SRF2019 - List of Authors (Hayano, H.)

Paper	Title	Page
MOP054	Fabrication of 3.0-GHz Single-cell Cavities for Thin-film Study	177
	T. Saeki, H. Hayano, H. Inoue, R. Katayama, T. Kubo KEK, Ibaraki, Japan F.E. Hannon, R.A. Rimmer, A-M. Valente-Feliciano JLab, Newport News, Virginia, USA H. Ito Sokendai, Ibaraki, Japan Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan
	Funding: This work is supported by JSPS KAKENHI JP17H04839, JSPS KAKENHI JP26600142, Japan-US Research Collaboration Program, and the Collaborative Research Program of ICR Kyoto Univ. (2018-13). We fabricated 3.0-GHz single-cell cavities with Cu and Nb materials for testing thin-film creations on the inner surface of the cavities in collaboration between Jefferson Laboratory (JLab) and KEK. The cavity was designed at JLab. According to the design of cavity, the press-forming dies and trimming fixtures for the cavity-cell were also designed and fabricated at JLab. These dies and trimming fixtures were transported to KEK, and the rest of fabrication processes were done at KEK. Finally nine Cu 3.0-GHz single-cell cavities and six Nb 3.0-GHz single-cell cavities were fabricated. Two Cu 3.0-GHz single-cell cavities were mechanically polished at Jlab. All of these cavities will be utilized for the tests of various thin-film creations at JLab and KEK. This presentation describes details of the fabrication of these cavities.
	Poster MOP054 [1.203 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP054
About •	paper received ※ 05 July 2019 paper accepted ※ 13 August 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

MOP064	Performance of First Prototype Multi-Cell Low-Surface-Field Shape Cavity	222
	R.L. Geng JLab, Newport News, Virginia, USA Y. Fuwa, Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan H. Hayano KEK, Ibaraki, Japan H. Ito Sokendai, Ibaraki, Japan Z. Li SLAC, Menlo Park, California, USA
	The idea of cavity shaping for higher ultimate acceleration gradients has been proposed for some time, Low Loss/Ichiro and Re-entrant being examples, both seeking a lower Hpk/E_acc at the expense of a higher Epk/E_acc. While experimental verification in single-cell cavities of those shapes was very successful including the record gradient of 59 MV/m, pushing multi-cell cavities of those shapes to higher gradients was prevented by field emission. The Low-Surface-Field (LSF) shape seeks not only a lower Hpk/E_acc but also a lower Epk/E_acc, therefore it has the advantage of raising ultimate gradient at reduced field emission. The first multi-cell LSF shape prototype cavity was built using the standard forming and welding techniques. RF tests have been carried out, following standard ILC TDR baseline surface processing and treatment recipe. Three out of five cells achieved Hpk values corresponding to E_acc 50 MV/m. The current limit is the field emission in end cells. Instrumented testing following end-cell wiping and HPR with larger nozzles is in progress. We will present detailed experimental results and preparation procedures.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP064
About •	paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP021	Effect of Cathode Rotation and Acid Flow in Vertical Electropolishing of 1.3 GHz Niobium Nine-Cell Cavity	448
	V. Chouhan, Y.I. Ida, K.N. Nii, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki KEK, Ibaraki, Japan
	We have been carrying out R&D on vertical electropolishing (VEP) technique to establish it as an alternate of the horizontal EP (HEP) technique used for the surface treatment of niobium (Nb) superconducting RF (SRF) cavities. We have earlier reported on a VEP parameter study for 1.3 GHz single and nine-cell Nb cavities. The optimized VEP parameters and a unique rotating cathode yielded uniform removal and a smooth surface in the single cell cavity. The unique cathode and a dual flow mechanism for acid circulation were applied to improve the removal uniformity in the nine-cell cavity. The vertically electropolished single and nine cell cavities achieved the same RF performance as achieved after the HEP processes. We are making efforts to further improve the removal uniformity in the nine-cell cavity. Here, we report on a VEP of the 1.3 GHz Nb nine-cell cavity at a higher cathode rotation speed of 50 rpm. The VEP results reveal that the speed could be considered for improving the uniformity in removal while maintaining the surface smoothness. Required improvements in the VEP facility and acid flow condition for achieving uniform EP and a smooth surface are also described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP021
About •	paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP027	Vertical Electropolishing of Niobium Nine-Cell Cavity with a Cavity Flipping System for Uniform Removal	467
	K.N. Nii, V. Chouhan, Y.I. Ida, T.Y. Yamaguchi MGH, Hyogo-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki KEK, Ibaraki, Japan
	Marui Galvanizing Co., Ltd. has been developing vertical electropolishing (VEP) technology for single and nine-cell niobium superconducting radio frequency cavities using a unique cathode namely Ninja cathode in collaboration with KEK. The VEP process usually results in non-uniform removal with a large asymmetry along the cavity length. In order to suppress the asymmetry in removal, we are making different approaches. Flipping of the cavity during the VEP process is one of the approaches applied so far. A unique VEP setup, which allows the flipping of a multi-cell cavity, has been developed as reported earlier. Here, we report the improvement in the setup with automation for cavity flipping. VEP experiments were conducted with the improved system. VEP parameters were studied and the VEP results including the removal trend are discussed in detail.
	Poster TUP027 [1.347 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP027
About •	paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP028	Development of Vertical Electropolishing Facility for Nb 9-Cell Cavity (3)	470
	Y.I. Ida, V. Chouhan, K.N. Nii MGH, Hyogo-ken, Japan T. Akabori, G. Mitoya, K. Miyano HKK, Morioka, Japan Y. Anetai, F. Takahashi WING. Co.Ltd, Iwate-ken, Japan H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe KEK, Ibaraki, Japan
	The 1st report was delivered in May, 2018 at the IPAC 18 in Vancouver, Canada. The 2nd report was delivered in September, 2018 at the LINAC 18 in Beijing, China. We will make our 3rd report in July, 2019 at the SRF-19 in Dresden, Germany. There will be two main points this time. The first is that by using our improved Ninja Electrode Premium, we can out-perform our number one and number two competitors in terms of uniform electropolishing of the interior of the 9-cell cavity. The second point is that we can remove hydrogen gas, reacted during electropolishing, from the cavity chambers in a manner that has not been successfully achieved by 1st report, May 2018 and 2nd report, September 2018. We will report our 9-cell vertical polishing revolver-type unit that solves the above two problems.
	Poster TUP028 [0.444 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP028
About •	paper received ※ 24 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP077	Nb₃Sn Thin Film Coating Method for Superconducting Multilayered Structure	628
	R. Ito, T. Nagata ULVAC, Inc, Chiba, Japan H. Hayano, R. Katayama, T. Kubo, T. Saeki KEK, Ibaraki, Japan H. Ito Sokendai, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan
	S-I-S (superconductor-insulator-superconductor) multilayered structure has been proposed in order to increase the maximum acceleration gradient of SRF cavities. Nb₃Sn is the material most expected as a superconducting layer of the S-I-S multilayered structure because it offers both a large critical temperature and large predicted Hsh. Most important in fabricating Nb₃Sn thin films is the stoichiometry of the material produced, and the lack of tin leads to performance degradation. We have launched a new in-house DC magnetron sputtering apparatus for Nb₃Sn deposition. Nb and Sn layers were alternately and repeatedly deposited on Si wafer while adjusting the film thickness of each layer, so we successfully obtained Nb-Sn films having appropriate composition ratio. The as-deposited films were annealed under the temperature of 600 degree C for 1 hour to generate the Nb₃Sn phase. The characteristics of Nb-Sn films evaluated by XRD, XRF, FE-SEM, and so on. We also measured critical temperature of the annealed films. In this paper, the detail of the Nb₃Sn coating method and the measurement result of the Nb-Sn films will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP077
About •	paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

TUP078	Lower Critical Field Measurement of NbN Multilayer Thin Film Superconductor at KEK	632
SUSP013	use link to see paper's listing under its alternate paper code
	H. Ito Sokendai, Ibaraki, Japan C.Z. Antoine CEA-IRFU, Gif-sur-Yvette, France H. Hayano, R. Katayama, T. Kubo, T. Saeki KEK, Ibaraki, Japan R. Ito, T. Nagata ULVAC, Inc, Chiba, Japan Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan
	Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839. The multilayer thin film structure of the superconductor has been proposed by A. Gurevich to enhance the maximum gradient of SRF cavities. The lower critical field Hc1 at which the vortex start penetrating the superconducting material will be improved by coating Nb with thin film superconductor such as NbN. It is expected that the enhancement of Hc1 depends on the thickness of each layer. In order to determine the optimum thickness of each layer and to compare the measurement results with the theoretical prediction proposed by T. Kubo, we developed the Hc1 measurement system using the third harmonic response of the applied AC magnetic field at KEK. For the Hc1 measurement without the influence of the edge or the shape effects, the AC magnetic field can be applied locally by the solenoid coil of 5mm diameter in our measurement system. ULVAC made the NbN-SiO₂ multilayer thin film samples of various NbN thicknesses. In this report, the measurement result of the bulk Nb sample and NbN-SiO₂ multilayer thin film samples of different thickness of NbN layer will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP078
About •	paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

WETEA6	Successful Beam Commissioning in STF-2 Cryomodules for ILC
	Y. Yamamoto, M. Akemoto, D.A. Arakawa, S. Araki, A. Aryshev, M. Egi, M.K. Fukuda, K. Hara, H. Hayano, Y. Honda, T. Honma, E. Kako, H. Katagiri, M. Kawamura, N. Kimura, Y. Kojima, Y. Kondou, T. Konomi, T. Matsumoto, S. Michizono, T. Miura, T. Miyajima, Y. Morikawa, H. Nakai, H. Nakajima, N. Nakamura, K. Nakanishi, T. Obina, T. Oyama, F. Qiu, T. Saeki, H. Sakai, T. Sanami, M. Shimada, H. Shimizu, T. Shishido, S.I. Takahara, K. Umemori, A. Yamamoto KEK, Ibaraki, Japan M. Kuriki, S. Notsu Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan S. Matsuba JASRI, Hyogo, Japan K. Sakaue The University of Tokyo, The School of Engineering, Tokyo, Japan
	Beam commissioning of the STF-2 accelerator was successfully done at the Superconducting RF Test Facility (STF) in KEK from February to March 2019. As a result of various cavity tuning, LLRF control tuning, and beam tuning, the beam energy finally reached 271 MeV, and the accelerating gradient of each cavity estimated from beam energy was 32.0 MV/m. This result satisfies 31.5 MV/m, which is the operating specification of the International Linear Collider (ILC) project, and is an important milestone in the ILC technology demonstration. In this talk, we will report on the detailed results of beam commissioning.
	Slides WETEA6 [13.702 MB]
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THFUA2	Evaluation of the Superconducting Characteristics of Multi-Layer Thin-Film Structures of NbN and SiO₂ on Pure Nb Substrate	807
	R. Katayama, H. Hayano, T. Kubo, T. Saeki KEK, Ibaraki, Japan C.Z. Antoine CEA-IRFU, Gif-sur-Yvette, France H. Ito Sokendai, Ibaraki, Japan R. Ito ULVAC, Inc, Chiba, Japan Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan T. Nagata ULVAC, Inc., Tsukuba, Japan
	In recent years, it has been pointed out that the maximum accelerating gradient of a superconducting RF cavity can be increased by coating the inner surface of the cavity with a multilayer thin-film structure consisting of alternating insulating and superconducting layers. In this structure, the principal parameter that limits the performance of the cavity is the critical magnetic field or effective Hc1 at which vortices begin penetrating into the superconductor layer. This is predicted to depend on the combination of the film thickness. We made samples that have a NbN/SiO₂ thin-film structure on a pure Nb substrate with several layers of NbN film deposited using DC magnetron sputtering method. Here, we report the measurement results of effective Hc1 of NbN/SiO₂(30 nm)/Nb multilayer samples with thicknesses of NbN layers in the range from 50 nm to 800 nm by using the third-harmonic voltage method. Experimental results show that an optimum thickness exists, which increases the effective Hc1 by 23.8 %.
	Slides THFUA2 [2.333 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUA2
About •	paper received ※ 03 July 2019 paper accepted ※ 05 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THP088	Updates on the Inspection System for SRF Cavities	1111
	Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan H. Hayano KEK, Ibaraki, Japan Y. Kuriyama Kyoto University, Research Reactor Institute, Osaka, Japan
	Optical inspections on superconducting cavities are familiar to those who are involved in the cavity fabrications. Further improvements on the Kyoto Camera have been carried out these years together with further processing technique developments, such as removing found defects by local grinding techniques. Improvements on Kyoto Camera includes implementation of color LEDs for illumination system, which improves the inspection efficiency. These progresses will be reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP088
About •	paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Fabrication of 3.0-GHz Single-cell Cavities for Thin-film Study

177

T. Saeki, H. Hayano, H. Inoue, R. Katayama, T. Kubo
KEK, Ibaraki, Japan
F.E. Hannon, R.A. Rimmer, A-M. Valente-Feliciano
JLab, Newport News, Virginia, USA
H. Ito
Sokendai, Ibaraki, Japan
Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan

Funding: This work is supported by JSPS KAKENHI JP17H04839, JSPS KAKENHI JP26600142, Japan-US Research Collaboration Program, and the Collaborative Research Program of ICR Kyoto Univ. (2018-13).
We fabricated 3.0-GHz single-cell cavities with Cu and Nb materials for testing thin-film creations on the inner surface of the cavities in collaboration between Jefferson Laboratory (JLab) and KEK. The cavity was designed at JLab. According to the design of cavity, the press-forming dies and trimming fixtures for the cavity-cell were also designed and fabricated at JLab. These dies and trimming fixtures were transported to KEK, and the rest of fabrication processes were done at KEK. Finally nine Cu 3.0-GHz single-cell cavities and six Nb 3.0-GHz single-cell cavities were fabricated. Two Cu 3.0-GHz single-cell cavities were mechanically polished at Jlab. All of these cavities will be utilized for the tests of various thin-film creations at JLab and KEK. This presentation describes details of the fabrication of these cavities.

Poster MOP054 [1.203 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP054

About •

paper received ※ 05 July 2019 paper accepted ※ 13 August 2019 issue date ※ 14 August 2019

Export •

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

MOP064

Performance of First Prototype Multi-Cell Low-Surface-Field Shape Cavity

222

R.L. Geng
JLab, Newport News, Virginia, USA
Y. Fuwa, Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan
H. Hayano
KEK, Ibaraki, Japan
H. Ito
Sokendai, Ibaraki, Japan
Z. Li
SLAC, Menlo Park, California, USA

The idea of cavity shaping for higher ultimate acceleration gradients has been proposed for some time, Low Loss/Ichiro and Re-entrant being examples, both seeking a lower Hpk/E_acc at the expense of a higher Epk/E_acc. While experimental verification in single-cell cavities of those shapes was very successful including the record gradient of 59 MV/m, pushing multi-cell cavities of those shapes to higher gradients was prevented by field emission. The Low-Surface-Field (LSF) shape seeks not only a lower Hpk/E_acc but also a lower Epk/E_acc, therefore it has the advantage of raising ultimate gradient at reduced field emission. The first multi-cell LSF shape prototype cavity was built using the standard forming and welding techniques. RF tests have been carried out, following standard ILC TDR baseline surface processing and treatment recipe. Three out of five cells achieved Hpk values corresponding to E_acc 50 MV/m. The current limit is the field emission in end cells. Instrumented testing following end-cell wiping and HPR with larger nozzles is in progress. We will present detailed experimental results and preparation procedures.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP064

About •

paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

TUP021

Effect of Cathode Rotation and Acid Flow in Vertical Electropolishing of 1.3 GHz Niobium Nine-Cell Cavity

448

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

We have been carrying out R&D on vertical electropolishing (VEP) technique to establish it as an alternate of the horizontal EP (HEP) technique used for the surface treatment of niobium (Nb) superconducting RF (SRF) cavities. We have earlier reported on a VEP parameter study for 1.3 GHz single and nine-cell Nb cavities. The optimized VEP parameters and a unique rotating cathode yielded uniform removal and a smooth surface in the single cell cavity. The unique cathode and a dual flow mechanism for acid circulation were applied to improve the removal uniformity in the nine-cell cavity. The vertically electropolished single and nine cell cavities achieved the same RF performance as achieved after the HEP processes. We are making efforts to further improve the removal uniformity in the nine-cell cavity. Here, we report on a VEP of the 1.3 GHz Nb nine-cell cavity at a higher cathode rotation speed of 50 rpm. The VEP results reveal that the speed could be considered for improving the uniformity in removal while maintaining the surface smoothness. Required improvements in the VEP facility and acid flow condition for achieving uniform EP and a smooth surface are also described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP021

About •

paper received ※ 23 June 2019 paper accepted ※ 02 July 2019 issue date ※ 14 August 2019

Export •

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

TUP027

Vertical Electropolishing of Niobium Nine-Cell Cavity with a Cavity Flipping System for Uniform Removal

467

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

Marui Galvanizing Co., Ltd. has been developing vertical electropolishing (VEP) technology for single and nine-cell niobium superconducting radio frequency cavities using a unique cathode namely Ninja cathode in collaboration with KEK. The VEP process usually results in non-uniform removal with a large asymmetry along the cavity length. In order to suppress the asymmetry in removal, we are making different approaches. Flipping of the cavity during the VEP process is one of the approaches applied so far. A unique VEP setup, which allows the flipping of a multi-cell cavity, has been developed as reported earlier. Here, we report the improvement in the setup with automation for cavity flipping. VEP experiments were conducted with the improved system. VEP parameters were studied and the VEP results including the removal trend are discussed in detail.

Poster TUP027 [1.347 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP027

About •

paper received ※ 24 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

TUP028

Development of Vertical Electropolishing Facility for Nb 9-Cell Cavity (3)

470

Y.I. Ida, V. Chouhan, K.N. Nii
MGH, Hyogo-ken, Japan
T. Akabori, G. Mitoya, K. Miyano
HKK, Morioka, Japan
Y. Anetai, F. Takahashi
WING. Co.Ltd, Iwate-ken, Japan
H. Hayano, S. Kato, H. Monjushiro, T. Saeki, M. Sawabe
KEK, Ibaraki, Japan

The 1st report was delivered in May, 2018 at the IPAC 18 in Vancouver, Canada. The 2nd report was delivered in September, 2018 at the LINAC 18 in Beijing, China. We will make our 3rd report in July, 2019 at the SRF-19 in Dresden, Germany. There will be two main points this time. The first is that by using our improved Ninja Electrode Premium, we can out-perform our number one and number two competitors in terms of uniform electropolishing of the interior of the 9-cell cavity. The second point is that we can remove hydrogen gas, reacted during electropolishing, from the cavity chambers in a manner that has not been successfully achieved by 1st report, May 2018 and 2nd report, September 2018. We will report our 9-cell vertical polishing revolver-type unit that solves the above two problems.

Poster TUP028 [0.444 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP028

About •

paper received ※ 24 June 2019 paper accepted ※ 29 June 2019 issue date ※ 14 August 2019

Export •

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

TUP077

Nb₃Sn Thin Film Coating Method for Superconducting Multilayered Structure

628

R. Ito, T. Nagata
ULVAC, Inc, Chiba, Japan
H. Hayano, R. Katayama, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
H. Ito
Sokendai, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan

S-I-S (superconductor-insulator-superconductor) multilayered structure has been proposed in order to increase the maximum acceleration gradient of SRF cavities. Nb₃Sn is the material most expected as a superconducting layer of the S-I-S multilayered structure because it offers both a large critical temperature and large predicted Hsh. Most important in fabricating Nb₃Sn thin films is the stoichiometry of the material produced, and the lack of tin leads to performance degradation. We have launched a new in-house DC magnetron sputtering apparatus for Nb₃Sn deposition. Nb and Sn layers were alternately and repeatedly deposited on Si wafer while adjusting the film thickness of each layer, so we successfully obtained Nb-Sn films having appropriate composition ratio. The as-deposited films were annealed under the temperature of 600 degree C for 1 hour to generate the Nb₃Sn phase. The characteristics of Nb-Sn films evaluated by XRD, XRF, FE-SEM, and so on. We also measured critical temperature of the annealed films. In this paper, the detail of the Nb₃Sn coating method and the measurement result of the Nb-Sn films will be reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP077

About •

paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

Export •

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

TUP078

Lower Critical Field Measurement of NbN Multilayer Thin Film Superconductor at KEK

632

SUSP013

use link to see paper's listing under its alternate paper code

H. Ito
Sokendai, Ibaraki, Japan
C.Z. Antoine
CEA-IRFU, Gif-sur-Yvette, France
H. Hayano, R. Katayama, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
R. Ito, T. Nagata
ULVAC, Inc, Chiba, Japan
Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan

Funding: The work is supported by Japan Society for the Promotion of Science Grant-in-Aid for Young Scientist (A) No.17H04839.
The multilayer thin film structure of the superconductor has been proposed by A. Gurevich to enhance the maximum gradient of SRF cavities. The lower critical field Hc1 at which the vortex start penetrating the superconducting material will be improved by coating Nb with thin film superconductor such as NbN. It is expected that the enhancement of Hc1 depends on the thickness of each layer. In order to determine the optimum thickness of each layer and to compare the measurement results with the theoretical prediction proposed by T. Kubo, we developed the Hc1 measurement system using the third harmonic response of the applied AC magnetic field at KEK. For the Hc1 measurement without the influence of the edge or the shape effects, the AC magnetic field can be applied locally by the solenoid coil of 5mm diameter in our measurement system. ULVAC made the NbN-SiO₂ multilayer thin film samples of various NbN thicknesses. In this report, the measurement result of the bulk Nb sample and NbN-SiO₂ multilayer thin film samples of different thickness of NbN layer will be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP078

About •

paper received ※ 23 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

Export •

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

WETEA6

Successful Beam Commissioning in STF-2 Cryomodules for ILC

Y. Yamamoto, M. Akemoto, D.A. Arakawa, S. Araki, A. Aryshev, M. Egi, M.K. Fukuda, K. Hara, H. Hayano, Y. Honda, T. Honma, E. Kako, H. Katagiri, M. Kawamura, N. Kimura, Y. Kojima, Y. Kondou, T. Konomi, T. Matsumoto, S. Michizono, T. Miura, T. Miyajima, Y. Morikawa, H. Nakai, H. Nakajima, N. Nakamura, K. Nakanishi, T. Obina, T. Oyama, F. Qiu, T. Saeki, H. Sakai, T. Sanami, M. Shimada, H. Shimizu, T. Shishido, S.I. Takahara, K. Umemori, A. Yamamoto
KEK, Ibaraki, Japan
M. Kuriki, S. Notsu
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
S. Matsuba
JASRI, Hyogo, Japan
K. Sakaue
The University of Tokyo, The School of Engineering, Tokyo, Japan

Beam commissioning of the STF-2 accelerator was successfully done at the Superconducting RF Test Facility (STF) in KEK from February to March 2019. As a result of various cavity tuning, LLRF control tuning, and beam tuning, the beam energy finally reached 271 MeV, and the accelerating gradient of each cavity estimated from beam energy was 32.0 MV/m. This result satisfies 31.5 MV/m, which is the operating specification of the International Linear Collider (ILC) project, and is an important milestone in the ILC technology demonstration. In this talk, we will report on the detailed results of beam commissioning.

Slides WETEA6 [13.702 MB]

Export •

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

THFUA2

Evaluation of the Superconducting Characteristics of Multi-Layer Thin-Film Structures of NbN and SiO₂ on Pure Nb Substrate

807

R. Katayama, H. Hayano, T. Kubo, T. Saeki
KEK, Ibaraki, Japan
C.Z. Antoine
CEA-IRFU, Gif-sur-Yvette, France
H. Ito
Sokendai, Ibaraki, Japan
R. Ito
ULVAC, Inc, Chiba, Japan
Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
T. Nagata
ULVAC, Inc., Tsukuba, Japan

In recent years, it has been pointed out that the maximum accelerating gradient of a superconducting RF cavity can be increased by coating the inner surface of the cavity with a multilayer thin-film structure consisting of alternating insulating and superconducting layers. In this structure, the principal parameter that limits the performance of the cavity is the critical magnetic field or effective Hc1 at which vortices begin penetrating into the superconductor layer. This is predicted to depend on the combination of the film thickness. We made samples that have a NbN/SiO₂ thin-film structure on a pure Nb substrate with several layers of NbN film deposited using DC magnetron sputtering method. Here, we report the measurement results of effective Hc1 of NbN/SiO₂(30 nm)/Nb multilayer samples with thicknesses of NbN layers in the range from 50 nm to 800 nm by using the third-harmonic voltage method. Experimental results show that an optimum thickness exists, which increases the effective Hc1 by 23.8 %.

Slides THFUA2 [2.333 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THFUA2

About •

paper received ※ 03 July 2019 paper accepted ※ 05 July 2019 issue date ※ 14 August 2019

Export •

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

THP088

Updates on the Inspection System for SRF Cavities

1111

Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
H. Hayano
KEK, Ibaraki, Japan
Y. Kuriyama
Kyoto University, Research Reactor Institute, Osaka, Japan

Optical inspections on superconducting cavities are familiar to those who are involved in the cavity fabrications. Further improvements on the Kyoto Camera have been carried out these years together with further processing technique developments, such as removing found defects by local grinding techniques. Improvements on Kyoto Camera includes implementation of color LEDs for illumination system, which improves the inspection efficiency. These progresses will be reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-THP088

About •

paper received ※ 02 July 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

Export •

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