1. LIGO-G050589-00-W Searching for Distant Sources of Gravitational Waves with LIGO Fred Raab, LIGO Hanford Observatory November 15, 2005

2. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO2 highlights Background on Gravity and its waves Initial LIGO detector Progress in commissioning and searching What have we learned from running S1  S4 Steps to S5; preparing for a long run Expectations »Range/duty cycle goals »Analysis goals

3. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO3 John Wheeler’s Picture of General Relativity Theory

4. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO4 General Relativity: A Picture Worth a Thousand Words

5. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO5 The New Wrinkle on Equivalence Not only the path of matter, but even the path of light is affected by gravity from massive objects Einstein Cross Photo credit: NASA and ESA A massive object shifts apparent position of a star

6. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO6 Gravitational Waves Gravitational waves are ripples in space when it is stirred up by rapid motions of large concentrations of matter or energy Rendering of space stirred by two orbiting black holes:

7. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO7 Gravitational waves are hard to find because spacetime is stiff! => Wave can carry huge energy with miniscule amplitude! h ~ (G/c 4 ) (E NS /r)

8. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO8 Basic Signature of Gravitational Waves for All Detectors

9. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO9 Initial LIGO: Power-recycled Fabry-Perot-Michelson suspended mirrors mark inertial frames antisymmetric port carries GW signal Symmetric port carries common-mode info Intrinsically broad band and size-limited by speed of light.

10. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO10 Core Optics Suspension and Control Local sensors/actuators provide damping and control forces Mirror is balanced on 1/100 th inch diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

11. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO11 The LIGO Observatories Adapted from “The Blue Marble: Land Surface, Ocean Color and Sea Ice” at visibleearth.nasa.gov NASA Goddard Space Flight Center Image by Reto Stöckli (land surface, shallow water, clouds). Enhancements by Robert Simmon (ocean color, compositing, 3D globes, animation). Data and technical support: MODIS Land Group; MODIS Science Data Support Team; MODIS Atmosphere Group; MODIS Ocean Group Additional data: USGS EROS Data Center (topography); USGS Terrestrial Remote Sensing Flagstaff Field Center (Antarctica); Defense Meteorological Satellite Program (city lights). LIGO Hanford Observatory (LHO) H1 : 4 km arms H2 : 2 km arms LIGO Livingston Observatory (LLO) L1 : 4 km arms 10 ms

12. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO12 What Limits Sensitivity of Interferometers? Seismic noise & vibration limit at low frequencies Atomic vibrations (Thermal Noise) inside components limit at mid frequencies Quantum nature of light (Shot Noise) limits at high frequencies Myriad details of the lasers, electronics, etc., can make problems above these levels DESIGN COMMISSIONING

13. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO13 Commissioning and Running Time Line NowInauguration 1999 2000200120022003 3 41 2 3 4 1 2 3 4 1 2 3 4 1 2 3 4 E2 Engineering E3 E5 E9E10 E7 E8 E11 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 ] 4x10 -23

14. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO14 Some of the technical challenges for design and commissioning Typical Strains < 10 -21 at Earth ~ 1 hair’s width at 4 light years Understand displacement fluctuations of 4-km arms at the millifermi level (1/1000 th of a proton diameter) Control arm lengths to 10 -13 meters RMS Detect optical phase changes of ~ 10 -10 radians Hold mirror alignments to 10 -8 radians Engineer structures to mitigate recoil from atomic vibrations in suspended mirrors Do all of the above 7x24x365 Now playing at an observatory near you…

15. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO15 Feedback & Control for Mirrors and Light Damp suspended mirrors to vibration-isolated tables »14 mirrors  (pos, pit, yaw, side) = 56 loops Damp mirror angles to lab floor using optical levers »7 mirrors  (pit, yaw) = 14 loops Pre-stabilized laser »(frequency, intensity, pre-mode-cleaner) = 3 loops Cavity length control »(mode-cleaner, common-mode frequency, common-arm, differential arm, michelson, power-recycling) = 6 loops Wave-front sensing/control »7 mirrors  (pit, yaw) = 14 loops Beam-centering control »3 points  (pit, yaw) = 6 loops

16. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO16 LIGO Science Runs and what we learned from them… S1: 17 days in Aug-Sep 2002 »3 LIGO interferometers in coincidence with GEO600 and ~2 days with TAMA300 S2: Feb 14 – Apr 14, 2003 »3 LIGO interferometers in coincidence with TAMA300 S3: Oct 31, 2003 – Jan 9, 2004 »3 LIGO interferometers in coincidence with periods of operation of TAMA300, GEO600 and Allegro S4: Feb 22 – Mar 23, 2005 »3 LIGO interferometers in coincidence with GEO600, Allegro, Auriga

17. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO17 After a lot of effort, it works!

18. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO18 LSC Search Papers (as of 14Nov05) S1: “Setting upper limits on the strength of periodic gravitational waves using the first science data from the GEO600 and LIGO detectors”, Phys. Rev. D 69, 082004 (2004) “First upper limits from LIGO on gravitational wave bursts”, Phys. Rev. D 69, 102001 (2004) “Analysis of LIGO data for gravitational waves from binary neutron stars”, Phys. Rev. D 69, 122001 (2004) “Analysis of first LIGO science data for stochastic gravitational waves”, Phys. Rev. D 69, 122004 (2004)

19. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO19 S2 Search Papers (as of 14Nov05) S2: “Limits on gravitational wave emission from selected pulsars using LIGO data”, Phys. Rev. Lett. 94, 181103 (2005). “A search for gravitational waves associated with the gamma ray burst GRB030329 using the LIGO detectors”, Phys. Rev. D 72, 042002 (2005) “Upper limits on gravitational wave bursts from LIGO’s second science run”, Phys. Rev. D 72, 062001 (2005) “Search for gravitational waves from galactic and extra–galactic binary neutron stars”, Phys. Rev. D 72, 082001 (2005) “Search for gravitational waves from primordial black hole binary coalescences in the Galactic Halo”, Phys. Rev. D 72, 082001 (2005)

20. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO20 S2 Search Papers (as of 14Nov05) S2: “Upper limits from the LIGO and TAMA detectors on the rate of gravitational-wave bursts”, gr-qc/0507081, accepted by Phys. Rev. D “First all-sky upper limits from LIGO on the strength of periodic gravitational waves using the Hough transform”, gr-qc/0508065, accepted by Phys. Rev. D “Search for gravitational waves from binary black hole inspirals in LIGO data”, gr-qc/0509129

21. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO21 S3 Search Papers (as of 14Nov05) S3: “Upper Limits on a Stochastic Background of Gravitational Waves”, astro-ph/0507254

22. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO22 S3/S4 Analyses Underway Einstein@Home “Screensaver” search for undiscovered neutron stars and strange quark stars Uses 40,000 host computers with capacity ~20 Tflops, 24x7 First-pass analysis for LIGO/GEO600 data

23. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO23 What to expect from S3/S4 analyses Pulsars: »Limits on GW emission from 93 known radio pulsars, coordinated with Jodrell-Bank Pulsar Group »expect best limits on neutron star ellipticities ~10 -6 »expect Crab sensitivity ~ 4  spindown limit »all-sky/all-frequency search underway Cosmic GW background limits expected to be near  GW ~10 -4 Sensitivity to neutron-star inspirals starting to include Virgo cluster First limits on cosmic strings

24. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO24 RunS3 L121.8% H169.3% H263.4% Triple15.8% S3 showed we could meet our RMS goal, but… Needed to fix the duty cycle Also wanted to improve high- frequency operation  more laser power

25. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO25 Installation of HEPI at Livingston has improved the stability of L1

26. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO26 S4 Science Duty Cycle H1: 80.5% H2: 81.4% L1: 74.5% HEPI delivers!

27. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO27 High laser power operation requires adaptive adjustments to optical figure CO 2 Laser ITM To ITM HR surface Thermal compensation system

28. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO28 We now think Initial LIGO detector is ready for a long run RunS4 S5 Target SRD goal L175%85%90% H181%85%90% H281%85%90% 3- way 57%70%75% Sensitivity targets * : H1 inspiral range ~ 10 Mpc L1 inspiral range ~ 10 Mpc H2 inspiral range ~ 5 Mpc * As measured by SenseMon Duty Cycle targets:

29. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO29 Automated Noise Budget

30. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO30 Binary Inspiral Search: LIGO Ranges Image: R. Powell binary neutron star range binary black hole range

31. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO31 What to expect from S5 analyses Sensitivity to bursts ~10 -21 RMS Sensitivity to neutron-star inspirals at Virgo cluster Pulsars »expect best limits on known neutron star ellipticities at few x10 -7 »expect to beat spindown limit on Crab pulsar »Hierarchical all-sky/all-frequency search Cosmic GW background limits expected to be near  GW ~10 -5 Perhaps a discovery?

32. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO32 These are exciting times! Pinning down origins of short GRBs will result in more solid estimates of NS-NS and NS-BH mergers Groups led by Burrows and Wheeler now have supernova models that explode! Expect to see action in re-computing GWB waveforms.

33. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO33 On the more speculative front… Graphic from KITP newsletter, heralding an observable string theory prediction: GWs from cosmological strings may be verified by LIGO in its first long science run.

34. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO34 Closing remarks… Progressive detector improvements have achieved design goals for Initial LIGO detector Early implementation of Advanced LIGO techniques helped achieve goals »HEPI for duty-cycle boost »Thermal compensation of mirrors for high-power operation Some commissioning breaks expected during S5 to improve performance and/or reliability Believe still room for post-S5 improvements before 2010 shutdown for Advanced LIGO upgrade

35. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO35 The Beginning

36. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO36 What’s next? Advanced LIGO… Major technological differences between LIGO and Advanced LIGO Initial Interferometers Advanced Interferometers Open up wider band Reshape Noise Advanced interferometry Signal recycling Active vibration isolation systems High power laser (180W) 40kg Quadruple pendulum: Silica optics, welded to silica suspension fibers

37. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO37 Also: keep tragedy away

38. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO38 LIGO S2 data Assumes H 0 = 72 km/s/Mpc, at design sensitivity LIGO S3 data Sensitivity to Isotropic Stochastic Background

39. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO39 Issues to resolve At current sensitivity and duty cycle, it would be a shame not to start a long run, but some issues remain to be resolved during the run Use monitors to identify sources of instrumental transients Identify low-frequency noise to extend range Upconversion is known to be important »Need better vetoes »Identify and mitigate sources Near “the wall” on high power operation »Protective shutters to handle loss of lock have a tough time »Steady state AS-port light is stressing photodiodes to limit »Need to design and implement an output mode cleaner to enable higher power operation (probably post-S5)

40. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO40 Low frequency noise not explained

41. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO41 Possible source: upconversion from stack motion Using HEPI, increase the suspension point motion at 1.5 Hz by a factor of 5 DARM noise increases significantly over a wide band Effect measured both at LHO & at LLO: H1 exhibits a day-to-night variation in low frequency noise, with a ~10% reduction in inspiral range during the day

42. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO42 Scattered light fringe wrapping? BRT ITM ETM E sc ~10 -6 E 0 For 1% reflection from beam reducing optics & excitation of ETMX only

43. LIGO-G050589-00-W Raab: Searching for Distant Sources w/ LIGO43 Stress at the antisymmetric port: Loss-of-lock: full beamsplitter power can be dumped out the AS port, in a ~10 msec width pulse PD damage due to »Too high trigger level »Shutter failure »Shutter too slow Damaged PDs can be noisy and position-dependent Working on shutter improvements Steady-state stress (principally due to AS_I saturation) needs relief ~100 W 5 msec Red: replaced damaged PDs An example of photodiode stress