum written by Peng Xu and published by . This book was released on 2019 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: Superconducting radio frequency (SRF) cavities fabricated from bulk high purity niobium (Nb) are increasingly used for particle accelerators to achieve continuous operation. Even in the superconducting regime, residual resistance and small imperfections on the RF surface can dissipate energy and cause local heating that leads to cavity quench. Large values of thermal conductivity can mitigate local temperature excursions and prevent cavity quench, thus improving cavity performance. Understanding thermal transport in bulk and thin film superconducting Nb may guide thermal design of current and next generation SRF cavities.The thermal conductivity of metals is composed of electronic and lattice (phonon) components. In normal conductors, the electronic component dominates, and in superconducting metals, as the temperature drops below the critical temperature, phonons become increasingly important carriers of thermal energy. A widely used model of thermal conductivity in superconductors omits explicit accounting of the effect of dislocations, which result from deformation. Here, this model is extended by accounting for the effects of phonons scattered by dislocations independent from boundary scattering. This extended model agrees better with measurements of thermal conductivity in deformed Nb samples, especially at temperatures T less than 3 K. An apparent threshold of dislocation density Nd is found to be Nd = O(1012) m−2 for Nb and when applied to tantalum (Ta), it is Nd = O(1011) m−2. There is little contribution to the thermal conductivity when the dislocation density is less than this threshold. This model can also be used to estimatethe dislocation density by fitting measured values of thermal conductivity.Examination of thermal conductivity data for superconducting Nb shows that there is often a local maximum, a so-called phonon peak, kpp. The temperature at which this kpp occurs Tpp is between 1.72 K and 2.35 K and shifts for samples after deformation. It is well known that the magnitude of kpp decreases as the material is deformed, and hence with increasing Nd. Less cited is that Tpp increases with increasing Nd. This may affect the operating temperature of an SRF cavity. At a certain level deformation (i.e., 4.7% deformation for a residual resistivity ratio RRR = 185), the phonon peak disappears. More deformation is needed for higher RRR, (i.e., greater purity).The models discussed above require estimating several parameters from thermal conductivity measurements and may be best suited to explaining the relative importance of the several scattering mechanisms. For predicting thermal conductivity from basic material variables, the Boltzmann transport equation (BTE) is solved by two methods to predict the lattice component of thermal conductivity. One method uses a substitution of variables from frequency to wavevector in the Callaway model to include the nonlinear phonon dispersion relationship for the longitudinal acoustic (LA) and transverse acoustic (TA) phonon polarizations. This model incorporates a relaxation time approximation using Matthiessen's rule to consider phonon scattering by electrons, boundaries, and dislocations. Another method to predict the lattice thermal conductivity uses an energy-based, variance-reduced Monte Carlo (MC) solution to the BTE for phonons. The MC solution allows more general consideration of the individual scattering mechanisms. It may also be generalized for more complex geometries. The MC solution technique was first verified by comparing the predicted thermal conductivity in bulk Si and Si nanowires with experimental results. Both solutions of the BTE for the lattice thermal conductivity of undeformed and deformed superconducting Nb agreed well with experimental values. The MC model was also used to demonstrate that interstitial impurities must be near saturation to change the lattice thermal conductivity of Nb. The MC solution was also effective in predicting the lattice thermal conductivity of superconducting Ta, with the appropriate change in dispersion relation and other material parameters.

Download or read book Thermal Conductivity of Superconducting Niobium written by Jon Ross Carlson and published by . This book was released on 1968 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermal Conductivity of Superconducting Niobium from 0 03k to 4k written by Stephen Carroll Smith and published by . This book was released on 1971 with total page 194 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermal Conductivity of Superconducting Niobium written by Byron Keith Moore and published by . This book was released on 1971 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermal Design Studies in Niobium and Helium for Superconducting Radio Frequency Cavities written by Ahmad Aizaz and published by . This book was released on 2006 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermomagnetic Effects in Normal and Superconducting Indium and Niobium written by Craig Hammann Stephan and published by . This book was released on 1971 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Ultrasonic and Thermal Effects in Superconductors written by Reynold Shigeru Kagiwada and published by . This book was released on 1966 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Some of the properties of three transition metals, niobium, vanadium, and tantalum, were investigated using the ultrasonic technique. The normal attenuation in niobium possessed a typical electron-phonon behavior with a temperature dependence of T to the -3.2 power. In the superconducting state, attenuation was measured in both the absence of a magnetic field and at various values of the external magnetic field. From the ratio of superconducting to normal conducting attenuation, the zero-degree energy gaps of niobium, vanadium, and tantalum were determined. For niobium, an energy gap of 2 delta (0) = 3.64 plus or minus 0.05 kT sub c was found for the 100 direction of propagation, and an energy gap of 3.70 plus or minus 0.06 kT sub c for the 111 direction. These measurements indicate an anisotropy of the energy gap. The zero-degree energy gap for vanadium was 2 delta (0) = 3.40 plus or minus 0.07 kT sub c in the 110 direction, and 3.10 plus or minus 0.07 kT sub c for tantalum in the 100 direction. (Author).

Download or read book Role of Metallurgy in the Thermal Conductivity of Superconducting Niobium written by Saravan Kumar Chandrasekaran and published by . This book was released on 2013 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Thermal Transport and Thermal magnetic Breakdown in Superconducting Cavities Made of High Thermal Conductivity Niobium written by Kathleen Rempel Krafft and published by . This book was released on 1983 with total page 408 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Nuclear Science Abstracts written by and published by . This book was released on 1976-05 with total page 912 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Effect of Electropolishing and Low Temperature Baking on the Superconducting Properties of Large Grain Niobium written by and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Measurements of superconducting properties such as bulk and surface critical fields and thermal conductivity have been carried out in the temperature range from 2 K to 8 K on large-grain samples of different purity and on a high-purity fine-grain sample, for comparison. The samples were treated by electropolishing and low temperature baking (120° C, 48 h). While the residual resistivity ratio changed by a factor of ~3 among the samples, no significant variation was found in their superconducting properties. The onset field for flux penetration at 2 K, Hffp, measured within a ~30 μm depth from the surface, was ~160 mT, close to the bulk value. The baking effect was mainly to increase the field range up to which a coherent superconducting phase persists on the surface, above the upper critical field.

Download or read book I Similarity Principle and Isotope Effect in Superconducting Indium written by Nail Mehmet Senozan and published by . This book was released on 1965 with total page 108 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1972 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book NBS Monograph written by and published by . This book was released on 1959 with total page 620 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Superconductivity written by Cambridge Scientific Abstracts, Inc and published by . This book was released on 1973 with total page 136 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Physical Properties of High Temperature Superconductors III written by Donald M. Ginsberg and published by World Scientific. This book was released on 1992 with total page 644 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume brings the reader up to date on transport phenomena, including electrical and thermal conductivity and infrared properties. In addition, electron tunneling and the characteristics and applications of films are discussed; the preparation of the necessary samples has proceeded, and a sizeable body of reproducible data has become available. Pressure effects are also presented; considerable progress has been made in relating them to the crystallographic and electronic structure of high temperature superconductors. The preparation and characterization of bulk samples is also reviewed.