Several Fun Research Projects at NAOJ for the Future GW Detectors Picture: Sora Kawamura Several Fun Research Projects at NAOJ for the Future GW Detectors LIGO Seminar @ Caltech Aug. 8, 2006 Seiji Kawamura National Astronomical Observatory of Japan

National Astronomical Observatory of Japan (NAOJ) NAOJ is located in Tokyo. TAMA300 is located on the NAOJ campus.

Other research projects at NAOJ Displacement-noise free Interferometer RSE DECIGO MHz GW detection QND

Displacement-noise free Interferometer

Motivation Displacement noise: seismic Noise, thermal noise, radiation pressure noise Cancel displacement noise  shot noise limited sensitivity Increase laser power  sensitivity improved indefinitely Diplacement noise Displacement noise Cancel displacement noise Shot noise Sensitivity Increase laser power PD Laser Frequency

Principle 1: GW and mirror motion interact with light differently On reflection On propagation Light Mirror motion Mirror motion Difference outstanding for GW wavelength  distance between masses

Principle 2: Mirror motion can be cancelled by combining interferometer outputs Laser Increase # of mirrors Implement many interferometers Take combination outputs  cancel mirror motion Mirror motion PD Laser PD Mirror motion Bi-directional MZ

Example of DFI Two 3-d bi-directional MZ Take combination of 4 outputs Mirror motion completely cancelled GW signal remains (f 2)

Experiment (Ideal) One bi-directional MZ GW Laser Mirror motion PD Extract GW  Mirror motion

Experiment (Practical) EOM used for GW and mirror motion Simulated mirror motion Simulated GW Mirror motion GW ～ ～ Laser Laser PD PD Ideal　　　　　　　　　　　　　　　　Practical

Results Mirror motion cancels out GW signal remains Mirror motion to output GW signal to output Difference Difference Mirror motion　　　　　　　　GW signal

Next step Implement cavity to reduce the effective frequency Demonstrate the cancellation of the BS motion using two bi-directional MZ References Kawamura and Chen, PRL, 93, (2004) 211103 Chen and Kawamura, PRL, 96 (2006) 231102 Chen, Pai, Somiya, Kawamura, Sato, Kokeyama, Ward, submitted to PRL (gr-qc/0603054) Sato, Kawamura, Kokeyama, Ward, Chen, Pai, and Somiya, to be submitted to PRL

RSE

4m RSE Supended mass RSE Miniature suspension system

Previous Accomplishments Tuned RSE (w/o PRM) locked Detuned RSE (w/o PRM) locked Optical spring effect observed Miyakawa, Somiya, Heinzel, and Kawamura, Class. and Quantum Grav., 19 (2002) p.1555-1560 Somiya, Beyersdorf, Arai, Sato, Kawamura, Miyakawa, Kawazoe, Sakata, Sekido, Mio, Appl. Opt. 44 (2005) pp. 3179-3191

Current Activity Try new signal extraction method Lock RSE (w/ PRM) Backup for Advanced LIGO Baseline for LCGT Lock RSE (w/ PRM)

New Signal Extraction Method

Signal Matrix Baseline Design for LCGT Black: Analytic results Red: Numerical simulation using “FINESSE” lp ls diagonal ls orthogonal Baseline Design for LCGT lp

Delocation Option for LCGT - Could have potential advantages

Current Status MZ locked only w/ PM FP Michelson locked Suspension system improved

DECIGO

What is DECIGO? Deci-hertz Interferometer Gravitational Wave Observatory - bridges the gap between LISA and terrestrial detectors. - could attain high sensitivity because of lower confusion noise. 10-18 10-24 10-22 10-20 LISA Terrestrial Detectors Strain [Hz-1/2] DECIGO Confusion Noise 10-4 10-2 100 102 104 Frequency [Hz]

Pre-conceptual Design FP-Michelson interferometer Arm length: 1000 km Laser power: 10 W Laser wavelength: 532 nm Mirror diameter: 1 m Mirror mass: 100 kg Finesse: 10 Orbit and constellation: TBD Drag-free satellite Arm cavity PD Laser Arm cavity Kawamura, et al., CQG 23 (2006) S125-S131 PD Drag-free satellite Drag-free satellite

Drag-free and FP Cavity Displacement Signal between S/C and Mirror Local Sensor Mirror Thruster Thruster Actuator Displacement signal between the two Mirrors

Requirements [Practical force noise] 4x10-17 N/Hz per mirror [Frequency Noise] @ 1 Hz First-stage stabilization： 1 Hz/Hz Stabilization gain by common-mode arm length： 105 Common-mode rejection ratio： 105

Science by DECIGO BH+BH(1000Msun) @z=1 NS+NS@z=1 Correlation for 3 years NS-NS (1.4+1.4Msun) z<1 (SN>26: 7200/yr) z<3 (SN>12: 32000/yr) z<5 (SN>9: 47000/yr) IMBH (1000+1000Msun) z<1 (SN>6000)

Acceleration of Expansion of the Universe Expansion ＋Acceleration? DECIGO GW NS-NS (z～1) Output Template (No Acceleration) Strain Real Signal ? Phase Delay～1sec (10 years) Time Seto, Kawamura, Nakamura, PRL 87, 221103 (2001)

Roadmap for DECIGO R&D Advanced R&D PF1 PF2 DECIGO 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 R&D Advanced R&D PF1 Design & Fabrication Observation PF2 Design & Fabrication Observation DECIGO 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24

DECIGO Pathfinder1 Objectives Drag-free system Cavity locking in space Modest sensitivity at 0.1 – 1 Hz Local Sensor Actuator Thruster

DECIGO Pathfinder2 Objectives DECIGO with modest specification Cavity locking between two satellites Meaningful sensitivity Drag-free satellite Arm cavity PD Laser Arm cavity PD Drag-free satellite Drag-free satellite

DECIGO Simulator Objectives Continual free-fall environment Clamp release Modest sensitivity down to 0.1Hz Possibility of long arm Clamp 2m Vertical Position 1 sec Release Hold Release Hold Release Hold Time

DECIGO Demonstrator Air-hockey table Objectives Lock acquisition Thruster Thruster Satellite A Satellite B Mirror A Mirror B Actuator Local sensor Local sensor Air-hockey table Objectives Lock acquisition

Budget and Working Group Will submit a budget request ($18M for 6 years) this fall R&D for DECIGO PF1 w/ Pulsar Timing DECIGO-WG: 120 members currently

MHz GW detection

Objectives and Scope GW Sources at MHz Detect GW at MHz Develop technologies for synchronous recycling GW Sources at MHz Inspiral of mini black holes GW from inflation period

Synchronous Recycling Recycling Mirror Laser BS Drever, 1983 Dark Fringe Photo detector

Response of Synchronous Recycling x h t y y x GW l Laser GW  4 l BS Photo detector GW effect synchronously enhanced!

Plan for Table-top Experiment Integration for 1 year h  10-26 Hz-1/2 F  105 h  10-21 Hz-1/2 l  75 cm fGW  100 MHz

Current Status Locked w/ low Finesse Noise Spectrum taken F  100 f 1 Non 50:50 Beam splitter 1 DOF to control EOM f 1 f GW - f 1 - BW Output

First Noise Spectrum

QND

Objectives and Scope Plan Beat SQL using ponderomotive squeezing Use FP Michelson w/ super light mirrors Plan Observe radiation pressure noise Reduce radiation pressure noise w/ homodyne detection Beat SQL Expand the effective frequency range

Ponderomotive Squeezing Squeezed by phase change caused by reflection by free mass Squeezing: frequency dependent Cannot beat SQL w/ RF method Laser Noise Signal Vacuum Caves, Walls & Milburn, Braginsky & Khalili, ...

Homodyne Detection Local light Laser Homodyne phase Signal Noise S/N can be improved by choosing appropriate homodyne phase!

Quantum Noise Radiation pressure noise can be completely cancelled at one frequency The frequency depends on homodyne phase

Strategy Use super-light mirror Use high finesse Increase radiation pressure noise Easier to detect Use tuned IFO (no optical spring)

Design Parameter and Noise Estimate Laser power 200 mW Injected power into the interferometer 120 mW Finesse 7500 Front mirror mass 200 g End mirror mass 23 mg Diameter of the end mirror 3 mm Thickness of the end mirror 1.5 mm Beam radius on the end mirror 500 mm Q factor of substrate 105 Loss angle of coating 4×10-4 Temperature 300 K Length of the fiber 1 cm Thickness of silica fiber 10 mm

Current Status Homodyne detection method verified Vacuum tank ready Design of set-up complete Fiber of 10 m drawn successfully

The End