IPAC2013 - List of Authors (Aull, S.)

Paper

Title

Page

RF Characterization of Niobium Films for Superconducting Cavities

2399

S. Aull, S. Calatroni, S. Döbert, T. Junginger, G. Terenziani
CERN, Geneva, Switzerland
S. Aull
University of Siegen, Siegen, Germany
A.P. Ehiasarian, G. Terenziani
Sheffield University, Sheffield, United Kingdom
J. Knobloch
HZB, Berlin, Germany

Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF)
The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The excited modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HiPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HiPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.

THOBB201

Pathway to a Post Processing Increase in Q0 of SRF Cavities

3129

O. Kugeler, J. Knobloch, J.M. Vogt
HZB, Berlin, Germany
S. Aull
CERN, Geneva, Switzerland

A significant improvement of Q0 to values larger than 3.2x10¹⁰ at 1.8K has been repeatedly achieved in an SRF cavity by thermal cycling, i.e. heating the cavity briefly above transition temperature and subsequent cooling. Conceivable explanations for this effect reach from effectivity deviations of the magnetic shielding to thermal currents to hydrogen diffusion. Experimental We have experimentally verified some of these explanations, leaving a direct impact of cooling dynamics on frozen flux as the most plausible one. The pathway to this finding is being presented and the application to SRF systems is elicited.

Slides THOBB201 [1.184 MB]

Paper	Title	Page
WEPWO044	RF Characterization of Niobium Films for Superconducting Cavities	2399
	S. Aull, S. Calatroni, S. Döbert, T. Junginger, G. Terenziani CERN, Geneva, Switzerland S. Aull University of Siegen, Siegen, Germany A.P. Ehiasarian, G. Terenziani Sheffield University, Sheffield, United Kingdom J. Knobloch HZB, Berlin, Germany
	Funding: Work supported by the Wolfgang-Gentner-Programme of the Bundesministerium für Bildung und Forschung (BMBF) The surface resistance RS of superconductors shows a complex dependence on the external parameters such as temperature, frequency or radio-frequency (RF) field. The excited modes of 400, 800 and 1200 MHz allow measurements at actual operating frequencies of superconducting cavities. Niobium films on copper substrates have several advantages over bulk niobium cavities. HiPIMS (High-power impulse magnetron sputtering) is a promising technique to increase the quality and therefore the performance of niobium films. This contribution will introduce CERNs recently developed HiPIMS coating apparatus. Moreover, first results of niobium coated copper samples will be presented, revealing the dominant loss mechanisms.

THOBB201	Pathway to a Post Processing Increase in Q0 of SRF Cavities	3129
	O. Kugeler, J. Knobloch, J.M. Vogt HZB, Berlin, Germany S. Aull CERN, Geneva, Switzerland
	A significant improvement of Q0 to values larger than 3.2x10¹⁰ at 1.8K has been repeatedly achieved in an SRF cavity by thermal cycling, i.e. heating the cavity briefly above transition temperature and subsequent cooling. Conceivable explanations for this effect reach from effectivity deviations of the magnetic shielding to thermal currents to hydrogen diffusion. Experimental We have experimentally verified some of these explanations, leaving a direct impact of cooling dynamics on frozen flux as the most plausible one. The pathway to this finding is being presented and the application to SRF systems is elicited.
	Slides THOBB201 [1.184 MB]