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Future LIGO Interferometers Moriond 07 La Thuille, Italy LIGO – G 070055 -00 -R Future LIGO Interferometers Moriond 07 La Thuille, Italy LIGO – G 070055 -00 -R Rana Adhikari Caltech 1

Advanced LIGO mission: detect gravitational waves and initiate GW astronomy Next detector » Should Advanced 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 Advanced LIGO 2 LIGO – G 070055 -00 -R

The next several years Other interferometers in operation (GEO, Virgo) NOW 4 Q ‘ The next several years Other interferometers in operation (GEO, Virgo) NOW 4 Q ‘ 06 4 Q ‘ 05 S 5 § 4 Q ‘ 07 4 Q ‘ 08 4 yrs 4 Q ‘ 09 ~2 years 4 Q ‘ 10 S 6 Between now and Adv. LIGO, there is some time to improve… 1) ~Few years of hardware improvements + 1 ½ year of observations. 1) Factor of ~2. 5 in noise, factor of ~10 in event rate. 2) 3 -6 interferometers running in coincidence ! Enhanced LIGO details in “Lessons from LIGO-I” talk on Thursday LIGO – G 070055 -00 -R Adv LIGO

Advanced LIGO Sketch 40 KG FUSED SILICA TEST MASSES ACTIVE SEISMIC ISOLATION FUSED SILICA, Advanced LIGO Sketch 40 KG FUSED SILICA TEST MASSES ACTIVE SEISMIC ISOLATION FUSED SILICA, MULTIPLE PENDULUM SUSPENSION 180 W LASER, MODULATION SYSTEM PRM BS ITM ETM SRM PD T ~ 1% Power Recycling Mirror Beam Splitter Input Test Mass End Test Mass Signal Recycling Mirror Photodiode 4 LIGO – G 070055 -00 -R

Parameter Equivalent strain noise, minimum Neutron star binary inspiral range Omega GW Interferometer configuration Parameter Equivalent strain noise, minimum Neutron star binary inspiral range Omega GW Interferometer configuration Laser Power in Arm Cavities Test masses Seismic wall frequency Beam size Test mass Q Suspension fiber Q LIGO – G 070055 -00 -R LIGO I Adv LIGO 3 x 10 -23/rt. Hz 2 x 10 -24/rt. Hz 15 Mpc 175 Mpc 3 x 10 -6 1. 5 -5 x 10 -9 Power-recycled MI w/ FP arm cavities LIGO I, plus signal recycling 15 k. W 800 k. W Fused silica, 10 kg Fused Silica, 40 kg 40 Hz 10 Hz 4 cm 6 cm Few million 200 million Few thousand ~30 million

Anatomy of the projected Adv LIGO detector performance Newtonian background, estimate for LIGO sites 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 10 -21 10 -22 Initial LIGO 10 -23 Advanced LIGO Unified quantum noise dominates at most frequencies for full 10 -24 power, broadband tuning NS-NS Tuning 10 Hz 100 Hz 1 k. Hz 6 LIGO – G 070055 -00 -R

Advanced LIGO Design Features 40 KG FUSED SILICA TEST MASSES ACTIVE SEISMIC ISOLATION FUSED Advanced LIGO Design Features 40 KG FUSED SILICA TEST MASSES ACTIVE SEISMIC ISOLATION FUSED SILICA, MULTIPLE PENDULUM SUSPENSION 180 W LASER, MODULATION SYSTEM PRM BS ITM ETM SRM PD Power Recycling Mirror Beam Splitter Input Test Mass End Test Mass Signal Recycling Mirror Photodiode 7 LIGO – G 070055 -00 -R

Why use Signal Recycling? no signal recycling Pbs = 10 Pbs Principal advantage of Why use Signal Recycling? no signal recycling Pbs = 10 Pbs Principal advantage of signal recycling is in power handling LIGO – G 070055 -00 -R

Ultra Stable Laser High power laser: 180 Watts Front end high power, injectionlocked stage Ultra Stable Laser High power laser: 180 Watts Front end high power, injectionlocked stage 12 W Master Oscillator 180 W Alternative front end 35 W (relative power fluctuations ~ 2 x 10 -9) Laser frequency stabilization Laser power stabilization » Wideband frequency actuation for further stabilization (~ 10 -7 Hz/r. Hz) Pre-mode cleaner for spatial clean-up and high-frequency filtering Work lead by AEI (Hanover) in collaboration with LZH (Laser Zentrum Hanover) LIGO – G 070055 -00 -R 9

ACTIVE SEISMIC ISOLATION Test Masses 40 KG SAPPHIRE TEST MASSES ACTIVE ISOLATION FUSED SILICA, ACTIVE SEISMIC ISOLATION Test Masses 40 KG SAPPHIRE TEST MASSES ACTIVE ISOLATION FUSED SILICA, MULTIPLE PENDULUM SUSPENSION QUAD SILICA SUSPENSION 200 W LASER, MODULATION SYSTEM 10 LIGO – G 070055 -00 -R

Core Interferometer Optics 40 kg Test Masses: 34 cm x 20 cm Large beam Core Interferometer Optics 40 kg Test Masses: 34 cm x 20 cm Large beam size on test masses (6. 0 cm radius), to reduce thermal noise 40 kg PRM T = 7% Challenges: Substrate polishing Dielectric coatings Metrology Substrate procurement LIGO – G 070055 -00 -R BS: 37 cm x 6 cm Compensation plates: 34 cm x 6. 5 cm ITM T = 0. 5% Round-trip optical loss: 75 ppm max SRM T = 7% Recycling Mirrors: 26. 5 cm x 10 cm 11

Substrates » Fused silica: Heraeus (for low absorption) or Corning » Specific grade Substrates » Fused silica: Heraeus (for low absorption) or Corning » Specific grade and absorption depends on optics » ITMs and BS most critical (need low absorption and good homogeneity) Compensation Polishing » Low micro-roughness (< 1 angstrom-rms) » Low residual figure distortion (< 1 nm-rms over central 120 mm diameter) » Accurate matching of radii-of-curvature » Surfaces for attachment of suspension fibers Core Optics Dielectric coatings before » Low absorption (0. 5 ppm or smaller) » Low scatter ( < 30 ppm) » Low mechanical loss (< 2 e-4) In-house Metrology » ROC, figure distortion, scattering, absorption LIGO – G 070055 -00 -R after 12

Seismic Isolation 40 KG SAPPHIRE TEST MASSES ACTIVE ISOLATION COATINGS QUAD SILICA SUSPENSION 200 Seismic Isolation 40 KG SAPPHIRE TEST MASSES ACTIVE ISOLATION COATINGS QUAD SILICA SUSPENSION 200 W LASER, MODULATION SYSTEM 13 LIGO – G 070055 -00 -R

14 LIGO – G 070055 -00 -R 14 LIGO – G 070055 -00 -R

Seismic Isolation: Active Platform Requirement BSC Chamber Value Payload Mass 800 kg Range ± Seismic Isolation: Active Platform Requirement BSC Chamber Value Payload Mass 800 kg Range ± 1 mm, ± 0. 5 mrad 3 x 10 -13 m/√Hz @10 Hz 10 nrad Table Noise Angular Noise 15 LIGO – G 070055 -00 -R

Quad Suspensions Quadruple pendulum: » ~107 attenuation @10 Hz Magnets » Controls applied to Quad Suspensions Quadruple pendulum: » ~107 attenuation @10 Hz Magnets » Controls applied to upper layers; noise filtered from test masses Electrostatic q Seismic isolation and suspension together: » 10 -19 m/rt. Hz at 10 Hz LIGO – G 070055 -00 -R Fused silica fiber w Welded to ‘ears’, hydroxy-catalysis bonded to optic

GW Readout 40 KG SAPPHIRE TEST MASSES ACTIVE ISOLATION COATINGS QUAD SILICA SUSPENSION 200 GW Readout 40 KG SAPPHIRE TEST MASSES ACTIVE ISOLATION COATINGS QUAD SILICA SUSPENSION 200 W LASER, MODULATION SYSTEM 17 LIGO – G 070055 -00 -R

@ the Caltech 40 m Lab LIGO – G 070055 -00 -R @ the Caltech 40 m Lab LIGO – G 070055 -00 -R

@ the Caltech 40 m Lab LIGO – G 070055 -00 -R @ the Caltech 40 m Lab LIGO – G 070055 -00 -R

@ the Caltech 40 m Lab DC Readout Beamline Controls and Noise Characterization Prototype @ the Caltech 40 m Lab DC Readout Beamline Controls and Noise Characterization Prototype PD ELECTRONICS MMT 1 OMC Tip/Tilt RF PICKOFF Squeezer Pickoff LIGO – G 070055 -00 -R MMT 2

Projected Noise Sources Seismic Noise 109 Suspension Thermal Noise 102 LIGO – G 070055 Projected Noise Sources Seismic Noise 109 Suspension Thermal Noise 102 LIGO – G 070055 -00 -R Initial LIGO Quantum Optical Noise is Tunable!

Opto-mechanical Spring Radiation pressure: F= 2 P/c Detuned Cavity -> d. F/dx Measured Transfer Opto-mechanical Spring Radiation pressure: F= 2 P/c Detuned Cavity -> d. F/dx Measured Transfer Functions from the 40 m prototype • ½ MW in the arms -> • ‘Optical Bar’ detector • ~75 Hz unstable optomechanical resonance • High Bandwidth servos Optical Spring stiffness ~ 107 N/m BMW Z 4 ~ 104 N/m Angular spring resonance ~ 2 Hz LIGO – G 070055 -00 -R

NS/NS Binary Area proportional to SNR Most of the sensitivity comes from a band NS/NS Binary Area proportional to SNR Most of the sensitivity comes from a band around 50 Hz LIGO – G 070055 -00 -R 50 Hz

There’s more… End Test Mass Arm Cavity Q Power Recycling mirror 2 k. W There’s more… End Test Mass Arm Cavity Q Power Recycling mirror 2 k. W Laser Input Test Mass 500 k. W 125 W 50/50 beam splitter Signal Cavity Q GW signal LIGO – G 070055 -00 -R Signal Recycling mirror

30% Sensitivity Improvement Low laser power! Lower Arm Cavity finesse Lower SRC finesse LIGO 30% Sensitivity Improvement Low laser power! Lower Arm Cavity finesse Lower SRC finesse LIGO – G 070055 -00 -R

Advanced LIGO Initial instruments, data helping to establish the field of interferometric GW detection Advanced LIGO Initial instruments, data helping to establish the field of interferometric GW detection Advanced LIGO promises exciting astrophysics Substantial progress in R&D, design Enhanced LIGO starts now!! Installation in 2011, Data ~2013 -2014 Steady stream of gravitational wave signals 26 LIGO – G 070055 -00 -R