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Special Physics Seminar Series 293 (2/3/17)

Date: 
February 3, 2017 - 9:00am

Gianluigi Ciovati, Old Dominion University

Abstract:

Niobium is the most common superconductor used in radio-frequency resonators for accelerator applications.  The surface impedance of a metal, whether normal conducting or superconducting, is defined as the ratio of the electric and magnetic field component of the plane wave in the metal. Expressions for the surface impedance of  superconductors have been calculated since the 1950s in the limit of weak fields. The quality factor of  superconducting radio-frequency cavities is inversely proportional to the average surface resistance, the real  part of the surface impedance. Experiments have shown that the quality factor exhibits significant field  dependencies at low, medium and high fields, revealing non-linearities in the surface resistance. Such non- linearities are related to specific surface preparation methods and typically result in an increase of the surface  resistance at high fields. However, recent developments in cavity preparation methods resulted in the decrease  of the surface resistance up to fields relevant for accelerator applications. In this presentation, we will review  some of the experimental results on the field dependence of the quality factor of niobium and we will discuss  some future challenges and opportunities.

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Location

Location: 
Social Sciences and Management Building 104

Contact Information

Name: 
Jay Sharping
Title: 
Associate Professor
Department: 
School of Natural Sciences, Physics
Address: 
5200 North Lake Rd.
Merced, CA 95343
United States
Address: 
5200 North Lake Rd.
Merced, CA 95343
United States