Intermediate review - ERC – February 9, 2009 – L. Pinard 1

Mirrors Sub-SystemMirrors Sub-System

Overview Introduction

Scope of the subsystem, main tasks

Job done since 1st Review of November 2008

Substrates Procurement Blank Material (fused silica) : material choice, specifications, planning, cost

Substrates Polishing Polishing : strategy, choice of the company,planning, cost

Coating : planning, cost

Optical Metrology Upgrade

Intermediate review - ERC – February 9, 2009 – L. Pinard 2

Introduction 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

Silica blanks, polishing (Robot – Corrective coating)

Mirrors with larger dimensions (thicker) Modification in the coating process (cleaning, handling) Coatings

Mirrors with RMS flatness better than 1 nm More accurate metrology Metrology modifications

Description

Intermediate review - ERC – February 9, 2009 – L. Pinard 3

Since the November ReviewSince the November Review

Mirror Construction Task form Description of all the tasks, of all the deliverables Time planning, Budget spending profile, Manpower

Mirror Finalization Task form Collecting the informations on all the open design questions Design question : the following decisions needs to be taken depending on open design issues

1) Physical dimensions of some main optics- Beam Splitter (diameter, Thickness)- Signal and power recycling mirrors in the Non Degenerate

cavity configuration- Compensation plates

2) Lateral Support for the monolithic suspensionNew design or classical support (flats+ears silicate bonded)

3) Polishing strategy for the AdV mirrors

Intermediate review - ERC – February 9, 2009 – L. Pinard 4

Substrates Fabrication : 1,5 year

Planning for 4 IM- 4 EM- 3 BS – 4 CP – 6 ndg cavities solution : spares included Serial production of the silica blanks. Possibility to produce in parallel

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

Compensation plates included : same silica as IM

Optimization of the planning with Heraeus (include production constraints) Possibility to reduce the silica Blanks budget by 15%

Substrates ProcurementSubstrates Procurement

Intermediate review - ERC – February 9, 2009 – L. Pinard 5

Substrates ProcurementSubstrates Procurement

Motivations for Fused silica choice

Manufacturer = HERAEUS (like in VIRGO)

For IM, BS, CP :

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 (0.6 ppm/cm) and mechanical properties

Cheaper

Non degenerate PR and SR cavities (3 mirrors 5-15 cm):

Herasil 102 : cheap

Properties satisfactory for this particular type of mirrors

Intermediate review - ERC – February 9, 2009 – L. Pinard 6

Substrates ProcurementSubstrates Procurement

What remains to do (design questions):

- Final dimensions for BS, CP and ndg cavities : OSD and PAY subsystem Dedicated internal meetings

- For ndg cavities : small mirrors – production time not long

not a problem for the planning if dimensions not yet decided

Intermediate review - ERC – February 9, 2009 – L. Pinard 7

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)

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

CP polishing included (planning optimized)

Coating starts as soon as possible (after characterization)

Substrates PolishingSubstrates Polishing

Polishing company able to polish the large BS Only one found – long delay taken into account

Intermediate review - ERC – February 9, 2009 – L. Pinard 8

New geometry of the mirrors (monolithic lateral supports) - TCS - Checked with polishers if feasible (2 possible positive answers) - First comments :

- silica bulk cost for IM and EM : + 15% - Lateral support machining : long (+2-3 months for each part) - Expensive : first approx. +30% for IM and EM

- Dedicated meeting

Critical point: flatness requirements (# 0.5 nm RMS) Simulations necessary to evaluate the crucial spatial frequency domain

Substrates PolishingSubstrates Polishing

Design Questions

Intermediate review - ERC – February 9, 2009 – L. Pinard 9

Substrates PolishingSubstrates Polishing

Design Questions

Polishing Strategy

Reference solution : Corrective coating technique (wavefront improvement by adding silica where it is necessary) – Convincing Results (<1 nm RMS)

New robot (sample-holder) : present system not reliableStudy quite finished with LAPP team, cost estimation in progress : ready in June 2009 for construction (LAPP – LMA projects manager)Advantage : can be used for future mirror upgrades

Alternative solution : Company able to reach flatness < 1 nm RMS on large area (Ion Beam Polishing)Contact establishedCost estimation in progress with preliminary specifications

Intermediate review - ERC – February 9, 2009 – L. Pinard 10

Substrates PolishingSubstrates Polishing

Design Questions

Contact polishing companies : General Optics, CSIRO, SESO, ZYGO, L-3 communications (Tinsley)

Find the best compromise between the price and the performances

Intermediate review - ERC – February 9, 2009 – L. Pinard 11

Mirrors Coating phase : # 2 years

Mirrors CoatingMirrors Coating

Global coating Task includes all the toolings necessary (cleaning, handling, Q factor Improvement, boxes…)

Coating start : as soon as 2 IM ready (polished, characterized) Coated at the same time (ITF arm symmetry) In the planning, a corrective coating phase included in the IM and EM coating

Coatings having the best available optical and mechanical features

CP coatings taken into account

Intermediate review - ERC – February 9, 2009 – L. Pinard 12

Metrology UpgradesMetrology Upgrades

Metrology mountings (IM/EM/BS)

New motorized sample holder coupled with stitching interferometry software for wavefront measurement (0°- 45°)Better accuracy and reproducibility

New motorized sample holder for the scattering and transmission measurement (BS)