Large-scale accelerator alignment using an inclinometer

• 71-m-long straightness was evaluated with standard deviations of less than 49 μm.
• The derived straightness was in good agreement with the other results.
• Reversal measurements were effective in eliminating offsets and drifts of our system.
• The estimated errors agree well with the obtained ones.
• This method can be applied for several hundred-meter-long objects.

A precise inclinometer (Talyvel 4) was adopted for evaluating aligning straightness of the first 71 m of the KEK electron/positron injector linear accelerator (linac). The straightness could be evaluated with a standard deviation of less than 49 μm. It is in good agreement with those obtained using a conventional alignment telescope and our laser-based alignment system.Error estimation based on the rules of error propagation shows that shape evaluation with a standard deviation of 0.3 mm for a distance of 500 m can be achieved using the proposed method. It indicates that this method is suitable for evaluating straightness of several hundred meters of linacs with sub-millimeter of accuracy.