New design proposal for an image slicer prototype: vibration tests and finite element calculations

During the IFU prototype study that the laboratory led for ESA in the frame of the JWST/NIRSpec technological development studies in 2004, an optomechanical concept was realized and tested at the laboratory. As some limitations of this design were demonstrated, the laboratory decided to develop a new concept of optomechanical interface to support glass image slicers, compliant with space environment specifications. This development was conducted in a very short time and with a tiger team. This prototype was designed and realized at LAM. It consists in an invar monolithic mechanical mount (including three blades) supporting an assembly of three zerodur optical parts tight together thanks to optical contact. The interface between invar and zerodur is done with glue. This prototype has been qualified at 10.5 g rms and 77K. It demonstrates the stability of the optical part within +/- 9 arcsec. The test campaign points up the evolution of the glue properties during time and thermal cycles. Thanks to a detailed FEM analysis, the change of the glue material damping has been estimated.