SRF2017 - List of Authors (Konomi, T.)

Paper	Title	Page
MOXA04	Superconducting Accelerator for ERL Based FEL EUV Light Source at KEK	13
	H. Sakai, E. Kako, T. Konomi, T. Kubo, K. Umemori KEK, Ibaraki, Japan T. Ota Toshiba, Yokohama, Japan M. Sawamura QST, Tokai, Japan
	An energy recovery linac (ERL)-based free electron laser (FEL) is a possible candidate of a tens of kW EUV source and open the era for next generation EUV-lithography. We have designed the 10 mA class ERL-based EUV-FEL source to generate more than 10 kW power. One of the key technologies is CW superconducting cavities to realize the energy recovery of high beam current of more than 10 mA by suppressing HOMs and high gradient acceleration of higher than 12 MV/m. This CW superconducting cavity had been developed through the construction of the Compact ERL facility in KEK and it successfully achieved the energy recovery of 1 mA CW beam until now. In this talk, first we express our design strategies of SRF cavities of the main linac of ERL-EUV light sources not only to suppress the HOMs but also to overcome the field emission problem by modifying the main linac cavity of Compact ERL more sophisticatedly. Next we show the recent development works for ERL-EUV superconducting cavity about HOM damper, cryomodule, and its clean string-assembly work by using horizontal test stand.
	Slides MOXA04 [5.938 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOXA04
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MOPB062	Development of HOM Absorbers for CW Superconducting Cavities in Energy Recovery Linac	191
	T. Ota, A. Miyamoto, K. Sato, M. Takasaki, M. Yamada Toshiba, Yokohama, Japan E. Kako, T. Konomi, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Higher Order Modes (HOM) absorbers for superconducting cavities have been developing at TOSHIBA in collaboration with High Energy Accelerator Research Organization (KEK) since 2015. Prototype HOM absorbers for 1.3 GHz 9-cell superconducting cavity were fabricated. An AlN lossy dielectrics cylinder was brazed with a copper cylinder, and the cool-down tests by nitrogen gas was carried out. Copper cylinders and SUS flanges were joined by electron beam welding to fabricate a whole prototype HOM absorber. Fabrication process of the prototype HOM absorber will be presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB062
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MOPB096	Estimation of Alignment Error by Measuring Higher-order-mode of Injector Superconducting Cavity at KEK-cERL	286
	Y. Honda, E. Kako, T. Konomi, T. Miyajima, T. Obina, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Precise alignment of accelerator cavities is important in realizing a low emittance beam. Especially in the cases of superconducting cavities installed in a cryomodule, it is difficult to mechanically measure the position of the cavities. By measuring higher-order-modes (HOM) excited by a beam, the electrical center of the cavities can be estimated. We have developed a HOM measurement system for the injector superconducting accelerator cavities of KEK ERL test accelerator (cERL).Comparing the HOM signals of the three independent cavities in the cryomodule, we estimated the relative positioning errors of the three cavities.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB096
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MOPB097	Degradation and Recovery of Cavity Performances in Compact-ERL Injector Cryomodule	289
	E. Kako, T. Konomi, T. Miura, H. Sakai, K. Umemori KEK, Ibaraki, Japan
	Injector cryomodule for cERL consists of three 2-cell cavities equipped with double-feeds input couplers, five antenna-type HOM couplers and a slide-jack tuner with two piezo actuators. After cryomodule assembly and first cool-down tests in 2012, the cERL injector cryomodule has been stably operated with beam for four years. Gradual increases of x-ray radiation levels due to field emission were observed during long term beam operation. High power pulsed RF conditioning as a cure method was applied in the cool-down period in 2016 and 2017, so that degraded cavity performances have almost recovered up to the original levels. Performance recovery status in three 2-cell cavities will be reported in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB097
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TUPB028	Improvement of Magnetic Condition for KEK-STF Vertical Test Facility Toward High-Q Study	444
	K. Umemori, T. Dohmae, E. Kako, T. Konomi, T. Kubo, M. Masuzawa, G.-T. Park, A. Terashima, K. Tsuchiya, R. Ueki KEK, Ibaraki, Japan T. Okada Sokendai, Ibaraki, Japan
	Improvement of unloaded Q-values of SRF cavities are important to reduce surface loss of cavity and heat loads of He refrigerators. R&D activities have been developed worldwide. We also started work toward high-Q, but soon realized that magnetic condition of KEK-STF vertical test facility was not good enough to carry out high-Q measurements. First, magnetized components were searched. Shafts to move variable coupler were found to be most magnetized one and exceed more than 1 Gauss. Magnetized components were exchanged to non-magnetized one. In order to further reduce remnant magnetic field, a solenoid coil was prepared and used to cancel it. To suppress flux trapping, a heater was located around an upper beampipe of cavity and made thermal gradient. Owing to these efforts, Q-value of more than 1x10¹¹ can be measured with a condition of residual resistance of ~3 nΩ. Clear flux expulsion signal can be also observed. In this presentation, we report about efforts to reduce ambient magnetic field and to realize high-Q measurements. Results of vertical tests, including flux expulsion measurements, are also presented.
	Poster TUPB028 [1.961 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB028
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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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THYA06	Long-term Operation Experience with Beams in Compact ERL Cryomodules	736
	K. Umemori, M. Egi, K. Enami, T. Furuya, Y. Honda, E. Kako, T. Konomi, H. Sakai KEK, Ibaraki, Japan T. Okada Sokendai, Ibaraki, Japan M. Sawamura QST, Tokai, Japan
	Compact ERL (cERL) was constructed at KEK as a prototype for 3GeV ERL light source. It consists of two types of SRF cavities. Three injector 2-cell SRF cavities and two main linac 9-cell SRF cavities. The beam operation started at 2013, with 100 nA (CW). Beam current increased step by step and currently reached to 1 mA (CW). Energy recovery has successfully achieved. Performance of the SRF cavities through long term beam operation has been investigated. With the beam induced HOMs, the beam position and the beam timing were studied. cERL has suffered from heavy field emissions in operation. Field emissions of the main linac cavity started just after module assembly work, and during beam operation, performances of both the main linac and the injector SRF cavities sometimes degraded. One reason of degradation was discharges occurred at beamline components due to charge up of electrons. Pulse aging technique helped to recover SRF performances. In this presentation, details of SRF beam operation, degradation, applied recovery methods are described.
	Slides THYA06 [4.973 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THYA06
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THPB021	Trial of Nitrogen Infusion and Nitrogen Doping by Using J-PARC Furnace	775
	T. Konomi, T. Dohmae, Y. Hori, E. Kako, T. Kubo, G.-T. Park, H. Sakai, K. Umemori KEK, Ibaraki, Japan J. Kamiya, K. Takeishi JAEA/J-PARC, Tokai-mura, Japan T. Nagata ULVAC, Inc., Tsukuba, Japan
	KEK has been carrying out SRF cavity developments toward higher Q-values and higher accelerating gradients. In the past nitrogen-doping was tested using the KEK furnaces, but it did not succeed. This time nitrogen infusion and nitrogen doping are tested using the J-PARC's furnace, which has an oil-free pumping system and is mainly pumped by a 10000 L/s cryopump and three 3000 L/s turbo pumps. Nitrogen pressure is controlled by a variable leak valve and an additional turbo pump. To avoid performance degradation during heat treatment, flanges of cavities are covered by Nb caps and foils. Nitrogen infusion at 120 degrees was applied to a single cell cavity and cavity performance was measured by vertical tests after HPR and assembly. Nitrogen doping at 800 degrees is also applied to another single cell cavity. After applying EP and HPR, vertical tests were carried out. Nb samples were also installed into the furnace during heat treatment. Surfaces are analyzed by SIMS and XPS. In this presentation, we report procedure of nitrogen infusion and doping, vertical test results and results of surface analysis.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB021
Export •	reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

Paper

Title

Page

Superconducting Accelerator for ERL Based FEL EUV Light Source at KEK

13

H. Sakai, E. Kako, T. Konomi, T. Kubo, K. Umemori
KEK, Ibaraki, Japan
T. Ota
Toshiba, Yokohama, Japan
M. Sawamura
QST, Tokai, Japan

An energy recovery linac (ERL)-based free electron laser (FEL) is a possible candidate of a tens of kW EUV source and open the era for next generation EUV-lithography. We have designed the 10 mA class ERL-based EUV-FEL source to generate more than 10 kW power. One of the key technologies is CW superconducting cavities to realize the energy recovery of high beam current of more than 10 mA by suppressing HOMs and high gradient acceleration of higher than 12 MV/m. This CW superconducting cavity had been developed through the construction of the Compact ERL facility in KEK and it successfully achieved the energy recovery of 1 mA CW beam until now. In this talk, first we express our design strategies of SRF cavities of the main linac of ERL-EUV light sources not only to suppress the HOMs but also to overcome the field emission problem by modifying the main linac cavity of Compact ERL more sophisticatedly. Next we show the recent development works for ERL-EUV superconducting cavity about HOM damper, cryomodule, and its clean string-assembly work by using horizontal test stand.

Slides MOXA04 [5.938 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOXA04

Export •

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

MOPB062

Development of HOM Absorbers for CW Superconducting Cavities in Energy Recovery Linac

191

T. Ota, A. Miyamoto, K. Sato, M. Takasaki, M. Yamada
Toshiba, Yokohama, Japan
E. Kako, T. Konomi, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Higher Order Modes (HOM) absorbers for superconducting cavities have been developing at TOSHIBA in collaboration with High Energy Accelerator Research Organization (KEK) since 2015. Prototype HOM absorbers for 1.3 GHz 9-cell superconducting cavity were fabricated. An AlN lossy dielectrics cylinder was brazed with a copper cylinder, and the cool-down tests by nitrogen gas was carried out. Copper cylinders and SUS flanges were joined by electron beam welding to fabricate a whole prototype HOM absorber. Fabrication process of the prototype HOM absorber will be presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB062

Export •

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

MOPB096

Estimation of Alignment Error by Measuring Higher-order-mode of Injector Superconducting Cavity at KEK-cERL

286

Y. Honda, E. Kako, T. Konomi, T. Miyajima, T. Obina, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Precise alignment of accelerator cavities is important in realizing a low emittance beam. Especially in the cases of superconducting cavities installed in a cryomodule, it is difficult to mechanically measure the position of the cavities. By measuring higher-order-modes (HOM) excited by a beam, the electrical center of the cavities can be estimated. We have developed a HOM measurement system for the injector superconducting accelerator cavities of KEK ERL test accelerator (cERL).Comparing the HOM signals of the three independent cavities in the cryomodule, we estimated the relative positioning errors of the three cavities.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB096

Export •

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

MOPB097

Degradation and Recovery of Cavity Performances in Compact-ERL Injector Cryomodule

289

E. Kako, T. Konomi, T. Miura, H. Sakai, K. Umemori
KEK, Ibaraki, Japan

Injector cryomodule for cERL consists of three 2-cell cavities equipped with double-feeds input couplers, five antenna-type HOM couplers and a slide-jack tuner with two piezo actuators. After cryomodule assembly and first cool-down tests in 2012, the cERL injector cryomodule has been stably operated with beam for four years. Gradual increases of x-ray radiation levels due to field emission were observed during long term beam operation. High power pulsed RF conditioning as a cure method was applied in the cool-down period in 2016 and 2017, so that degraded cavity performances have almost recovered up to the original levels. Performance recovery status in three 2-cell cavities will be reported in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-MOPB097

Export •

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

TUPB028

Improvement of Magnetic Condition for KEK-STF Vertical Test Facility Toward High-Q Study

444

K. Umemori, T. Dohmae, E. Kako, T. Konomi, T. Kubo, M. Masuzawa, G.-T. Park, A. Terashima, K. Tsuchiya, R. Ueki
KEK, Ibaraki, Japan
T. Okada
Sokendai, Ibaraki, Japan

Improvement of unloaded Q-values of SRF cavities are important to reduce surface loss of cavity and heat loads of He refrigerators. R&D activities have been developed worldwide. We also started work toward high-Q, but soon realized that magnetic condition of KEK-STF vertical test facility was not good enough to carry out high-Q measurements. First, magnetized components were searched. Shafts to move variable coupler were found to be most magnetized one and exceed more than 1 Gauss. Magnetized components were exchanged to non-magnetized one. In order to further reduce remnant magnetic field, a solenoid coil was prepared and used to cancel it. To suppress flux trapping, a heater was located around an upper beampipe of cavity and made thermal gradient. Owing to these efforts, Q-value of more than 1x10¹¹ can be measured with a condition of residual resistance of ~3 nΩ. Clear flux expulsion signal can be also observed. In this presentation, we report about efforts to reduce ambient magnetic field and to realize high-Q measurements. Results of vertical tests, including flux expulsion measurements, are also presented.

Poster TUPB028 [1.961 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-TUPB028

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)

THYA06

Long-term Operation Experience with Beams in Compact ERL Cryomodules

736

K. Umemori, M. Egi, K. Enami, T. Furuya, Y. Honda, E. Kako, T. Konomi, H. Sakai
KEK, Ibaraki, Japan
T. Okada
Sokendai, Ibaraki, Japan
M. Sawamura
QST, Tokai, Japan

Compact ERL (cERL) was constructed at KEK as a prototype for 3GeV ERL light source. It consists of two types of SRF cavities. Three injector 2-cell SRF cavities and two main linac 9-cell SRF cavities. The beam operation started at 2013, with 100 nA (CW). Beam current increased step by step and currently reached to 1 mA (CW). Energy recovery has successfully achieved. Performance of the SRF cavities through long term beam operation has been investigated. With the beam induced HOMs, the beam position and the beam timing were studied. cERL has suffered from heavy field emissions in operation. Field emissions of the main linac cavity started just after module assembly work, and during beam operation, performances of both the main linac and the injector SRF cavities sometimes degraded. One reason of degradation was discharges occurred at beamline components due to charge up of electrons. Pulse aging technique helped to recover SRF performances. In this presentation, details of SRF beam operation, degradation, applied recovery methods are described.

Slides THYA06 [4.973 MB]

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THYA06

Export •

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

THPB021

Trial of Nitrogen Infusion and Nitrogen Doping by Using J-PARC Furnace

775

T. Konomi, T. Dohmae, Y. Hori, E. Kako, T. Kubo, G.-T. Park, H. Sakai, K. Umemori
KEK, Ibaraki, Japan
J. Kamiya, K. Takeishi
JAEA/J-PARC, Tokai-mura, Japan
T. Nagata
ULVAC, Inc., Tsukuba, Japan

KEK has been carrying out SRF cavity developments toward higher Q-values and higher accelerating gradients. In the past nitrogen-doping was tested using the KEK furnaces, but it did not succeed. This time nitrogen infusion and nitrogen doping are tested using the J-PARC's furnace, which has an oil-free pumping system and is mainly pumped by a 10000 L/s cryopump and three 3000 L/s turbo pumps. Nitrogen pressure is controlled by a variable leak valve and an additional turbo pump. To avoid performance degradation during heat treatment, flanges of cavities are covered by Nb caps and foils. Nitrogen infusion at 120 degrees was applied to a single cell cavity and cavity performance was measured by vertical tests after HPR and assembly. Nitrogen doping at 800 degrees is also applied to another single cell cavity. After applying EP and HPR, vertical tests were carried out. Nb samples were also installed into the furnace during heat treatment. Surfaces are analyzed by SIMS and XPS. In this presentation, we report procedure of nitrogen infusion and doping, vertical test results and results of surface analysis.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-SRF2017-THPB021

Export •

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