1. LIGO-G050478-00-W Commissioning and Performance of the LIGO Interferometers Reported on behalf of LIGO colleagues by Fred Raab, LIGO Hanford Observatory (Substituting for Brian O’Reilly, LIGO Livingston Observatory, whose trip was cancelled by Hurricane Katrina)

2. LIGO-G050478-00-W LIGO Detector Commissioning2 Time Line NowInauguration 19992000200120022003 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 Runs First Science Data S1 S4 Science S2S3S5 10 -22 4K strain noiseat 150 Hz [Hz -1/2 ]

3. LIGO-G050478-00-W LIGO Detector Commissioning3 Schematic of Initial LIGO Detector (LIGO-1) suspended mirrors mark inertial frames antisymmetric port carries GW signal Symmetric port carries common-mode info

4. LIGO-G050478-00-W LIGO Detector Commissioning4 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

5. LIGO-G050478-00-W LIGO Detector Commissioning5 Vibration Isolation Systems »Reduce in-band seismic motion by 4 - 6 orders of magnitude »Little or no attenuation below 10Hz »Large range actuation for initial alignment and drift compensation »Quiet actuation to correct for Earth tides and microseism at 0.15 Hz during observation HAM Chamber BSC Chamber

6. LIGO-G050478-00-W LIGO Detector Commissioning6 Core Optics Substrates: SiO 2 »25 cm Diameter, 10 cm thick »Homogeneity < 5 x 10 -7 »Internal mode Q’s > 2 x 10 6 Polishing »Surface uniformity < 1 nm rms »Radii of curvature matched < 3% Coating »Scatter < 50 ppm »Absorption < 2 ppm »Uniformity <10 -3 Production involved 6 companies, NIST, and LIGO

7. LIGO-G050478-00-W LIGO Detector Commissioning7 Core Optics Suspension and Control Shadow sensors & voice-coil actuators provide damping and control forces Mirror is balanced on 30 micron diameter wire to 1/100 th degree of arc Optics suspended as simple pendulums

8. LIGO-G050478-00-W LIGO Detector Commissioning8 Pre-stabilized Laser (PSL) Custom-built 10 W Nd:YAG Laser, joint development with Lightwave Electronics (now commercial product) Frequency reference cavity (inside oven) Cavity for defining beam geometry, joint development with Stanford

9. LIGO-G050478-00-W LIGO Detector Commissioning9 IO Frequency Stabilization of the Light Employs Three Stages Pre-stabilized laser delivers light to the long mode cleaner Start with high-quality, custom-built Nd:YAG laser Improve frequency, amplitude and spatial purity of beam Actuator inputs provide for further laser stabilization Wideband Tidal 10-Watt Laser PSL Interferometer 15m 4 km

10. LIGO-G050478-00-W LIGO Detector Commissioning10 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 »2 arms  (pit, yaw) = 4 loops

11. LIGO-G050478-00-W LIGO Detector Commissioning11 Digital Interferometer Sensing & Control System

12. LIGO-G050478-00-W LIGO Detector Commissioning12 LIGO-1 Signal Recovery Configuration AS REFL POB

13. LIGO-G050478-00-W LIGO Detector Commissioning13 Now Look at LSC Screen

14. LIGO-G050478-00-W LIGO Detector Commissioning14 AS, PO, REFL Inputs

15. LIGO-G050478-00-W LIGO Detector Commissioning15 Input Matrix Decodes Input into DARM, CARM, MICH, PRC

16. LIGO-G050478-00-W LIGO Detector Commissioning16 Separate Filtering and Gain Sections for Each Loop

17. LIGO-G050478-00-W LIGO Detector Commissioning17 Output Matrix Translates Loop Feedback into Actuator Signals

18. LIGO-G050478-00-W LIGO Detector Commissioning18 Digital Controls screen example Analog In Analog Out Digital calibration input

19. LIGO-G050478-00-W LIGO Detector Commissioning19 LIGO Sensitivity Over Time Livingston 4km Interferometer May 01 Jan 03

20. LIGO-G050478-00-W LIGO Detector Commissioning20

21. LIGO-G050478-00-W LIGO Detector Commissioning21 Interferometer Strain Sensitivity

22. LIGO-G050478-00-W LIGO Detector Commissioning22 It works! Long-term search begins Nov05

23. LIGO-G050478-00-W LIGO Detector Commissioning23 Why is Locking Difficult? One meter Human hair, about 100 microns Wavelength of light, about 1 micron LIGO sensitivity, 10 -18 meter Nuclear diameter, 10 -15 meter Atomic diameter, 10 -10 meter Earthtides, about 100 microns Microseismic motion, about 1 micron Precision required to lock, about 10 -10 meter

24. LIGO-G050478-00-W LIGO Detector Commissioning24 RunS3S4 L121.8%74.5% H169.3%80.5% H263.4%81.4% Triple15.8%56.9% Progress: Duty Cycle

25. LIGO-G050478-00-W LIGO Detector Commissioning25 Why Had Duty Cycle Been Lower in Livingston

26. LIGO-G050478-00-W LIGO Detector Commissioning26 Improved Isolation with the Hydraulic External Pre-Isolator (HEPI) Adv. LIGO approach, accelerated & adapted for use in initial LIGO

27. LIGO-G050478-00-W LIGO Detector Commissioning27 HEPI

28. LIGO-G050478-00-W LIGO Detector Commissioning28 HAM BSC Active External Pre-Isolators Seismic Retrofit at Livingston

29. LIGO-G050478-00-W LIGO Detector Commissioning29 One-Arm Test of External Pre- Isolation Confirms Performance

30. LIGO-G050478-00-W LIGO Detector Commissioning30 Thermal Compensation Over-heat Correction Inhomogeneous Correction Under-heat Correction CO 2 Laser ? ZnSe Viewport Over-heat pattern Inner radius = 4cm Outer radius =11cm  Cold power recycling cavity is unstable: poor buildup and mode shape for the RF sidebands  ITM thermal lens power of ~0.00003 diopters needed to achieve a stable, mode-matched cavity  intended to be produced by ~25 mW absorbed from 1μm beam ITM

31. LIGO-G050478-00-W LIGO Detector Commissioning31 Sideband Images as Function of Thermal Heating No Heating 30 mW 60 mW 90 mW 120 mW 150 mW 180 mW Input beam Best match

32. LIGO-G050478-00-W LIGO Detector Commissioning32 Close-up of estimated noise sources for L1

33. LIGO-G050478-00-W LIGO Detector Commissioning33 Ongoing story of photodiode damage Loss-of-lock: full beamsplitter power can be dumped out the AS port, in a ~10 msec width pulse »Mechanical shutter cuts off the beam, with a trigger delay of about 6 msec PD damage due to »Too high trigger level »Shutter too slow (wrong type) Damaged PDs can be noisy Solution (in progress): »All shutters of proper type »Carefully set trigger level »Looking at cutting off PD bias voltage on lock-loss ~100 W 5 msec Red: replaced damaged PDs

34. LIGO-G050478-00-W LIGO Detector Commissioning34 Upconversion from stack motion Using HEPI, increase the suspension point motion at 1.5 Hz by a factor of 5 DARM noise increases by a factor of ~5 over a wide band Effect first seen at LHO, & measured recently at LLO:

35. LIGO-G050478-00-W LIGO Detector Commissioning35 Scattered light fringe wrapping BRT ITM ETM E sc ~10 -10 E 0 Data looks a lot like what you’d expect from scattered light Don’t know where light is scattering off Beam tube baffles were made to cut stray rays: 270 mm aperture May be possible to use feedback to reduce optical table motion

36. LIGO-G050478-00-W LIGO Detector Commissioning36 Closing remarks… Progressive sensitivity improvements have achieved design goals Early implementation of Advance LIGO techniques helped achieve goals »HEPI for duty-cycle boost »Thermal compensation of mirrors for high-power operation Some technical issues being worked to improve long- term robustness and reliability »Loss-of-lock protection for photodiodes »Upconversion mitigation Believe still room for post-S5 improvements