Advanced Virgo and LIGO: today and tomorrow

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1 Advanced Virgo and LIGO: today and tomorrow Michał Was for the LIGO and Virgo collaborations Michał Was (SFP Gravitation) 2017 Nov 22 1 / 21

2 d Basics of interferometric gravitational wave detections Need two ingredients: two test masses and a ruler Michał Was (SFP Gravitation) 2017 Nov 22 2 / 21

3 d Basics of interferometric gravitational wave detections Need two ingredients: two test masses and a ruler Test mass Free falling objects that sense the gravitational wave Michał Was (SFP Gravitation) 2017 Nov 22 2 / 21

4 d Basics of interferometric gravitational wave detections Need two ingredients: two test masses and a ruler Test mass Ruler Free falling objects that sense the gravitational wave Michał Was (SFP Gravitation) laser light the wavelength is the ruler tick mark 2017 Nov 22 2 / 21

5 Basics of interferometric gravitational wave detections Need two ingredients: two test masses and a ruler Mirror Mirror L = 3km L = 3km Partially reflective beam-splitter Laser Photodiode Longer arms larger effect Michał Was (SFP Gravitation) 2017 Nov 22 3 / 21

6 Basics of interferometric gravitational wave detections Noise can spoil measurements in many different ways Mirror Displacement noise Mirror L = 3km L = 3km Laser noise Partially reflective beam-splitter Sensing noise Laser Photodiode Noises don t increase with arm length Michał Was (SFP Gravitation) 2017 Nov 22 4 / 21

7 d Michał Was (SFP Gravitation) 2017 Nov 22 5 / 21

8 Advanced detectors time-line Early Mid Late Design LIGO O O O3 190 Virgo O O KAGRA Michał Was (SFP Gravitation) 2017 Nov 22 6 / 21

9 O2 vs O1 in LIGO Binary neutron star range: Average horizon distance Horizon 2.26 range Similar sensitivity Longer duration O1: 16 weeks, 50 days of coincident operations O2: 37 weeks, 120 days of coincident operations Michał Was (SFP Gravitation) 2017 Nov 22 7 / 21

10 advanced Virgo joined O2 for last month Strain (1/ Hz) Virgo Hanford Livingston Frequency (Hz) Only 3.5 weeks Sensitivity 2-3 times lower than LIGO Very good stability, 82% duty cycle: 20 days of data Lots of science Michał Was (SFP Gravitation) 2017 Nov 22 8 / 21

11 Advanced Virgo design B8 SWEB WE Input Mode Cleaner WI 200W SIB1 Faraday Isolator SPRB B4 BS CP CP NI NE SNEB Laser PRM POP B7 B2 SIB2 SRM OMCs SDB1 B1 SDB2 Michał Was (SFP Gravitation) 2017 Nov 22 9 / 21

12 Advanced Virgo during O2 B8 SWEB WE Input Mode Cleaner WI 14W SIB1 Faraday Isolator SPRB B4 CP BS CP NI 70kW NE SNEB Laser PRM POP 500W B7 B2 SIB2 SRM OMCs 20mW B1 SDB1 SDB2 Michał Was (SFP Gravitation) 2017 Nov / 21

13 Advanced detectors time-line Early Mid Late Design LIGO O O O3 190 Virgo O O KAGRA Michał Was (SFP Gravitation) 2017 Nov / 21

14 Advanced Virgo full noise budget Michał Was (SFP Gravitation) 2017 Nov / 21

15 Advanced Virgo main limitations Michał Was (SFP Gravitation) 2017 Nov / 21

16 Thermal fluctuation: mirror surface moves by itself ~10-17 m Laser ~1nm Atoms fluctuate by 10 9 m Laser probes over 10 cm 10 cm N atoms Statistics saves us: 10 9 m/ N m Michał Was (SFP Gravitation) 2017 Nov / 21

17 Thermal fluctuation: mirror surface moves by itself Low loss material high Q Concentrate thermal fluctuations at a single frequency Reduce fluctuations elsewhere by 1/ Q Q m Q m Michał Was (SFP Gravitation) 2017 Nov / 21

18 Thermal fluctuation: mirror surface moves by itself Fused silica (suprasil) 40 kg mirrors Polished with roughness of 0.05 nm on 1 mm scale Curvature deviation of 1 nm over 10 cm Avoid glass-steel friction suspend mirrors on 0.4 mm glass fiber Improves Q from 10 6 to 10 8 factor 10 in thermal noise In 2016 glass fibers systematically broken by dust temporarily suspended mirrors on steel wires Michał Was (SFP Gravitation) 2017 Nov / 21

19 Quantum shot noise Quantum fluctuations in number of detected photon in time τ P hc P = τλp Ways to reduce quantum shot noise: higher power P, noise 1/ P squeeze the light quantum state Michał Was (SFP Gravitation) 2017 Nov / 21

20 Improvements planned for 2018 High power laser 35 W 100 W Squeezing Mirror suspended on fused silica fiber Michał Was (SFP Gravitation) 2017 Nov / 21

21 Improvements planned for 2018 High power laser 35 W 100 W Squeezing Mirror suspended on fused silica fiber Michał Was (SFP Gravitation) 2017 Nov / 21

22 Improvement at LIGO Replace mirror with point defect at Hanford Change high power laser (200 W 70 W) less jitter due to water cooling Replace end mirrors and reaction mass Better quality of coatings Annular reaction mass remove squeezed film gas damping Monolithic signal recycling mirror Michał Was (SFP Gravitation) 2017 Nov / 21

23 Advanced detectors time-line Early Mid Late Design LIGO O O O3 190 Virgo O O KAGRA O3 starts end of 2018 for 1 year Michał Was (SFP Gravitation) 2017 Nov / 21

24 Following step after 2019 data taking signal recycling Install signal recycling mirror... Michał Was (SFP Gravitation) 2017 Nov / 21

25 Summary Early Mid Late Design LIGO O O O3 190 Virgo O O KAGRA LIGO and Virgo finished a very successful observing run in August 2017 Many upgrades on-going till end of 2018 A year long observation in 2019 More improvements will follow Michał Was (SFP Gravitation) 2017 Nov / 21