Straightness Measurement of Long Cylinder for Construction of Linear Collider

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The purpose of this study is to develop an accurate straightness measuring system for the purpose of constructing a next generation of linear collider. This linear collider is approximately 20km in length and is going to be constructed by aligning components consisting of three cylinders with a length of 1.5m. To construct the entire linear collider straight enough, it is necessary to align each component with a straightness in approximately 10 microns. For this purpose, an accurate measurement system, which can measure the straightness of long cylinders up to 5 m with an accuracy of several microns, must be established. Considering the ratio of accuracy to length and the measuring environment, scanning probe technique is the only approach to satisfy this request. In this study, a new scanning multi-probe method for accurately measuring straightness profiles has been developed. This scanning probe method is developed from the traditional three-probe method, which can measure the profil … More e accurately without the influence of motion errors of the scanning stage. In the three-probe method, zero-adjustment errors between probes are the largest error source, and so far there was no good methods to accurately adjust the zero-adjustment error. In this study, a new method was proposed, in which two sets of three-probe method sensor units are used. The two sensor units are placed in the two sides of the collider component and are used to scan the two opposed generatrices of the component simultaneously. One of the cylinders in the component is then rotated 180 degrees and scanned by the probe units again. The zero-adjustment error, as well as the straightness profiles of the component can be accurately evaluated from the output data of the two measurements. An experimental setup based on the proposed method was constructed to measure the collider component of 5m in length. Six capacitance probes with a resolution of several nanometers were employed. The probe distance was set to be 150 mm. The straightness of the entire component was measured with an accuracy of several microns, and this indicated the feasibility of the developed straightness measuring system. Less