1. Rana Adhikari Caltech The Next Gravity Wave Interferometers

2. 2  Gravitational Waves = “Ripples in space-time”  Two transverse polarizations - quadrupolar: + and x Gravitational Waves? Example: Ring of test masses responding to wave propagating along z Amplitude parameterized by dimensionless strain h:  L ~ h(t) x L Need to measure strain of ~ 10 -21 -10 -22 We want a very large ‘L’

3. 3  Compact binary inspirals: “chirp” standard candle.  NS-NS waveforms are well described. 1.4 M solar NS/NS inspiral is a standard candle.  BH-BH waveforms are rapidly improving  Supernovae / Mergers: “burst”  Short signals. Waveforms not well known.  Search in coincidence between two or more interferometers and possibly with electromagnetic and/or neutrinos signals  Spinning NS: “continuous”  search for signals from observed pulsars  all-sky search computing challenging  Cosmic Background: “stochastic”  Metric fluctuations amplified by inflation, phase transitions in early universe, topological defects  Unresolved foreground sources GW Sources in LIGO Band 50-1000 Hz

4. 4 LIGO Observatories Livingston, LA (L1 4km) Hanford, WA (H1 4km, H2 2km) - Interferometers are aligned to be as close to parallel to each other as possible - Observing signals in coincidence increases the detection confidence - Determine source location on the sky, propagation speed and polarization of the gravity wave LIGOGEO Virgo TAMA AIGO (proposed)

5. 5 Michelson Interferometer Anti-Symmetric (Dark) Port LyLy LxLx Reflected Port P AS  P BS x sin 2 (  ) dP/d   P BS x sin(  )cos(  )  = 2  (  L y -  L x ) / d  dh  L Laser Noise   P AS

6. 6 End Test Mass 50/50 Beam Splitter Photo detector Laser Michelson Interferometer Michelson Interferometer 4 km Fabry-Perot arm cavity with Fabry-Perot Arm Cavities Input Test Mass 6 W Power Recycled Power Recycling Mirror 300 W 20 kW Interferometer Optical Layout Signal  Phase shift between the arms due to GW

7. 7 Science Requirements Doc: The LIGO-I Sensitivity Goal Seismic: Natural and anthropogenic ground motions, filtered by active/passive isolation systems. Depends strongly on in-vac seismic isolation. Thermal: Brownian noise in the mirrors and in the mirrors’ steel suspension wires. Depends mostly on internal rubbing in the suspension wires. Shot Noise: Photon counting statistics -- > 10 kW in the cavities ~ 200 mW detected power - Goes down with increased laser power and better fringe contrast

8. 8 5 years of debuggin’ in Louisiana…

9. 9

10. 10 What Is Inside 1.2 m diameter - 3mm stainless 50 km of weld 10 -9 torr vacuum and no leaks! Seismic isolation Stack of masses and springs Coils and magnets to control the mirror Fused silica mirror 25 cm diameter 10 kg mass

11. 11 Dark Port Optical Table 2 mm diameter InGaAs photodiode

12. 12 Time Line Now Inauguration 19992000200120022003 3 41 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 First LockFull Lock all IFO 10 -17 10 -18 10 -20 10 -21 20042005 1 2 3 4 1 2 3 4 1 2 3 4 2006 First Science Data S1 S4 Science S2 Runs S3S5 10 -22 4K strain noiseat 150 Hz [Hz -1/2 ] 2006 HEPI at LLO

13. 13 Caltech LIGO Laboratory MIT LIGO Hanford Observatory LIGO Livingston Observatory University of Adelaide ACIGA Australian National University ACIGA Balearic Islands University Caltech LIGO Caltech Experimental Gravitation CEGG Caltech Theory CART University of Cardiff GEO Carleton College Cornell University Embry-Riddle Aeronautical University University of Florida-Gainesville Glasgow University GEO NASA-Goddard Spaceflight Center Hobart – Williams University India-IUCAA IAP Nizhny Novgorod IUCCA India Iowa State University Loyola New Orleans Louisiana State University Louisiana Tech University MIT LIGO Max Planck (Honnover) GEO Max Planck (Potsdam) GEO University of Michigan Moscow State University NAOJ - TAMA Northwestern University University of Oregon Pennsylvania State University Southeastern Louisiana University Southern University Stanford University Syracuse University University of Texas-Brownsville Washington State University-Pullman University of Western Australia ACIGA University of Wisconsin-Milwaukee LIGO Scientific Collaboration ~40 institutions, ~550 scientists

14. 14 LIGO Science Run  The fifth science run started in November 2005  S5 goal is to collect one year of triple coincidence data at the design sensitivity  Optimistic event rates: NS/NS ~3/year, BH/NS ~30/year Nakar, Gal-Yam, Fox, astro-ph/0511254  Plan to reach the Crab pulsar spin down limit  Expect to beat the Big-Bang Nucleosynthesis limit on gravitational wave density in the LIGO band  GEO interferometer joined the S5 run in January 2006.  Virgo interferometer plans to join S5 later this year.

15. 15 NS-NS Inspiral Range Improvement Time progression since the start of S5 Histogram Design Goal Commissioning breaks Stuck ITMY optic at LLO

16. 16 S5 Duty Factor S5 Goal is 85% for single interferometer and 70% for triple coincidence One week running average Commissioning breaks Stuck ITMY optic at LLO

17. 17 H1H2L1 Uptime72%79%60% Wind, Storms, Earthquakes4.5%9% Nearby Logging, Construction, Trains--10% Maintenance, Commissioning, Calibration 10%9% Hardware and Software Failures3.5%7% Lock Acquisition, Other10%5% S5 Duty Factor H1&H2&L1 = 45% H1||H2||L1||G1 close to 100%

18. 18 Triple Coincidence Accumulation 100% ~ 45% ~ 61% Expect to collect one year of triple coincidence data by summer-fall 2007

19. 19 Sometimes You Get Lucky  Large mirror (ITMY) was wedged into the earth quake stops  Vented the vacuum and released it. Adjusted EQ stop.  Noise improved!? 12->14 Mpc Earth quake stop before after Charge Dissipation on the optic?

20. 20 Advanced LIGO  LIGO mission: detect gravitational waves and initiate GW astronomy  Next detector  Should have assured detectability of known sources  Should be at the limits of reasonable extrapolations of detector physics and technologies  Must be a realizable, practical, reliable instrument  Daily gravitational wave detections  R&D is mature, prototypes exist  Installation start in 2011 Advanced LIGO

21. 21 10 Hz100 Hz1 kHz 10 -22 10 -23 10 -24 10 -21 Anatomy of the projected Adv LIGO detector performance  Newtonian background, estimate for LIGO sites  Seismic ‘cutoff’ at 10 Hz  Suspension thermal noise  Test mass thermal noise  Unified quantum noise dominates at most frequencies for full power, broadband tuning Initial LIGO Advanced LIGO NS-NS Tuning

22. 22 End Test Mass 50/50 beam splitter GW signal Optical Configuration Laser Michelson Interferometer Michelson Interferometer 4 km Fabry-Perot arm cavity with Fabry-Perot Arm Cavities Input Test Mass 125 W Power Recycled Power Recycling mirror 2 kW 500 kW Signal Recycling mirror Dual recycled

23. 23 Detuned Signal Recycling frequency offset from carrier [Hz] Responses of GW USB and GW LSB are different due to the detuning of the signal recycling cavity. IFO Differential Arm mode is detuned from resonance at operating point SRCDARM Carrier frequency Sideband amplitude [a.u.] FWHM USB LSB f sig IFO DARM/CARM from R. Ward

24. 24 Opto-mechanical Spring Optical Spring stiffness ~ 10 7 N/m Angular spring resonance ~ 2 Hz ½ MW in the arms -> ‘Optical Bar’ detector ~75 Hz unstable opto- mechanical resonance High Bandwidth servos Measured Transfer Functions from the 40m prototype BMW Z4 ~ 10 4 N/m Radiation pressure: F = 2 P / c Detuned Cavity -> dF/dx

25. 25 The next several years  Between now and AdvLIGO, there is some time to improve…  ~Few years of hardware improvements + 1 ½ year of observations.  Factor of ~2.5 in noise, factor of ~10 in event rate.  3-6 interferometers running in coincidence ! S5 S6 4Q ‘05 4Q ‘06 4Q ‘07 4Q ‘08 4Q ‘10 4Q ‘09 Adv LIGO ~2 years Other interferometers in operation (GEO, Virgo) NOW 4 yrs

26. 26 NS/NS Binary Most of the sensitivity comes from a band around 50 Hz 50 Hz Area proportional to SNR

27. 27 30/30 M  BH/BH Most of the sensitivity comes from a band around 30 Hz Area proportional to SNR 30 Hz

28. 28 Astrophysical Motivation How does the number of surveyed galaxies increase as the sensitivity is improved? From astro-ph/0402091, Nutzman et al. Power law: 2.7 For NS-NS binaries Prop. to inspiral range Factor of 2.5 reduction in strain noise,  factor of 10 increase in # of sources S4

29. 29 Baseline Goals  Dark Port Filter Cavity (Caltech/MIT)  Reduce amount of junk light, reduce shot noise  Reducing detected light power allows higher laser power  Upgrade the detection system to the Advanced LIGO style.  Higher power laser (Hannover)  Our (10 W) laser company was bought out by JDS Uniphase.  Collaborators at AEI/LZH are offering us 35 W lasers (for free!)  High Power Input Optics (UF, Gainesville)  Miscellaneous …

30. 30 Seismic: No modification in seismic isolation systems Thermal: Good wires, good mirrors, and control of “technical” noises Shot Noise: - New in-vac filter cavity - - 4-5x more laser power - - Advanced readout technique

31. 31 Increased Power + Enhanced Readout Lower Thermal Noise Estimate

32. 32 The Plan  Improvements on the 4km IFOs starting in Sep07  Do Louisiana first (pathfinder). Start Hanford in Jan08.  Some modest Suspension electronics fixes  Then some more science running. Not enough time/manpower to do all 3 IFOs. A factor of 2.5 on H1/L1 is better than a factor of 2 on all three. We don’t gain more AdvLIGO knowledge by doing 3 IFOs. After the pumpdown, H2 can join Virgo in a science run.

33. 33 Conclusions  1 more year of R&D to support the upgrade  Starting installation in Sep ’07  Next Science Run (w/ improved sensitivity) starts in Sep ’09.  Reduces much technical risk for Advanced LIGO  Its time to make the first gravitational wave detection.

34. 34 Short, Hard GRBs  Several Short Hard Gamma-Ray Bursts since last year  Detected by Swift, HETE-2, then Hubble, Chandra, and BATSE  SHGRBs (< 2 s) different from ‘Long Soft GRBs’ (supernova explosions)  Candidates for progenitors of SHGRBs: double neutron star (NS/NS) or neutron star-black hole (NS/BH 1.4/10) coalescences  Optimistic rates for Initial LIGO (S5) could be as high as a few/year Nakar, Gal-Yam, Fox, astro-ph/0511254 Double Neutron Star Merger Dana Berry / NASA

35. 35  Suspension wire re-working  Change the clamp to reduce excess noise (no evidence so far)  Change the wire to reduce the intrinsic noise  Needs some serious coil driver redesigns capitalize on lower noise.  Need to know more about the excess noise first.  Squeezed Light  Implement on one IFO instead of the laser upgrade; more speculative, but doesn’t require new IO equipment.  An opportunity to commission another AdvLIGO system  Signal Recycling  No real sensitivity improvement; lots of work.  Double Suspension  Not directly applicable to AdvLIGO. Substantial reworking req.  Not clear if we can get the technical noises out of the way. Beyond ‘Fixes’

36. 36  Cross-correlation estimator  Theoretical variance  Optimal Filter Strain Power: Choose N such that: Detection Strategy, point source Point Spread Function

37. 37 S4 Upper Limit map, H(f)=const