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 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 Superconducting Cavities from High Thermal Conductivity Niobium for CEBAF written by and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The Continuous Electron Beam Accelerator Facility (CEBAF) is presently under construction in Newport News, VA. The accelerator consists of approximately 169 meters of 5-cell niobium cavities made from high thermal conductivity niobium with RRR values> 250. Cavities have been manufactured of material from three different suppliers. The material properties like thermal conductivity, residual resistivity and tensile behavior are compared. Results on the performance of these cavities in the presence of high rf fields are reported. Q(sub)0 values as high as 10^10 at 2 K and accelerating gradient of E> 14 MV/m have been achieved.

Download or read book RF Superconductivity written by Hasan Padamsee and published by John Wiley & Sons. This book was released on 2009-04-20 with total page 465 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the second book to RF Superconducting, written by one of the leading experts. The book provides fast and up-to-date access to the latest advances in the key technology for future accelerators. Experts as well as newcomers to the field will benefit from the discussion of progress in the basic science, technology as well as recent and forthcoming applications. Researchers in accelerator physics will also find much that is relevant to their discipline.

Download or read book Superconducting Cavities from High Thermal Conductivity Niobium for CEBAF February 1991 written by Peter Kneisel and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Superconductivity Cavities from High Thermal Conductivity Niobium for CEBAF January 1991 written by Peter Kneisel and published by . This book was released on 1991 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Dissertation Abstracts International written by and published by . This book was released on 1983 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book INIS Atomindex written by and published by . This book was released on 1986 with total page 1634 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Probing the Fundamental Limit of Niobium in High Radiofrequency Fields by Dual Mode Excitation in Superconducting Radiofrequency Cavities written by and published by . This book was released on 2011 with total page 4 pages. Available in PDF, EPUB and Kindle. Book excerpt: We have studied thermal breakdown in several multicell superconducting radiofrequency cavity by simultaneous excitation of two TM010 passband modes. Unlike measurements done in the past, which indicated a clear thermal nature of the breakdown, our measurements present a more complex picture with interplay of both thermal and magnetic effects. JLab LG-1 that we studied was limited at 40.5 MV/m, corresponding to B{sub peak} = 173 mT, in 8?/9 mode. Dual mode measurements on this quench indicate that this quench is not purely magnetic, and so we conclude that this field is not the fundamental limit in SRF cavities.

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 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 Investigation of the Superconducting Properties of Niobium Radio frequency Cavities written by Gianluigi Ciovati and published by . This book was released on 2005 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Engineering Superconductivity written by Peter J. Lee and published by John Wiley & Sons. This book was released on 2001-05-02 with total page 677 pages. Available in PDF, EPUB and Kindle. Book excerpt: Comprehensive coverage of superconductivity from the Wiley Encyclopedia of Electrical and Electronics Engineering Engineering Superconductivity features fifty articles selected from the Wiley Encyclopedia of Electrical and Electronics Engineering, the one truly indispensable reference for electrical engineers. Superconductor technology has made highly advanced experiments possible in chemistry, biochemistry, particle physics, and health sciences, and introduced new applications currently in use in fields from medicine to cellular communications. Taken together, these articles-written by acknowledged experts in the field-provide the most complete and in-depth accounting of superconductivity in existence. The book brings together a wealth of information that would not be available to those who do not have access to the full 24-volume encyclopedia. This thorough survey looks at the application of superconductors from an engineer's practical perspective rather than a theoretical approach. Engineering Superconductivity provides full coverage of the fundamentals of superconducting behavior and explains the properties and fabrication methods of commercially produced superconductors. Up-to-date material on superconductor applications as well as competing technologies is included. The fifty articles presented here are divided into three sections: Superconductivity and magnetism Superconductors Applications and related technology Engineering Superconductivity is a complete and up-to-date reference for engineers, physicists, chemists, materials scientists, and anyone working with superconductors.

Download or read book On Magnetic thermal Breakdown in Superconducting Rf Cavities written by Jürgen Halbritter and published by . This book was released on 1972 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Comprehensive Dissertation Index written by and published by . This book was released on 1989 with total page 1016 pages. Available in PDF, EPUB and Kindle. Book excerpt:

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 Energy Research Abstracts written by and published by . This book was released on 1987 with total page 1316 pages. Available in PDF, EPUB and Kindle. Book excerpt: