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

2. 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

3. 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

4. COC optical requirements
From G040003, COC DRR
LIGO Scientific Collaboration

5. LIGO Scientific Collaboration
From G040003, COC DRR
LIGO Scientific Collaboration

6. 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

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

8. 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

9. 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

10. LIGO Scientific Collaboration
FEBRUARY 2004 DATA 50
LIGO Scientific Collaboration

11. LIGO Scientific Collaboration

12. LIGO Scientific Collaboration
~30
LIGO Scientific Collaboration

13. LIGO Scientific Collaboration

14. 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

15. 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

16. Sapphire Annealing Results
Roger Route, Stanford
LIGO Scientific Collaboration

17. Fused Silica Test Mass Requirements
P. Fritschel, et al., LIGO T ; G. Billingsley, et al., LIGO-T
*assumes active thermal compensation
LIGO Scientific Collaboration

18. Absorption – Fused Silica
LIGO Scientific Collaboration

19. Sapphire vs. Fused Silica: Mechanical Loss
AdL Downselect Doc, LIGO-T 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

20. 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

21. Advanced LIGO Test Mass Coatings: Requirements
G. Harry, et al.,
LIGO-C 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

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

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

24. AdL Core Optics Research: Flat top beams
LIGO Scientific Collaboration

25. LIGO Scientific Collaboration
Flat top beams
LIGO Scientific Collaboration

26. LIGO Scientific Collaboration
Flat top beams
LIGO Scientific Collaboration

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

28. 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