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Full-Text Articles in Physics

Effect Of High Temperature Heat Treatments On The Quality Factor Of A Large-Grain Superconducting Radio-Frequency Niobium Cavity, P Dhakal, G Ciovati, G R. Myneni, K E. Gray, N Groll, P Maheshwari, D M. Mcrae, Robert D. Pike, T Proslier, F Stevie, R P. Walsh, Q Yang, J Zasadzinzki Apr 2013

Effect Of High Temperature Heat Treatments On The Quality Factor Of A Large-Grain Superconducting Radio-Frequency Niobium Cavity, P Dhakal, G Ciovati, G R. Myneni, K E. Gray, N Groll, P Maheshwari, D M. Mcrae, Robert D. Pike, T Proslier, F Stevie, R P. Walsh, Q Yang, J Zasadzinzki

Chemistry Articles & Book Chapters

Large-grain Nb has become a viable alternative to fine-grain Nb for the fabrication of superconducting radio-frequency cavities. In this contribution we report the results from a heat treatment study of a large-grain 1.5 GHz single-cell cavity made of “medium purity” Nb. The baseline surface preparation prior to heat treatment consisted of standard buffered chemical polishing. The heat treatment in the range 800–1400°C was done in a newly designed vacuum induction furnace. Q0 values of the order of 2×1010 at 2.0 K and peak surface magnetic field (Bp) of 90 mT were achieved reproducibly. A Q0 ...


Advanced Topographic Characterization Of Variously Prepared Niobium Surfaces And Linkage To Rf Losses, Chen Xu Jan 2013

Advanced Topographic Characterization Of Variously Prepared Niobium Surfaces And Linkage To Rf Losses, Chen Xu

Dissertations, Theses, and Masters Projects

Superconducting radio frequency (SRF) technology is widely adopted in particle accelerators. The shallow penetration (∼ 40 nm) of the RF into superconducting niobium lends great importance to SRF cavity interior surface chemistry and topography. These in turn are strongly influenced by the chemical etching "surface clean-up" that follows fabrication.;The principal surface smoothing methods are buffered chemical polish (BCP) and electropolish (EP). The resulting topography is characterized by atomic force microscopy (AFM). The power spectral density (PSD) of AFM data provides a more thorough description of the topography than a single-value roughness measurement. In this work, one dimensional average PSD functions ...


First Principles Linear Response Calculations Of Lattice Dynamics, Cheng-Zhang Wang Jan 1995

First Principles Linear Response Calculations Of Lattice Dynamics, Cheng-Zhang Wang

Dissertations, Theses, and Masters Projects

First principles calculations, using the density-functional theory and particularly the local density approximation (LDA), have achieved remarkable success in studying the properties of solid state systems. Although the basic results of these calculations are the electronic structures (eigenvalues, eigenfunctions, etc.) and the total energy of ground state, many other related physical properties can be deduced from them by investigating their response under external perturbations. Using the linear response method with linearized-augmented-plane-wave (LAPW) basis, we have calculated lattice dynamical properties of important semiconductors CuCl, SiC and ferroelectric KNbO{dollar}\sb3.{dollar} CuCl is known to exhibit large anharmonic effects and possibly ...