The alignment of the accelerator modules of the Cool Copper Collider C³ with the Rasnik 3-point alignment syste

For C³, some 2000 accelerator modules must be 5D positioned, within 10 µm transversal, on a 2.3 km long straight line, for both linacs. In the Rasnik alignment system, light from a point-like monochromatic source falls on a zone lens, forming a Fraunhofer diffraction pattern on an image pixel sensor. The alignment of three objects can be obtained by analyzing the position of the diffraction pattern on the sensor. The alignment of a large number of objects can be realized by fixing a stick on each object, carrying all three Rasnik components. With this leap frog geometry, all sticks are mutually coupled, forming a multipoint alignment system.

The system should operate in ambient air, in vacuum, and in liquid nitrogen. Due to the heat dissipation of these components, bubbles are formed, causing an error in the measured alignment when crossing the optical path. Various methods of beam shielding are presented. With the Quarter Cryo Module (QCM), essential studies will be carried out, enabling the realization of C³. The QCM will be equipped with four Rasnik chains, measuring alignment parameters with redundancy. In addition, the bubble-induced vibrations of the accelerator components can be registered accurately.