Industrialization of LHC main quadrupole cold masses up to series production

Whereas the prototypes of the main quadrupoles had been pursued at CEA Saclay under contract with CERN, the contract to build all MQ magnets and the complete cold masses had been placed with ACCEL Instruments GmbH. After careful evaluation of design concepts and fabrication processes some revisions have been introduced to ease an industrial fabrication of the 400 MQ magnets and cold masses to be delivered to CERN. First batches of magnets were successfully cold tested. We report about the upgrading of the fabrication facility including the MQ specific layout of all machinery, the upgrading and qualifying of personnel resources and processes, the technical performance of the products and main activities and experiences on the way to series production.     

Compact optical position feedback scheme for MOEMS mirrors

Recently, we have realized a novel, very compact position sensing device for MOEMS mirrors, which is based on the measurement of a reflected light beam with a quadrant diode. This scheme is applicable to arbitrary trajectories and in this work we present the characteristics of this device, showing experimental results obtained with a test set-up, but also theoretical considerations and optical ray-tracing simulations.     

MOEMS translatory actuator characterisation,position encoding and closed-loop control

Recent developments in optical micro-electro-mechanical systems (MEMS) have produced rapidly oscillating translatory micro-mirrors with out-of-plane mirror displacements exceeding ±100 μm, which have a great potential for various applications requiring high-speed optical path difference modulation. A key factor affecting their practical applicability is a reliable operation control of the MEMS element. Presented here is a pro-active solution combining a laser reference interferometer with a novel position detection scheme and a dedicated control circuitry. By demodulating and processing the laser reference signal, the zero-crossing point of the moving MEMS device can be detected with an accuracy of one interference fringe only. This allows generating a highly accurate mirror control signal in real-time, enabling the implementation of a unique closed-loop control of such MEMS devices and thus ensuring optimally stable MEMS operation and maximal mechanical amplitudes even under varying environmental conditions. The presented solution so provides a vital step forward in the real-world deployment of optical systems using translatory micro-devices.