SRF2015 - List of Authors (Nishiwaki, M.)

Paper	Title	Page
MOPB116	Developments of Horizontal High Pressure Rinsing for SuperKEKB SRF Cavities	443
	Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki KEK, Ibaraki, Japan
	The Q factors of the eight superconducting accelerating cavities gradually degraded during the long-term operation of the KEKB accelerator. Since we will re-use those SRF cavities for the SuperKEKB, the performance degradation will be a serious problem. Several cavities degraded their performance significantly at high accelerating fields. The Q degradation is still acceptable for the 1.5 MV operations at SuperKEKB. However, further degradation will make the operation difficult. In order to recover the cavity performance, we developed horizontal high pressure water rinsing (HHPR). This method uses a horizontal high pressure water nozzle and inserts it directly into the cavity module. We applied this method to two degraded cavities and their degraded Q factors recovered above 10⁹ at around 2 MV. In this paper we will present the HHPR method, high power test results after the HHPR and the residual gas analysis.
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THPB071	Developments of SiC Damper for SuperKEKB Superconducting Cavity	1289
	M. Nishiwaki, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, Y. Morita KEK, Ibaraki, Japan
	Upgrade works for SuperKEKB is in the final stage and the commissioning operation will start in this JFY. Eight superconducting accelerating cavities were operated for more than ten years at KEKB electron ring and are to be used at SuperKEKB. The cavity operation at those high current accelerators requires sufficient absorption of the beam-induced HOM power. In KEKB, the absorbed HOM power of 16 kW in two ferrite dampers attached to each cavity was achieved at the beam current of 1.4 A. On the other hand, the expected HOM power at SuperKEKB is calculated to be 37 kW in the beam current of 2.6 A. To cope with the HOM power issue, we developed additional HOM dampers made of SiC to be installed to the downstream of the cavity module. From precise calculations, it was found that the additional dampers reduce the HOM power loads of the ferrite dampers more effectively than the large beam pipe model of cavity module, which is another option to reduce the HOM loads. New SiC dampers were fabricated and high power-tested. Those SiC dampers successfully absorbed the expected HOM power. In this report, we will describe the results of calculations and high-power RF tests of new SiC dampers.
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Paper

Title

Page

Developments of Horizontal High Pressure Rinsing for SuperKEKB SRF Cavities

443

Y. Morita, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, M. Nishiwaki
KEK, Ibaraki, Japan

The Q factors of the eight superconducting accelerating cavities gradually degraded during the long-term operation of the KEKB accelerator. Since we will re-use those SRF cavities for the SuperKEKB, the performance degradation will be a serious problem. Several cavities degraded their performance significantly at high accelerating fields. The Q degradation is still acceptable for the 1.5 MV operations at SuperKEKB. However, further degradation will make the operation difficult. In order to recover the cavity performance, we developed horizontal high pressure water rinsing (HHPR). This method uses a horizontal high pressure water nozzle and inserts it directly into the cavity module. We applied this method to two degraded cavities and their degraded Q factors recovered above 10⁹ at around 2 MV. In this paper we will present the HHPR method, high power test results after the HHPR and the residual gas analysis.

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

THPB071

Developments of SiC Damper for SuperKEKB Superconducting Cavity

1289

M. Nishiwaki, K. Akai, T. Furuya, A. Kabe, S. Mitsunobu, Y. Morita
KEK, Ibaraki, Japan

Upgrade works for SuperKEKB is in the final stage and the commissioning operation will start in this JFY. Eight superconducting accelerating cavities were operated for more than ten years at KEKB electron ring and are to be used at SuperKEKB. The cavity operation at those high current accelerators requires sufficient absorption of the beam-induced HOM power. In KEKB, the absorbed HOM power of 16 kW in two ferrite dampers attached to each cavity was achieved at the beam current of 1.4 A. On the other hand, the expected HOM power at SuperKEKB is calculated to be 37 kW in the beam current of 2.6 A. To cope with the HOM power issue, we developed additional HOM dampers made of SiC to be installed to the downstream of the cavity module. From precise calculations, it was found that the additional dampers reduce the HOM power loads of the ferrite dampers more effectively than the large beam pipe model of cavity module, which is another option to reduce the HOM loads. New SiC dampers were fabricated and high power-tested. Those SiC dampers successfully absorbed the expected HOM power. In this report, we will describe the results of calculations and high-power RF tests of new SiC dampers.

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