Deformation of J-PARC linac after the Tohoku earthquake in Japan

Morishita, Takatoshi  ; Asano, Hiroyuki; Ikegami, Masanori*

J-PARC linac has finalized its precise alignment at the end of summer 2006, and the beam provision to the RCS has been started at Sept. 2007. Since then, the deformation of the accelerator tunnel is small enough to keep the soundness of the alignment accuracy in the beam operation. Therefore, the linac has been operated without re-alignment of the accelerator components for these four years. However, the alignment has seriously been damaged due to the large earthquake at Mar. 11th, 2011 in eastern Japan. There has been observed more than 40 mm settlement and about 25 mm jackknife - like deformation horizontally at the straight section in the linac accelerator tunnel. After that earthquake, there continued a directional settlement in the straight section for two months. Now, re-alignment started for restoration of linac alignment. In this report, the deformation of the linac tunnel floor due to the earthquake is reported. We also report the stability of the tunnel floor.