LIGO Scientific Collaboration Advanced LIGO Core Optics Working Group Report Dave Reitze University of Florida for the Core Optics Working Group LIGO Scientific Collaboration

Overview of the Core Optics WG Progress Advanced LIGO Systems Design Requirements successfully completed in January 2004 Sapphire test mass R&D New results on absorption in large sapphire substrates New results in annealing for absorption reduction Fused silica test mass R&D Absorption maps Annealing studies underway Advanced Core Optics R&D Flat top beam research Cavities without coatings Coating R&D Sheila Rowan will summarize in next talk LIGO Scientific Collaboration

Core Optics Design Moving Forward Design Requirements Review held January 5, 2004 Review committee accepts DR as substantially complete Still need to decide on test mass material, but the requirements for TMs definable Some issues will keep us busy… Scattering a new issue Coating absorption LIGO Scientific Collaboration

COC optical requirements From G040003, COC DRR LIGO Scientific Collaboration

LIGO Scientific Collaboration From G040003, COC DRR LIGO Scientific Collaboration

Test Mass Material Down Select Date: June 30, 2004 Meeting this afternoon at 17:30 pm in main building multi-purpose room LIGO Scientific Collaboration

Requirements for Advanced LIGO Sapphire Test Masses P. Fritschel, et al., LIGO T010075-00; G. Billingsley, et al., LIGO-T020103-05 *ITM only **assumes active thermal compensation above ~40 ppm/cm LIGO Scientific Collaboration

Large Sapphire Substrates LSC possesses 3 large polished, sapphire substrates 314 mm dia. x 130 mm (2x) 250 mm dia. X 100 mm (Glasgow) Characterization to date Mechanical loss Absorption ‘Polish-ability’ LIGO Scientific Collaboration

LIGO Scientific Collaboration Mean absorption: 67 ppm.cm-1 f 200 mm scan 2.5 mm steps PRESENTED IN AUGUST 2003 Absorption map at Z = -63 mm Mean absorption: 101 ppm.cm-1 3.5x3.5 mm² zoom 0.1 mm steps J. M. Mackowsky, SMA-Virgo Université Lyon I SMA LIGO Scientific Collaboration

LIGO Scientific Collaboration FEBRUARY 2004 DATA 50 LIGO Scientific Collaboration

LIGO Scientific Collaboration

LIGO Scientific Collaboration ~30 LIGO Scientific Collaboration

LIGO Scientific Collaboration

Absorption in Large Sapphire Substrates New results are better than first piece … but somewhat puzzling since: One of the pieces is visibly pink More measurements are needed and will be performed over the next few months. Comparative study between LMA-Virgo and Stanford underway Agreement is to within 20% LIGO Scientific Collaboration

Reducing Optical Absorption in Sapphire Roger Route, Stanford Investigations taking place on annealing of sapphire to reduce absorption Photothermal common path interferometry Prior to last LSC meeting High temperature reducing anneal Rapid cooling > 20 samples annealed and analyzed since August 2003 using PTI High temperature vacuum annealing alleviates need for rapid cooling! Absorption levels reduced to below 15 ppm Tantalizing! LIGO Scientific Collaboration

Sapphire Annealing Results Roger Route, Stanford LIGO Scientific Collaboration

Fused Silica Test Mass Requirements P. Fritschel, et al., LIGO T010075-00; G. Billingsley, et al., LIGO-T020103-05 *assumes active thermal compensation LIGO Scientific Collaboration

Absorption – Fused Silica LIGO Scientific Collaboration

Sapphire vs. Fused Silica: Mechanical Loss AdL Downselect Doc, LIGO-T020103-05-D, G. Billingsley, et al sapphire loss dominated by thermo-elastic noise fused silica looks much better for large Q’s not plagued by thermoelastic noise LIGO Scientific Collaboration

Fused Silica Annealing Program Steve Penn, HWS High Q fused silica LIGO 1 TMs: Q> 1 x 108 Annealing fused silica shown to reduce loss Small samples: Program at HWS College to explore annealing parameter space Best Case ‘Q’ LIGO Scientific Collaboration

Advanced LIGO Test Mass Coatings: Requirements G. Harry, et al., LIGO-C030187-00-R Sheila Rowan will summarize progress in coatings in the next talk Coating Working Group Discussion tomorrow at 9 am in main building multi-purpose room LIGO Scientific Collaboration

Sapphire Test Mass Requirements Redux = ‘good’ ( ) = ‘getting there’ Legend: ? = ‘jury still out’ ** ( ) Coatings ? ? ? ( ) *homogeneity may an issue ** engineered solution LIGO Scientific Collaboration

Fused Silica Requirements Redux ( ) Coatings ? ? ? LIGO Scientific Collaboration

AdL Core Optics Research: Flat top beams LIGO Scientific Collaboration

LIGO Scientific Collaboration Flat top beams LIGO Scientific Collaboration

LIGO Scientific Collaboration Flat top beams LIGO Scientific Collaboration

AdL Optics Research: Cavities without Coatings V. Braginsky and S. Vyatchanin, MSU LIGO Scientific Collaboration

LIGO Scientific Collaboration Summary Advanced LIGO Core Optics Moving Forward DRD completed Some hard work ahead Progress on flat tops Test mass down-select date: June 30, 2004 Meeting today at 17:30 in Main Building Multi-purpose room Sapphire Progress Characterization of large sapphire substrates Absorption promising, but needs more work Annealing treatment progressing in the right direction Fused silica R&D A viable alternative to sapphire Q results forthcoming in time for informed decision LIGO Scientific Collaboration