SRF2017 - List of Authors (Saeki, T.)

Paper	Title	Page
TUYBA01	Progress on Characterization and Optimization of Multilayers	368
	C.Z. Antoine CEA/DSM/IRFU, France M. Aburas, A. Four CEA/DRF/IRFU, Gif-sur-Yvette, France H. Hayano, S. Kato, T. Kubo, T. Saeki KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan
	Multilayers MgO/NbN/MgO/Nb with several thicknesses are being tested by local magnetometry, Scanning tunneling and various standard structural techniques experiment providing usefull information to compare experiments and recent theoretical advances proposed by A. Gurevich or T. Kubo.
	Slides TUYBA01 [5.819 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUYBA01
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TUPB073	Vertical Electro-polishing Collaboration Between Cornell, KEK, and Marui Galvanizing Co. Ltd	563
	F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J. Sears Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, T. Saeki KEK, Ibaraki, Japan
	Cornell's SRF group, KEK, and Marui Galvanizing Co. Ltd (MGI) have collaborated since 2014 on Vertical Electro-Polishing (VEP) R&D as a part of a US/Japan Program for Cooperation in High Energy Physics. We have focused on an improvement of removal uniformity during the VEP process. MGI and KEK have developed their original VEP cathode named i-cathode Ninja®, which has four retractable wing-shape parts per cell. Cornell processed one single cell cavity with VEP using this cathode and performed a vertical test. KEK also provided one 9-cell cavity to Cornell. Cornell then performed surface treatments including Cornell VEP and RF test on this 9-cell cavity. The progress by the VEP collaboration and RF test results are presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB073
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TUPB091	Study on Vertical Electropolising of 9-cell Niobium Coupon Cavity	602
	V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan
	Authors report a study on vertical electropolishing (VEP) carried out for a 1.3 GHz 9-cell niobium (Nb) coupon cavity using a unique cathode namely 'Ninja Cathode'. The design of the cathode for VEP of a 9-cell cavity was based on the Ninja cathode used for 1-cell cavity since the 1-cell Ninja cathode was found effective to reduce longitudinal asymmetry in material removal and to obtain a smooth surface of a 1-cell cavity. Moreover, 1-cell Nb cavities after being treated in VEP using the Ninja cathode showed good performance in vertical RF tests. The 9-cell coupon cavity used in this study was designed to have totally nine coupons set on the iris and equator positions of the first, fifth and ninth cells. These three cells contain viewports as well at their upper and lower iris positions. Measurement of currents from the individual coupons and in-situ observation are possible using the cavity to understand EP phenomenon at different locations of the cavity. VEP results, which include removal thicknesses at different positions of the cavity and surface study of the coupons, are discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB091
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TUPB092	Analysis of Niobium Surface and Generated Particles in Vertical Electropolishing of Single-cell Coupon Cavity	607
	V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan
	In our previous studies, we have reported parameter investigation for vertical electropolishing (VEP) of 1-cell niobium (Nb) tesla/ILC type cavities using a Ninja cathode. A 1-cell coupon cavity containing six Nb disk coupons at its different positions was found effective to reduce time and cost to establish an optimized VEP recipe. In this work, we present surface analyses of VEPed Nb coupon surfaces using scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS). Surfaces contained micro- and nano-sized particles which were found with random distributions and different number densities on the beam pipe and iris coupons. Surfaces of equator coupons were found to have relatively less number of particles or almost clean. To analyze particles, a few particles were picked-up from a coupon surface using a tungsten tip under SEM and analyzed with EDX while the coupon was moved out from the SEM chamber to avoid its effect in EDX spectra. The particles were confirmed as oxygen-rich niobium and contained fluorine and carbon also. XPS analysis of the coupon surfaces was also carried out for further study of surface chemistry.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB092
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TUPB093	Nb Single-cell Cavity Vertical Electro-polishing with Ninja Cathode and Evaluation of its Accelerating Gradient	612
	K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi MGH, Hyogo-ken, Japan P. Carbonnier, Y. Gasser, L. Maurice CEA/IRFU, Gif-sur-Yvette, France F. Éozénou, C. Servouin CEA/DSM/IRFU, France H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan Th. Proslier CEA/DRF/IRFU, Gif-sur-Yvette, France
	Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technology for Nb superconducting RF cavity in collaboration with KEK. In this collaboration, we developed a unique cathode namely Ninja cathode for VEP treatment of Nb cavities. We have already reported that longitudinal symmetry in niobium removal and surface state of a single cell cavity were improved after VEP using the Ninja cathode. In this article, we report a result of accelerating gradient evaluation for 1.3 GHz single cell RF cavity after VEP with Ninja cathode in collaboration with KEK and CEA Saclay.
	Poster TUPB093 [0.704 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB093
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TUPB097	R&D of Electro-polishing (EP) Process with HF-free Neutral Electrolyte by Bipolar-pulse (BP) Method	623
	J. Taguchi, Y. Mochida, T. Nakajima Nomura Plating Co, Ltd., Osaka, Japan H. Hayano, T. Saeki KEK, Ibaraki, Japan S. Kakudo, M. Kunieda The University of Tokyo, Tokyo, Japan
	Currently the Electro-Polishing (EP) process of Superconducting Radio-Frequency (SRF) accelerating cavity is performed with the electrolyte that is the mixture of hydrofluoric and sulfuric acids. However, the electrolyte is very dangerous and the environmental load in the disposal process of electrolyte is very heavy. This is the reason why the high cost is necessary in the safe design of facility and the safe operation of process in the conventional EP method. In such situation, considering the reduction of cost and environmental load in the EP process, we performed the R&D of novel EP process with HF-free neutral electrolyte by Bipolar-Pulse (BP) method. In this presentation, we will report the removal rate, surface roughness and the results of surface analysis for the Nb-coupon samples that were processed by the BP-EP with HF-free neutral electrolyte.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB097
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THYA02	Achievement of Stable Pulsed Operation at 36 MV/m in STF-2 Cryomodule at KEK	722
	Y. Yamamoto, T. Dohmae, M. Egi, K. Hara, T. Honma, E. Kako, Y. Kojima, T. Konomi, T. Kubo, T. Matsumoto, T. Miura, H. Nakai, K. Nakanishi, G.-T. Park, T. Saeki, H. Shimizu, T. Shishido, T. Takenaka, K. Umemori KEK, Ibaraki, Japan
	In the Superconducting RF Test Facility (STF) in KEK, the cooldown test for the STF-2 cryomdoule with 12 cavities has been done totally three times since 2014. In 2016, the 3rd cooldown test for the STF-2 cryomodule including the capture cryomodule with 2 cavities was successfully carried out. The main achievement is the vector-sum operation with 8 cavities at average accelerating gradient of 31 MV/m as the ILC specification (2 of 8 cavities achieved 36 MV/m with piezo compensation), and the others are the measurement for Lorenz Force Detuning (LFD) and unloaded Q value, and Low Level RF (LLRF) study, etc. In this paper, the result for the STF-2 cryomodule in three cooldown tests will be presented in detail.
	Slides THYA02 [4.042 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THYA02
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THPB058	R&D of Thin Film Coating on Superconductors	877
	Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan H. Hayano, T. Kubo, T. Saeki KEK, Ibaraki, Japan M. Hino Kyoto University, Research Reactor Institute, Osaka, Japan H. Oikawa Utsunomiya University, Utsunomiya, Japan
	Funding: This research is partially supported by Grant-in-Aid for Exploratory Research JSPS KAKENHI Grant Number 26600142, and Photon and Quantum Basic Research Coordinated Development Program from the MEXT. Multilayer thin film coating is a promising technology to enhance performance of superconducting cavities. Until recently, principal parameters to achieve the sufficient performance had not been known, such as the thickness of each layer. We proposed a method to deduce a set of the parameters to exhibit a good performances. In order to verify the scheme, we are trying to make some experiments on the subject at Kyoto. The sample preparation and the test setup for the measurement apparatus will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB058
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Progress on Characterization and Optimization of Multilayers

368

C.Z. Antoine
CEA/DSM/IRFU, France
M. Aburas, A. Four
CEA/DRF/IRFU, Gif-sur-Yvette, France
H. Hayano, S. Kato, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan

Multilayers MgO/NbN/MgO/Nb with several thicknesses are being tested by local magnetometry, Scanning tunneling and various standard structural techniques experiment providing usefull information to compare experiments and recent theoretical advances proposed by A. Gurevich or T. Kubo.

Slides TUYBA01 [5.819 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUYBA01

Export •

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

TUPB073

Vertical Electro-polishing Collaboration Between Cornell, KEK, and Marui Galvanizing Co. Ltd

563

F. Furuta, M. Ge, T. Gruber, J.J. Kaufman, M. Liepe, J. Sears
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, T. Saeki
KEK, Ibaraki, Japan

Cornell's SRF group, KEK, and Marui Galvanizing Co. Ltd (MGI) have collaborated since 2014 on Vertical Electro-Polishing (VEP) R&D as a part of a US/Japan Program for Cooperation in High Energy Physics. We have focused on an improvement of removal uniformity during the VEP process. MGI and KEK have developed their original VEP cathode named i-cathode Ninja®, which has four retractable wing-shape parts per cell. Cornell processed one single cell cavity with VEP using this cathode and performed a vertical test. KEK also provided one 9-cell cavity to Cornell. Cornell then performed surface treatments including Cornell VEP and RF test on this 9-cell cavity. The progress by the VEP collaboration and RF test results are presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB073

Export •

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

TUPB091

Study on Vertical Electropolising of 9-cell Niobium Coupon Cavity

602

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

Authors report a study on vertical electropolishing (VEP) carried out for a 1.3 GHz 9-cell niobium (Nb) coupon cavity using a unique cathode namely 'Ninja Cathode'. The design of the cathode for VEP of a 9-cell cavity was based on the Ninja cathode used for 1-cell cavity since the 1-cell Ninja cathode was found effective to reduce longitudinal asymmetry in material removal and to obtain a smooth surface of a 1-cell cavity. Moreover, 1-cell Nb cavities after being treated in VEP using the Ninja cathode showed good performance in vertical RF tests. The 9-cell coupon cavity used in this study was designed to have totally nine coupons set on the iris and equator positions of the first, fifth and ninth cells. These three cells contain viewports as well at their upper and lower iris positions. Measurement of currents from the individual coupons and in-situ observation are possible using the cavity to understand EP phenomenon at different locations of the cavity. VEP results, which include removal thicknesses at different positions of the cavity and surface study of the coupons, are discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB091

Export •

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

TUPB092

Analysis of Niobium Surface and Generated Particles in Vertical Electropolishing of Single-cell Coupon Cavity

607

V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

In our previous studies, we have reported parameter investigation for vertical electropolishing (VEP) of 1-cell niobium (Nb) tesla/ILC type cavities using a Ninja cathode. A 1-cell coupon cavity containing six Nb disk coupons at its different positions was found effective to reduce time and cost to establish an optimized VEP recipe. In this work, we present surface analyses of VEPed Nb coupon surfaces using scanning electron microscope (SEM), energy dispersive x-ray spectroscopy (EDX) and x-ray photoelectron spectroscopy (XPS). Surfaces contained micro- and nano-sized particles which were found with random distributions and different number densities on the beam pipe and iris coupons. Surfaces of equator coupons were found to have relatively less number of particles or almost clean. To analyze particles, a few particles were picked-up from a coupon surface using a tungsten tip under SEM and analyzed with EDX while the coupon was moved out from the SEM chamber to avoid its effect in EDX spectra. The particles were confirmed as oxygen-rich niobium and contained fluorine and carbon also. XPS analysis of the coupon surfaces was also carried out for further study of surface chemistry.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB092

Export •

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

TUPB093

Nb Single-cell Cavity Vertical Electro-polishing with Ninja Cathode and Evaluation of its Accelerating Gradient

612

K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi
MGH, Hyogo-ken, Japan
P. Carbonnier, Y. Gasser, L. Maurice
CEA/IRFU, Gif-sur-Yvette, France
F. Éozénou, C. Servouin
CEA/DSM/IRFU, France
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan
Th. Proslier
CEA/DRF/IRFU, Gif-sur-Yvette, France

Marui Galvanizing Co. Ltd. has been improving Vertical Electro-Polishing (VEP) technology for Nb superconducting RF cavity in collaboration with KEK. In this collaboration, we developed a unique cathode namely Ninja cathode for VEP treatment of Nb cavities. We have already reported that longitudinal symmetry in niobium removal and surface state of a single cell cavity were improved after VEP using the Ninja cathode. In this article, we report a result of accelerating gradient evaluation for 1.3 GHz single cell RF cavity after VEP with Ninja cathode in collaboration with KEK and CEA Saclay.

Poster TUPB093 [0.704 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB093

Export •

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

TUPB097

R&D of Electro-polishing (EP) Process with HF-free Neutral Electrolyte by Bipolar-pulse (BP) Method

623

J. Taguchi, Y. Mochida, T. Nakajima
Nomura Plating Co, Ltd., Osaka, Japan
H. Hayano, T. Saeki
KEK, Ibaraki, Japan
S. Kakudo, M. Kunieda
The University of Tokyo, Tokyo, Japan

Currently the Electro-Polishing (EP) process of Superconducting Radio-Frequency (SRF) accelerating cavity is performed with the electrolyte that is the mixture of hydrofluoric and sulfuric acids. However, the electrolyte is very dangerous and the environmental load in the disposal process of electrolyte is very heavy. This is the reason why the high cost is necessary in the safe design of facility and the safe operation of process in the conventional EP method. In such situation, considering the reduction of cost and environmental load in the EP process, we performed the R&D of novel EP process with HF-free neutral electrolyte by Bipolar-Pulse (BP) method. In this presentation, we will report the removal rate, surface roughness and the results of surface analysis for the Nb-coupon samples that were processed by the BP-EP with HF-free neutral electrolyte.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB097

Export •

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

THYA02

Achievement of Stable Pulsed Operation at 36 MV/m in STF-2 Cryomodule at KEK

722

Y. Yamamoto, T. Dohmae, M. Egi, K. Hara, T. Honma, E. Kako, Y. Kojima, T. Konomi, T. Kubo, T. Matsumoto, T. Miura, H. Nakai, K. Nakanishi, G.-T. Park, T. Saeki, H. Shimizu, T. Shishido, T. Takenaka, K. Umemori
KEK, Ibaraki, Japan

In the Superconducting RF Test Facility (STF) in KEK, the cooldown test for the STF-2 cryomdoule with 12 cavities has been done totally three times since 2014. In 2016, the 3rd cooldown test for the STF-2 cryomodule including the capture cryomodule with 2 cavities was successfully carried out. The main achievement is the vector-sum operation with 8 cavities at average accelerating gradient of 31 MV/m as the ILC specification (2 of 8 cavities achieved 36 MV/m with piezo compensation), and the others are the measurement for Lorenz Force Detuning (LFD) and unloaded Q value, and Low Level RF (LLRF) study, etc. In this paper, the result for the STF-2 cryomodule in three cooldown tests will be presented in detail.

Slides THYA02 [4.042 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THYA02

Export •

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

THPB058

R&D of Thin Film Coating on Superconductors

877

Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
H. Hayano, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
M. Hino
Kyoto University, Research Reactor Institute, Osaka, Japan
H. Oikawa
Utsunomiya University, Utsunomiya, Japan

Funding: This research is partially supported by Grant-in-Aid for Exploratory Research JSPS KAKENHI Grant Number 26600142, and Photon and Quantum Basic Research Coordinated Development Program from the MEXT.
Multilayer thin film coating is a promising technology to enhance performance of superconducting cavities. Until recently, principal parameters to achieve the sufficient performance had not been known, such as the thickness of each layer. We proposed a method to deduce a set of the parameters to exhibit a good performances. In order to verify the scheme, we are trying to make some experiments on the subject at Kyoto. The sample preparation and the test setup for the measurement apparatus will be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB058

Export •

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