Gravitational Wave Experiments

GRAVITATIONAL WAVE EXPERIMENTS

Rainer Weiss MIT&LIGO Gravitation: A Decennial Perspective June 8, 2003 Center for Gravitational Physics and Geometry Pennsylvania State University Other relevant presentations

• 6/8/03 Gabriela Gonzalez Data Analysis of Gravitational Wave Data

• 6/10/03 Scott Hughes Gravitational Wave Astronomy with LISA V. FAFONE 15th SIGRAV Conference, September 11, 2002 Direct detection of gravitational waves from astrophysical sources

Physics » Observations of gravitation in the strong field, high velocity limit » Determination of wave kinematics – polarization and propagation » Tests for alternative relativistic gravitational theories Astrophysics » Measurement of coherent inner dynamics – stellar collapse, pulsar formation…. » Compact binary coalescence – neutron star/neutron star, black hole/black hole » Neutron star equation of state » Primeval cosmic spectrum of gravitational waves Gravitational wave survey of the universe

LIGO-G9900XX-00-M

THE RADIATION FIELD

Transverse Plane Wave Solutions with \Electric"

and \Magnetic" Terms

Geometric Interpretation

2 i j

ds = g dx dx

g = + h weak eld

ij ij ij

0 1

1 0

Minkowski Metric of

B C

@ A

0 1

Sp ecial Relativity

Gravity Wave Propagating in the x Direction

0 1

0 0 0 0

B C

h = all h 1

@ A

ij ij

0 0 h h

22 23

0 0 h h

32 33

Plane Wave

h = h h = h

22 33 23 32

+ p olarization p olarization

And All Only Function of x ct 1

Measurement challenge

Needed technology development to measure:

h = ∆L/L < 10-21 ∆L < 4 x 10-18 meters

LIGO-G9900XX-00-M

INTERPRETATION AS TIDAL FORCE

Useful If Masses Not Free

m,T,Q,f

bar detector motion transducer

x x x

Mo died Geo desic Deviation

Plane Wave k Polarization

x c R l x h l

R R zz

Nested Toroidal Resonators

Resonance of outer toroid < f Resonance of inner toroid > f

Gravitational wave “tidal” force at frequency f

Displacement of surface at frequency f test mass

light storage arm

ligh t stora test mass ge arm test mass test mass

beam splitter photodetector

power recycling mirror

laser FRINGE SENSING

light fringe wavelength 1 x 10 -6 m CE NTERED

photo detector current x λ h = --- ∼ ------L · RF p h a s e m o d u la t ion L b N τ

POSITI VE

arm length = 4000 m

in tegration time

equivalent # of passes = 100

NEGA TIVE number of quanta/second at the beam splitter 300 watts at beam splitter = 1021 identical photons/sec

h = 6 x 10 - 22 integration time 10-2 sec

LIGO Laboratory 7

G020477-00-R ττ= PENDULUM THERMAL NOISE

Pendulum Brownian motion Zener dampin g

Dissipation leads to fluctuations T + d T

T Tc = coherence or damping time = Q x period of oscillator

Exchange with surroundings:

E(thermal) = kT t Tc

Large Tc => smaller fluctuations

Doppler (gas) dampin g

LIGO Laboratory 2

G020477-00-R SEISMIC -19 SU 10 S P EN S IO N

G T H R R A E LIGO I AV D R ) I M I A z A T T -21 Y L

H I O 10 G N

/ R P A R D E OT (1 S I SH E S f N U () T R ˜ h TES E T M ASS TH ERM -23 AL 10 -6 RESIDUAL GAS, 10 TORR H S 2 TR A Y FACILITY L IG H T -9 RESIDUAL GAS, 10 TORR H2 -25 10 1 10 100 1000 10000 Frequency (Hz) Table 1: Initial detector parameters Nominal Initial Parameter Interferometer Arm length 4000 m Laser type @wavelength Nd:YAGλ = 1064 nm Input power at recycling cavity 6 W Contrast defect 1-c < 3 x 10-3 Mirror loss < 1 x 10-4 Power recycling gain 30 Arm cavity storage time 880µ sec Cavity input mirror transmission 3 x 10-2 Mirror mass 10.7 kg Mirror diameter 25 cm Mirror internal Q 1 x 106 Pendulum Q (structure damping) 1 x 105 Pendulum period (single) 1 sec Seismic isolation system T(100Hz) = -110dB

Table 2: Sample detector parameters with advanced sub-systems

sample enhanced parameter value

Laser power 100 W contrast defect < 1 x 10-3 mirror loss 2 x 10-5 arm cavity storage time 880µ sec mirror mass 30 kg mirror internal Q 3 x 108 Pendulum Q (double pendulum) 1 x 108 seismic isolation T(100Hz) = -120 dB LIGO Observatory Facilities

LIGO Hanford Observatory [LHO] LIGO Livingston Observatory [LLO]

26 km north of Richland, WA 42 km east of Baton Rouge, LA 2 km + 4 km interferometers in same vacuum envelope Single 4 km interferometer far mirror

near mirror slave laser power recycling mirror beam splitter

first second far mirror mode mode near mirror master cleaner cleaner signal laser recycling mirror

output mode cleaner

photodetector

BH/BH 10/10 NS/NS 1Mly

1Mly

current bars 10Mly GEO narrowband 10Mly

GEO broadband VIRGO 100Mly

100Mly Mo 16T initial LIGO advanced LIGO dual toroidsSQL 1Gly SiC 60T 1Gly advanced LIGO narrow band envelope 7 average density of stars = 8.6 x 10 /Mly3

incomplete selected clusters

Virgo cluster

our galaxy and local group

DATA: Cosmology of the Local Group G.Lake Astrophysical Quantities C.W. Allen

Displacement noise level of TAMA300 -7 (August, 31 2002) 10 -8 10 -9 10 2001/06/02 (Recombine3) -10

] 2002/08/31 (Recycling1 HP)

2 10

1 / Phase2 limit z -11 10 -12 10 -13 10 -14 10 -15 10 -16 10

D i s p l a c e m n t o [ / H -17 10 -18 10 -19 10 -20 10 0 1 2 3 4 5 10 10 10 10 10 10 Frequency [Hz] S1

6 Jan -17 -18 -19 -20 -21 L4k strain noise @Commissioning 150 Hz [Hz-1/2] 10 10 History10 10 10 1999 2000 2001 2002 2003 4Q 1Q 2Q 3Q 4Q 1Q 2Q 3Q 4Q 1Q 2Q 3Q 4Q 1Q

Inauguration E1 E2 E3 E4 E5 E6 E7 E8 E9 One Arm S1 S2 Power Recycled Michelson Science Science Recombined Interferometer Run Run

Full Interferometer

First Lock Washington 2K Louisiana 4k Washington LHO 2k wire Washington 4K Now earthquake accident LIGO Scientific Collaboration Member Institutions

University of Adelaide ACIGA LIGO Livingston LIGOLA Australian National University ACIGA LIGO Hanford LIGOWA Balearic Islands University Loyola New Orleans California State Dominquez Hills Louisiana State University Caltech CACR Louisiana Tech University Caltech LIGO MIT LIGO Caltech Experimental Gravitation CEGG Max Planck (Garching) GEO Caltech Theory CART Max Planck (Potsdam) GEO University of Cardiff GEO University of Michigan Carleton College Moscow State University Cornell University NAOJ - TAMA Fermi National Laboratory Northwestern University University of Florida @ Gainesville University of Oregon Glasgow University GEO Pennsylvania State University NASA-Goddard Spaceflight Center Southeastern Louisiana University University of Hannover GEO Southern University Hobart – Williams University Stanford University India-IUCAA Syracuse University IAP Nizhny Novgorod University of Texas@Brownsville Iowa State University Washington State University@ Pullman Joint Institute of Laboratory Astrophysics University of Western Australia ACIGA Salish Kootenai College University of Wisconsin@Milwaukee

LIGO-G0200XX-00-M LIGO Scientific Collaboration Astrophysical source upper limit groups

z Combined groups of experimenters and theorists z Develop data analysis proposals Purpose: z Test the LIGO Data Analysis System z Set scientifically useful upper limits using engineering and early science data z Publish first astrophysically interesting results from LIGO Groups: (Data Analysis) Burst sources : Sam Finn, Penn State, Peter Saulson, Syracuse Inspiral sources: Pat Brady, Univ of Wisconsin, Gabriela Gonzalez, LSU Periodic sources: Maria A Papa , AEI , Michael Landry, LIGO Hanford Stochastic background: Joe Romano, UT Brownsville, Peter Fritschel, MIT

LIGO-G0200XX-00-M LIGO Scientific Collaboration THINGS TO THINK ABOUT DETECTORS:

Matched detection filters • Time domain optimization: NS/NS binaries - vary amplitude recycling mirror position to follow spectrum • Frequency domain optimization with multiple cavities and/or time delay at antisymmetric port Detector output S(f) = N(f) + M(f)

Detector filter function T(f)

Source model M(f)

Least square minimization of dif- ference detector output - model

reflection T(f) = M(f)/(N(f) + M(f)) filter

detector

example reflection filter: diffraction grating with multiple cavities

diffraction grating

DATA ANALYSIS • Work on the gravitational waveform inverse problem determine the dynamics at the source from the waveform Advanced Interferometer Concept

» Signal recycling » 180-watt laser » 40 kg Sapphire test masses » Larger beam size » Quadruple suspensions » Active seismic isolation » Active thermal correction » Output mode cleaner

LIGO-G020272-00-D Projected Performance

−21 10 Optical noise ! Seismic ‘cutoff’ at 10 Hz Int. thermal Susp. thermal Total noise

−22 ! Suspension thermal noise 10 I IGO L ica sil ! Internal thermal noise ire

1/2 h pp −23 a 10 s

! Unified quantum noise h(f) / Hz dominates at

most frequencies −24 10 ! ‘technical’ noise (e.g., laser frequency) levels held in general well −25 below these ‘fundamental’ 10 1 2 3 10 10 10 noises f / Hz

LIGO-G020272-00-D The Gravitational-Wave Spectrum

LISA 7 LISA Massive Black Holes in Merging Galaxies

-15.5 7 7 MBH-MBH Binaries at z=1 10 /10 M¤

-16.5

h 6 6 10-17 10 /10 M¤

-17.5

5 5 10 /10 M¤

-18.5 10-19

-19.5

-20.5 10-21 Binary Confusion -21.5 Noise Threshold Estimate; Gravitational Wave Amplitude 1 yr, S/N=5 LISA Instrumental Threshold -22.5 1 yr, S/N=5 10-23 -23.5 -5.5 -4.5 -3.5 -2.5 -1.5 -0.5 10-4 -5 -4 -3 -2 -1 -0 10 10 Log 10Frequency (Hz) 10 10 10 Frequency (Hz)

LISA 15 LISA Mission Concept

LISA 25 LISA Spacecraft Orbits

• Spacecraft orbits evolve under gravitational forces only • Spacecraft fly “drag-free” to shield proof masses from non-gravitational forces

LISA 29 LISA Optical System

LISA 33 LISA