An experiment for developing a micro-crack alert system for large thin mirror

摘要

We have a plan to install a micro-crack alert system for the primary mirror of Subaru Telescope based on the monitoring of the acoustic emission from any incident events. We report the results of our preliminary experiment for characterizing the acoustic properties of actual Subaru primary mirror. The attenuation of acoustic wave was confirmed to be small enough to allow detection of such events at any locations of the mirror. The position of incident events that might lead to the generation of possible micro-cracks can be identified within less than 3 cm accuracy by placing seven acoustic sensors along the circumference of the primary mirror.