National Technical Reports Library

The National Technical Information Service acquires, indexes, abstracts, and archives the largest collection of U.S. government-sponsored technical reports in existence. The NTRL offers online, free and open access to these authenticated government technical reports. Technical reports and documents in its repository may be available online for free either from the issuing federal agency, the U.S. Government Publishing Office’s Federal Digital System website, or through search engines.

Details

Measurement of RF Losses Due to Trapped Flux in a Large-Grain Niobium Cavity.

DE2008922265

Publication Date	2008
Personal Author	Ciovati, G.; Gurevich, A.
Page Count	5
Abstract	Trapped magnetic field in superconducting niobium is a well known cause of radio-frequency (RF) residual losses. In this contribution, we present the results of RF tests on a single-cell cavity made of high-purity large grain niobium before and after allowing a fraction of the Earth magnetic field to be trapped in the cavity during the cooldown below the critical temperature Tc. This experiment has been done on the cavity before and after a low temperature baking. Temperature mapping allowed us to determine the location of hot-spots with high losses and to measure their field dependence. The results show not only an increase of the low-field residual resistance, but also a larger increase of the surface resistance for intermediate RF field (higher medium field Q-slope), which depends on the amount of the trapped flux. These additional field-dependent losses can be described as losses of pinned vortices oscillating under the applied RF magnetic field.
Keywords	Niobium Superconductivity Rf systems Magnetic field Hot spots Losses Single cell cavities
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Thomas Jefferson National Accelerator Facility, Newport News, VA.; Department of Energy, Washington, DC. Office of Science.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC. Office of Science.
Document Type	Technical Report
NTIS Issue Number	200814
Contract Number	AC05-06OR23177

Measurement of RF Losses Due to Trapped Flux in a Large-Grain Niobium Cavity.

Measurement of RF Losses Due to Trapped Flux in a Large-Grain Niobium Cavity.
DE2008922265

Publication Date	2008
Personal Author	Ciovati, G.; Gurevich, A.
Page Count	5
Abstract	Trapped magnetic field in superconducting niobium is a well known cause of radio-frequency (RF) residual losses. In this contribution, we present the results of RF tests on a single-cell cavity made of high-purity large grain niobium before and after allowing a fraction of the Earth magnetic field to be trapped in the cavity during the cooldown below the critical temperature Tc. This experiment has been done on the cavity before and after a low temperature baking. Temperature mapping allowed us to determine the location of hot-spots with high losses and to measure their field dependence. The results show not only an increase of the low-field residual resistance, but also a larger increase of the surface resistance for intermediate RF field (higher medium field Q-slope), which depends on the amount of the trapped flux. These additional field-dependent losses can be described as losses of pinned vortices oscillating under the applied RF magnetic field.
Keywords	Niobium Superconductivity Rf systems Magnetic field Hot spots Losses Single cell cavities
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Thomas Jefferson National Accelerator Facility, Newport News, VA.; Department of Energy, Washington, DC. Office of Science.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC. Office of Science.
Document Type	Technical Report
NTIS Issue Number	200814
Contract Number	AC05-06OR23177