Design and optimisation of the Compact Linear Collider main LINAC module for micron-level stability and alignment

The Compact Linear Collider (CLIC) study is developing a Multi-TeV $e^+e^-$ linear collider. An acceleration gradient of 100 MV m−1 will be achieved in the Main LINACs using 11.994 GHz Super Accelerating Structures (SAS). To achieve the required luminosity, the SAS will be prealigned within modules to less than 14 μm and maintain their position to within 1.4 μm when exposed to local sources of mechanical noise. A module design is presented and Finite Element Analysis (FEA) is used to optimise the harmonic frequencies of this module and thereby minimise the potential impact of unknown sources of vibration. A module with a fundamental frequency of 60 Hz is presented. Historical ground noise data from the LHC at CERN is used to statistically quantify the magnitude of SAS misalignments unavoidably induced by local ground noise. The one-standarddeviation average vertical misalignment due to ground noise is less than 0.044 μm above 0.1 Hz for all SAS.