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IMPEDANCE MEASUREMENTS OF RF CAVITIES IN J-PARC SYNCHROTRONS
Masahiro Nomura#, Fumihiko Tamura, Alexander Schnase, Masanobu Yamamoto, Katushi Hasegawa, Taihei Shimada,
Keigo Hara, Makoto Toda, Chihiro Ohomori, Masahito Yoshii
KEK and JAEA J-PARC center
2-4 Shirakata-Shirane, Tokai, Ibaraki, 319-1195, Japan
Abstract J-PARC 3 GeV RCS and 50 GeV MR employ Magnetic Alloy (MA) loaded RF cavities to achieve a high
accelerating voltage. RCS RF cavities employ MA un-cut cores and MR RF cavities use MA cut cores. We observed the impedance reductions of the RCS RF cavities due to the MA core buckling. The MA core buckling was caused by the thermal stress that was enhanced due to the impregnation with low viscosity epoxy resin. We improved the MA cores by avoiding the low viscosity epoxy resin impregnation and replaced MA cores in three RF cavities with them. Up to now, we don't observe the impedance reduction of those three RF cavities due to the core buckling. We have a plan to finish the replacement with cores without the low viscosity epoxy resin in the remaining eight RF cavities by 2013. MR RF cavities showed the impedance reductions caused by the corrosion on the MA core cutting surfaces. The copper ions in the cooling water from copper hollow conductors of the main magnets accelerated the corrosion process. To solve the issue of cutting surface corrosion, we have two different approaches. One is improving the cooling water quality. We plan to separate the cooling system of the RF cavities from the main magnets by the end of November. Another is coating of cutting surfaces to prevent rusting. The coating on the cutting surface with inorganic polymer was effective against rusting. We also observed the effectiveness of sealing the whole cutting parts with RTV gum from cooling water. We also report how the RF systems were affected by the great East Japan earthquake.
J-PARC RF
1. J-PARC (RCS, MR) RF
RCS MRQ 0.6 26
RCSMR
2011 3 11
2. RCS RCS 2007 9
4 RF 1 2
1 27 4 5 1
J-PARC MA 18 m35mm
[1]
4 57 4 5
( )
1
32~3
2013
____________________________________________ # [email protected]
Proceedings of the 8th Annual Meeting of Particle Accelerator Society of Japan (August 1-3, 2011, Tsukuba, Japan)
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1: RF 1 6
()
2: RF 7 11
1
3. MR
MR 2008 122
MR 3
3: MR
31 4 1
RF12
3 4 6
3 6
13 4
64 6
4 5
63 6
67
4: MR 1
Proceedings of the 8th Annual Meeting of Particle Accelerator Society of Japan (August 1-3, 2011, Tsukuba, Japan)
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5: MR 4
6: MR 3 6
FRPRTV
89
6 3 6
RTV
RTV4
RTV
MR
7 8 12
7: 6
8: FRP RTV
9: MR 2
RTV
4. RCS RF
MR OFFRF
RCS
Proceedings of the 8th Annual Meeting of Particle Accelerator Society of Japan (August 1-3, 2011, Tsukuba, Japan)
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11 2 IGBT 1IGBT 1 15IGBT 10
RCS
11MR
RF RF
11
10: IGBT
11:
5. RCS (
) 4 5 7
12 22013
MR
RF12
RTV
RTV
MR7 8
RFRCS
IGBT RCS11
MR
RF
[1] M. Nomura et al., " The origin of Magnetic Alloy
core buckling in J-PARC 3GeV RCS ", Nuclear Instruments and Methods in Physics Research A 623 (2010) 903–909.
Proceedings of the 8th Annual Meeting of Particle Accelerator Society of Japan (August 1-3, 2011, Tsukuba, Japan)
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