IPAC2017 - List of Keywords (radio-frequency)

Paper	Title	Other Keywords	Page
MOOCA2	First Results From New Single-Cell Nb3Sn Cavities Coated at Cornell University	cavity, niobium, factory, SRF	40
	D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Cavities coated with Nb3Sn at Cornell University demonstrate quality factors of >10¹⁰ at 4.2 K, outperforming equivalent niobium cavities by a factor of >30 at these bath temperatures. These quality factors have been maintained up to fields of 17-18 MV/m without significant Q-slope. Recently, new single-cell cavities have been added to the Cornell Nb3Sn programme in an effort to improve statistics and allow further exploration of the available parameter space. In this paper we report on the first results of these new cavities, as well as the latest performance from other cavities already in use on the programme. Furthermore, continuing work to optimise the coating procedure is reported on, and the latest understanding of the ideal coating profile is discussed.
	Slides MOOCA2 [10.366 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA2
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MOPVA050	Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities	cavity, SRF, niobium, experiment	975
	B. Schmitz, K.Alomari. Alomari, J. Knobloch, O. Kugeler, J.M. Köszegi, Y. Tamashevich HZB, Berlin, Germany
	Flux trapping is the major contribution to the residual resistance of superconducting cavities. In order to gain a better understanding of the mechanisms involved and aiming at an eventual minimization of trapped flux, a measurement setup based on AMR sensors was devised that allows for monitoring the magnetic field vector at various positions near the cavity surface. First results of the efforts are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA050
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MOPVA057	Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities	niobium, SRF, vacuum, cavity	996
	M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, N. Pietralla TU Darmstadt, Darmstadt, Germany F. Hug IKP, Mainz, Germany
	Funding: Work supported by BMBF through 05H15RDRBA. Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic delta-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the alpha-Nb phase results in higher quality factors.* Nb samples will be N-doped at the refurbished UHV furnace at IKP Darmstadt. The first results on the structural investigations of the processed Nb samples at the Materials Research Department of TU Darmstadt are presented. * Grassellino et al., Proc. SRF2015, MOBA06, 48.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA057
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MOPVA062	Test, Diagnostics and Computed Tomographic Inspection of a Large Grain 3.9 GHz Prototype Cavity	cavity, niobium, SRF, diagnostics	1011
	M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore INFN/LASA, Segrate (MI), Italy G. Ciovati, G.R. Myneni JLab, Newport News, Virginia, USA C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	A large grain 3.9 GHz prototype cavity made of RRR = 10⁵ ±10 has been tested at LASA. The cavity suffered of quench at moderate levels of accelerating field, for all nine fundamental pass-band modes. Several diagnostic techniques have been employed to determine the quench positions, which occur close to significant grain-boundary steps, visible from the external cavity surface. The cavity has been scanned with a high resolution X-ray tomographic machine, confirming the existence of remarkable topographic features on the inner RF surface at the suspected quench positions. A strategy for a future surface treatment for recover the cavity performances is here presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA062
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MOPVA116	Quench Studies in Single-Cell Nb3Sn Cavities Coated Using Vapour Diffusion	cavity, accelerating-gradient, monitoring, niobium	1119
	D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna Cornell University, Ithaca, New York, USA
	The superconductor Nb3Sn is known to have a superheating field, Hsh, of approximately 400 mT. This critical field represents the ultimate achievable gradient in a superconducting cavity, and is equivalent to an accelerating gradient of 90 MV/m in an ILC single-cell cavity for this value of Hsh. However, the currently best performing Nb3Sn single-cell cavities remain limited to accelerating gradients of 17-18 MV/m, translating to a peak surface magnetic field of approx. 70 mT. In this paper, we consider theoretical models of candidate quench mechanisms, and compare them to experimental data from surface analysis and cavity tests.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA116
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WEPIK064	Eigenvalue Calculations Based on the Finite Element Method With Physically Motivated Field Smoothing Using the Kirchhoff Integral	cavity, electromagnetic-fields, simulation, extraction	3074
	W. Ackermann, H. De Gersem, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany
	In current linear particle accelerators, the actual acceleration of the charged particles is realized with the help of the electric field strength within driven radio frequency resonators. The characterization and optimization of the applied resonating structures can be reliably performed based on numerical simulation techniques. Efficient numerical methods have been introduced in the last decades to determine the electromagnetic fields while special care has been put in the correct description of the geometry and the material distribution of the structures. Although the resonators are operated in a driven setup, one of the advantageous numerical strategies here is given by an eigendecomposition of the fields which is realized by the application of accurate eigenmode calculations together with suitable postprocessing steps. In particular, the extraction of representative field maps used for particle tracking for example requires an accurate numerical modeling of the field at any position inside the structure. In order to avoid numerically motivated discontinuities of the fields a proper smoothing algorithm based on the vector equivalents of the Kirchhoff integral is proposed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK064
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WEPIK086	Wave Propagation in a Fractal Wave Guide		3128
	V.G. Ziemann, A.K. Bhattacharyya, M. Holz, J. Ögren Uppsala University, Uppsala, Sweden
	We analyze the propagation of electro-magnetic waves in a wave guide that has the shape of Koch's snowflake, a well-known fractal.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK086
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WEPVA145	Analysis of Mean Free Path and Field Dependent Surface Resistance	cavity, niobium, SRF, electron	3609
	J.T. Maniscalco, F. Furuta, D.L. Hall, P.N. Koufalis, M. Liepe Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: NSF-PHY 1416318 Work from Cornell in 2016 built on recent theoretical research in the field of SRF to link the electron mean free path to the field-dependent BCS surface resistance. This research relates the magnitude of the ‘‘anti-Q-slope'', the puzzling reduction of surface resistance with increasing RF field intensity observed in certain cavities, to the doping level of nitrogen-doped niobium, quantified by the mean free path: shorter mean free paths correspond directly with stronger anti-Q-slopes. The theoretical connection comes through the overheating of the quasiparticles, which more effectively transfer their energy to the lattice at short mean free paths. In this report, we present an update of this analysis, investigating recent test results of low-temperature-doped single-cell and nine-cell cavities. We also study the theoretical implications for cavities at frequencies higher and lower than the often-studied 1.3~GHz.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA145
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THPIK108	Bead Pull Measurements of the FETS RFQ at RAL	rfq, cavity, quadrupole, site	4349
	W. Promdee, T.R. Edgecock IIAA, Huddersfield, United Kingdom G.E. Boorman Royal Holloway, University of London, Surrey, United Kingdom G.E. Boorman JAI, Egham, Surrey, United Kingdom T.R. Edgecock, J.K. Pozimski STFC/RAL, Chilton, Didcot, Oxon, United Kingdom A.P. Letchford STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom J.K. Pozimski Imperial College of Science and Technology, Department of Physics, London, United Kingdom
	A Radio Frequency Quadrupole (RFQ) is a part of the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL), Didcot, UK. The aim of the FETS project is to produce a 60 mA H⁻ beam at 3 MeV. The RFQ is a four-vane type with 4 modules, each of 1 m length, and is designed to accelerate the beam from 65 keV to 3 MeV at 324 MHz. A bead pull system has been designed to measure the field along the RFQ. This will be used in conjunction with 64 tuners to produce a uniform field. In order to optimise the tuning procedure, a model of the RFQ has been creat-ed in COMSOL Multiphysics. This study shows the results from the bead pull measurements and the tuning studies.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK108
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Other Keywords

Page

MOOCA2

First Results From New Single-Cell Nb3Sn Cavities Coated at Cornell University

cavity, niobium, factory, SRF

40

D.L. Hall, J.J. Kaufman, M. Liepe, R.D. Porter, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Cavities coated with Nb3Sn at Cornell University demonstrate quality factors of >10¹⁰ at 4.2 K, outperforming equivalent niobium cavities by a factor of >30 at these bath temperatures. These quality factors have been maintained up to fields of 17-18 MV/m without significant Q-slope. Recently, new single-cell cavities have been added to the Cornell Nb3Sn programme in an effort to improve statistics and allow further exploration of the available parameter space. In this paper we report on the first results of these new cavities, as well as the latest performance from other cavities already in use on the programme. Furthermore, continuing work to optimise the coating procedure is reported on, and the latest understanding of the ideal coating profile is discussed.

Slides MOOCA2 [10.366 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOOCA2

Export •

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MOPVA050

Setup of a Spatially Resolving Vector Magnetometry System for the Investigation of Flux Trapping in Superconducting Cavities

cavity, SRF, niobium, experiment

975

B. Schmitz, K.Alomari. Alomari, J. Knobloch, O. Kugeler, J.M. Köszegi, Y. Tamashevich
HZB, Berlin, Germany

Flux trapping is the major contribution to the residual resistance of superconducting cavities. In order to gain a better understanding of the mechanisms involved and aiming at an eventual minimization of trapped flux, a measurement setup based on AMR sensors was devised that allows for monitoring the magnetic field vector at various positions near the cavity surface. First results of the efforts are presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA050

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPVA057

Structural Investigations of Nitrogen-Doped Niobium for Superconducting RF Cavities

niobium, SRF, vacuum, cavity

996

M. Major, L. Alff, M. Arnold, J. Conrad, S. Flege, R. Grewe, N. Pietralla
TU Darmstadt, Darmstadt, Germany
F. Hug
IKP, Mainz, Germany

Funding: Work supported by BMBF through 05H15RDRBA.
Niobium is the standard material for superconducting RF (SRF) cavities. Superconducting materials with higher critical temperature or higher critical magnetic field allow cavities to work at higher operating temperatures or higher accelerating fields, respectively. Enhancing the surface properties of the superconducting material in the range of the penetration depth is also beneficial. One direction of search for new materials with better properties is the modification of bulk niobium by nitrogen doping. In the Nb-N phase diagram the cubic delta-phase of NbN has the highest critical temperature (16 K). Already slight nitrogen doping of the alpha-Nb phase results in higher quality factors.* Nb samples will be N-doped at the refurbished UHV furnace at IKP Darmstadt. The first results on the structural investigations of the processed Nb samples at the Materials Research Department of TU Darmstadt are presented.
* Grassellino et al., Proc. SRF2015, MOBA06, 48.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA057

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reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPVA062

Test, Diagnostics and Computed Tomographic Inspection of a Large Grain 3.9 GHz Prototype Cavity

cavity, niobium, SRF, diagnostics

1011

M. Bertucci, A. Bignami, A. Bosotti, J.F. Chen, C.G. Maiano, P. Michelato, L. Monaco, R. Paparella, P. Pierini, D. Sertore
INFN/LASA, Segrate (MI), Italy
G. Ciovati, G.R. Myneni
JLab, Newport News, Virginia, USA
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

A large grain 3.9 GHz prototype cavity made of RRR = 10⁵ ±10 has been tested at LASA. The cavity suffered of quench at moderate levels of accelerating field, for all nine fundamental pass-band modes. Several diagnostic techniques have been employed to determine the quench positions, which occur close to significant grain-boundary steps, visible from the external cavity surface. The cavity has been scanned with a high resolution X-ray tomographic machine, confirming the existence of remarkable topographic features on the inner RF surface at the suspected quench positions. A strategy for a future surface treatment for recover the cavity performances is here presented.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA062

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOPVA116

Quench Studies in Single-Cell Nb3Sn Cavities Coated Using Vapour Diffusion

cavity, accelerating-gradient, monitoring, niobium

1119

D.L. Hall, M. Liepe, J.T. Maniscalco, R.D. Porter
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
P. Cueva, D. Liarte, D.A. Muller, J.P. Sethna
Cornell University, Ithaca, New York, USA

The superconductor Nb3Sn is known to have a superheating field, Hsh, of approximately 400 mT. This critical field represents the ultimate achievable gradient in a superconducting cavity, and is equivalent to an accelerating gradient of 90 MV/m in an ILC single-cell cavity for this value of Hsh. However, the currently best performing Nb3Sn single-cell cavities remain limited to accelerating gradients of 17-18 MV/m, translating to a peak surface magnetic field of approx. 70 mT. In this paper, we consider theoretical models of candidate quench mechanisms, and compare them to experimental data from surface analysis and cavity tests.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPVA116

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK064

Eigenvalue Calculations Based on the Finite Element Method With Physically Motivated Field Smoothing Using the Kirchhoff Integral

cavity, electromagnetic-fields, simulation, extraction

3074

W. Ackermann, H. De Gersem, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany

In current linear particle accelerators, the actual acceleration of the charged particles is realized with the help of the electric field strength within driven radio frequency resonators. The characterization and optimization of the applied resonating structures can be reliably performed based on numerical simulation techniques. Efficient numerical methods have been introduced in the last decades to determine the electromagnetic fields while special care has been put in the correct description of the geometry and the material distribution of the structures. Although the resonators are operated in a driven setup, one of the advantageous numerical strategies here is given by an eigendecomposition of the fields which is realized by the application of accurate eigenmode calculations together with suitable postprocessing steps. In particular, the extraction of representative field maps used for particle tracking for example requires an accurate numerical modeling of the field at any position inside the structure. In order to avoid numerically motivated discontinuities of the fields a proper smoothing algorithm based on the vector equivalents of the Kirchhoff integral is proposed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK064

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPIK086

Wave Propagation in a Fractal Wave Guide

3128

V.G. Ziemann, A.K. Bhattacharyya, M. Holz, J. Ögren
Uppsala University, Uppsala, Sweden

We analyze the propagation of electro-magnetic waves in a wave guide that has the shape of Koch's snowflake, a well-known fractal.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPIK086

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WEPVA145

Analysis of Mean Free Path and Field Dependent Surface Resistance

cavity, niobium, SRF, electron

3609

J.T. Maniscalco, F. Furuta, D.L. Hall, P.N. Koufalis, M. Liepe
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: NSF-PHY 1416318
Work from Cornell in 2016 built on recent theoretical research in the field of SRF to link the electron mean free path to the field-dependent BCS surface resistance. This research relates the magnitude of the ‘‘anti-Q-slope'', the puzzling reduction of surface resistance with increasing RF field intensity observed in certain cavities, to the doping level of nitrogen-doped niobium, quantified by the mean free path: shorter mean free paths correspond directly with stronger anti-Q-slopes. The theoretical connection comes through the overheating of the quasiparticles, which more effectively transfer their energy to the lattice at short mean free paths. In this report, we present an update of this analysis, investigating recent test results of low-temperature-doped single-cell and nine-cell cavities. We also study the theoretical implications for cavities at frequencies higher and lower than the often-studied 1.3~GHz.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA145

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPIK108

Bead Pull Measurements of the FETS RFQ at RAL

rfq, cavity, quadrupole, site

4349

W. Promdee, T.R. Edgecock
IIAA, Huddersfield, United Kingdom
G.E. Boorman
Royal Holloway, University of London, Surrey, United Kingdom
G.E. Boorman
JAI, Egham, Surrey, United Kingdom
T.R. Edgecock, J.K. Pozimski
STFC/RAL, Chilton, Didcot, Oxon, United Kingdom
A.P. Letchford
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
J.K. Pozimski
Imperial College of Science and Technology, Department of Physics, London, United Kingdom

A Radio Frequency Quadrupole (RFQ) is a part of the Front End Test Stand (FETS) at the Rutherford Appleton Laboratory (RAL), Didcot, UK. The aim of the FETS project is to produce a 60 mA H⁻ beam at 3 MeV. The RFQ is a four-vane type with 4 modules, each of 1 m length, and is designed to accelerate the beam from 65 keV to 3 MeV at 324 MHz. A bead pull system has been designed to measure the field along the RFQ. This will be used in conjunction with 64 tuners to produce a uniform field. In order to optimise the tuning procedure, a model of the RFQ has been creat-ed in COMSOL Multiphysics. This study shows the results from the bead pull measurements and the tuning studies.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPIK108

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)