1. Overview of Advanced LIGO March 2011 Rencontres de Moriond Sheila Rowan For the LIGO Scientific Collaboration

2. The Global Network of Gravitational Wave Detectors GEO600 Germany VIRGO Italy LIGO TAMA Japan

3. LIGO sites (US) LIGO Livingston Observatory 1 interferometer 4 km arms 2 interferometers 4 km, 2 km arms LIGO Hanford Observatory LIGO Observatories are operated by Caltech and MIT

4. 4 The LIGO Scientific Collaboration (LSC) The LSC carries out the scientific program of LIGO – instrument science, data analysis. The 3 LIGO interferometers and the GEO600 instrument are analyzed as one data set (also share our data with French-Italian Virgo) Approximately 800 members ~ 50 institutions including the LIGO Laboratory Participation from (at least) Australia, Germany, India, China, Korea, Italy, Hungary Japan, Russia, Spain, the U.K. and the U.S.A.

5. Timeline of GW searches to 2011 We are here Data analysis ongoing 1989 LIGO Proposal submitted to NSF 1995 Construction started 1999 Inauguration Advanced LIGO construction funded

6. The worldwide GW roadmap for the future We are here

7. 7 Advanced LIGO Factor of 10 greater sensitivity than initial LIGO Factor 4 lower start to sensitive frequency range » ~10 Hz instead of ~40 Hz » More massive astrophysical systems, greater reach, longer observation of inspirals Intended to start gravitational-wave astronomy Frequent detections expected – exact rates to be determined, of course » Most likely rate for NS-NS inspirals observed: ~40/year 100 million light years Advanced LIGO Enhanced LIGO Initial LIGO (See J. Abadie et al “Predictions for the Rates of Compact Binary Coalescences Observable by Ground-based Gravitational-wave Detectors”,arXiv:1003.2480; submitted to CQG)arXiv:1003.2480

8. 8 Advanced LIGO Scope Re-use of vacuum system, buildings, technical infrastructure Replacement of virtually all initial LIGO detector components » Re-use of a small quantity of components where possible Three interferometers, as for Initial LIGO All three interferometers 4km in length » For initial LIGO, one of the two instruments at Hanford is 2km

9. Advanced LIGO – path to improved sensitivity Advanced LIGO (See Roman Schnabel’s talk on thoughts on how to improve on quantum noise limited sensitivities..)

10. Design Outline 10 l Recombined Fabry-Perot Michelson with l Signal recycling (increase sensitivity, add tunability) l Active seismic isolation, quadruple pendulum suspensions (seismic noise wall moves from 40Hz  10 Hz) l Fused Silica Suspension (decreased low-frequency thermal noise) l 40 kg test masses (lower photon pressure noise) l Larger test mass surfaces, low-mechanical-loss optical coatings (decreased mid-band thermal noise) l ~20x higher input power (lower shot noise) Laser Test Masses M Arms of length L Cavity finesse F INITIAL LIGO LAYOUT Power recycling mirror to increase circulating power Michelson for sensing strain Fabry-Perot arms to increase interaction time GW signal Signal Recycling Mirror to tune response ADVANCED

11. aLIGO – seismic Isolation – outside and inside the tanks

12. aLIGO Suspension Systems – What They Need to Do l Support the optics to minimise the effects of » seismic noise acting at the support point » thermal noise in the suspension Test mass noise requirement: 10 -19 m/√Hz at 10 Hz l Provide damping of low frequency suspension resonances (local control), and l Provide means to maintain interferometer arm lengths (global control) » while not compromising low thermal noise of mirror » and not introducing noise through control loops l Provide interface with seismic isolation system and core optics system l Support optic so that it is constrained against damage from earthquakes

13. Main suspensions 40kg fused silica mirror suspended on 4 fused silica fibres to give low-thermal-noise suspension ~£8.2M contribution from GEO UK (Science and Technology Facilities Council) Prototype fused silica monolithic suspension successfully installed at MIT test facility (See talk from Angus Bell) Most test mass suspension components at both observatories are now cleaned, baked, and assembled into sub-assemblies 13

14. l 40 kg substrates of high optical quality fused silica » Available in suitably large sizes » Low optical absorption at 1064nm » Can be suitably polished and coated » Low mechanical loss Main mirrors (test masses) l For mirrors with spatially inhomogeneous mechanical loss we should not simply add incoherently the noise from the thermally excited modes of a mirror – loss from a volume close to the laser beam dominates. l The loss of the dielectric multilayer coatings used to form highly reflective mirrors at 1064nm could be expected to be an important parameter

15. Thermal noise from optical mirror coatings Current coatings in all detectors are made of alternating layers of ion-beam- sputtered SiO 2 (low refractive index) and Ta 2 O 5 (high index) Experiments suggest: » Thermal noise from mechanical loss of the dielectric mirror coatings will limit sensitivity of 2 nd generation interferometric gravitational wave detectors Coating thermal noise will limit sensitivity between ~ 40 and 200 Hz 10 1 10 2 10 3 Frequency (Hz) 10 -24 10 -23 10 -22 Strain (1/  Hz) » Ta 2 O 5 is the dominant source of dissipation in current SiO 2 /Ta 2 O 5 coatings » Doping the Ta 2 O 5 with TiO 2 can reduce the mechanical dissipation = aLIGO baseline design l (Just one example of impact of experimental GW research on other fields: » Coating noise limits performance of laser stabilisation cavities; frequency combs; other precision physics expts » Very active research area both for ‘beyond advanced’ GW detectors and other apps) Projected Advanced LIGO sensitivity curve

16. The aLIGO laser 2W 35W 180W165W (for more info on high power laser development see talk by Patrick Kwee) ~$14M contribution from GEO Germany (Max Planck Society) 3 complete laser systems, including lasers, servos, reference cavities, etc. Installation of first article laser at Livingston Observatory has started

17. aLIGO thermal compensation Wavefront sensors for Thermal Compensation System (Adelaide) Cavity pre-lock length stabilization system, and ‘tip-tilt’ in-vacuum steering mirrors, for Interferometer Sensing and Control (ANU) ~$1.7M from Australian Research Council

18. ‘LIGO-Australia’ (see talk from David Blair) Goal– a southern hemisphere interferometer early in the Advanced LIGO & Advanced Virgo operating era Install one of the Advanced LIGO interferometers planned for Hanford into infrastructure in Australia provided by Australia for possible detector operation in 2017 In-principle approval from NSF Australian proposal for construction funds submitted March 2011 IndIGO is preparing proposal for significant funding to participate in and contribute to LIGO- Australia. Figure from: LIGO-DOC: T1000251

19. Status of project to date Half way done! – excellent progress 20 th October 2010 : Handoff of the LIGO Observatories to the aLIGO project First new parts going in NOW System upgrades staggered Last IFO should realistically be back online in 2015. Tuning and optimizing to reach design sensitivity

20. Conclusions l Initial LIGO attained its design sensitivity and has produced astronomically important upper limits on gravitational wave production. l Advanced LIGO should increase our sensitivity by more than 10. At that sensitivity, GW detection should be a frequent occurrence. l Advanced LIGO is scheduled to be online by 2015. l Collaboration in the worldwide GW community is growing. The LIGO- Virgo Collaboration (LIGO, GEO, and Virgo) share data, analysis efforts, and technical knowledge. l Exciting (and unexpected?) physics awaits us!

21. Extra slides follow

23. 23 Advanced LIGO: Sensitivity As for Initial LIGO, we specify the sensitivity of Advanced LIGO by an RMS sensitivity: 10 -22 h RMS in a 100 Hz band » A factor of 10 improvement over Initial LIGO Flexibility of tuning will allow a range of responses Anticipated performance is better than above – roughly 3x10 -23 h RMS in a 100 Hz band, around 250 Hz, tuned for NS -NS inspirals