1. HLS Installation at KEKB Main Ring after the Great East Japan Earthquake Takashi Kawamoto, Mika Masuzawa, Ryuhei Sugahara High Energy Accelerator Research Organization (KEK), 1-1 Oho, Tsukuba, Ibaraki 305-0801 Japan Fig.4: Measurement of KEKB tunnel levels Fig.5.1: Level (after the quake) - level (before the quake) Fig.5.3: Adding up levels(after quake) - adding up levels(before quake) Fig.2: Crack on an expansion joint KEK Epicenter Fig.1: Great East Japan Earthquake (Mar.11, 2011) JMA seismic intensity is 6- at Tsukuba Fig.5.2: Adding up levels (red: after the quake, blue: before the quake) Fig.5.4: Level transition(2001 ~ 2009) Level measurement takes a lot of time! Introduced HLS (Hydrostatic Leveling System). （ Fig.6 ） Continuous measurement is possible. 1 st stage: 190m, 10 sensors (Jul.2011 ~ Jan.2012) 2 nd stage: 330m, 8 sensors & 210m, 5 sensors (Apr.2012 ~ ) Fig.6: HLS installed area Fuji straight section Oho straight section HLS sensor HLS specs Temperature(ground) Temperature(tunnel) Tide level Fig.7: HLS outputs, temperature & tide level Coupling of the KEKB tunnel and the PS building is a concern. Is the soil surrounding the KEKB tunnel firm enough? Any sign of liquefaction of the ground caused by the earthquake? Fig.3: Gaps of expansion joints were changed by earthquakes. Earth quakes Gap motion [mm] Magnets of the KEKB accelerator were out of alignment due to the Great East Japan Earthquake? Many expansion joints of KEKB tunnel were damaged, (Fig.2) and gaps of joints were changed by earthquakes. (Fig.3) Measured KEKB tunnel levels again. (Fig.4) Compared with levels measured before the Great East Japan Earthquake. (Fig.5) Due to effects of the Great East Japan Earthquake, it was expected that the KEKB accelerator electromagnets would be out of alignment. Therefore we surveyed the level of the KEKB tunnel and compared it with data taken before the earthquake. As a result, large displacements were observed in many places. Because it was thought that the tunnel level was still varying after the earthquake, we introduced a system called HLS (Hydrostatic Leveling System) and decided to measure the level continuously. Here, we report the results of the level survey and the level displacement observed by HLS. Crane truck arrived here and left here Loading of RF cavities It has been observed that the south arc is very sensitive to activities above ground, such as loading and unloading in the truck yard above the tunnel. (Fig.9) HLS detected tide level, but is affected by ground temperature. (Fig.7) And HLS sometimes observed level shift of KEKB tunnel, caused by earthquakes. (Fig.8) Fig.8 : Level shift of KEKB tunnel caused by a earthquake (May 18, 2012, JMA seismic intensity is 3 at Tsukuba) Fig.9: Level shift of KEKB tunnel caused by heavy load above the tunnel. Crane truck: 40t Truck: 4t Load: RF cavity (~4t x 4 times) KEKB tunnel was built under the Proton Synchrotron (PS) linac building. The space between the building and the KEKB tunnel was filled with excavated soil and sand. ↓ Fig.10: KEKB tunnel goes under the PS linac building. An RF cavity was divided to 4 parts and loaded on a truck just above #7 sensor. The tunnel is too sensitive to activity above ground! Will this kind of coupling hurt the SuperKEKB beam operation? KEKEpicenter Tsukuba Oho Fuji Nikko Tsukuba Refer to Hiroshi Yamaoka, et al., “Investigation of vibrational properties of the KEKB tunnel after the Great East Japan Earthquake” (IWAA2012)