Central heating radius of curvature correction (CHRoCC) for use in large scale gravitational wave interferometers

An asymmetry in radii of curvature of the mirrors in the arms of an interferometric gravitational-wave detector can degrade the performance of such a detector. In addition, the non-perfect mirror surface figures can excite higher order modes if the radii of curvature are close to higher order mode degeneracy. In this paper, we present a novel technique for changing the radii of curvature of arm cavity end mirrors by Central Heating Radius of Curvature Correction. This system was installed in the Virgo experiment in Cascina and proved to be an efficient, non-invasive solution with a large dynamic range. We present how the interferometer was tuned using such a system in order to obtain the best duty-cycles and sensitivity achieved with Virgo to date.