SRF2013 - List of Keywords (superconducting-RF)

Paper	Title	Other Keywords	Page
MOP032	Statistic to Eddy-Current Scanning of Niobium Sheets for European XFEL	niobium, cavity, controls, survey	171
	A. Brinkmann, S. Arnold, A. Ermakov, J. Iversen, M. Lengkeit, A. Poerschmann, L. Schaefer, W. Singer, X. Singer DESY, Hamburg, Germany
	The fabrication experiences of superconducting cavities for FLASH have shown that eddy-current scanning of the Nb-sheets foreseen for half-cells reduces the cavity failures. New eddy current devices have been developed and build together with the industry for the production of 800 pieces 1.3 GHz superconducting niobium cavities for European XFEL. More than 15.000 Nb-sheets provided by three companies have been tested by eddy-current scanning. The sheets that demonstrated local deviations of the signal have been subsequently non-destructively examined by 3d-microscope and X-Ray element analysis. The surface defects (dents, holes, scratches) are the mainly detected flaws. In addition several types of foreign material inclusions observed. Statistic concerning eddy-current signal deviation and rejection rates for each supplier will be presented.

MOP079	Design and Test of a Cryogenic Seal for Rectangular Waveguide Using VATSEAL Technology	vacuum, cryogenics, detector, controls	325
	J.D. Fuerst, J.P. Holzbauer, J.A. Kaluzny, C.R. Montiel, Y. Shiroyanagi, B.K. Stillwell ANL, Argonne, USA
	Funding: This work was supported by the U. S. Department of Energy, Office of Science, under contract No. DE-AC02-06CH11357. A commercially available rectangular metal seal from VAT Vacuum Valves AG has been evaluated and cold tested as a possible cryogenic seal for srf cavities. A program of analysis and cryogenic testing was undertaken to evaluate seal parameters and suitability. Seal line loads, bolt torque and resultant flange/seal deformation at low temperature and during thermal cycling were calculated both statically and via time-dependent numerical simulation to confirm the mechanical integrity of the flange/seal system. Cold testing of flange/waveguide assemblies included thermal shocks in liquid nitrogen and realistic cool-downs below the λ point. Acceptable seal performance has been demonstrated under all test conditions although seal joint assembly is sensitive to details including bolt torque, flange flatness, and surface finish.

TUP023	Evidence of Magnetic Breakdown on the Defects With Thermally Suppressed Critical Field in High Gradient SRF Cavities	SRF, site, superconductivity, niobium	472
	G.V. Eremeev, A.D. Palczewski JLAB, Newport News, Virginia, USA
	Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. At SRF 2011 we presented the study of quenches in high gradient SRF cavities with dual mode excitation technique[]. The data differed from measurements done in 80’s that indicated thermal breakdown nature of quenches in SRF cavities. In this contribution we present analysis of the data that indicates that our recent data for high gradient quenches is consistent with the magnetic breakdown on the defects with thermally suppressed critical field. From the parametric fits derived within the model we estimate the critical breakdown fields and RF resistances at the breakdown site. [] G. Eremeev et al.,. In Proceedings of the 15th Superconducting RF conference,pp. 746-749, July 2011.

TUP028	Investigation of Spatial Variation of the Surface Resistance of a Superconducting RF Cavity	cavity, resonance, SRF, superconductivity	483
	D. Gonnella, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA R.E. French Corning Community College, Corning, USA
	Funding: NSF Cornell has recently completed a single cell temperature mapping system with a resolution of a few tenths of a millikelvin, corresponding to a surface resistance resolution of 1 nOhm. A superconducting RF cavity was tested using temperature mapping and the surface resistance was extracted from the temperature mapping data as function of position on the cavity surface. The surface resistance was profiled across the surface of the cavity between 5 and 35 MV/m and at different temperatures between 1.6 and 2.1 K. From BCS fitting of the local surface resistance, the spatial variation and the field dependence of the mean free path, energy gap, and residual resistance was found. These studies give interesting new insight into the degree of variation of the properties of the superconductor over the surface of the cavity.

TUP088	NbTiN Based SIS Multilayer Structures for SRF Applications	cavity, SRF, lattice, radiation	670
	A-M. Valente-Feliciano, G.V. Eremeev, H.L. Phillips, C.E. Reece JLAB, Newport News, Virginia, USA A.D. Batchelor NCSU AIF, Raleigh, North Carolina, USA R.A. Lukaszew The College of William and Mary, Williamsburg, USA J.K. Spradlin JLab, Newport News, Virginia, USA Q.G. Yang NSU, Norfolk, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. For the past three decades, bulk niobium has been the material of choice for SRF cavities applications. RF cavity performance is now approaching the theoretical limit for bulk niobium. For further improvement of RF cavity performance for future accelerator projects, Superconductor-Insulator-Superconductor (SIS) multilayer structures (as recently proposed by Alex Gurevich) present the theoretical prospect to reach RF performance beyond bulk Nb, using thinly layered higher-Tc superconductors with enhanced Hc1. Jefferson Lab (JLab) is pursuing this approach with the development of NbTiN and AlN based multilayer SIS structures via magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS). This paper presents the results on the characteristics of NbTiN and insulator films and the first RF measurements on NbTiN-based multilayer structure on thick Nb films.

WEIOD02	Magnetic Shielding: Our Experience with Various Shielding Materials	shielding, cryogenics, simulation, linac	808
	M. Masuzawa, A. Terashima, K. Tsuchiya KEK, Ibaraki, Japan A. Daël, O. Napoly, J. Plouin CEA/DSM/IRFU, France
	Magnetic shielding is a key technology for superconducting RF cavities. The tolerance of the ambient magnetic field depends on factors such as the operating RF frequency and acceleration gradient, but it can be as small as a few mG. Some high-Ni-content alloys, such as Cryperm 10 or Cryophy, which are claimed to maintain high permeability at cryogenic temperatures where superconducting cavities are operated, are commercially available at present and are used for magnetic shielding of superconducting cavities at many laboratories. Permeability measurements were made in order to understand the characteristics of such materials at both room and cryogenic temperatures, and the results will be used as a database for designing magnetic shields. It was found that the catalog performance of such materials was not always reproduced in the measurements. Some degradation was observed which depended on how the material was handled. The results of investigation into possible causes for the performance degradation of the shielding material at cryogenic temperature will be presented, along with permeability measurement results for various materials at different temperatures.
	Slides WEIOD02 [8.475 MB]

THP047	Performance Degradation of a Superconducting Cavity Quenching in Magnetic Field	cavity, cryomodule, RF-structure, superconductivity	1013
	I. Terechkine, T.N. Khabiboulline, D.A. Sergatskov Fermilab, Batavia, USA
	Although degradation of a superconducting RF (SRF) cavity performance induced by magnetic field trapped in its walls is a well understood phenomenon, a criterion for an acceptable level of magnetic field existing in the vicinity of an SRF cavity and generated after the cavity is cooled down has not been agreed upon. The bulk of superconducting Nb should protect the RF surface of the cavity from the magnetic field on the outside; nevertheless a failure mode exists when the cavity quenches while the external field is applied. The amount of trapped magnetic flux in this case depends on the size of normally conducting zone developed in walls of the cavity during quenching. Although propagation of the normally conducting zone in walls of a cavity can be modeled, no dedicated studies of this process that would include experimental verifications of its impact on the cavity performance could be found. We tried to address his issue in a special study by using as an example a superconducting coil mounted near a quenching cavity; the method and some results of the study can be applied to any RF structure and magnetic system.

Paper

Title

Other Keywords

Page

MOP032

Statistic to Eddy-Current Scanning of Niobium Sheets for European XFEL

niobium, cavity, controls, survey

171

A. Brinkmann, S. Arnold, A. Ermakov, J. Iversen, M. Lengkeit, A. Poerschmann, L. Schaefer, W. Singer, X. Singer
DESY, Hamburg, Germany

The fabrication experiences of superconducting cavities for FLASH have shown that eddy-current scanning of the Nb-sheets foreseen for half-cells reduces the cavity failures. New eddy current devices have been developed and build together with the industry for the production of 800 pieces 1.3 GHz superconducting niobium cavities for European XFEL. More than 15.000 Nb-sheets provided by three companies have been tested by eddy-current scanning. The sheets that demonstrated local deviations of the signal have been subsequently non-destructively examined by 3d-microscope and X-Ray element analysis. The surface defects (dents, holes, scratches) are the mainly detected flaws. In addition several types of foreign material inclusions observed. Statistic concerning eddy-current signal deviation and rejection rates for each supplier will be presented.

MOP079

Design and Test of a Cryogenic Seal for Rectangular Waveguide Using VATSEAL Technology

vacuum, cryogenics, detector, controls

325

J.D. Fuerst, J.P. Holzbauer, J.A. Kaluzny, C.R. Montiel, Y. Shiroyanagi, B.K. Stillwell
ANL, Argonne, USA

Funding: This work was supported by the U. S. Department of Energy, Office of Science, under contract No. DE-AC02-06CH11357.
A commercially available rectangular metal seal from VAT Vacuum Valves AG has been evaluated and cold tested as a possible cryogenic seal for srf cavities. A program of analysis and cryogenic testing was undertaken to evaluate seal parameters and suitability. Seal line loads, bolt torque and resultant flange/seal deformation at low temperature and during thermal cycling were calculated both statically and via time-dependent numerical simulation to confirm the mechanical integrity of the flange/seal system. Cold testing of flange/waveguide assemblies included thermal shocks in liquid nitrogen and realistic cool-downs below the λ point. Acceptable seal performance has been demonstrated under all test conditions although seal joint assembly is sensitive to details including bolt torque, flange flatness, and surface finish.

TUP023

Evidence of Magnetic Breakdown on the Defects With Thermally Suppressed Critical Field in High Gradient SRF Cavities

SRF, site, superconductivity, niobium

472

G.V. Eremeev, A.D. Palczewski
JLAB, Newport News, Virginia, USA

Funding: Work supported by DOE. Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
At SRF 2011 we presented the study of quenches in high gradient SRF cavities with dual mode excitation technique[*]. The data differed from measurements done in 80’s that indicated thermal breakdown nature of quenches in SRF cavities. In this contribution we present analysis of the data that indicates that our recent data for high gradient quenches is consistent with the magnetic breakdown on the defects with thermally suppressed critical field. From the parametric fits derived within the model we estimate the critical breakdown fields and RF resistances at the breakdown site.
[*] G. Eremeev et al.,. In Proceedings of the 15th Superconducting RF conference,pp. 746-749, July 2011.

TUP028

Investigation of Spatial Variation of the Surface Resistance of a Superconducting RF Cavity

cavity, resonance, SRF, superconductivity

483

D. Gonnella, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
R.E. French
Corning Community College, Corning, USA

Funding: NSF
Cornell has recently completed a single cell temperature mapping system with a resolution of a few tenths of a millikelvin, corresponding to a surface resistance resolution of 1 nOhm. A superconducting RF cavity was tested using temperature mapping and the surface resistance was extracted from the temperature mapping data as function of position on the cavity surface. The surface resistance was profiled across the surface of the cavity between 5 and 35 MV/m and at different temperatures between 1.6 and 2.1 K. From BCS fitting of the local surface resistance, the spatial variation and the field dependence of the mean free path, energy gap, and residual resistance was found. These studies give interesting new insight into the degree of variation of the properties of the superconductor over the surface of the cavity.

TUP088

NbTiN Based SIS Multilayer Structures for SRF Applications

cavity, SRF, lattice, radiation

670

A-M. Valente-Feliciano, G.V. Eremeev, H.L. Phillips, C.E. Reece
JLAB, Newport News, Virginia, USA
A.D. Batchelor
NCSU AIF, Raleigh, North Carolina, USA
R.A. Lukaszew
The College of William and Mary, Williamsburg, USA
J.K. Spradlin
JLab, Newport News, Virginia, USA
Q.G. Yang
NSU, Norfolk, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the past three decades, bulk niobium has been the material of choice for SRF cavities applications. RF cavity performance is now approaching the theoretical limit for bulk niobium. For further improvement of RF cavity performance for future accelerator projects, Superconductor-Insulator-Superconductor (SIS) multilayer structures (as recently proposed by Alex Gurevich) present the theoretical prospect to reach RF performance beyond bulk Nb, using thinly layered higher-Tc superconductors with enhanced Hc1. Jefferson Lab (JLab) is pursuing this approach with the development of NbTiN and AlN based multilayer SIS structures via magnetron sputtering and High Power Impulse Magnetron Sputtering (HiPIMS). This paper presents the results on the characteristics of NbTiN and insulator films and the first RF measurements on NbTiN-based multilayer structure on thick Nb films.

WEIOD02

Magnetic Shielding: Our Experience with Various Shielding Materials

shielding, cryogenics, simulation, linac

808

M. Masuzawa, A. Terashima, K. Tsuchiya
KEK, Ibaraki, Japan
A. Daël, O. Napoly, J. Plouin
CEA/DSM/IRFU, France

Magnetic shielding is a key technology for superconducting RF cavities. The tolerance of the ambient magnetic field depends on factors such as the operating RF frequency and acceleration gradient, but it can be as small as a few mG. Some high-Ni-content alloys, such as Cryperm 10 or Cryophy, which are claimed to maintain high permeability at cryogenic temperatures where superconducting cavities are operated, are commercially available at present and are used for magnetic shielding of superconducting cavities at many laboratories. Permeability measurements were made in order to understand the characteristics of such materials at both room and cryogenic temperatures, and the results will be used as a database for designing magnetic shields. It was found that the catalog performance of such materials was not always reproduced in the measurements. Some degradation was observed which depended on how the material was handled. The results of investigation into possible causes for the performance degradation of the shielding material at cryogenic temperature will be presented, along with permeability measurement results for various materials at different temperatures.

Slides WEIOD02 [8.475 MB]

THP047

Performance Degradation of a Superconducting Cavity Quenching in Magnetic Field

cavity, cryomodule, RF-structure, superconductivity

1013

I. Terechkine, T.N. Khabiboulline, D.A. Sergatskov
Fermilab, Batavia, USA

Although degradation of a superconducting RF (SRF) cavity performance induced by magnetic field trapped in its walls is a well understood phenomenon, a criterion for an acceptable level of magnetic field existing in the vicinity of an SRF cavity and generated after the cavity is cooled down has not been agreed upon. The bulk of superconducting Nb should protect the RF surface of the cavity from the magnetic field on the outside; nevertheless a failure mode exists when the cavity quenches while the external field is applied. The amount of trapped magnetic flux in this case depends on the size of normally conducting zone developed in walls of the cavity during quenching. Although propagation of the normally conducting zone in walls of a cavity can be modeled, no dedicated studies of this process that would include experimental verifications of its impact on the cavity performance could be found. We tried to address his issue in a special study by using as an example a superconducting coil mounted near a quenching cavity; the method and some results of the study can be applied to any RF structure and magnetic system.