SRF2011 - List of Authors (Watanabe, K.)

Paper

Title

Page

Development of STF Input Couplers for ILC

364

M. Satoh, E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto
KEK, Ibaraki, Japan

High power tests of the STF-Phase 1 cryomodule was carried out at KEK-STF (Superconducting RF Test facility) in 2008. Vacuum leaks at the cold ceramic window of STF-1 input couplers were found in the disassembly of the cryomodule after warm-up. It was considered that the vacuum leaks might be caused by the thermal cycles. Structures of brazing parts at a ceramic disk was investigated to reduce the thermal strain. The STF-2 input couplers with an improved brazing structure for S1-Global cryomodule was designed after the thermal cycle tests of the sample RF windows. The results of the thermal cycle tests of the sample RF windows and the high power performance of the improved STF-2 input couplers will be reported.

Poster TUPO007 [1.034 MB]

TUPO029

Gradient Improvement by Removal of Identified Local Defects

436

R.L. Geng, W.A. Clemens
JLAB, Newport News, Virginia, USA
C.A. Cooper
Fermilab, Batavia, USA
H. Hayano, K. Watanabe
KEK, Ibaraki, Japan

Funding: This work was authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177
Recent experience of ILC cavity processing and testing at Jefferson Lab has shown that some 9-cell cavities are quench limited at a gradient in the range of 15-25 MV/m. Further studies reveal that these quench limits are often correlated with sub-mm sized and highly localized geometrical defects at or near the equator weld. There are increasing evidence to show that these genetic defects have their origin in the material or in the electron beam welding process (for example due to weld irregularities or splatters on the RF surface and welding porosity underneath the surface). A local defect removal method has been proposed at Jefferson Lab by locally re-melting the niobium material. Several 1-cell cavities with known local defects have been treated by using the JLab local e-beam re-melting method, resulting in gradient and Q0 improvement. We also sent 9-cell cavities with known gradient limiting local defects to KEK for local grinding and to FNAL for global mechanical polishing. We report on the results of gradient improvements by removal of local defects in these cavities.

TUPO030

Status of the 9-Cell Superconducting Cavity R&D for ILC at Hitachi

439

T. Watanuki, T. Semba, M. Watanabe
Hitachi Ltd., Ibaraki-ken, Japan
H. Hayano, E. Kako, S. Noguchi, T. Saeki, T. Shishido, K. Watanabe, Y. Yamamoto
KEK, Ibaraki, Japan

Hitachi is developing 9-cell superconducting cavities for ILC project in collaboration with KEK. We focus on electron beam welding (EBW) and plastic forming techniques. In 2010, Hitachi’s first 9-cell cavity without HOM couplers was completed successfully. Surface treatments and performance test of the cavity were carried out at KEK and the accelerating gradient reached 35.2 MV/m. We have undertaken the next 9-cell cavity with HOM couplers since January 2011. We will report the fabrication procedure and test result of first cavity and the current status of the next cavity.

TUPO032

Updates on R&D of Nondestructive Inspection Systems for SRF Cavities

447

Y. Iwashita, H. Tongu
Kyoto ICR, Uji, Kyoto, Japan
H. Hayano, T. Saeki, K. Watanabe
KEK, Ibaraki, Japan

We are developing high resolution eddy current scan and High density Tmap and X-map. The high resolution eddy current scan showed 100 μm diameter hole with 50μm depth that was drilled on a Nb plate. The surface mount print circuit technology is applied to the high density Tmap and X-map devices, which will be ready soon to test at a vertical test bench. In addition, radiography using Xrays and neutrons are also under study. The results and status will be presented.

Poster TUPO032 [2.362 MB]

WEIOB02

Cavity Inspection and Repair Techniques

598

K. Watanabe, H. Hayano
KEK, Ibaraki, Japan
Y. Iwashita
Kyoto ICR, Uji, Kyoto, Japan

The cavity inspection and repair techniques are important to study a quality control of the superconducting rf cavity for better yield with high accelerating gradient. A high-resolution camera system was developed for optical inspection in 2008. It enables 2-D analysis by image processing on inner surface of the cavity. Therefore, the cause to limit the cavity performance can be categorized into a geometrical defect or an assembly work and the surface treatment. In addition, by perfoming the optical inspection at each treatment, we can obtain an information when a defect appeared. The cavities that quenched at the low field were inspected. One or few geometrical defects were found around quench location on some of these cavities. It is a possibility that the cavity performance can be recovered by removing the geometrical defect at the quench location. A local grinding machine was developed for this purpose. This method was tested on the 9-cell cavities, and we succeeded to recover the cavity performance with combination of local grinding and light EP. The method and results of the cavity inspection as well as the replica techniques will be presented in this talk.

THPO027

Optical Observation of Geometrical Features and Correlation With RFTest Results

773

J. Dai, K. Zhao
PKU/IHIP, Beijing, People's Republic of China
R.L. Geng
JLAB, Newport News, Virginia, USA
K. Watanabe
KEK, Ibaraki, Japan

Funding: *Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
Three kinds of geometrical features analysis techniques were adopted in association with cavity gradient R&D at Jefferson Lab: (1) Feature shape analysis by Kyoto camera system; (2) 3D shape analysis using a HIROX KH-7700 High Resolution Digital-Video Microscopy System; (3) Replica technique plus surface profiler for profile measurement of geometrical features. Up to now, many features were found in two nine cell SRF cavities: PKU2 from Peking University in China and NR1 from Niowave-Roark in America. Both of them have been RF tested at 2K. The shape analysis of geometrical surface features and correlation with RF test results using a thermal analysis code will be presented here.
daijin@pku.edu.cn

THIOA01

Test Results of the International S1-Global Cryomodule

615

Y. Yamamoto, M. Akemoto, S. Fukuda, K. Hara, H. Hayano, N. Higashi, E. Kako, H. Katagiri, Y. Kojima, Y. Kondo, T. Matsumoto, H. Matsushita, S. Michizono, T. Miura, H. Nakai, H. Nakajima, K. Nakanishi, S. Noguchi, N. Ohuchi, T. Saeki, M. Satoh, T. Shidara, T. Shishido, T. Takenaka, A. Terashima, N. Toge, K. Tsuchiya, K. Watanabe, S. Yamaguchi, A. Yamamoto, K. Yokoya, M. Yoshida
KEK, Ibaraki, Japan
C. Adolphsen, C.D. Nantista
SLAC, Menlo Park, California, USA
T.T. Arkan, S. Barbanotti, M.A. Battistoni, H. Carter, M.S. Champion, A. Hocker, R.D. Kephart, J.S. Kerby, D.V. Mitchell, T.J. Peterson, Y.M. Pischalnikov, M.C. Ross, W. Schappert, B.E. Smith
Fermilab, Batavia, USA
A. Bosotti, C. Pagani, R. Paparella, P. Pierini
INFN/LASA, Segrate (MI), Italy
K. Jensch, D. Kostin, L. Lilje, A. Matheisen, W.-D. Möller, P. Schilling, M. Schmökel, N.J. Walker, H. Weise
DESY, Hamburg, Germany

S1-Global collaborative project by joint efforts of INFN, DESY, FNAL, SLAC and KEK, finished successfully at KEK- STF on February in 2011, is a crucial project for ILC. For this project, 8 SRF cavities, 2 from DESY, 2 from FNAL and 4 from KEK, were installed into one cryomodule with the thermal shields and the cooling pipes of liquid helium and nitrogen, cooled down to 2K totally three times, and cold-tested by using the three different frequency tuning systems (Blade tuner from INFN/FNAL, Saclay tuner from DESY and Slide-Jack tuner from KEK) and two types of input couplers (TTF III from DESY and STF#2 from KEK). During the cold test with high power, cavity performance, LFD (Lorentz Force Detuning) compensation by Piezo actuator, simultaneous 7 SRF cavities operation, dynamic heating loss measurement including static loss and DRFS (Distributed RF Scheme) operation with LLRF (Low Level RF) feedback system, were established successfully. In this talk, the results of the S1-Global cryomodule test are reported, discussed and summarized.

Slides THIOA01 [11.254 MB]

FRIOA06

Construction of cERL Cryomodules for Injector and Main Linac

956

K. Umemori, T. Furuya, E. Kako, S. Noguchi, H. Sakai, M. Satoh, T. Shishido, K. Watanabe, Y. Yamamoto
KEK, Ibaraki, Japan
E. Cenni
Sokendai, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan
K. Shinoe
ISSP/SRL, Chiba, Japan

The Compact ERL (cERL) project is advanced in Japan. Its aim is to demonstrate the circulation of 100 mA electron beams with energy of 35-200 MeV. Superconducting cavities are key components for realizing ERL. At injector part, electron beams are accelerated up to 5-10 MeV by three 2-cell cavities. Prototype 2-cell cavities show excellent performance of about 40 MV/m. However, heating problem exists on HOM couplers. Improvement of cooling is essential for stable CW operation. Input coupler is another big issue. High power test stand was constructed using a 300 kW klystron. Prototype couplers could deliver from several tens to a hundred kW of RF power. At main linac part, HOM damped 9-cell cavities are applied. Two prototype cavities were manufactured. Initially their performance was limited by field emission. But it was overcome and they reached to more than 20 MV/m. A prototype input coupler is also fabricated for main linac. It successfully propagates 25 kW standing wave and also thermal cycle tests were passed. Prototype HOM absorbers are also fabricated and several tests were carried out. For both parts, cryomodules are under construction. They will be completed in 2012.

Slides FRIOA06 [6.489 MB]

Paper	Title	Page
TUPO007	Development of STF Input Couplers for ILC	364
	M. Satoh, E. Kako, S. Noguchi, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan
	High power tests of the STF-Phase 1 cryomodule was carried out at KEK-STF (Superconducting RF Test facility) in 2008. Vacuum leaks at the cold ceramic window of STF-1 input couplers were found in the disassembly of the cryomodule after warm-up. It was considered that the vacuum leaks might be caused by the thermal cycles. Structures of brazing parts at a ceramic disk was investigated to reduce the thermal strain. The STF-2 input couplers with an improved brazing structure for S1-Global cryomodule was designed after the thermal cycle tests of the sample RF windows. The results of the thermal cycle tests of the sample RF windows and the high power performance of the improved STF-2 input couplers will be reported.
	Poster TUPO007 [1.034 MB]

TUPO029	Gradient Improvement by Removal of Identified Local Defects	436
	R.L. Geng, W.A. Clemens JLAB, Newport News, Virginia, USA C.A. Cooper Fermilab, Batavia, USA H. Hayano, K. Watanabe KEK, Ibaraki, Japan
	Funding: This work was authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177 Recent experience of ILC cavity processing and testing at Jefferson Lab has shown that some 9-cell cavities are quench limited at a gradient in the range of 15-25 MV/m. Further studies reveal that these quench limits are often correlated with sub-mm sized and highly localized geometrical defects at or near the equator weld. There are increasing evidence to show that these genetic defects have their origin in the material or in the electron beam welding process (for example due to weld irregularities or splatters on the RF surface and welding porosity underneath the surface). A local defect removal method has been proposed at Jefferson Lab by locally re-melting the niobium material. Several 1-cell cavities with known local defects have been treated by using the JLab local e-beam re-melting method, resulting in gradient and Q0 improvement. We also sent 9-cell cavities with known gradient limiting local defects to KEK for local grinding and to FNAL for global mechanical polishing. We report on the results of gradient improvements by removal of local defects in these cavities.

TUPO030	Status of the 9-Cell Superconducting Cavity R&D for ILC at Hitachi	439
	T. Watanuki, T. Semba, M. Watanabe Hitachi Ltd., Ibaraki-ken, Japan H. Hayano, E. Kako, S. Noguchi, T. Saeki, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan
	Hitachi is developing 9-cell superconducting cavities for ILC project in collaboration with KEK. We focus on electron beam welding (EBW) and plastic forming techniques. In 2010, Hitachi’s first 9-cell cavity without HOM couplers was completed successfully. Surface treatments and performance test of the cavity were carried out at KEK and the accelerating gradient reached 35.2 MV/m. We have undertaken the next 9-cell cavity with HOM couplers since January 2011. We will report the fabrication procedure and test result of first cavity and the current status of the next cavity.

TUPO032	Updates on R&D of Nondestructive Inspection Systems for SRF Cavities	447
	Y. Iwashita, H. Tongu Kyoto ICR, Uji, Kyoto, Japan H. Hayano, T. Saeki, K. Watanabe KEK, Ibaraki, Japan
	We are developing high resolution eddy current scan and High density Tmap and X-map. The high resolution eddy current scan showed 100 μm diameter hole with 50μm depth that was drilled on a Nb plate. The surface mount print circuit technology is applied to the high density Tmap and X-map devices, which will be ready soon to test at a vertical test bench. In addition, radiography using Xrays and neutrons are also under study. The results and status will be presented.
	Poster TUPO032 [2.362 MB]

WEIOB02	Cavity Inspection and Repair Techniques	598
	K. Watanabe, H. Hayano KEK, Ibaraki, Japan Y. Iwashita Kyoto ICR, Uji, Kyoto, Japan
	The cavity inspection and repair techniques are important to study a quality control of the superconducting rf cavity for better yield with high accelerating gradient. A high-resolution camera system was developed for optical inspection in 2008. It enables 2-D analysis by image processing on inner surface of the cavity. Therefore, the cause to limit the cavity performance can be categorized into a geometrical defect or an assembly work and the surface treatment. In addition, by perfoming the optical inspection at each treatment, we can obtain an information when a defect appeared. The cavities that quenched at the low field were inspected. One or few geometrical defects were found around quench location on some of these cavities. It is a possibility that the cavity performance can be recovered by removing the geometrical defect at the quench location. A local grinding machine was developed for this purpose. This method was tested on the 9-cell cavities, and we succeeded to recover the cavity performance with combination of local grinding and light EP. The method and results of the cavity inspection as well as the replica techniques will be presented in this talk.

THPO027	Optical Observation of Geometrical Features and Correlation With RFTest Results	773
	J. Dai, K. Zhao PKU/IHIP, Beijing, People's Republic of China R.L. Geng JLAB, Newport News, Virginia, USA K. Watanabe KEK, Ibaraki, Japan
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. Three kinds of geometrical features analysis techniques were adopted in association with cavity gradient R&D at Jefferson Lab: (1) Feature shape analysis by Kyoto camera system; (2) 3D shape analysis using a HIROX KH-7700 High Resolution Digital-Video Microscopy System; (3) Replica technique plus surface profiler for profile measurement of geometrical features. Up to now, many features were found in two nine cell SRF cavities: PKU2 from Peking University in China and NR1 from Niowave-Roark in America. Both of them have been RF tested at 2K. The shape analysis of geometrical surface features and correlation with RF test results using a thermal analysis code will be presented here. daijin@pku.edu.cn*

THIOA01	Test Results of the International S1-Global Cryomodule	615
	Y. Yamamoto, M. Akemoto, S. Fukuda, K. Hara, H. Hayano, N. Higashi, E. Kako, H. Katagiri, Y. Kojima, Y. Kondo, T. Matsumoto, H. Matsushita, S. Michizono, T. Miura, H. Nakai, H. Nakajima, K. Nakanishi, S. Noguchi, N. Ohuchi, T. Saeki, M. Satoh, T. Shidara, T. Shishido, T. Takenaka, A. Terashima, N. Toge, K. Tsuchiya, K. Watanabe, S. Yamaguchi, A. Yamamoto, K. Yokoya, M. Yoshida KEK, Ibaraki, Japan C. Adolphsen, C.D. Nantista SLAC, Menlo Park, California, USA T.T. Arkan, S. Barbanotti, M.A. Battistoni, H. Carter, M.S. Champion, A. Hocker, R.D. Kephart, J.S. Kerby, D.V. Mitchell, T.J. Peterson, Y.M. Pischalnikov, M.C. Ross, W. Schappert, B.E. Smith Fermilab, Batavia, USA A. Bosotti, C. Pagani, R. Paparella, P. Pierini INFN/LASA, Segrate (MI), Italy K. Jensch, D. Kostin, L. Lilje, A. Matheisen, W.-D. Möller, P. Schilling, M. Schmökel, N.J. Walker, H. Weise DESY, Hamburg, Germany
	S1-Global collaborative project by joint efforts of INFN, DESY, FNAL, SLAC and KEK, finished successfully at KEK- STF on February in 2011, is a crucial project for ILC. For this project, 8 SRF cavities, 2 from DESY, 2 from FNAL and 4 from KEK, were installed into one cryomodule with the thermal shields and the cooling pipes of liquid helium and nitrogen, cooled down to 2K totally three times, and cold-tested by using the three different frequency tuning systems (Blade tuner from INFN/FNAL, Saclay tuner from DESY and Slide-Jack tuner from KEK) and two types of input couplers (TTF III from DESY and STF#2 from KEK). During the cold test with high power, cavity performance, LFD (Lorentz Force Detuning) compensation by Piezo actuator, simultaneous 7 SRF cavities operation, dynamic heating loss measurement including static loss and DRFS (Distributed RF Scheme) operation with LLRF (Low Level RF) feedback system, were established successfully. In this talk, the results of the S1-Global cryomodule test are reported, discussed and summarized.
	Slides THIOA01 [11.254 MB]

FRIOA06	Construction of cERL Cryomodules for Injector and Main Linac	956
	K. Umemori, T. Furuya, E. Kako, S. Noguchi, H. Sakai, M. Satoh, T. Shishido, K. Watanabe, Y. Yamamoto KEK, Ibaraki, Japan E. Cenni Sokendai, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan K. Shinoe ISSP/SRL, Chiba, Japan
	The Compact ERL (cERL) project is advanced in Japan. Its aim is to demonstrate the circulation of 100 mA electron beams with energy of 35-200 MeV. Superconducting cavities are key components for realizing ERL. At injector part, electron beams are accelerated up to 5-10 MeV by three 2-cell cavities. Prototype 2-cell cavities show excellent performance of about 40 MV/m. However, heating problem exists on HOM couplers. Improvement of cooling is essential for stable CW operation. Input coupler is another big issue. High power test stand was constructed using a 300 kW klystron. Prototype couplers could deliver from several tens to a hundred kW of RF power. At main linac part, HOM damped 9-cell cavities are applied. Two prototype cavities were manufactured. Initially their performance was limited by field emission. But it was overcome and they reached to more than 20 MV/m. A prototype input coupler is also fabricated for main linac. It successfully propagates 25 kW standing wave and also thermal cycle tests were passed. Prototype HOM absorbers are also fabricated and several tests were carried out. For both parts, cryomodules are under construction. They will be completed in 2012.
	Slides FRIOA06 [6.489 MB]