SRF2017 - List of Authors (Masuzawa, M.)

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)

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)