3D Measurement of the Inner Shape of a 1-Cell Accelerator Cavity

We strive to develop a 3D coordinate measuring machine, which is able to measure the inner shape of intricately-shaped accelerator cavities. At present day, the ILC (International Linear Collider) project is progressing through international collaboration. The major goal of ILC is to produce and investigate Higgs bosons. ILC consists of two linear accelerators facing each other, and will hurl electrons and positrons toward each other at nearly the speed of light. Accelerator cavities are important components to accelerate particles to near light speed. A cavity’s inner shape influences the accelerating performance. Therefore, it is important to measure the inner 3D shape of a cavity. However, it is difficult to measure the inner shape of cavities with complex shapes. Additionally, we must measure them without contact because a micro defect on the surface causes serious degradation of performance. We are developing inner shape measuring machine with high accuracy using triangulation method. However, optical condition of the internal surface is bad for precision measurement. Therefore, we have to improve accuracy. In order to measure precisely, we developed calibration system using a cylindrical artefact. In this paper, we measured inner 3D shape of a one-cell cavity. Final goal is to measure 9-cell cavities.