1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 1 Mirrors Sub-System Overview  Introduction  Scope of the subsystem, main tasks  Substrates Procurement  Blank Material (fused silica) : material choice, specifications, planning, cost  Polishing : strategy, choice of the company, planning, cost  Coating : planning, cost

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 2 Introduction Mir Sub-system  Procurement and preparation of the AdV test masses and spares Input and End mirrors, Beam Splitter, mirrors for non-degenerate Power and Signal Recycling cavities, Compensation Plates  Mirrors with larger dimensions (thicker) Modification in the coating process  Mirrors with RMS flatness better than 1 nm Polishing and Coating strategy More accurate metrology Description

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 3 Introduction Mir Sub-system Main Tasks  Substrates: Blank materials procurement (fused silica), Choice of the best material (Company), Order preparation  Polishing: Definition of the specifications, Geometry (ROC, monolithic suspension..) Flatness requirements, Definition of the polishing strategy (Corrective Coating) Call for tender for the micropolishing, Order preparation. Control of the different substrates delivered (Defects, roughness, ROC, flatness, bulk absorption, Birefringence) - Characterization report  Coatings: Coating process modification linked to the mirror weight increase (mirror handling tools, new sample-holder (robot) for Corrective Coating) Design optimization, use of the best high index material (thermal noise), annealing  Metrology : Modification of the sample holder on optical metrology benches (Abs./Scat. bench) New ITF bench to measure the wavefront at 0° and 45° of 0.5 nm RMS (TBC) on the AdV test masses

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 4 Introduction Mir Sub-system AdV Mirrors : Reference Solution Geometry and performances Input Mirror IM End Mirror EM Beam Splitter BS Compensation Plate CP Non degenerate Power and Signal recycling Cavities PRM3/SRM3PRM2/SRM2PRM1/SRM1 Number of parts Fused Silica Nature Suprasil 3002Suprasil 312Suprasil 3001Herasil 102 Diameter 350 mm <550 mm (TBC) 280 mm (TBC) 150 mm (TBC) 50 mm (TBC) 50 mm (TBC) Thickness 200 mm 65 mm 100 mm (TBC) 50 mm Roughness Reflective side <1 Å RMS RMS Flatness Reflective side 0.5 nm RMS (TBC)  150 mm 0.5 nm RMS (TBC)  200 mm 3 nm RMS (TBC)  150 mm 3 nm RMS (TBC)  150 mm 3 nm RMS (TBC)  100 mm 3 nm RMS (TBC)  20 mm 3 nm RMS (TBC)  20 mm Transmission Reflective side 0.7 % (TBC) # 10 ppm (TBC) 50 %#100 % # 10 ppm (TBC) # 10 ppm (TBC) TBD

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 5 Detailed revised DRAFT Planning if starting on 01/07/2009 Estimation based on real delay for the manufacturing of the silica and on the real time necessary for the VIRGO + substrates polishing - Mirrors Delivery : beginning of 2012 Mirrors production Plan

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 6 Substrates Fabrication : 1,5 year o Planning for 4 IM-4 EM-2 BS solution (one spare for each mirror) Serial production of the silica blanks. Possibility to produce in parallel but limitation = polishing phase o Heraeus production : first bulk substrate produced after 4 month, then one bulk/2 weeks o Choose the best material for each type of component Compromise between optical/mechanical performances and price Substrates Procurement

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 7 Fused Silica properties comparison

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 8 Substrates Procurement Motivations for Fused silica choice  No real advantages to choose Corning (performances, cost), limitation in size Manufacturer = HERAEUS (like in VIRGO)  For IM, BS : New fused silica (Suprasil 3001/3002) same optical performances Better bulk absorption (0.2 ppm/cm measured): better for thermal lensing Comparable price  For EM : Suprasil 312 Good optical and mechanical properties Cheaper  Non degenerate PR and SR cavities (3 mirrors 5-15 cm) and CP: Herasil 102 : cheap Properties satisfactory for this particular type of mirrors

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 9 Substrates Procurement Real Fused Silica Cost (IM/EM thickness 20 cm) Solution 4 IM/ 4 EM/ 2 BS/ 6 PR-SR cavities/ 4 CP If thickness 30 cm for IM and EM : extra cost # +30 % CostIM/EM/BS/SR+PR/CPCost - Thickness 30 cm Reference Solution ,00 € 3002 / 312 / 3001 / Herasil ,00 €

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 10 Substrates Polishing : # 2,5 years (for all spares)  Real Time estimation with General Optics production time for the Virgo + mirrors (2007) (6 months for the first substrate, after 1 parts/month) Different from one polisher to the other P olishing starts as soon as first bulk substrate received (nov 2009)  Coating starts as soon as possible Substrates Polishing

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 11  New strategy for the Larger beam splitter (< 55 cm- TBC) Several polishers contacted to check feasibility (in progress)  New geometry of the mirrors (monolithic lateral supports) Check with polishers if feasible (in progress)  Critical point: flatness requirements (# 0.5 nm RMS) Simulations necessary to evaluate the crucial spatial frequency domain Flatness metrology improvement (better accuracy and reproducibility) New bench : stitching interferometry, stable sample holder, measurement also at 45° Substrates Polishing

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 12 Substrates Polishing Two Paths Corrective Coating (LMA) New opportunity Flatness reached with Ion Beam polishing Polisher not able to guarantee the flatness specifications (Best effort) Polisher able to guarantee the flatness specifications Development of a new Robot Reference solution To be tested Cost (?) Future AdV Mirrors upgrades

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 13 Substrates Polishing : Corrective coating Substrate Interferometer Ion source Robot mask Silica target Sputtered atoms Substrate  156 mm VIRGO type Before correction (  120 mm) 3.3 nm R.M.S. / 16 nm P.V. After correction (  120 mm) 0.98 nm R.M.S. /10 nm P.V.

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 14 Substrates Polishing Polishing cost Solution 4 IM/ 4 EM/ 2 BS/ 6 PR-SR cavities / 4 CP Cost estimation obtained for VIRGO+ (2007)  Contact polishing companies : General Optics, CSIRO, SESO (?)  Find the best compromise between the price and the performances k€

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 15 Mirrors Coating : # 2 years Mirrors Coating  Coating start : as soon as 2 IM ready (polished, characterized) Coated at the same time (ITF arm symmetry)  Coatings having the best available optical and mechanical features  Reference path : flatness correction by “Corrective Coating” (IM, EM) 2 CP

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 16  For “Corrective Coating”: new robot in the Virgo large coater (ordered at the same time as the polishing, end 2009) – 300 k€  Study of the robot already started Help from LAPP (P. Mugnier, L. Giacobone) for the technical study of the robot Test on a real large substrate (old VEM ?) Simulation with a corrected wavefront (Nice group) : see if CC improves or not  CC : Quite no impact on the coating planning (limitation : polishing)  Alternative strategy : Advanced polishing company able to reach the 0.5 nm specification by Ion Beam Polishing (final step after a classical polishing). Coating test on this type of substrate Mirrors Coating

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 17 Mirrors Coating Coating cost Cleaning Facility (real) Tooling for cleaning Tooling for coating Handling Tools Robot Ion Assist source (Q improvement) Under vacuum furnace Coating (corrective coating) Total (€) k€

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 18 Mirrors Coating Metrology cost : 300 k€ Lots of modifications to control heavier and thicker substrates Metrology mountings (IM/EM/BS) New motorized sample holder for the scattering and transmission measurement (BS) New motorized sample holder coupled with stitching interferometry software for wavefront measurement (0°- 45°)