Mobile CT system for in-situ inspection of the LHC at CERN

The world's biggest particle accelerator, the Large Hadron Collider (LHC) was recently commissioned at CERN. It was found that a condition monitoring system for its connecting elements would be useful. A monitoring system of this kind must be able to function without opening connecting elements, without breaking the vacuum, and without heating up the inspection sector as this would be too costly and time-consuming. Further, the system should be mobile in order to be applicable in all positions of the 27 km long accelerator. A radiographic system will be used, with the intention to get an identifiable image of all structures in the connecting elements of the accelerator. The minimum requirement is an image that enables an assessment of the structural integrity and correct position of all important components. 3D CT is the ideal solution, but owing to the limited space it is impossible to move an X-ray tube and detector completely around the connecting elements. A mobile 3D CT unit was therefore developed which enables maximum scanning variety within the given limits and provides 3D images based on a strongly limited range of scanning angles. The system is described in the paper, along with the results achieved so far and with an outlook onto further applications. (orig.)