SRF2015 - List of Authors (Umemori, K.)

Paper	Title	Page
TUPB021	Measurement of the Cavity Performances of Compact ERL Main Linac Cryomodule During Beam Operation	592
	H. Sakai, M. Egi, K. Enami, T. Furuya, S. Michizono, T. Miura, F. Qiu, K. Shinoe, K. Umemori KEK, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	We developed ERL main linac cryomodule for Compact ERL (cERL) in KEK. The module consists of two 9-cell 1.3 GHz superconducting cavities, two 20 kW high power coupler, two mechanical tuner and three HOM dampers. After construction of cERL recirculation loop, beam operation was started in 2013 Dec. First electron beam of 20 MeV successfully passed the main linac cavities. After adjusting beam optics, energy recovery operation was achieved. Main linac cavity was enough stable for ERL beam operation with digital LLRF system and energy recovery was successfully done with CW 80 uA beam. However, field emission was a problem for long term operation. In this paper, we express the measurement of the cavity performances of long term beam operation.
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WEBA06	Design Studies for Quarter-Wave Resonators and Cryomodules for the Riken SC-LINAC	976
	N. Sakamoto, O. Kamigaito, H. Okuno, K. Ozeki, K. Suda, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan H. Hara, K. Okihira, K. Sennyu, T. Yanagisawa MHI, Hiroshima, Japan E. Kako, H. Nakai, K. Umemori KEK, Ibaraki, Japan
	Recently we proposed a new project aimed at intensity upgrade of uranium beams of RIKEN RIBF. In this new project, construction of a superconducting linac is planned replacing the injector cyclotron so called RRC. The RIKEN superconducting linac consists of 14 cryomodules each of which contains four quarter-wave-resonators (QWRs) in each. The QWR operates at an rf frequency of 73 MHz in the continuous wave mode with beta as low as 0.055-1.008. A coaxial probe-type RF fundamental power-coupler which transmits RF power of several kW will be utilized for beam loading of 1.3 kW/resonator at the maximum with Qext of several x10⁶. Tuning of the resonant frequency will be realized with a mechanical tuner pressing the resonator wall in the direction parallel to the beam. This year, we started a development of a test cryomodule with SC-QWRs. In this paper, design studies for a SC-QWR and its cryomodule, e.g., QWR, coupler, and, tuner will be presented together with a construction schedule of the prototype. Prototyping of a superconducting cavity and its test cryomodule was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
	Slides WEBA06 [17.564 MB]
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THAA04	Comparison of Cavity Fabrication and Performances Between Fine Grains, Large Grains and Seamless Cavities	1006
	K. Umemori, H. Inoue, T. Kubo, H. Shimizu, Y. Watanabe, M. Yamanaka KEK, Ibaraki, Japan A. Hocker Fermilab, Batavia, Illinois, USA T. Tajima LANL, Los Alamos, New Mexico, USA
	In KEK-CFF, L-band SRF cavity fabrication studies have been actively proceeded. Main target of the R&D is investigation of cavity fabrication methods using different Nb materials. In this talk, we report mainly focus on the experiences obtained from single cell cavity fabrications. First, different Nb materials are compared, between fine grain Nb and large grain(LG) Nb from different vendors including low RRR LG Nb, in which, cavities were fabricated by electron beam welding method. Difficulty on LG cavity fabrication come from deformation due to stressed grain boundaries. In addition to nominal electron beam welded cavities, hydro-formed seamless cavities have been fabricated. Relatively large difference of equator and iris ratio cause difficulty on expansion of Nb pipes. Good qualified Nb pipe is essential and control of hydro-forming steps including annealing of materials is also important. In order to evaluate these cavity performances, vertical tests were carried out. Generally, they showed good performances. In this presentation, fabrication processes, technical difficulties, mitigation strategies and vertical test results are presented.
	Slides THAA04 [2.810 MB]
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THAA06	Precise Studies on He-Processing and HPR for Recovery From Field Emission by Using X-Ray Mapping System	1019
	H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori KEK, Ibaraki, Japan M. Sawamura JAEA, Ibaraki-ken, Japan
	We usually met the degradation of superconducting RF cavity on the cryomodule test and beam operation even if the performance of this cavity is good on the vertical test (V.T). Field emission is the most severe problem for this degradation after reassembly work from vertical test. Not only high pressure rinsing (HPR) but also He-processing, which is more suitable method without the reassembly work for recovery, is recommended and tried to recover this degradation. However, we did not investigate the details of how field emission sources were processed and removed after HPR and He-processing. We deeply investigated the processing procedure during He-processing and how many field emission sources removed after HPR by using rotating X-ray mapping system* in V.T . *H.Sakai et.al., Proc. of IPAC10 p2950-2952.
	Slides THAA06 [4.347 MB]
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THPB030	Fabrication and Evaluation of Low RRR Large Grain 1-Cell Cavity	1146
	H. Shimizu, H. Inoue, E. Kako, T. Saeki, K. Umemori, Y. Watanabe, M. Yamanaka KEK, Ibaraki, Japan
	Successive R&D studies of SRF cavities are ongoing at KEK by using existing facilities of Cavity Fabrication Facility (CFF) and other equipment of Superconducting Test facility (STF). Recently, there are studies on the low RRR of niobium material with high and uniform concentration of tantalum which could be used for the fabrication of high performance SRF cavity, and hence it could reduce the fabrication cost of cavities [1]. In order to confirm the advantage of the material, a large-grain single-cell cavity was fabricated at CFF/KEK with sheets sliced from a low RRR niobium ingot with high and uniform concentration of tantalum. The resistivity measurement of sample from sliced sheet showed the RRR value of 100, whereas it is about 400 for the nominal qualification of fine-grain sheets at KEK. The low RRR large-grain single-cell cavity was already fabricated at CFF/KEK. The quality control of the fabrication processes are well under control. Then several vertical tests of the cavity were done at STF/KEK. In this presentation, the results of the vertical tests are shown. The potential of the low RRR niobium material for SRF cavity are discussed. *P.Kneisel et al, NIM A774(2015)133
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THPB041	Hydroforming SRF Cavities from Seamless Niobium Tubes	1176
	M. Yamanaka, H. Inoue, H. Shimizu, K. Umemori KEK, Ibaraki, Japan A. Hocker Fermilab, Batavia, Illinois, USA T. Tajima LANL, Los Alamos, New Mexico, USA
	The authors are developing the manufacturing method for super conducting radio frequency (SRF) cavities by using a hydroforming instead of an electron beam welding, which is the major manufacturing method. We expect a cost reduction by hiring the hydroforming. To realize this development, getting a high-purity seamless niobium tube with good forming ability and an advancement of hydroforming technique are necessary. We got the seamless niobium tube made by ATI Wah Chang with the cooperation of Fermilab, and succeeded to manufacture the 1-cell cavity by hydroforming. The accelerating gradient attained to 36 MV/m, and we confirmed it was available to use as the SRF cavity.
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THPB059	Design, Fabrication and Performance of SRF-Gun Cavity	1243
	T. Konomi, E. Kako, Y. Kobayashi, K. Umemori, S. Yamaguchi KEK, Ibaraki, Japan R. Matsuda Mitsubishi Heavy Industries Ltd. (MHI), Takasago, Japan T. Yanagisawa MHI, Hiroshima, Japan
	The development of superconducting RF gun has been started at KEK. The performance targets are that average current is 100 mA, normalized emittance is less than 1 μm.rad, beam energy is 2 MeV and energy spread is less than 0.1 %. The SRF gun consists of 1.3 GHz and 1.5 cell elliptical cavity and backward illuminated photocathode. The cavity shape was designed by using SUPERFISH and GPT. The cavity has been fabricated by Japanese industry. Accelerating field tuning and vertical test without cathode plug was done. The surface peak electric field reached 66 MV/m, and this meet the target value 42 MV/m sufficiently. For next vertical test, cathode rod without photocathode is in preparation. In the workshop, the SRF-Gun concepts and vertical test results will be reported.
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THPB084	Design of Input Coupler for RIKEN Superconducting Quarter-Wavelength Resonator	1335
	K. Ozeki, O. Kamigaito, H. Okuno, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada RIKEN Nishina Center, Wako, Japan E. Kako, H. Nakai, K. Umemori KEK, Ibaraki, Japan K. Okihira, K. Sennyu, T. Yanagisawa MHI, Hiroshima, Japan
	In RIKEN Nishina Center, for the purpose of development of elemental technology for the superconducting linear accelerator, the designing and construction of accelerator system based on superconducting quarter-wavelength resonator are carried out. The basic designs of the input coupler are as follows: The resonance frequency of the cavity is 75.5 MHz and assumed beam loading is about 1 kW. Double vacuum windows, which are disk-type, are adopted. A thermal anchor of 40 K is installed near the cold-window. The optimum positions of the cold-window and the thermal anchor depending on the effective RRR of copper-plate are being studied. In this contribution, the details of these designs will be reported. This work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).
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Paper

Title

Page

Measurement of the Cavity Performances of Compact ERL Main Linac Cryomodule During Beam Operation

592

H. Sakai, M. Egi, K. Enami, T. Furuya, S. Michizono, T. Miura, F. Qiu, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

We developed ERL main linac cryomodule for Compact ERL (cERL) in KEK. The module consists of two 9-cell 1.3 GHz superconducting cavities, two 20 kW high power coupler, two mechanical tuner and three HOM dampers. After construction of cERL recirculation loop, beam operation was started in 2013 Dec. First electron beam of 20 MeV successfully passed the main linac cavities. After adjusting beam optics, energy recovery operation was achieved. Main linac cavity was enough stable for ERL beam operation with digital LLRF system and energy recovery was successfully done with CW 80 uA beam. However, field emission was a problem for long term operation. In this paper, we express the measurement of the cavity performances of long term beam operation.

Export •

reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

WEBA06

Design Studies for Quarter-Wave Resonators and Cryomodules for the Riken SC-LINAC

976

N. Sakamoto, O. Kamigaito, H. Okuno, K. Ozeki, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
H. Hara, K. Okihira, K. Sennyu, T. Yanagisawa
MHI, Hiroshima, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan

Recently we proposed a new project aimed at intensity upgrade of uranium beams of RIKEN RIBF. In this new project, construction of a superconducting linac is planned replacing the injector cyclotron so called RRC. The RIKEN superconducting linac consists of 14 cryomodules each of which contains four quarter-wave-resonators (QWRs) in each. The QWR operates at an rf frequency of 73 MHz in the continuous wave mode with beta as low as 0.055-1.008. A coaxial probe-type RF fundamental power-coupler which transmits RF power of several kW will be utilized for beam loading of 1.3 kW/resonator at the maximum with Qext of several x10⁶. Tuning of the resonant frequency will be realized with a mechanical tuner pressing the resonator wall in the direction parallel to the beam. This year, we started a development of a test cryomodule with SC-QWRs. In this paper, design studies for a SC-QWR and its cryomodule, e.g., QWR, coupler, and, tuner will be presented together with a construction schedule of the prototype. Prototyping of a superconducting cavity and its test cryomodule was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

Slides WEBA06 [17.564 MB]

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THAA04

Comparison of Cavity Fabrication and Performances Between Fine Grains, Large Grains and Seamless Cavities

1006

K. Umemori, H. Inoue, T. Kubo, H. Shimizu, Y. Watanabe, M. Yamanaka
KEK, Ibaraki, Japan
A. Hocker
Fermilab, Batavia, Illinois, USA
T. Tajima
LANL, Los Alamos, New Mexico, USA

In KEK-CFF, L-band SRF cavity fabrication studies have been actively proceeded. Main target of the R&D is investigation of cavity fabrication methods using different Nb materials. In this talk, we report mainly focus on the experiences obtained from single cell cavity fabrications. First, different Nb materials are compared, between fine grain Nb and large grain(LG) Nb from different vendors including low RRR LG Nb, in which, cavities were fabricated by electron beam welding method. Difficulty on LG cavity fabrication come from deformation due to stressed grain boundaries. In addition to nominal electron beam welded cavities, hydro-formed seamless cavities have been fabricated. Relatively large difference of equator and iris ratio cause difficulty on expansion of Nb pipes. Good qualified Nb pipe is essential and control of hydro-forming steps including annealing of materials is also important. In order to evaluate these cavity performances, vertical tests were carried out. Generally, they showed good performances. In this presentation, fabrication processes, technical difficulties, mitigation strategies and vertical test results are presented.

Slides THAA04 [2.810 MB]

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THAA06

Precise Studies on He-Processing and HPR for Recovery From Field Emission by Using X-Ray Mapping System

1019

H. Sakai, K. Enami, T. Furuya, M. Satoh, K. Shinoe, K. Umemori
KEK, Ibaraki, Japan
M. Sawamura
JAEA, Ibaraki-ken, Japan

We usually met the degradation of superconducting RF cavity on the cryomodule test and beam operation even if the performance of this cavity is good on the vertical test (V.T). Field emission is the most severe problem for this degradation after reassembly work from vertical test. Not only high pressure rinsing (HPR) but also He-processing, which is more suitable method without the reassembly work for recovery, is recommended and tried to recover this degradation. However, we did not investigate the details of how field emission sources were processed and removed after HPR and He-processing. We deeply investigated the processing procedure during He-processing and how many field emission sources removed after HPR by using rotating X-ray mapping system* in V.T .
*H.Sakai et.al., Proc. of IPAC10 p2950-2952.

Slides THAA06 [4.347 MB]

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THPB030

Fabrication and Evaluation of Low RRR Large Grain 1-Cell Cavity

1146

H. Shimizu, H. Inoue, E. Kako, T. Saeki, K. Umemori, Y. Watanabe, M. Yamanaka
KEK, Ibaraki, Japan

Successive R&D studies of SRF cavities are ongoing at KEK by using existing facilities of Cavity Fabrication Facility (CFF) and other equipment of Superconducting Test facility (STF). Recently, there are studies on the low RRR of niobium material with high and uniform concentration of tantalum which could be used for the fabrication of high performance SRF cavity, and hence it could reduce the fabrication cost of cavities [1]. In order to confirm the advantage of the material, a large-grain single-cell cavity was fabricated at CFF/KEK with sheets sliced from a low RRR niobium ingot with high and uniform concentration of tantalum. The resistivity measurement of sample from sliced sheet showed the RRR value of 100, whereas it is about 400 for the nominal qualification of fine-grain sheets at KEK. The low RRR large-grain single-cell cavity was already fabricated at CFF/KEK. The quality control of the fabrication processes are well under control. Then several vertical tests of the cavity were done at STF/KEK. In this presentation, the results of the vertical tests are shown. The potential of the low RRR niobium material for SRF cavity are discussed.
*P.Kneisel et al, NIM A774(2015)133

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THPB041

Hydroforming SRF Cavities from Seamless Niobium Tubes

1176

M. Yamanaka, H. Inoue, H. Shimizu, K. Umemori
KEK, Ibaraki, Japan
A. Hocker
Fermilab, Batavia, Illinois, USA
T. Tajima
LANL, Los Alamos, New Mexico, USA

The authors are developing the manufacturing method for super conducting radio frequency (SRF) cavities by using a hydroforming instead of an electron beam welding, which is the major manufacturing method. We expect a cost reduction by hiring the hydroforming. To realize this development, getting a high-purity seamless niobium tube with good forming ability and an advancement of hydroforming technique are necessary. We got the seamless niobium tube made by ATI Wah Chang with the cooperation of Fermilab, and succeeded to manufacture the 1-cell cavity by hydroforming. The accelerating gradient attained to 36 MV/m, and we confirmed it was available to use as the SRF cavity.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB059

Design, Fabrication and Performance of SRF-Gun Cavity

1243

T. Konomi, E. Kako, Y. Kobayashi, K. Umemori, S. Yamaguchi
KEK, Ibaraki, Japan
R. Matsuda
Mitsubishi Heavy Industries Ltd. (MHI), Takasago, Japan
T. Yanagisawa
MHI, Hiroshima, Japan

The development of superconducting RF gun has been started at KEK. The performance targets are that average current is 100 mA, normalized emittance is less than 1 μm.rad, beam energy is 2 MeV and energy spread is less than 0.1 %. The SRF gun consists of 1.3 GHz and 1.5 cell elliptical cavity and backward illuminated photocathode. The cavity shape was designed by using SUPERFISH and GPT. The cavity has been fabricated by Japanese industry. Accelerating field tuning and vertical test without cathode plug was done. The surface peak electric field reached 66 MV/m, and this meet the target value 42 MV/m sufficiently. For next vertical test, cathode rod without photocathode is in preparation. In the workshop, the SRF-Gun concepts and vertical test results will be reported.

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reference for this paper to ※ BibTeX, ※ LaTeX, ※ Text, ※ RIS/RefMan, ※ EndNote (xml)

THPB084

Design of Input Coupler for RIKEN Superconducting Quarter-Wavelength Resonator

1335

K. Ozeki, O. Kamigaito, H. Okuno, N. Sakamoto, K. Suda, Y. Watanabe, K. Yamada
RIKEN Nishina Center, Wako, Japan
E. Kako, H. Nakai, K. Umemori
KEK, Ibaraki, Japan
K. Okihira, K. Sennyu, T. Yanagisawa
MHI, Hiroshima, Japan

In RIKEN Nishina Center, for the purpose of development of elemental technology for the superconducting linear accelerator, the designing and construction of accelerator system based on superconducting quarter-wavelength resonator are carried out. The basic designs of the input coupler are as follows: The resonance frequency of the cavity is 75.5 MHz and assumed beam loading is about 1 kW. Double vacuum windows, which are disk-type, are adopted. A thermal anchor of 40 K is installed near the cold-window. The optimum positions of the cold-window and the thermal anchor depending on the effective RRR of copper-plate are being studied. In this contribution, the details of these designs will be reported. This work was funded by ImPACT Program of Council for Science, Technology and Innovation (Cabinet Office, Government of Japan).

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