抄録
In order to establish a method for aligning the structures of large linear particle accelerators, i.e., to evaluate straightness within sub-millimeter accuracy for a length of several kilometers, straightness measurement using the 3-point method with zero adjustment has been studied. This method uses 2 sets of 3 displacementmeters facing each other and eliminates their zero differences by reversal method. Here, the obtained profiles are not affected by zero differences or their fluctuations with two restrictions. The first is that the distance between at least one set of 2 displacementmeters facing each other is stable. The other is that the zero differences should be reproducible. This has been analytically and experimentally confirmed. Then, the meanings of these two restrictions are considered and the conditions that are applied to general straightness measurements are explained.
