6WDWXVRI/,*2. Laser Interferometer Gravitational-wave Observatory. Nergis Mavalvala MIT IAU214, August 2002 LIGO-G D

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1 6WDWXVRI/,*2 Laser Interferometer Gravitational-wave Observatory Hanford, WA Livingston, LA Nergis Mavalvala MIT IAU214, August 2002

2 *UDYLWDWLRQDOZDYH,QWHUIHURPHWHUVWKHSULQ LSOH General Relativity (Einstein 1916) predicts freely propagating transverse space-time distortions λ L L P IN L- L L+ L φ=0 L = h L φ= φ h ~ Michelson Interferometer Pirani 56, Gerstenshtein and Pustovoit, Weber, Weiss 72

3 :K\DQ2EVHUYDWRU\" Two sites Three interferometers Coincidence Long lifetime Facilities limits First detector (LIGO I) Now This talk Advanced detectors (LIGO II and beyond) Advanced Initial

4 3DVW«)XWXUH Construction underway (mostly civil) Facilities Construction (vacuum system) Interferometer Construction (facilities completed) Construction Completed (interferometers installed in vacuum) Detector Installation (commissioning subsystems) Commission Interferometers (first coincidences) Sensitivity Studies (initial LIGO I Science Run) LIGO I Data Run (one year integrated data at h ~ ) Begin advanced LIGO installation

5 ,QLWLDO/,*26HQVLWLYLW\*RDO Strain sensitivity < 3x /Hz 1/2 at 200 Hz Displacement Noise Seismic motion Thermal Noise Radiation Pressure Sensing Noise Photon Shot Noise Residual Gas Facilities limits much lower

6 'HWH WRU2YHUYLHZ 10 W Laser Vacuum 20 kw Input Optics 300 W 4 km

7 6HLVPL,VRODWLRQ Seismic isolation stacks Stainless steel masses Î 600 kg each stage Helicoil springs with lossy viscoelastic layer Î Q ~ 40 3 to 4 stages Î 10-6 to 10-8 for f > 10 Hz

8 &RUH2SWL V 25 cm diameter, 10 kg fused silica optics Polished substrates Micro-roughness Î < 10 ppm scatter Optical coatings < 2 ppm scatter < 1 ppm absorption Metrology Î Surface uniformity ~1 nm rms

9 6XVSHQVLRQV Single wire loop suspensions Four electromagnetic actuators Four shadow sensors for local position sensing Small optic Large optic

10 2SWL DO'HVLJQRIWKH,QWHUIHURPHWHUV Requires test masses to be held in position to meter: Locking the interferometer Light is recycled ~30 to 50 times Light bounces in arm cavities ~130 times D increased phase sensitivity Laser Input Optics signal Dark fringe

11 ,QWHUIHURPHWHU6HQVLQJDQG &RQWURO Pre-Mode Cleaner Laser

12 (QJLQHHULQJ5XQ( /,*2*(2$//(*52

13 6WUDLQ6HQVLWLYLW\GXULQJ(

14 Major improvements Front-end electronics (ADC) noise Æ whiten signal Laser frequency noise Æ common-mode servo Output electronics (DAC) noise Æ whiten signal Sensing electronics noise Æ increase light level (YROXWLRQRIVWUDLQVHQVLWLYLW\

15 /,*2,6WDWXV6XPPDU\ :KDWZRUNV All three interferometers locked for hours at a time in powerrecycled configuration D G rec ~ Lock acquisition is done using sys id methods D MTTL ~ 1 2 minute Optical parameters consistent with lab metrology D mirror losses < 70 ppm Tidal feedback systems operational D range of 200 µm pk-pk Mechanical (internal) modes of test masses excited D 10 4 < Q < 10 7 Laser input power 1 5 W but all light power not detected (PD saturations) Coupling to environment, e.g. Aircrafts flying by can be seen (heard?) Earthquakes Trains twice a day at Livingston Anthropogenic noise

16 /,*2,6WDWXV6XPPDU\ :KDWGRHVQ W\HW Seismic pre-isolation system At LLO 10x reduction in rms displacement of optics desired Active sensing and piezoelectric actuation system installed Hydraulic actuation prototyping underway for installation in 2003 Digital controls for optics suspension systems Greater flexibility for tuning servos Easier to orthogonalize displacement and angles of optic Installed/tested on Hanford 4km L4k, e.g., limited by coil driver noise at low frequencies Alignment control systems Partially operational (feedback loops closed on 2 4 of 12 degrees of freedom) Necessary to reduce spurious signals at AS port that causes photodiode saturations Increase detected light levels Î overcome sensing noise at high frequencies Electronics improvements New system layout being designed (EMI/RFI mitigation) Lower noise A/D converters

17 7KH7DVN$KHDG Engineering runs Characterize and improve detector sensitivity and reliability Exercise data analysis system end-to-end pipeline Science runs Upper limits (E7 and beyond) Scientific searches (S1 begins 08/23/02) Commissioning remaining subsystems Factor of 100 (above 400 Hz) to (at 40 Hz) improvement needed to reach design sensitivity LIGO II R&D already underway

18 'HWH WLRQ6WUDWHJ\ &RLQ LGHQ HV Two sites three interferometers Single interferometer Î 50/hr (non-gaussian level) Hanford 4km + 2km Î 1/day (correlated rate) Hanford + Livingston Î 0.1/yr (uncorrelated) Data recording (time series) Gravitational wave signal = 0.2 MB/sec Total data = 16 MB/sec On-line filters, diagnostics, data compression Off-line data analysis, archiving Signal extraction Signal from noise (vetoes, noise analysis) Templates, wavelets