SRF2015 - List of Keywords (coupling)

Paper	Title	Other Keywords	Page
MOPB003	Superconducting Cavity for the Measurements of Frequency, Temperature, RF Field Dependence of the Surface Resistance	cavity, plasma, cryogenics, experiment	70
	H. Park, S.U. De Silva, J.R. Delayen ODU, Norfolk, Virginia, USA H. Park JLab, Newport News, Virginia, USA
	In order to better understand the contributions of the various physical processes to the surface resistance of superconductors the ODU Center for Accelerator Science is developing a half-wave resonator capable of operating between 325 MHz and 1.3 GHz. This will allow the measurement of the temperature and rf field dependence of the surface resistance on the same surface over the range of frequency of interest for particle accelerators and identify the various sources of power dissipation.
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TUPB089	High-Precision Measurements of the Quality Factor of Superconducting Cavities at the FREIA Laboratory	cavity, impedance, network, SRF	810
	V.A. Goryashko, K.J. Gajewski, L. Hermansson, H. Li, H. Nicander, R.J.M.Y. Ruber, R. Santiago Kern, S. Teerikoski Uppsala University, Uppsala, Sweden D.S. Dancila Uppsala University, Department of Engineering Sciences, Uppsala, Sweden
	In this paper we propose a high-precision method of measuring Q0 of SRF cavities. A common way to study the performance of an SRF cavity is to build an oscillator around it that is referred to as a self-exciting loop. In the standard approach, by tuning the loop phase for a maximum field level in the cavity and measuring forward and reflected waves, one finds the cavity coupling. Then, performing a time-decay measurement and finding the total quality factor, one gets Q0. However, this approach suffers from a deficiency originating from a single data-point measurement of the reflection coefficient. In our method by varying the loop phase shift, one obtains amplitudes of the reflection coefficient of the cavity as a function of its phases. The complex reflection coefficient describes a perfect circle in polar coordinates. Fitting the overdetermined set of data to that circle allows more accurate calculation of Q0 via the least-squares procedure. The method has been tested at the FREIA Laboratory on two cavities from IPN Orsay: a single spoke and a prototype ESS double spoke.
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TUPB091	Systematic Uncertainties in RF-Based Measurement of Superconducting Cavity Quality Factors	cavity, resonance, factory, superconducting-cavity	814
	W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov, D.A. Sergatskov Fermilab, Batavia, Illinois, USA
	Measurements of cavity quality factor measurements are subject to at least three potentially large sources of systematic error that have not been previously recognized. Imperfect coupler directivity (cross-talk) can lead to large errors in the cavity coupling factor when the cavity coupling factor is significantly different than unity. Energy re-reflected from the circulator can systematically bias the measured cavity decay time which is used to determine the loaded quality factor. Use of the peak probe power or the minimum of the reflected power to determine the cavity resonance frequency rather than the peak of the probe/forward transfer function may lead to errors in the resonance frequency that can also affect quality factors. Each effect is illustrated with measurements in the Fermilab VTS, simulations and analytic calculations. If the magnitude and phase of the cavity RF signals are measured, these effects can be measured and corrected for. If only signal magnitudes are recorded or these effects are not measured, they must be treated as sources of systematic uncertainty.
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TUPB098	Error Analysis on RF Measurement Due to Imperfect RF Components	cavity, SRF, LLRF, radio-frequency	840
	G. Wu, S. Aderhold, M. Checchin, M. Martinello, J.P. Ozelis Fermilab, Batavia, Illinois, USA
	Funding: Work supported by FRA under DOE contract DE-AC02-07CH11359 An accurate cavity test involves the accurate power measurement and decay time measurement. The directional coupler in a typical cavity test llrf system usually has low directivity due to broadband requirement and fabrication errors. The imperfection of the directional coupler brings unexpected systematic errors for cavity power measurement in both forward and reflect power. An error analysis will be giving and new specification of directional coupler is proposed.
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THPB006	Improvements of Buildcavity Code	cavity, HOM, interface, simulation	1070
	J.F. Chen, M. Moretti, C. Pagani, P. Pierini INFN/LASA, Segrate (MI), Italy C. Pagani Università degli Studi di Milano & INFN, Segrate, Italy
	Recentely, we improve the BuildCavity code, which is a graphics interface to SUPERFISH for the study of superconducting cavities of elliptical shape. Now it works with latest SUPERFISH 7 and can be installed also on newer Windows system such as Win 7 and 8. Several improvements have been done in the code. As an example, a design of ESS median-beta cavity with BuildCavity will also be presented.
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THPB028	ESS Medium Beta Cavity Prototypes Manufacturing	cavity, HOM, linac, cryomodule	1136
	E. Cenni, C. Arcambal CEA/IRFU, Gif-sur-Yvette, France P. Bosland, G. Devanz, X. Hanus, P. Hardy, V.M. Hennion, F. Leseigneur, F. Peauger, J. Plouin, D. Roudier CEA/DSM/IRFU, France G. Costanza Lund University, Lund, Sweden C. Darve ESS, Lund, Sweden
	The ESS elliptical superconducting linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity linac) up to the full energy at 2 GeV. The last linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. We describe here the procedures and numerical analysis leading from half-cells to a complete medium cavity assembly, which take into account not only the frequency of the fundamental accelerating mode but also the higher order modes near the machine line. The half cell selection process to form dumb bells will be described, as well as the reshaping and trimming procedure.
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THPB079	Improved Capacitive Coupling Type RF Power Couplers for a Cryomodule With Two 9-Cell Cavities	impedance, cryomodule, SRF, simulation	1313
	D.H. Zhuang, P.L. Fan, L.W. Feng, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Z.L. Wang PKU, Beijing, People's Republic of China
	Funding: Work supported by Major State Basic Research Development Program of China(Grant No. 2011CB808302 and 2011CB808304) A capacitive coupling RF power coupler was used for the DC-SRF photoinjector at Peking University. Recently, improved capacitive coupling power couplers, which will be used for a new cryomodule with two 9-cell cavities have been designed and fabricated. The main modifications include enlarging the supporting rods of inner conductors in order to increase heat conduction, moving the bellows from the quarter-wave transformer to the 50 Ω coaxial line to avoid the mismatch during Qext adjusting. Two modified power coupler have already finished RF conditioning up to 10kW, TW, duty factor 30%. In this paper, detailed design based on multi-physics analysis and the conditioning of this improved capacitive coupling RF Power coupler will be presented.
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THPB081	FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities	HOM, cavity, dipole, operation	1321
	A.R.J. Tutte, G. Burt Cockcroft Institute, Lancaster University, Lancaster, United Kingdom R. Calaga, A. Macpherson, E. Montesinos CERN, Geneva, Switzerland S.U. De Silva ODU, Norfolk, Virginia, USA Z. Li SLAC, Menlo Park, California, USA B. P. Xiao BNL, Upton, Long Island, New York, USA
	The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.
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THPB089	HOM Coupler Performance in CW Regime in Horizontal and Vertical Tests	HOM, cavity, operation, higher-order-mode	1349
	N. Solyak, M.H. Awida, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov, N. Solyak Fermilab, Batavia, Illinois, USA J.K. Sekutowicz DESY, Hamburg, Germany
	Power dissipation in HOM coupler antenna can limit cavity gradient in cw operation. XFEL design of HOM coupler, feedthrough and thermal connection to 2K pipe was accepted for LCLS-II cavity based on simulation results. Recently a series of vertical and horizontal tests was done to prove design for cw operation. In vertical test was found no effect of HOM coupler heating on high-Q cavity performance. In horizontal cryostat HOM coupler was tested up-to 23MV/m in continuous wave mode. Result proves that XFEL HOM coupler meets LCLS-II specifications.
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THPB105	Demonstration of Coaxial Coupling Scheme at 26 MV/m for 1.3 GHz Tesla-Type SRF Cavities	cavity, niobium, SRF, HOM	1397
	Y. Xie, A. Kanareykin Euclid TechLabs, LLC, Solon, Ohio, USA T.N. Khabiboulline, A. Lunin, V. Poloubotko, A.M. Rowe, N. Solyak, V.P. Yakovlev Fermilab, Batavia, Illinois, USA J. Rathke AES, Medford, New York, USA
	Superconducting ILC-type cavities have an rf input coupler that is welded on. A detachable input coupler will reduce conditioning time (can be conditioned separately), reduce cost and improve reliability. The problem with placing an extra flange in the superconducting cavity is about creating a possible quench spot at the seal place. Euclid Techlabs LLC has developed a coaxial coupler which has an on the surface with zero magnetic field (hence zero surface current). By placing a flange in that area we are able to avoid disturbing surface currents that typically lead to a quench. The coupler is optimized to preserve the axial symmetry of the cavity and rf field. The surface treatments and rf test of the proto- type coupler with a 1.3 GHz ILC-type single-cell cavity at Fermilab will be reported and discussed.
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Paper

Title

Other Keywords

Page

MOPB003

Superconducting Cavity for the Measurements of Frequency, Temperature, RF Field Dependence of the Surface Resistance

cavity, plasma, cryogenics, experiment

70

H. Park, S.U. De Silva, J.R. Delayen
ODU, Norfolk, Virginia, USA
H. Park
JLab, Newport News, Virginia, USA

In order to better understand the contributions of the various physical processes to the surface resistance of superconductors the ODU Center for Accelerator Science is developing a half-wave resonator capable of operating between 325 MHz and 1.3 GHz. This will allow the measurement of the temperature and rf field dependence of the surface resistance on the same surface over the range of frequency of interest for particle accelerators and identify the various sources of power dissipation.

Export •

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

TUPB089

High-Precision Measurements of the Quality Factor of Superconducting Cavities at the FREIA Laboratory

cavity, impedance, network, SRF

810

V.A. Goryashko, K.J. Gajewski, L. Hermansson, H. Li, H. Nicander, R.J.M.Y. Ruber, R. Santiago Kern, S. Teerikoski
Uppsala University, Uppsala, Sweden
D.S. Dancila
Uppsala University, Department of Engineering Sciences, Uppsala, Sweden

In this paper we propose a high-precision method of measuring Q0 of SRF cavities. A common way to study the performance of an SRF cavity is to build an oscillator around it that is referred to as a self-exciting loop. In the standard approach, by tuning the loop phase for a maximum field level in the cavity and measuring forward and reflected waves, one finds the cavity coupling. Then, performing a time-decay measurement and finding the total quality factor, one gets Q0. However, this approach suffers from a deficiency originating from a single data-point measurement of the reflection coefficient. In our method by varying the loop phase shift, one obtains amplitudes of the reflection coefficient of the cavity as a function of its phases. The complex reflection coefficient describes a perfect circle in polar coordinates. Fitting the overdetermined set of data to that circle allows more accurate calculation of Q0 via the least-squares procedure. The method has been tested at the FREIA Laboratory on two cavities from IPN Orsay: a single spoke and a prototype ESS double spoke.

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TUPB091

Systematic Uncertainties in RF-Based Measurement of Superconducting Cavity Quality Factors

cavity, resonance, factory, superconducting-cavity

814

W. Schappert, J.P. Holzbauer, Y.M. Pischalnikov, D.A. Sergatskov
Fermilab, Batavia, Illinois, USA

Measurements of cavity quality factor measurements are subject to at least three potentially large sources of systematic error that have not been previously recognized. Imperfect coupler directivity (cross-talk) can lead to large errors in the cavity coupling factor when the cavity coupling factor is significantly different than unity. Energy re-reflected from the circulator can systematically bias the measured cavity decay time which is used to determine the loaded quality factor. Use of the peak probe power or the minimum of the reflected power to determine the cavity resonance frequency rather than the peak of the probe/forward transfer function may lead to errors in the resonance frequency that can also affect quality factors. Each effect is illustrated with measurements in the Fermilab VTS, simulations and analytic calculations. If the magnitude and phase of the cavity RF signals are measured, these effects can be measured and corrected for. If only signal magnitudes are recorded or these effects are not measured, they must be treated as sources of systematic uncertainty.

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TUPB098

Error Analysis on RF Measurement Due to Imperfect RF Components

cavity, SRF, LLRF, radio-frequency

840

G. Wu, S. Aderhold, M. Checchin, M. Martinello, J.P. Ozelis
Fermilab, Batavia, Illinois, USA

Funding: Work supported by FRA under DOE contract DE-AC02-07CH11359
An accurate cavity test involves the accurate power measurement and decay time measurement. The directional coupler in a typical cavity test llrf system usually has low directivity due to broadband requirement and fabrication errors. The imperfection of the directional coupler brings unexpected systematic errors for cavity power measurement in both forward and reflect power. An error analysis will be giving and new specification of directional coupler is proposed.

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

THPB006

Improvements of Buildcavity Code

cavity, HOM, interface, simulation

1070

J.F. Chen, M. Moretti, C. Pagani, P. Pierini
INFN/LASA, Segrate (MI), Italy
C. Pagani
Università degli Studi di Milano & INFN, Segrate, Italy

Recentely, we improve the BuildCavity code, which is a graphics interface to SUPERFISH for the study of superconducting cavities of elliptical shape. Now it works with latest SUPERFISH 7 and can be installed also on newer Windows system such as Win 7 and 8. Several improvements have been done in the code. As an example, a design of ESS median-beta cavity with BuildCavity will also be presented.

Export •

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

THPB028

ESS Medium Beta Cavity Prototypes Manufacturing

cavity, HOM, linac, cryomodule

1136

E. Cenni, C. Arcambal
CEA/IRFU, Gif-sur-Yvette, France
P. Bosland, G. Devanz, X. Hanus, P. Hardy, V.M. Hennion, F. Leseigneur, F. Peauger, J. Plouin, D. Roudier
CEA/DSM/IRFU, France
G. Costanza
Lund University, Lund, Sweden
C. Darve
ESS, Lund, Sweden

The ESS elliptical superconducting linac consists of two types of 704.42 MHz cavities, medium and high beta, to accelerate the beam from 216 MeV (spoke cavity linac) up to the full energy at 2 GeV. The last linac optimization, called Optimus+, has been carried out taking into account the limitations of SRF cavity performance (field emission). The medium and high-beta parts of the linac are composed of 36 and 84 elliptical cavities, with geometrical beta values of 0.67 and 0.86 respectively. We describe here the procedures and numerical analysis leading from half-cells to a complete medium cavity assembly, which take into account not only the frequency of the fundamental accelerating mode but also the higher order modes near the machine line. The half cell selection process to form dumb bells will be described, as well as the reshaping and trimming procedure.

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THPB079

Improved Capacitive Coupling Type RF Power Couplers for a Cryomodule With Two 9-Cell Cavities

impedance, cryomodule, SRF, simulation

1313

D.H. Zhuang, P.L. Fan, L.W. Feng, L. Lin, K.X. Liu, S.W. Quan, F. Wang, Z.L. Wang
PKU, Beijing, People's Republic of China

Funding: Work supported by Major State Basic Research Development Program of China(Grant No. 2011CB808302 and 2011CB808304)
A capacitive coupling RF power coupler was used for the DC-SRF photoinjector at Peking University. Recently, improved capacitive coupling power couplers, which will be used for a new cryomodule with two 9-cell cavities have been designed and fabricated. The main modifications include enlarging the supporting rods of inner conductors in order to increase heat conduction, moving the bellows from the quarter-wave transformer to the 50 Ω coaxial line to avoid the mismatch during Qext adjusting. Two modified power coupler have already finished RF conditioning up to 10kW, TW, duty factor 30%. In this paper, detailed design based on multi-physics analysis and the conditioning of this improved capacitive coupling RF Power coupler will be presented.

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THPB081

FPC and HOM Coupler Test Boxes for HL-LHC Crab Cavities

HOM, cavity, dipole, operation

1321

A.R.J. Tutte, G. Burt
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
R. Calaga, A. Macpherson, E. Montesinos
CERN, Geneva, Switzerland
S.U. De Silva
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
B. P. Xiao
BNL, Upton, Long Island, New York, USA

The LHC luminosity upgrade will involve the installation of thirty-two 400 MHz SRF crab cavities. The cavities have two variants known as the RF dipole and double quarter-wave crab cavities. Each cavity has a fundamental power coupler (FPC) at 400 MHz and two or three HOM couplers. Before integration onto the cavities it is necessary to condition the FPC, and to measure the transmission on the HOM couplers at low power to ensure the operate as designed, each requiring a special test box. The FPC test box should provide a high transmission between two couplers without creating high surface fields. The low power HOM test boxes should be terminated to a load such that the natural stop and pass-bands of the couplers are preserved allowing the reflection to me measured and compared to simulations. In addition, due to the possibility of high HOM power in the LHC crab cavities, the concept of creating a broadband high power HOM coupler test box in order to condition and test the couplers at high power has been investigated. The Rf design of all test boxes is presented and discussed.

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THPB089

HOM Coupler Performance in CW Regime in Horizontal and Vertical Tests

HOM, cavity, operation, higher-order-mode

1349

N. Solyak, M.H. Awida, A. Grassellino, C.J. Grimm, A. Hocker, J.P. Holzbauer, T.N. Khabiboulline, O.S. Melnychuk, A.M. Rowe, D.A. Sergatskov, N. Solyak
Fermilab, Batavia, Illinois, USA
J.K. Sekutowicz
DESY, Hamburg, Germany

Power dissipation in HOM coupler antenna can limit cavity gradient in cw operation. XFEL design of HOM coupler, feedthrough and thermal connection to 2K pipe was accepted for LCLS-II cavity based on simulation results. Recently a series of vertical and horizontal tests was done to prove design for cw operation. In vertical test was found no effect of HOM coupler heating on high-Q cavity performance. In horizontal cryostat HOM coupler was tested up-to 23MV/m in continuous wave mode. Result proves that XFEL HOM coupler meets LCLS-II specifications.

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THPB105

Demonstration of Coaxial Coupling Scheme at 26 MV/m for 1.3 GHz Tesla-Type SRF Cavities

cavity, niobium, SRF, HOM

1397

Y. Xie, A. Kanareykin
Euclid TechLabs, LLC, Solon, Ohio, USA
T.N. Khabiboulline, A. Lunin, V. Poloubotko, A.M. Rowe, N. Solyak, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA
J. Rathke
AES, Medford, New York, USA

Superconducting ILC-type cavities have an rf input coupler that is welded on. A detachable input coupler will reduce conditioning time (can be conditioned separately), reduce cost and improve reliability. The problem with placing an extra flange in the superconducting cavity is about creating a possible quench spot at the seal place. Euclid Techlabs LLC has developed a coaxial coupler which has an on the surface with zero magnetic field (hence zero surface current). By placing a flange in that area we are able to avoid disturbing surface currents that typically lead to a quench. The coupler is optimized to preserve the axial symmetry of the cavity and rf field. The surface treatments and rf test of the proto- type coupler with a 1.3 GHz ILC-type single-cell cavity at Fermilab will be reported and discussed.

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