Proton in SRF Niobium

Abstract

Hydrogen is a difficult impurity to physically deal with in superconducting radio frequency (SRF) niobium, therefore, its properties in the metals should be well understood to allow the metal's superconducting properties to be optimized for minimum loss in the construction of resonant accelerator cavities. It is known that hydrogen is a paramagnetic impurity in niobium from NMR studies. This paramagnetism and its effect on superconducting properties are important to understand. To that end analytical induction measurements aimed at isolating the magnetic properties of hydrogen in SRF niobium are introduced along with optical reflection spectroscopy which is also sensitive to the presence of hydrogen. From the variety, magnitude and rapid kinetics found in the optical and magnetic properties of niobium contaminated with hydrogen forced a search for an atomic model. This yielded quantum mechanical description that correctly generates the activation energy for diffusion of the proton and its isotopes not only in niobium but the remaining metals for which data is available. This interpretation provides a frame work for understanding the individual and collective behavior of protons in metals. 1

Checkerboard Neighborhood

“…Stuart Wallace, who not only was in charge of the initial sales but also oversaw subsequent sales for the next four years, noted that selling to whites in Princeton was not a problem; faculty from the university and relocated workers wanted to live in the new housing because of its value and to a lesser extent because of its ideals and social goals. 60 Princeton's exclusivity and desirability were two of the main selling points for whites. Newton recalled clearly how people were willing to pay more for less housing simply to live in Princeton.…”