Science and technology at LIGO

Joseph A. GiaimeLIGO Livingston observatory head (Caltech),

Prof. of physics and astronomy (LSU), for the LIGO Scientific Collaboration

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LIGO Scientific Collaboration

http://rhcole.com/apps/GWplotter/,

Efforts to observe gravitational waves

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GenerationofGW’s

• GWradiationrequiresatime-varyingnon-zeroquadrupolemomentofthesource’smass.

• Constantsofnaturecometogethertomaketheeffectverytiny,evenforenormoussources.

• ‘Hertzian’experimentprobablyimpossible.• Sourcesincludeinspiralingbinarycompactobjects,non-

sphericalcoreimplosion,drivenorrelaxingnormalmodesofcompactobjects,…

whereisthenon-sphericalkineticenergyofthesource.Thisformulaisroughlythebest-case,withoptimalorientation.

4

Ensk

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HowLIGOseesthewaves

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Patienceandstewardshipovergenerations:~100yearsago:AlbertEinsteinpublishedhistheoryofGeneralRelativity,includingpredictionofgravitationalwaves.~50yearsago:Weberbuildsbarantennastoattemptdetectionofthewaves.~45yearsago:KeyideasforinterferometricantennasdevelopedbyWeissandothers.Barantennaworkcontinues,includingcryogenics.~40yearsago:(U.S.)NationalScienceFoundationfundingofpre-LIGOR&D,continuedGWdetectorresearchinternationally,includingGlasgowintheU.K.andMPQinGermany.~25yearsago:LIGOproposedtotheNSFbyMITandCaltech.~20yearsago:LIGOsiteconstructionbegan.~15yearsago:initialLIGOrunningatdesignsensitivity.~6yearsago:AdvancedLIGOinstallationbeganwithmajorinternationalcontributions,includingfromtheU.K.andGermany.~now:AdvancedLIGOdetectorsseeastrophysicalsignals.

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LIGO Hanford and LIGO Livingston

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Advanced LIGO Detectors:installation 2010, first run fall 2015

G1700789-v1 9PRL 116, 06112 (2016)

1938seismicisolationtechnology

G1700789-v1 10GeneralMotors

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ActiveSeismicIsolation

21st Century Seismic Isolation• HEPI: Hydraulic External Pre-Isolator

large throw, isolation below ~5 Hz

• ISI: Internal Seismic IsolationIsolates above ~0.2 Hz

• Quadruple pendulum: superior performance at 10 Hz and above

HEPI

ISI

Test Massat end of quad pendulum

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Isolationperformance

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MonolithicMirrorSuspensions:Fusedsilicatestmass,hungfromsimilarmassviapuresilicafiberand‘ears.’

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DesignfromU.K.-GermanGEO600suspension

GEO600photo

QuadruplePendulum fortestmassmirrors

• UKsupplied,GlasgowIGR-developed• Fusedsilicasuspensions,fibre-pulling,bonding

andwelding• CoatingR&D,majorGlasgowactivity 15

Installation

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FI

SRM

T=1.4%

ITM

ETM

Input Mode

Cleaner

OutputMode

Cleaner

PRM

BS

4 km

T= 3%

Laser ϕm

PDGW readout

FI

ITM ETM125 W

5.2 kW 750 kW

CP

ERM

SR3

SR2

PR2

PR3 ERM

FABRY-PEROT ARMS

INPUT OPTICS

MICHELSON

OUTPUT OPTICS

Advanced LIGO design

Opticalalignmentandcontrol…justonepart:

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LIGOcontrolroom:lockacquisition

G1700789-v1 20PRL116,06112(2016)

G1700789-v1 21PRL116,06112(2016)

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Blackholeinspiral,collisionandring-down

G1700789-v1 23PRL116,06112(2016)

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1×10-6 metergroundvibration,1micrometer.

4×1049 J/speakpowerofsource,40yotta yotta watt.

4×103 meterLIGOarmlength,4kilometer.2×100 metertestmasssuspensionlength,2meter.

1×10-18 meterarmdifferenceatpeaksignal,1 attometer.

1×1025 meterdistancetosource,10yotta meter.S.I.prefixchart…kindofdull.

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Events during Advanced LIGO’s first observational run:

G1700789-v1 25LIGO & Caltech Press Office

Three events compared

G1700789-v1 26Phys. Rev. Lett. 116, 241103, Phys. Rev. X 6, 041015 (2016)

Whathavewelearnedaboutthesystemsthatemittedthewaves?Howdowelearnmore?

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journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.241103,arxiv.org/abs/1606.04856(acceptedtoPRX)

• Accuracyofmostparametersimproveswithsignal-to-noiseratio.

• Skylocalizationimprovesasmoreobservatoriesareadded.

• Someparameters,likespin,arehardtomeasure!

Commissioning between O1 and O2 runs● High power stage of LIGO Hanford laser activated.

» Development of techniques to reduce buildup of opto-mechanical parametric instabilities.

» Thermal compensation and higher power.» Study of beam jitter/geometry noise coupling to detector.

● Diagnosis and reduction of noise from scattered light off moving surfaces» Several scattering sites identified in LIGO Livingston.» Compensation plate now “correctly” misaligned.» Scattering from photon calibrator periscope mirror identified, will be addressed later.» Scattering and relative motion among one end station optics partially addressed.

● Test-mass bounce/roll dampers, new photodiodes, new pre-mode cleaner, Faraday isolator, etc., in L1.

● Removed accidental noise from temperature sensor instrumentation in L1G1700789-v1 28

Second aLIGO observational run

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● The second Advanced LIGO run began on November 30, 2016 and is currently in progress. As of March 1, 2017, approx. 34 days (0.093 year) of cumulative coincident data have been taken with L1 and H1, with a scheduled break between December 22, 2016 and January 4, 2017.

● Average reach of the LIGO network for binary merger events have been around 70 Mpc for 1.4+1.4 Msun, 300 Mpc for 10+10 Msun and 700 Mpc for 30+30 Msun mergers, with relative variations in time of the order of 10%.

Frequency [Hz] 100 1000

Stra

in S

ensi

tivity

[1 /

Hz]

10-23

10-22

20

Instrument Noise in O2H1, O2 range: BNS = 68 Mpc, BBH 30/30 = 831 MpcL1, O2 range: BNS = 84 Mpc, BBH 30/30 = 1029 Mpc

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NS-NS range in O2 run …

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roughonlinecalibration(±10%)

Approx 70 days of coincident data taken so far.

PlausibleObservingRunTimeline

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O1 O2 O3

60-100Mpc 120-170Mpctarget65-80Mpc

2016 2017 2018 20192015

200Mpctarget

BinaryNeutronStarrange

VirgojoinsO2(TBD)

(plansstillunderdevelopmentwithintheLIGOandVirgoCollaborations)

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G1700789-v1 32https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=28751

displacementnoise,m/p

Hz

frequency,Hz

10�20

10�19

10 100 1000

Displacement noise

• Noise model of high-range data segment in Livingston (M. Evans).

• Tracks shot noise at high frequencies.

• Tracks servo-induced noise at low frequencies.

• Slight excess 30-100 Hz, attributed to light scattering from moving surfaces.

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101 102 103

10−20

10−19

10−18

Frequency (Hz)

Noise

(m/rt

Hz)

measured − 25 W Oct 2016, BNS range 94 Mpcprojected − 50 W or 25 W + 3 dB φSQZ, 108 Mpcprojected − 125 W or 25 W + 7 dB φSQZ, 123 MpcQuantum noiseCoating thermal noiseResidual gas noiseQN +2 CTN +2 RGN, 132/145/153 Mpc

Potential effect of additional laser power

displacementnoise,m/p

Hz

frequency,Hz

10�2

0

10�1

9

10 100 1000https://alog.ligo-la.caltech.edu/aLOG/index.php?callRep=28936

• V. Frolov’s noise model of current best-case detector with higher laser power.

• Assumes current excess, coating and gas noises. Quantum adjusted.

• Current 25 W range, 94Mpc, might reach 108/123 Mpc with 50/125 W or 3/7 dB phase squeezing.

LIGOScienceEducationCenter:apartnershipwithSouthernUniversity,theSFExploratorium,andeducators.

• TheU.S.NSFhasfundedSouthernUniv.BR,CaltechandtheBatonRougeAreaFoundationtobuildandcarryouteducationalprogramsrelatedtoLIGOscienceandinquiry-basedlearning.

• TheLIGOSECprogramsreachover20,000peopleeachyear,focusingonclassroomvisitsandteachertraining.

• Docentsserveasrolemodelsforchildrenwhowishtopursuescienceandtechnologycareers.

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RecentLSUandSoutherngraduatesatthehelmsofbothLIGOdetectorsasthewavewasdetected

G1700789-v1 35Nutsinee Kijbunchoo andWilliamParker

Thank you!

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