SRF2019 - List of Authors (Sakai, H.)

Paper	Title	Page
MOP027	Study on Nitrogen Infusion using KEK New Furnace	95
	K. Umemori, E. Kako, T. Konomi, S. Michizono, H. Sakai KEK, Ibaraki, Japan T. Okada Sokendai, Ibaraki, Japan J. Tamura JAEA/J-PARC, Tokai-mura, Japan
	KEK has been carried out high-Q/high-G R&D, to realize high performance of SRF cavities toward ILC. KEK constructed a new furnace, which is dedicated for N-infusion studies. We performed more than 10 times of N-infusion trials using 1.3 GHz single-cell cavities. Some results showed better Q-values up to high field, however, some results showed degraded Q-E slopes probably due to contamination. Improvement of accelerating gradient is not observed at moment. We have tried to clean the furnace and Nitrogen injection line to reduce the effect of contamination. Details of procedures of N-infusion, results of vertical tests, condition of the furnace including RGA spectrum and Nb sample analysis results are shown.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP027
About •	paper received ※ 04 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
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MOP055	Fabrication and Performance of Superconducting Quarter-Wavelength Resonators for SRILAC	182
	K. Suda, O. Kamigaito, K. Ozeki, N. Sakamoto, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa MHI-MS, Kobe, Japan E. Kako, H. Nakai, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	A new superconducting booster linac (SRILAC) at the RIKEN heavy-ion linac is under construction. Ten 73-MHz low-beta quarter-wavelength resonators (QWRs) that operate at 4 K have been fabricated from pure niobium sheets. The cavity parts were assembled by electron beam welding. The resonant frequency for each cavity was adjusted by changing the lengths of the straight sections before welding. The performance and frequency were evaluated by vertical tests. All the cavities exceeded the design specifications of Q₀ = 1x10⁹ and E_acc = 6.8 MV/m. Details of the fabrication and frequency tuning as well as the performance of the cavities are reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP055
About •	paper received ※ 17 July 2019 paper accepted ※ 13 August 2019 issue date ※ 14 August 2019
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TUP007	Electromagnetic Design of the Prototype Spoke Cavity for the JAEA-ADS Linac	399
	J. Tamura, K. Hasegawa, Y. Kondo, F.M. Maekawa, S.I. Meigo, B. Yee-Rendón JAEA/J-PARC, Tokai-mura, Japan E. Kako, T. Konomi, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	The Japan Atomic Energy Agency (JAEA) is proposing an accelerator-driven subcritical system (ADS) as a future project to transmute long-lived nuclides to short-lived or stable ones. In the JAEA-ADS, a high-power proton beam of 30 MW with a final beam energy of 1.5 GeV is required with a high reliability. Furthermore, the accelerator needs to be operated in a continuous wave mode in order to be compatible with the reactor operation. As the first step toward the detailed design of the JAEA-ADS linac, we are planning to demonstrate a high-field measurement by prototyping a low-beta single spoke resonator (SSR1). We performed the electromagnetic design, and confirmed that the cavity performances of the SSR1 model with and without dimensional constraint.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP007
About •	paper received ※ 02 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019
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TUP060	Development of Temperature and Magnetic Field Mapping System for Superconducting Cavities at KEK	583
SUSP019	use link to see paper's listing under its alternate paper code
	T. Okada, E. Kako, T. Konomi, H. Sakai, K. Umemori Sokendai, Ibaraki, Japan E. Kako, T. Konomi, M. Masuzawa, H. Sakai, K. Tsuchiya, R. Ueki, K. Umemori KEK, Ibaraki, Japan A. Poudel, T. Tajima LANL, Los Alamos, New Mexico, USA
	A temperature and magnetic field mapping system for a single cell superconducting cavity is being developed at KEK. The mapping system is used to observe the temperature distribution and the ambient magnetic field distribution around the outer surface of the cavity. A total of 36 boards at every 10 degrees are attached on the cavity. Each board consists of 15 carbon resistors of 100 Ω at room temperature and 3 AMR sensors of X, Y and Z directions at the equator. The calibration of the resisters and AMR sensors were carefully and precisely carried out at low temperature. The data logging system using NI loggers is enabled to measure within 1 ms in the whole cavity surface. The initial test results in the vertical test of the single-cell cavity will be reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP060
About •	paper received ※ 05 July 2019 paper accepted ※ 05 July 2019 issue date ※ 14 August 2019
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TUP104	Improvement of a Clean Assembly Work for Superconducting RF Cryomodule and Its Application to the KEK-STF Cryomodule	721
	H. Sakai, E. Kako, T. Konomi, K. Umemori, Y. Yamamoto KEK, Ibaraki, Japan T. Ebisawa, A. Kasugai QST, Aomori, Japan
	We usually encountered the degradation of the superconducting RF cavities on the cryomodule test even though the performance of these cavities was good on the vertical test. In reality, the degradation of Q-values of two cavities of cERL main-linac were observed after cryomodule assembly in KEK [1] and STF cryomodule also met the degradation after the cryomodule assembly [2]. Some dusts and invisible particles might enter the cavity and generate field emission during the assembly work. Field emission is the most important cause of this degradation. In this paper, first we introduce some trials for the improved clean assembly work to SRF cavity by re-examining our clean assembly work and vacuum work. For example, slow pumping system with vacuum particle monitor was developed to know and control the particle movement during slow pumping and venting. Next we show the application of this improved work to the STF re-assemble cryomodule work in KEK. [1} H. Sakai et al., SRF’13, Paris, France, p.855, 2013. [2] Y. Yamamoto et al., IPAC’16, Busan, Korea, p.2158, 2016.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP104
About •	paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019
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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]
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FRCAB4	Development of High Intensity, High Brightness, CW SRF Gun with Bi-Alkali Photocathode	1219
	T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi KEK, Ibaraki, Japan
	Superconducting conduction electron guns can realize high acceleration voltage and high beam repetition. KEK has been developing the 1.3 GHz elliptical type 1.5 cell superconducting RF gun to investigate fundamental performance. The surface cleaning methods and tools were developed by using KEK SRF gun cavity #1 and surface peak electric field reached to 75 MV/m without field emission. We will apply this technique to the SRF gun cavity #2 for beam operation. The gun cavity #2 equips the helium jacket, frequency tuner cathode position adjuster to operate the electron beam. The RF structure was designed based on the gun cavity #1. The cathode rod is made of Nb. The photocathode deposited on the cathode rod will be cool down to 2K to minimize thermal emittance. The fabrication of the gun cavity #2 and helium jacket were completed. 4 times vertical tests were carried out. We will report the vertical test results and preparation of the horizontal test.
	Slides FRCAB4 [10.826 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB4
About •	paper received ※ 23 June 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

Study on Nitrogen Infusion using KEK New Furnace

95

K. Umemori, E. Kako, T. Konomi, S. Michizono, H. Sakai
KEK, Ibaraki, Japan
T. Okada
Sokendai, Ibaraki, Japan
J. Tamura
JAEA/J-PARC, Tokai-mura, Japan

KEK has been carried out high-Q/high-G R&D, to realize high performance of SRF cavities toward ILC. KEK constructed a new furnace, which is dedicated for N-infusion studies. We performed more than 10 times of N-infusion trials using 1.3 GHz single-cell cavities. Some results showed better Q-values up to high field, however, some results showed degraded Q-E slopes probably due to contamination. Improvement of accelerating gradient is not observed at moment. We have tried to clean the furnace and Nitrogen injection line to reduce the effect of contamination. Details of procedures of N-infusion, results of vertical tests, condition of the furnace including RGA spectrum and Nb sample analysis results are shown.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP027

About •

paper received ※ 04 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

Export •

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

MOP055

Fabrication and Performance of Superconducting Quarter-Wavelength Resonators for SRILAC

182

K. Suda, O. Kamigaito, K. Ozeki, N. Sakamoto, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
H. Hara, A. Miyamoto, K. Sennyu, T. Yanagisawa
MHI-MS, Kobe, Japan
E. Kako, H. Nakai, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

A new superconducting booster linac (SRILAC) at the RIKEN heavy-ion linac is under construction. Ten 73-MHz low-beta quarter-wavelength resonators (QWRs) that operate at 4 K have been fabricated from pure niobium sheets. The cavity parts were assembled by electron beam welding. The resonant frequency for each cavity was adjusted by changing the lengths of the straight sections before welding. The performance and frequency were evaluated by vertical tests. All the cavities exceeded the design specifications of Q₀ = 1x10⁹ and E_acc = 6.8 MV/m. Details of the fabrication and frequency tuning as well as the performance of the cavities are reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-MOP055

About •

paper received ※ 17 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)

TUP007

Electromagnetic Design of the Prototype Spoke Cavity for the JAEA-ADS Linac

399

J. Tamura, K. Hasegawa, Y. Kondo, F.M. Maekawa, S.I. Meigo, B. Yee-Rendón
JAEA/J-PARC, Tokai-mura, Japan
E. Kako, T. Konomi, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

The Japan Atomic Energy Agency (JAEA) is proposing an accelerator-driven subcritical system (ADS) as a future project to transmute long-lived nuclides to short-lived or stable ones. In the JAEA-ADS, a high-power proton beam of 30 MW with a final beam energy of 1.5 GeV is required with a high reliability. Furthermore, the accelerator needs to be operated in a continuous wave mode in order to be compatible with the reactor operation. As the first step toward the detailed design of the JAEA-ADS linac, we are planning to demonstrate a high-field measurement by prototyping a low-beta single spoke resonator (SSR1). We performed the electromagnetic design, and confirmed that the cavity performances of the SSR1 model with and without dimensional constraint.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP007

About •

paper received ※ 02 July 2019 paper accepted ※ 04 July 2019 issue date ※ 14 August 2019

Export •

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

TUP060

Development of Temperature and Magnetic Field Mapping System for Superconducting Cavities at KEK

583

SUSP019

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

T. Okada, E. Kako, T. Konomi, H. Sakai, K. Umemori
Sokendai, Ibaraki, Japan
E. Kako, T. Konomi, M. Masuzawa, H. Sakai, K. Tsuchiya, R. Ueki, K. Umemori
KEK, Ibaraki, Japan
A. Poudel, T. Tajima
LANL, Los Alamos, New Mexico, USA

A temperature and magnetic field mapping system for a single cell superconducting cavity is being developed at KEK. The mapping system is used to observe the temperature distribution and the ambient magnetic field distribution around the outer surface of the cavity. A total of 36 boards at every 10 degrees are attached on the cavity. Each board consists of 15 carbon resistors of 100 Ω at room temperature and 3 AMR sensors of X, Y and Z directions at the equator. The calibration of the resisters and AMR sensors were carefully and precisely carried out at low temperature. The data logging system using NI loggers is enabled to measure within 1 ms in the whole cavity surface. The initial test results in the vertical test of the single-cell cavity will be reported in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP060

About •

paper received ※ 05 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)

TUP104

Improvement of a Clean Assembly Work for Superconducting RF Cryomodule and Its Application to the KEK-STF Cryomodule

721

H. Sakai, E. Kako, T. Konomi, K. Umemori, Y. Yamamoto
KEK, Ibaraki, Japan
T. Ebisawa, A. Kasugai
QST, Aomori, Japan

We usually encountered the degradation of the superconducting RF cavities on the cryomodule test even though the performance of these cavities was good on the vertical test. In reality, the degradation of Q-values of two cavities of cERL main-linac were observed after cryomodule assembly in KEK [1] and STF cryomodule also met the degradation after the cryomodule assembly [2]. Some dusts and invisible particles might enter the cavity and generate field emission during the assembly work. Field emission is the most important cause of this degradation. In this paper, first we introduce some trials for the improved clean assembly work to SRF cavity by re-examining our clean assembly work and vacuum work. For example, slow pumping system with vacuum particle monitor was developed to know and control the particle movement during slow pumping and venting. Next we show the application of this improved work to the STF re-assemble cryomodule work in KEK.
[1} H. Sakai et al., SRF’13, Paris, France, p.855, 2013.
[2] Y. Yamamoto et al., IPAC’16, Busan, Korea, p.2158, 2016.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-TUP104

About •

paper received ※ 20 June 2019 paper accepted ※ 30 June 2019 issue date ※ 14 August 2019

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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)

FRCAB4

Development of High Intensity, High Brightness, CW SRF Gun with Bi-Alkali Photocathode

1219

T. Konomi, Y. Honda, E. Kako, Y. Kobayashi, S. Michizono, T. Miyajima, H. Sakai, K. Umemori, S. Yamaguchi
KEK, Ibaraki, Japan

Superconducting conduction electron guns can realize high acceleration voltage and high beam repetition. KEK has been developing the 1.3 GHz elliptical type 1.5 cell superconducting RF gun to investigate fundamental performance. The surface cleaning methods and tools were developed by using KEK SRF gun cavity #1 and surface peak electric field reached to 75 MV/m without field emission. We will apply this technique to the SRF gun cavity #2 for beam operation. The gun cavity #2 equips the helium jacket, frequency tuner cathode position adjuster to operate the electron beam. The RF structure was designed based on the gun cavity #1. The cathode rod is made of Nb. The photocathode deposited on the cathode rod will be cool down to 2K to minimize thermal emittance. The fabrication of the gun cavity #2 and helium jacket were completed. 4 times vertical tests were carried out. We will report the vertical test results and preparation of the horizontal test.

Slides FRCAB4 [10.826 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2019-FRCAB4

About •

paper received ※ 23 June 2019 paper accepted ※ 03 July 2019 issue date ※ 14 August 2019

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