Alignment of heavy ion therapy center vertical terminal

Wuwei heavy ion therapy center is the first Chinese heavy ion accelerator facility developed for cancer therapy, in which four terminals are distributed and the height of the vertical terminal is up to 18 m. Installation units of vertical terminal are diverse and complex, moreover, these units present poor alignment visibility. Thereby, it is difficult to perform the alignment among these components. Based on the laser tracker and high precision three-dimensional surveying control network, this paper proposes an efficient alignment method using multiple conversion of magnet fiducial data and pre-alignment of complex magnet unit. All the components are successfully aligned, and meanwhile the installation efficiency of vertical terminals is improved. Alignment accuracy of magnets is less than 0.1 mm. Error analysis presents that this alignment method achieves its goal.