SRF2011 - List of Authors (Gurevich, A.V.)

Paper

Title

Page

Multilayer Coatings: Opportunities and Challenges.

280

A.V. Gurevich
Old Dominion University, Norfolk, Virginia, USA

Funding: DOE, Argonne National Lab. Award #313641
The use of multilayer coatings may enable significant increase of the breakdown fields or operating temperatures of SRF cavities by utilizing materials with the thermodynamic critical field Hc higher than Hc = 200 mT for Nb. However, such coating materials have shorter coherence length so the significant effects of impurities or grain boundaries on the surface resistance should be understood. In this talk I’ll analyze the dynamics of penetration of vortices along grain boundaries and dissipation in a thin film coating in strong rf fields. I’ll also discuss the role of impurities, in particular their contribution to the nonlinear Meissner effect which affects the surface resistance in the dirty limit. And finally I’ll discuss the nonlinear response in two-band superconductors like MgB2 in which strong rf fields can cause decoupling of bands at fields H < Hc, which can contribute to the high-field Q slope.

Slides TUIOA02 [1.925 MB]

THPO016

Preliminary Results on the Laser Heating Investigation of Hotspots in a Large-Grain Nb Cavity

745

G. Ciovati, C. Baldwin, G. Cheng, R. J. Flood, K. Jordan, P. Kneisel, M.L. Morrone, L. Turlington, K.M. Wilson, S. Zhang
JLAB, Newport News, Virginia, USA
S. M. Anlage
UMD, College Park, Maryland, USA
A.V. Gurevich
Old Dominion University, Norfolk, Virginia, USA
G. Nemes
Astigmat, Santa Clara, USA

Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.

Poster THPO016 [0.983 MB]

Paper	Title	Page
TUIOA02	Multilayer Coatings: Opportunities and Challenges.	280
	A.V. Gurevich Old Dominion University, Norfolk, Virginia, USA
	Funding: DOE, Argonne National Lab. Award #313641 The use of multilayer coatings may enable significant increase of the breakdown fields or operating temperatures of SRF cavities by utilizing materials with the thermodynamic critical field Hc higher than Hc = 200 mT for Nb. However, such coating materials have shorter coherence length so the significant effects of impurities or grain boundaries on the surface resistance should be understood. In this talk I’ll analyze the dynamics of penetration of vortices along grain boundaries and dissipation in a thin film coating in strong rf fields. I’ll also discuss the role of impurities, in particular their contribution to the nonlinear Meissner effect which affects the surface resistance in the dirty limit. And finally I’ll discuss the nonlinear response in two-band superconductors like MgB2 in which strong rf fields can cause decoupling of bands at fields H < Hc, which can contribute to the high-field Q slope.
	Slides TUIOA02 [1.925 MB]

THPO016	Preliminary Results on the Laser Heating Investigation of Hotspots in a Large-Grain Nb Cavity	745
	G. Ciovati, C. Baldwin, G. Cheng, R. J. Flood, K. Jordan, P. Kneisel, M.L. Morrone, L. Turlington, K.M. Wilson, S. Zhang JLAB, Newport News, Virginia, USA S. M. Anlage UMD, College Park, Maryland, USA A.V. Gurevich Old Dominion University, Norfolk, Virginia, USA G. Nemes Astigmat, Santa Clara, USA
	Magnetic vortices pinned near the inner surface of SRF Nb cavities are a possible source of RF hotspots, frequently observed by temperature mapping of the cavities outer surface at RF surface magnetic fields of about 100 mT. Theoretically, we expect that the thermal gradient provided by a 10 W green laser shining on the inner cavity surface at the RF hotspot locations can move pinned vortices to different pinning locations. The experimental apparatus to send the beam onto the inner surface of a photoinjector-type large-grain Nb cavity is described. Preliminary results on the changes in thermal maps observed after applying the laser heating are also reported.
	Poster THPO016 [0.983 MB]