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?
Current mirror
• Small 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 GS- Lumonics
– 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? (GS- Lumonics)
• 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
