Mateusz Sosin

Position Monitoring System for HL-LHC Crab Cavities

The high luminosity upgrade for the LHC at CERN (HL-LHC project) will extend the discovery potential of the LHC by a factor 10. It relies on key innovative technologies like superconducting cavities for beam rotation, named “crab cavities”. Two crab cavities will be hosted in a superconducting cryostat working at a cold (<3 K). The position of each cavity will be monitored during the cool-down and the operation in order to comply with the tight alignment tolerances: the misalignment of a cavity axis w.r.t. the other will have to be lower than 0.5 mm and each cavity roll w.r.t. the cryostat axis will have to be lower than 1 mrad. Moreover, the monitoring system will have to be radiation hard (up to 10 MGy) and maintenance free. We propose a solution based on the Frequency Scanning Interferometry to provide the position monitoring of the crab cavities. This paper describes the design and study of such a solution, including the engineering approach, the issues encountered and the lessons learnt.

Integration and Testing of 3 Consecutive CLIC Two-Beam Modules

CLIC (Compact LInear Collider) is a study of a 50 km long linear electron-positron collider, consisting of approximately 20,000 repetitive 2 m long modules. Micron level manufacturing and alignment tolerances are required for the RF and magnet components due to the nanometre beam size and luminosity goal. The effect of thermal, vacuum and mechanical loads needs to be assessed, both in transient and in steady state conditions. The dynamic behaviour of mock-ups was investigated on the prototype two-beam module. Two additional two-beam modules are installed to further investigate the interconnections between them, in a machine-like environment. The array of three consecutive modules allows for alignment tests of the module sequence, while thermal and vacuum tests can be executed simultaneously. A transportation experiment is foreseen, investigating the feasibility of installing prealigned modules. Finally, new design of components is being tested, based on the experience gathered from the first module and leading to a new generation module.