SRF2015 - List of Authors (Calatroni, S.)

Paper	Title	Page
TUPB027	Developments on SRF Coatings at CERN	617
	A. Sublet, S. Aull, B. Bártová, S. Calatroni, T. Richard, G.J. Rosaz, M. Taborelli, M. Therasse, W. Venturini Delsolaro, P. Zhang CERN, Geneva, Switzerland
	The thin films techniques applied to Superconducting RF (SRF) has a long history at CERN. A large panel of cavities have been coated from LEP, to LHC. For the current and future projects (HIE-ISOLDE, HL-LHC, FCC) there is a need for further higher RF-performances with focus on minimizing residual resistance Rres and maximizing quality factor Q0 of the cavities. This paper will present CERN’s developments on thin films to achieve these goals through the following main axes of research: The first one concerns the application of different coating techniques for Nb (DC-bias diode sputtering, magnetron sputtering and HiPIMS). Another approach is the investigation of alternative materials like Nb3Sn. These lines of development will be supported by a material science approach to characterize and evaluate the layer properties by means of FIB-SEM, TEM, XPS, XRD, etc. In addition a numerical tool for plasma simulation will be exploited to develop adapted coating systems and optimize the coating process, from plasma generation to thin film growth.
	Poster TUPB027 [1.070 MB]
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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]
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TUPB051	Development of Nb3Sn Coatings by Magnetron Sputtering for SRF Cavities	691
	G.J. Rosaz, S. Calatroni, F.M. Leaux, F. Motschmann, Z. Mydlarz, M. Taborelli, W. Vollenberg CERN, Geneva, Switzerland
	Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453 Cost and energy savings are an integral requirement in the design of future particle accelerators. Very low losses SRF accelerating systems, together with high-efficiency cryogenics systems, have the potential of low running costs. The association to the capital cost reduction allowed by thin films coated copper cavities may represent the best overall cost-performance compromise. This strategy has been applied for instance in LEP, the LHC and HIE-ISOLDE with the niobium thin films technology. New materials must be considered to improve the quality factor of the cavities, such as Nb3Sn, which could also ideally operate at higher temperature thus allowing further energy savings. The study considers the possibility to coat a copper resonator with an Nb3Sn layer by means of magnetron sputtering using an alloyed target. We present the impact of the process parameters on the as-deposited layer stoichiometry. The latter is in good agreement with previous results reported in the literature and can be tuned by acting on the coating pressure. The effect of post-coating annealing temperature on the morphology, crystallinity and superconducting properties of the film was also investigated.
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TUPB052	HTS Coatings for Impedance Reduction of Beam-Induced RF Image Currents in the FCC	695
	S. Calatroni CERN, Geneva, Switzerland
	The FCC-hh presently under study at CERN will make use of 16 T superconducting dipoles for achieving 100 TeV p-p center-of-mass collision energy in a 100 km ring collider. A copper coated beam screen, like in the LHC, is envisaged to shield the 1.9 K dipole cold bores from the 28 W/m/beam of synchrotron radiation. Operating temperature should be in the 50 K range, as best compromise temperature in order to minimize the wall-plug power consumption of the cryogenic system. However, preliminary studies indicate that copper at 50 K might not provide low enough beam coupling impedance in the FCC-hh. It has then been proposed to reduce the beam impedance by a thin layer of a High-Temperature Superconductor (HTS), which will thus effectively shield the beam-induced RF image currents. Purpose of this paper is to define the basic requirements for an HTS film in the RF field induced by beam image currents and exposed to a high magnetic field, and to identify the best candidate materials and coating processes.
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THPB048	Design of a Compact Superconducting Crab-Cavity for LHC Using Nb-on-Cu-Coating Technique	1205
	A. Grudiev, S. Atieh, R. Calaga, S. Calatroni, O. Capatina, F. Carra, G. Favre, L.M.A. Ferreira, J.-F. Poncet, T. Richard, A. Sublet, C. Zanoni CERN, Geneva, Switzerland
	The design of a compact superconducting crab-cavity for LHC using Nb-on-Cu-coating technique is presented. The cavity shape is based on the ridged waveguide resonator with wide open apertures to provide access to the inner surface of the cavity for coating. It also provides natural damping for HOMs and rather low longitudinal and transverse impedances. The results of the cavity shape optimization taking into account RF performance, coating, and thermo-mechanical considerations as well as the design and fabrication plans of the first prototype for coating and cold tests are presented.
	Poster THPB048 [0.534 MB]
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Paper

Title

Page

Developments on SRF Coatings at CERN

617

A. Sublet, S. Aull, B. Bártová, S. Calatroni, T. Richard, G.J. Rosaz, M. Taborelli, M. Therasse, W. Venturini Delsolaro, P. Zhang
CERN, Geneva, Switzerland

The thin films techniques applied to Superconducting RF (SRF) has a long history at CERN. A large panel of cavities have been coated from LEP, to LHC. For the current and future projects (HIE-ISOLDE, HL-LHC, FCC) there is a need for further higher RF-performances with focus on minimizing residual resistance Rres and maximizing quality factor Q0 of the cavities. This paper will present CERN’s developments on thin films to achieve these goals through the following main axes of research: The first one concerns the application of different coating techniques for Nb (DC-bias diode sputtering, magnetron sputtering and HiPIMS). Another approach is the investigation of alternative materials like Nb3Sn. These lines of development will be supported by a material science approach to characterize and evaluate the layer properties by means of FIB-SEM, TEM, XPS, XRD, etc. In addition a numerical tool for plasma simulation will be exploited to develop adapted coating systems and optimize the coating process, from plasma generation to thin film growth.

Poster TUPB027 [1.070 MB]

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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]

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TUPB051

Development of Nb3Sn Coatings by Magnetron Sputtering for SRF Cavities

691

G.J. Rosaz, S. Calatroni, F.M. Leaux, F. Motschmann, Z. Mydlarz, M. Taborelli, W. Vollenberg
CERN, Geneva, Switzerland

Funding: The work is part of EuCARD-2, partly funded by the European Commission, GA 312453
Cost and energy savings are an integral requirement in the design of future particle accelerators. Very low losses SRF accelerating systems, together with high-efficiency cryogenics systems, have the potential of low running costs. The association to the capital cost reduction allowed by thin films coated copper cavities may represent the best overall cost-performance compromise. This strategy has been applied for instance in LEP, the LHC and HIE-ISOLDE with the niobium thin films technology. New materials must be considered to improve the quality factor of the cavities, such as Nb3Sn, which could also ideally operate at higher temperature thus allowing further energy savings. The study considers the possibility to coat a copper resonator with an Nb3Sn layer by means of magnetron sputtering using an alloyed target. We present the impact of the process parameters on the as-deposited layer stoichiometry. The latter is in good agreement with previous results reported in the literature and can be tuned by acting on the coating pressure. The effect of post-coating annealing temperature on the morphology, crystallinity and superconducting properties of the film was also investigated.

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TUPB052

HTS Coatings for Impedance Reduction of Beam-Induced RF Image Currents in the FCC

695

S. Calatroni
CERN, Geneva, Switzerland

The FCC-hh presently under study at CERN will make use of 16 T superconducting dipoles for achieving 100 TeV p-p center-of-mass collision energy in a 100 km ring collider. A copper coated beam screen, like in the LHC, is envisaged to shield the 1.9 K dipole cold bores from the 28 W/m/beam of synchrotron radiation. Operating temperature should be in the 50 K range, as best compromise temperature in order to minimize the wall-plug power consumption of the cryogenic system. However, preliminary studies indicate that copper at 50 K might not provide low enough beam coupling impedance in the FCC-hh. It has then been proposed to reduce the beam impedance by a thin layer of a High-Temperature Superconductor (HTS), which will thus effectively shield the beam-induced RF image currents. Purpose of this paper is to define the basic requirements for an HTS film in the RF field induced by beam image currents and exposed to a high magnetic field, and to identify the best candidate materials and coating processes.

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

THPB048

Design of a Compact Superconducting Crab-Cavity for LHC Using Nb-on-Cu-Coating Technique

1205

A. Grudiev, S. Atieh, R. Calaga, S. Calatroni, O. Capatina, F. Carra, G. Favre, L.M.A. Ferreira, J.-F. Poncet, T. Richard, A. Sublet, C. Zanoni
CERN, Geneva, Switzerland

The design of a compact superconducting crab-cavity for LHC using Nb-on-Cu-coating technique is presented. The cavity shape is based on the ridged waveguide resonator with wide open apertures to provide access to the inner surface of the cavity for coating. It also provides natural damping for HOMs and rather low longitudinal and transverse impedances. The results of the cavity shape optimization taking into account RF performance, coating, and thermo-mechanical considerations as well as the design and fabrication plans of the first prototype for coating and cold tests are presented.

Poster THPB048 [0.534 MB]

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