Study and development of a laser based alignment system for the compact linear collider

The first objective of the PhD thesis is to develop a new type of positioning sensor to align components at micrometre level over 200 m with respect to a laser beam as straight line reference. The second objective is to estimate the measurement accuracy of the total alignment system over 200 m. The context of the PhD thesis is the Compact Linear Collider project, which is a study for a future particle accelerator. The proposed positioning sensor is made of a camera and an open/close shutter. The sensor can measure the position of the laser beam with respect to its own coordinate system. To do a measurement, the shutter closes, a laser spot appears on it, the camera captures a picture of the laser spot and the coordinates of the laser spot centre are reconstructed in the sensor coordinate system with image processing. Such a measurement requires reference targets on the positioning sensor. To reach the rst objective of the PhD thesis, we used laser theory and cam- era model to de ne an accurate image processing and we performed experiments to validate a prototype of a positioning sensor. For the second objective, we could not obtain results regarding measurement accuracy because we could not develop a full alignment system under vacuum over 200 m. However, we could estimate laser pointing stability over 200 m by extrapolating results obtained over 12 m. As a result, we present in this report a sensor design, a calibration protocol and estimations regarding measurement uncertainty. In case of a separate cali- bration with theodolites, we estimated the measurement uncertainty of the po- sitioning sensor to be 4 μ m for all coordinates. In case of a full auto-calibration, we estimated the measurement uncertainty of the positioning sensor to be 10 μ m for the radial and the vertical coordinates and 20 μ m for the depth coordinate. Concerning the extrapolation over long distance, we estimated laser pointing stability to be 10 μ m for a laser beam propagation distance of 200 m. Our work does not provide a complete laser beam alignment system at mi- crometre level over 200 m but it is the rst necessary step towards it.