Ground-based GW detectors: status of experiments and collaborations

Transcription

1 Ground-based GW detectors: status of experiments and collaborations C.N.Man Univ. Nice-Sophia-Antipolis, CNRS, Observatoire de Cote d Azur A short history GW & how to detect them with interferometry What are their sensitivities to GW and to noises The network of detectors in the world and their peculiarities Status of the detectors and combined observations Advanced detectors to improve sensitivity in LF range with Monolithic suspension Astrophysics with these detectors (just a flavor) Summary 1

2 Prehistory of GREX More than 25 years ago, GREX had an ancestor Informal meetings triggered by Philippe Tourrenc French scientists detection of GW Meetings in ENS or IHP with Ch.Bordé, C.Cohen-Tannoudji, T.Damour, GREX = Gravitation Expérimentale Mathematicians Experimentalists Thanks to that initiative and to those people, Virgo has been supported by CNRS and exists today This GREX community meets regularly and is growing up every day. 2

3 GW itf detection brief story 1973 Noise studies and initial design: Rainer Weiss (M.I.T) 1975 Prototypes in Glasgow and Garching 1980 s Recycling interferometers: Ron Drever (Glasgow and Caltech) 1982 First activities in France and Italy (optics, seismic isolation) Proposals for kilometric projects Construction starts in USA and Italy Commissioning 2007: First coincidence runs of initial detectors 2007: CLIO (cryo detector), design of advanced detectors matured 2008: First upgrades Virgo+, enhanced LIGO 2009: more advanced detectors Europe, Australia 3

4 Gravitational waves Emitted in extreme conditions of density and speed Strain sensitivity : h # to / Hz 4

5 GW sources Bursts: neutron stars or black holes «chirp» Ex of wave emitted by 2 coalescing NS Continuous wave sources: rapid rotating neutron star, coalescing of massive binaries Stochastic background: astrophysical, cosmological (BB) 5

6 Detecting GW with laser interferometry Michelson s transmission on dark fringe GW shifts dark fringe interference of the order of to rd/ Hz 6

7 Typical optical configuration Fabry-Perot in each arm to have longer arm length Power recycling to reach the kw level on the BS Typical control system AC detection to avoid VLF noise of the laser source 7

8 Noise limitations => sensitivity 8

9 World-wide network 4 & 2 km 600 m 3 km TAMA 300 m TAMA 4 km AIGO AIGO 3 kilometric detectors + a few hundred meters prototype + Ultra cryo resonant detectors (Italy) and LISA to come. 9

10 TAMA 300 (m) Located at N.A.O near Tokyo Project started in 1995 Fabry-Perot Michelson config. with power recycling similar to LIGO and Virgo Best world sensitivity between (first hundred meters itf to run) 10

11 TAMA sensitivity recognized need for better seismic isolation = new development with LIGO based on Virgo s earlier concept Performance achieved 11

12 CLIO (100m proto in Kamioka mine) 20 K 12

13 AIGO (australian intern l GW observatory) 13

14 AIGO site 14

15 World-wide network 4 & 2 km 600 m 3 km TAMA 300 m AIGO 4 km 15

16 GEO 600 (m) Simple Michelson, no Fabry- Perot, the only one today with signal recycling Located near Hannover Position of SR mirror changes frequency response 16

17 World-wide network 4 & 2 km 600 m 3 km TAMA 300 m AIGO 4 km 17

18 2 x LIGO (laser itf gw observatory) 18

19 LSC LIGO labs a self-governing collaboration seeking to detect GW works toward this goal through R&D, commissioning and exploitation of the detectors. Founded in 1997, the LSC is currently > 700 members from > 50 institutions and countries. carries out the science of the LIGO Observatories, in Hanford, Livingston, + GEO600 Nov 2007, Virgo and LSC signed agreement to jointly analyse all future common runs 19

20 Combined observations LIGO-Virgo-GEO First common run in May 2007, 5 months of data (LIGO S5, Virgo VSR1) Results of the initial detectors Virgo 20

21 World-wide network 4 & 2 km 600 m 3 km TAMA 300 m AIGO 4 km 21

22 Virgo 3 kms arms, Fabry-Perot Michelson with power recycling French-Italian detector + groups in Poland, Netherlands, Hungary Best seismic isolation => best in range < 80 Hz 22

23 Seismic Isolation of Virgo The Super-attenuator (SA) is a multi-stage seismic attenuator with an inverted pendulum as pre-isolator Expected Hz > ! World best LF sensitivity 23

24 Test-Mass Mirrors Material: low loss fused silica (special Virgo) Dimension: 35 cm diameter, 10 cm thick Mass: ~ 21 Kg Substrate absorption: 1 ppm/cm Coating losses: <5 ppm Surface deformation: < λ/100 (<100 ppm) Specific technologies for: -Low loss silica -Metrology -Coatings (DIBS, corrective) -Polishing (flatness+roughness) 24

25 Virgo detection capability 25

26 Compared sensitivities of LIGO S6-Virgo VSR2 (17/10/09) Virgo 26

27 Advanced interferometers Sensitivity goal better than initial ones by a factor 10 with new technologies: Dual recycled interferometer (power and signal recyclings) 42 kg mirrors and Fabry-Perot of finesse 800 (instead of 50 in Virgo) Larger beam spot on mirrors to lower thermal noise 200W laser power at input Thermal compensation of mirrors heating by CO2 laser & ring heater Monolithic suspension in the last stage Detection photodiodes under vacuum Adv Virgo plans to be ready to take data at the same time as Adv LIGO (2014) (Adv LIGO approved by NSB on March 2008 for a 7 years project of 205 M$) 27

28 Key technologies shortlist Ultra high vacuum at low cost: lower outgassing rate, welding, Seismic isolation: need >= at 10 Hz (all DoF) Laser: very low noise (Freq &Power), MTBF, high power, beam stability Optics: ultra low losses (substrates and coatings) Optical materials: high Q for low thermal noise Monolithic suspensions (silicate bonding) Real time control system: > 100 servo loops, many DoF, very low noise from mhz to MHz Data processing: high rate (6MB/s), fast processing (Tflop) 28

29 AdV sensitivity vs Finesse t IN Finesse G P BS BNS BBH

30 Advanced detectors goal sensitivity AdV + no SR AdV with SR 30

31 Some thoughts on the existing detectors LIGO has two/three detectors => could make all the first detections on their own if GW signal strong enough in their sensitivity range ( 50 Hz-2 khz) Virgo has the best sensitivity in the LF range thanks to the performant suspension => could detect GW emitted by pulsars in the LF range by integrating signal over months (from 10 Hz). For Advanced Virgo, it s worth adding monolithic suspension to lower suspension thermal noise. An agreement has been made in order not to stop all the detectors at the same time in case something happens near our galaxy: ASTRO-WATCH 31

32 Adv: Test-mass residual motion requirements Residual angular motion of Test masses in absence of rad press= 5x10-18 rad/ Hz at 10 Hz Other recycling mirrors and BS = rad/ Hz rad/ Hz Decentering < 1mm Today s Virgo performances Test masses = rad/sqrt(hz) A factor 1000 in LF to gain by taking care of. 32

33 Last stage of the Virgo suspension F7 Coil Pots The role of the Last Suspension Stage is to compensate the residual seismic noise +to steer the mirrors to maintain the relative position of the interferometer mirrors. 33

34 Advanced Virgo payload Total Payload Mass ~ 180 kg Marionette (Virgo+ like, monolithic suspensions compliant ~ 100 kg mass) Mirror: 350 mm ø, 200 mm thickness, 42 kg Marionette Recoil Mass (MRM): R&D Marionette steering No coil pots and filter 7 legs Allows to suspend mirrors with diameter > 370 mm Mass ~ 85 kg (filter 7 legs) Recoil Mass (Virgo+ like, monolithic suspensions compliant, ~ 42 kg mass) 34

35 AdV sensitivity vs Fiber geometry The ribbon choice reduced considerably the contribution of susp. th. noise, but The benefits on the sensitivity are limited by radiation pressure, newtonian and CONTROL NOISE fiber cylindrical ribbon geometry Finesse 885 G 23.5 P BS 2.9 kw BNS BBH

36 The monolithic assembly on the mirrors Steel box to host the upper silica clamp on the marionetta Silicate bonding Silica Clamps on the marionette 20 October 2009 Silica anchors Coupling to the mirror flats through lateral supports 36 36

37 Crab Pulsar Young neutron star, rotates 30 times/sec The rotation period is slowing down (38 ns/day) due to some energy carried away The LIGO data gives no GW signal for the Crab pulsar => set a superior limit to the GW energy to no more than 4% With a few months of data taken by Virgo (best 30 Hz), more results to come soon for the Crab pulsar Other limits coming from LSC/Virgo joint data on LSC.org web site 37

38 Summary The ground-based experiments have achieved their expected performance with the 1st generation Not yet detected any GW but first data analysis set limits to some known sources, better results to come They are ready to proceed to the 2nd generation detectors to detect GWs Philippe Tourrenc s action in the 80 s has now largely reached its goal and the detectors performances are beyond our hopes 38