1st advanced virgo review – november 3-4, 2008 – l. pinard 1 mirrors sub-system overview ...

1st Advanced Virgo Review – November 3-4, 2008 – L. Pinard 1

Advanced VirgoAdvanced VirgoMirrors Sub-SystemMirrors 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


Advanced VirgoAdvanced VirgoIntroduction Mir Sub-systemIntroduction 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



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



AdV Mirrors : Reference SolutionGeometry and performances

Input MirrorIM

End Mirror EM

Beam SplitterBS

Compensation Plate

CP

Non degenerate Power and Signal recycling Cavities

PRM3/SRM3 PRM2/SRM2 PRM1/SRM1

Number of parts 4 4 2 2 3 3 3

Fused Silica Nature Suprasil 3002 Suprasil 312 Suprasil 3001 Herasil 102 Herasil 102 Herasil 102 Herasil 102

Diameter 350 mm 350 mm<550 mm

(TBC)280 mm(TBC)

150 mm (TBC)

50 mm(TBC)

50 mm(TBC)

Thickness 200 mm 200 mm 65 mm100 mm(TBC)

50 mm 50 mm 50 mm

RoughnessReflective side <1 Å RMS <1 Å RMS <1 Å RMS <1 Å RMS <1 Å RMS <1 Å RMS <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

TransmissionReflective side

0.7 % (TBC)

# 10 ppm(TBC)

50 % #100 %# 10 ppm

(TBC)# 10 ppm

(TBC)TBD


Advanced VirgoAdvanced Virgo

Detailed revised DRAFT Planning if starting on 01/07/2009Estimation based on real delay for the manufacturing of the silica and on the real timenecessary for the VIRGO + substrates polishing - Mirrors Delivery : beginning of 2012

Mirrors production PlanMirrors production Plan



Substrates Fabrication : 1,5 year

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

Heraeus production : first bulk substrate produced after 4 month, then one bulk/2 weeks

Choose the best material for each type of component Compromise between optical/mechanical performances and price

Substrates ProcurementSubstrates Procurement


Advanced VirgoAdvanced VirgoFused Silica properties comparisonFused Silica properties comparison


Advanced VirgoAdvanced VirgoSubstrates ProcurementSubstrates 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


Advanced VirgoAdvanced VirgoSubstrates ProcurementSubstrates 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 %

Cost IM/EM/BS/SR+PR/CP Cost - Thickness 30 cm

Reference Solution

1 277 880,00 € 3002 / 312 / 3001 / Herasil 102 1 667 072,00 €



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

Polishing starts as soon as first bulk substrate received (nov 2009)

Coating starts as soon as possible

Substrates PolishingSubstrates Polishing



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 domainFlatness metrology improvement (better accuracy and reproducibility)New bench : stitching interferometry, stable sample holder,

measurement also at 45°

Substrates PolishingSubstrates Polishing


Advanced VirgoAdvanced VirgoSubstrates PolishingSubstrates Polishing

Two Paths

Corrective Coating (LMA)New opportunity

Flatness reached with Ion Beam polishing

Polisher not able to guaranteethe flatness specifications

(Best effort)

Polisher able to guaranteethe flatness specifications

Development of a new Robot

Refere

nce so

lutio

n

To be testedCost (?)Future AdV Mirrors upgrades


Advanced VirgoAdvanced VirgoSubstrates Polishing : Corrective coatingSubstrates 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.


Advanced VirgoAdvanced VirgoSubstrates PolishingSubstrates Polishing

Polishing costSolution 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

1 300 k€



Mirrors Coating : # 2 years

Mirrors CoatingMirrors 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



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 CoatingMirrors Coating


Advanced VirgoAdvanced VirgoMirrors CoatingMirrors 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 (€) 1 050 k€


Advanced VirgoAdvanced VirgoMirrors CoatingMirrors 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°)

1st advanced virgo review – november 3-4, 2008 – l. pinard 1 mirrors sub-system overview ...

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