New MC mirror

New MC mirror M.Punturo New MC mirror? Scattering in the end mirror of the IMC is the first cause of the ISYS upgrade Poor quality of the substrate has been the diagnosis The REOSC company selected by D.Enard and Lyon to perform the polishing of the new MC mirror failed and abandoned the polishing Both offers from WP and REOSC are on a best effort basis, meaning the requirements are considered as objectives. This was already the case

for the past orders for the existing core optics but a quality reasonably close to our requirements was finally obtained. In a similar way, Reosc accepted our requirements as objectives while committing on slightly degraded requirements. We MUST CONFIDE in the properties of the Faraday Isolator to avoid the fringes that hindered the ITF locking What to do? Small mirror: Current mirror

8 cm diam, 3 cm thick Back face crowded Only 360g with all the components Mirror unbalanced by the components Pendulum elastic constant determined by the coil wires instead of the suspension wires (125 m Cu-Be wires) Problems in controls, handling and radiation pressure (?)

Small IMC mirror? Two blanks are available with the usual MC size They should be retired from REOSC and sent to GSLumonics A 6 month polishing time is foreseen If we are lucky we will have a low scattering mirror with all the control and noise problems we have now Can we do better? Large substrates 6 Large Herasil end substrates are available in Lyon 350mm diameter, 100 mm thick Unusable for Virgo+, because of the low Q of Herasil (Tama)

Could we polish one with the IMC requirements? (GSLumonics) Changes New Marionetta Maybe we loose the translation degree of freedom New reference mass Retuning of the suspension Retuning of the controls More standard situation