SRF2015 - List of Authors (Junginger, T.)

Paper	Title	Page
TUBA03	On the Understanding of Q-Slope of Niobium Thin Films	494
	S. Aull, T. Junginger, A. Sublet, W. Venturini Delsolaro, P. Zhang CERN, Geneva, Switzerland J. Knobloch HZB, Berlin, Germany J. Knobloch University of Siegen, Siegen, Germany A-M. Valente-Feliciano JLab, Newport News, Virginia, USA
	The Q-slope of niobium coated copper cavities at medium fields is still the limiting factor for the application the Nb/Cu technology in accelerators. This paper presents a dedicated study of a niobium coating with bulk-like characteristics which shows a Q-slope comparable to bulk Nb at 400 MHz and 4 K. Combining the bulk like film with recent findings of the HIE Isolde indicates that the film microstructure and the Nb/Cu interface are the key aspects to understanding the Q-slope.
	Slides TUBA03 [3.414 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

TUPB050	Secondary Electron Yield of SRF Materials	686
	S. Aull, T. Junginger, H. Neupert CERN, Geneva, Switzerland S. Aull, J. Knobloch University of Siegen, Siegen, Germany J. Knobloch HZB, Berlin, Germany
	The secondary electron yield (SEY) describes the number of electrons emitted to the vacuum per arriving electron at the surface. For a given geometry, the SEY is the defining factor for multipacting activity. In the quest of superconducting RF materials beyond bulk niobium, we studied the SEY of the currently most important candidates for future SRF applications: Nb3Sn, NbTiN and MgB2. All studies were done on clean but technical surfaces, i.e. on clean surfaces exposed to air and with their native oxides as it would be the case for SRF cavities.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

TUPB080	Diagnostic Developments at CERN’s SRF Testing Facility	778
	A. Macpherson, S. Aull, A. Benoit, P.F. Fernández López, K.G. Hernández-Chahín, C. Jarrige, P. Maesen, K.M. Schirm, R. Torres-Sanchez, R. Valera Teruel CERN, Geneva, Switzerland K.G. Hernández-Chahín DCI-UG, León, Mexico T. Junginger HZB, Berlin, Germany T. Junginger TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
	As part of CERN’s re-establishment of an SRF cold testing facility for bulk niobium cavities, diagnostic instrumentation and testing procedures on our vertical cryostat have been upgraded, with particular attention given to quench location, ambient magnetic field control, thermometry and thermal cycling techniques. In addition, preparation and measurement procedures have been addressed, allowing for improved measurement of cavity properties and detailed study of transient effects during the course of cavity testing.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB049	High Flux Three Dimensional Heat Transport in Superfluid Helium and Its Application to a Trilateration Algorithm for Quench Localization With OSTs	201
	T. Junginger TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada P. Horn TU Dresden, Dresden, Germany T. Koettig, K.C. Liao, A. Macpherson CERN, Geneva, Switzerland B.J. Peters KIT, Karlsruhe, Germany
	Oscillating superleak transducers of second sound can be used to localize quench spots on superconducting cavities by trilateration. However propagation speeds faster than the velocity of second sound are usually observed imped- ing the localization. Dedicated experiments show that the fast propagation cannot be correlated to the dependence of the velocity on the heat flux density, but rather to boiling effects in the vicinity of the hot spot. 17 OSTs were used to detect quenches on a 704MHz one-cell elliptical cavity. Two different algorithms for quench localization have been tested and implemented in a computer program enabling direct crosschecks. The new algorithm gives more consis- tent results for different OST signals analyzed for the same quench spot.
	Poster MOPB049 [0.901 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB050	Characterization of SRF Materials at the TRIUMF muSR Facility	205
	R.E. Laxdal, T.J. Buck, T. Junginger, P. Kolb, Y.Y. Ma, L. Yang, Z.Y. Yao TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada S.H. Abidi University of Toronto, Toronto, Ontario, Canada R. Kiefl UBC & TRIUMF, Vancouver, British Columbia, Canada
	MuSR is a powerful tool to probe local magnetism and hence can be used to diagnose flux penetration in Type-II superconductors. Samples produced at TRIUMF and with collaborators in both coin shaped and ellipsoidal geometries have been characterized by applying either transverse or parallel fields between 0 and 300mT and measuring flux entry as a function of applied field. Samples include Nb treated in standard ways including forming, chemistry, and heat treatments. Further, Nb samples have been doped with Nitrogen and coated with a 2 micron layer of Nb3Sn by collaborators from FNAL and Cornell respectively and measured in three field/geometry configurations. Analysis of the method in particular the effects of geometry and the role of pinning will be presented. Results of the measurements will be presented.
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB051	Muon Spin Rotation on Treated Nb Samples in Parallel Field Geometry	210
	S. Gheidi UBC, Vancouver, B.C., Canada T.J. Buck, T. Junginger, R.E. Laxdal, G. Morris TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada M. Dehn TUM/Physik, Garching bei München, Germany R. Kiefl UBC & TRIUMF, Vancouver, British Columbia, Canada
	MuSR is a powerful tool to probe local magnetism and hence can be used to diagnose the entry of magnetic flux in superconductors. First measurements on SRF samples were done with an external DC field applied perpendicular to the sample1 (transverse geometry) with the muons applied to the sample face. Here the results are strongly impacted by demagnetization, pinning strength and edge effects. A new spectrometer has been developed to allow sample testing with a field varying from 0 to 300mT applied along the sample face (parallel geometry) analogous to rf fields in SRF resonators. The geometry is characterized by a small demagnetization factor reducing the impact of pinning and edge effects on field of first flux entry. The beamline installation and first results comparing transverse and parallel results will be presented. 1 Grassellino et al. Muon spin rotation studies of niobium for superconducting rf applications. Phys. Rev. ST Accel. Beams, 16:062002, Jun 2013.
	Poster MOPB051 [0.719 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

TUPB042	Low Energy Muon Spin Rotation and Point Contact Tunneling Applied to Niobium Films for SRF Cavities	656
	T. Junginger TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada S. Calatroni, G. Terenziani CERN, Geneva, Switzerland T. Prokscha, Z. Salman, A. Suter PSI, Villigen PSI, Switzerland Th. Proslier ANL, Argonne, Illinois, USA G. Terenziani Sheffield University, Sheffield, United Kingdom J. Zasadzinski IIT, Chicago, Illinois, USA
	Muon spin rotation (muSR) and point contact tunneling (PCT) are used since several years for bulk niobium studies. Here we present studies on niobium thin film samples of different deposition techniques (diode, magnetron and HIPIMS) and compare the results with RF measurements and bulk niobium results. It is consistently found from muSR and RF measurements that HIPIMS can be used to produce thin films of high RRR. Hints for magnetism are especially found on the HIPIMS samples. These could possibly contribute to the field dependent losses of superconducting cavities, which are strongly pronounced on niobium on copper cavities.
	Poster TUPB042 [0.932 MB]
Export •	reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

Paper

Title

Page

On the Understanding of Q-Slope of Niobium Thin Films

494

S. Aull, T. Junginger, A. Sublet, W. Venturini Delsolaro, P. Zhang
CERN, Geneva, Switzerland
J. Knobloch
HZB, Berlin, Germany
J. Knobloch
University of Siegen, Siegen, Germany
A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA

The Q-slope of niobium coated copper cavities at medium fields is still the limiting factor for the application the Nb/Cu technology in accelerators. This paper presents a dedicated study of a niobium coating with bulk-like characteristics which shows a Q-slope comparable to bulk Nb at 400 MHz and 4 K. Combining the bulk like film with recent findings of the HIE Isolde indicates that the film microstructure and the Nb/Cu interface are the key aspects to understanding the Q-slope.

Slides TUBA03 [3.414 MB]

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

TUPB050

Secondary Electron Yield of SRF Materials

686

S. Aull, T. Junginger, H. Neupert
CERN, Geneva, Switzerland
S. Aull, J. Knobloch
University of Siegen, Siegen, Germany
J. Knobloch
HZB, Berlin, Germany

The secondary electron yield (SEY) describes the number of electrons emitted to the vacuum per arriving electron at the surface. For a given geometry, the SEY is the defining factor for multipacting activity. In the quest of superconducting RF materials beyond bulk niobium, we studied the SEY of the currently most important candidates for future SRF applications: Nb3Sn, NbTiN and MgB2. All studies were done on clean but technical surfaces, i.e. on clean surfaces exposed to air and with their native oxides as it would be the case for SRF cavities.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

TUPB080

Diagnostic Developments at CERN’s SRF Testing Facility

778

A. Macpherson, S. Aull, A. Benoit, P.F. Fernández López, K.G. Hernández-Chahín, C. Jarrige, P. Maesen, K.M. Schirm, R. Torres-Sanchez, R. Valera Teruel
CERN, Geneva, Switzerland
K.G. Hernández-Chahín
DCI-UG, León, Mexico
T. Junginger
HZB, Berlin, Germany
T. Junginger
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada

As part of CERN’s re-establishment of an SRF cold testing facility for bulk niobium cavities, diagnostic instrumentation and testing procedures on our vertical cryostat have been upgraded, with particular attention given to quench location, ambient magnetic field control, thermometry and thermal cycling techniques. In addition, preparation and measurement procedures have been addressed, allowing for improved measurement of cavity properties and detailed study of transient effects during the course of cavity testing.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB049

High Flux Three Dimensional Heat Transport in Superfluid Helium and Its Application to a Trilateration Algorithm for Quench Localization With OSTs

201

T. Junginger
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
P. Horn
TU Dresden, Dresden, Germany
T. Koettig, K.C. Liao, A. Macpherson
CERN, Geneva, Switzerland
B.J. Peters
KIT, Karlsruhe, Germany

Oscillating superleak transducers of second sound can be used to localize quench spots on superconducting cavities by trilateration. However propagation speeds faster than the velocity of second sound are usually observed imped- ing the localization. Dedicated experiments show that the fast propagation cannot be correlated to the dependence of the velocity on the heat flux density, but rather to boiling effects in the vicinity of the hot spot. 17 OSTs were used to detect quenches on a 704MHz one-cell elliptical cavity. Two different algorithms for quench localization have been tested and implemented in a computer program enabling direct crosschecks. The new algorithm gives more consis- tent results for different OST signals analyzed for the same quench spot.

Poster MOPB049 [0.901 MB]

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB050

Characterization of SRF Materials at the TRIUMF muSR Facility

205

R.E. Laxdal, T.J. Buck, T. Junginger, P. Kolb, Y.Y. Ma, L. Yang, Z.Y. Yao
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
S.H. Abidi
University of Toronto, Toronto, Ontario, Canada
R. Kiefl
UBC & TRIUMF, Vancouver, British Columbia, Canada

MuSR is a powerful tool to probe local magnetism and hence can be used to diagnose flux penetration in Type-II superconductors. Samples produced at TRIUMF and with collaborators in both coin shaped and ellipsoidal geometries have been characterized by applying either transverse or parallel fields between 0 and 300mT and measuring flux entry as a function of applied field. Samples include Nb treated in standard ways including forming, chemistry, and heat treatments. Further, Nb samples have been doped with Nitrogen and coated with a 2 micron layer of Nb3Sn by collaborators from FNAL and Cornell respectively and measured in three field/geometry configurations. Analysis of the method in particular the effects of geometry and the role of pinning will be presented. Results of the measurements will be presented.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

MOPB051

Muon Spin Rotation on Treated Nb Samples in Parallel Field Geometry

210

S. Gheidi
UBC, Vancouver, B.C., Canada
T.J. Buck, T. Junginger, R.E. Laxdal, G. Morris
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
M. Dehn
TUM/Physik, Garching bei München, Germany
R. Kiefl
UBC & TRIUMF, Vancouver, British Columbia, Canada

MuSR is a powerful tool to probe local magnetism and hence can be used to diagnose the entry of magnetic flux in superconductors. First measurements on SRF samples were done with an external DC field applied perpendicular to the sample1 (transverse geometry) with the muons applied to the sample face. Here the results are strongly impacted by demagnetization, pinning strength and edge effects. A new spectrometer has been developed to allow sample testing with a field varying from 0 to 300mT applied along the sample face (parallel geometry) analogous to rf fields in SRF resonators. The geometry is characterized by a small demagnetization factor reducing the impact of pinning and edge effects on field of first flux entry. The beamline installation and first results comparing transverse and parallel results will be presented.
1 Grassellino et al. Muon spin rotation studies of niobium for superconducting rf applications.
Phys. Rev. ST Accel. Beams, 16:062002, Jun 2013.

Poster MOPB051 [0.719 MB]

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

TUPB042

Low Energy Muon Spin Rotation and Point Contact Tunneling Applied to Niobium Films for SRF Cavities

656

T. Junginger
TRIUMF, Canada's National Laboratory for Particle and Nuclear Physics, Vancouver, Canada
S. Calatroni, G. Terenziani
CERN, Geneva, Switzerland
T. Prokscha, Z. Salman, A. Suter
PSI, Villigen PSI, Switzerland
Th. Proslier
ANL, Argonne, Illinois, USA
G. Terenziani
Sheffield University, Sheffield, United Kingdom
J. Zasadzinski
IIT, Chicago, Illinois, USA

Muon spin rotation (muSR) and point contact tunneling (PCT) are used since several years for bulk niobium studies. Here we present studies on niobium thin film samples of different deposition techniques (diode, magnetron and HIPIMS) and compare the results with RF measurements and bulk niobium results. It is consistently found from muSR and RF measurements that HIPIMS can be used to produce thin films of high RRR. Hints for magnetism are especially found on the HIPIMS samples. These could possibly contribute to the field dependent losses of superconducting cavities, which are strongly pronounced on niobium on copper cavities.

Poster TUPB042 [0.932 MB]

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)