SRF2017 - List of Authors (Okada, T.)

Paper	Title	Page
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)

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)

Paper

Title

Page

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)

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)