Dynamic short- and large-coherence interferometry to characterize the induced vibrations and topology change of the cryogenic mirror of the Einstein Telescope prototype
Jesús Vilaboa Pérez (Université de Liège)
J. Loicq (TU Delft - Spaceborne Instrumentation)
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Abstract
The E-TEST project builds a prototype for the Einstein Telescope (ET). ET is a proposed gravitational-wave observatory. E-TEST includes a silicon mirror of 30 cm up to 40 cm diameter, suspended and cooled down at cryogenic temperatures from 20 K to 30 K. During the cooling down, the mirror will be affected by surface topology changes, wavefront deformation, and induced vibrations. We present a metrology device based on short-coherence interferometry to characterize the mirror surface with a sub-nanometer resolution. We design an innovative phase mask to achieve dynamic or single-frame white light interferometry. Moreover, we discuss different interferogram analysis methods. We also discuss the implementation of a long-coherence source to facilitate the measurements with the low-coherence source.