LIGO Update ------------ “ The Search for Gravitational Waves”

LIGO-G020412-00-M

LIGO Update------------

“The Search for Gravitational Waves”

Barry Barish

Caltech Trustees

10-Sept-02

10-Sept-02 Caltech Board of Trustees 2LIGO-G020412-00-M

Laser Interferometer Gravitational-wave Observatory

Goals » First direct detection of gravitational waves

» Open new window on the universe – “gravitational wave astronomy”

NSF funded construction in 1994 for $296M» Caltech has fiduciary responsibility

» Joint Caltech/MIT technical and scientific team

» Construction completed in both Louisiana and Washington in 2000

Commissioning, Operations and Scientific Programs» First Interferometer “locked” – (Oct 2000)

» First coincidence running of both sites – (Dec 2001)

» First scientific data run “upper limits” – (Sept 2002)

» Search for gravitational waves – (2003 through 2006)

We propose to install “Advanced LIGO” in 2007» Cost ~ $125M total -- international collaboration


LIGO Scientific Collaboration

Member Institutions

University of Adelaide ACIGA

Australian National University ACIGA

California State Dominquez Hills

Caltech LIGO

Caltech Experimental Gravitation CEGG

Caltech Theory CART

University of Cardiff GEO

Carleton College

Cornell University

University of Florida @ Gainesville

Glasgow University GEO

University of Hannover GEO

Harvard-Smithsonian

India-IUCAA

IAP Nizhny Novgorod

Iowa State University

Joint Institute of Laboratory Astrophysics

LIGO Livingston LIGOLA

LIGO Hanford LIGOWA

Louisiana State University

Louisiana Tech University

MIT LIGO

Max Planck (Garching) GEO

Max Planck (Potsdam) GEO

University of Michigan

Moscow State University

NAOJ - TAMA

University of Oregon

Pennsylvania State University Exp

Pennsylvania State University Theory

Southern University

Stanford University

University of Texas@Brownsville

University of Western Australia ACIGA

University of Wisconsin@Milwaukee

LSC Membership35 institutions > 350 collaborators

International India, Russia,

Germany, U.K, Japan

and Australia.

The international partners are

involved in all aspects of the LIGO research

program.


Livingston Optical Telescopebroad outreach/education program

Telescope facts:

16 inch Richey Chretien telescope built by Optical Guidance Systems

Telescope provided by state funds via LSU. LIGO provides site and internet connection and incorporates telescope use into outreach program.

Internet accessible to facilitate classroom use

Proposed telescope location on fire access road gives clear view to south

Draft building concept utilizes surplus beam tube enclosures on raised footings with roll-off roof


Budget LIGO Operations (2002 thru 2006)

Operations of LIGO funded beginning in 2002 for 5 years at a total funding of $160M

We function as one distributed laboratory (LIGO Laboratory) » Caltech (85 staff); MIT (25staff); Hanford (25 staff); Livingston (25 staff)

Advanced LIGO construction (not included) to be proposed next year

FY 2002

($M)

FY 2003

($M)

FY 2004

($M)

FY 2005

($M)

FY 2006

($M)

Operations $24 $29 $30 $30 $30

Advanced R&D

$4 $4 $3 $3 $3

+ $5M


LIGO at Caltech Faculty

» Barish, Drever, Libbrecht, Prince and Weinstein (Exp) & Thorne(Th)

Scientists/Postdocs/Students» PhD theses; talented junior and senior scientists

LIGO Management» Directorate, Administration

LIGO Technical» Engineering center – precision engineering; controls; electronics

» 40 meter prototype; Optical laboratories, etc

LIGO Data Analysis and Computing» Simulations; Analysis infrastructure, Networking, Data Archive

» Scientific data analysis efforts

Source Simulations – Numerical Relativity


Einstein’s Theory of Gravitationgravitational waves

• A necessary consequence of Special Relativity with its finite speed for information transfer

• Time dependent gravitational fields come from the acceleration of masses and propagate away from their sources as a space-time

warpage at the speed of light

Newton’s Theory“instantaneous action at a distance”Einstein’s Theoryinformation carried by gravitational radiation at the speed of light


Direct Detectionastrophysical sources

Detectors in space

LISA

Gravitational Wave Astrophysical Source

Terrestrial detectors

LIGO, TAMA, Virgo,AIGO


International network (LIGO, Virgo, GEO, TAMA, AIGO) of suspended mass Michelson-type interferometers on earth’s surface detect distant astrophysical sources

Interferometersterrestrial

suspended test masses

free massesfree masses


Suspended Mass Interferometerthe concept

An interferometric gravitational wave detector

» A laser is used to measure the relative lengths of two orthogonal cavities (or arms)

As a wave passes, the arm lengths change

in different ways….

…causing the interference pattern

to change at the photodiode

• Arms in LIGO are 4km» Current technology then allows one

to measure h = L/L ~ 10-21 which turns out to be an interesting target


How Small is 10-18 Meter?

Wavelength of light, about 1 micron100

One meter, about 40 inches

Human hair, about 100 microns000,10

LIGO sensitivity, 10-18 meter000,1

Nuclear diameter, 10-15 meter000,100

Atomic diameter, 10-10 meter000,10


What Limits Sensitivityof Interferometers?

• Seismic noise & vibration limit at low frequencies

• Atomic vibrations (Thermal Noise) inside components limit at mid frequencies

• Quantum nature of light (Shot Noise) limits at high frequencies

• Myriad details of the lasers, electronics, etc., can make problems above these levels


Noise Floor40 m prototype

• displacement sensitivityin 40 m prototype. • comparison to predicted contributions from various noise sources

sensitivity demonstration


LIGOlong baseline interferometers (4 km)

Hanford Observatory

LivingstonObservatory

Laser Interferometer Gravitational-wave Observatory (LIGO)


LIGO Livingston Observatory


LIGO Hanford Observatory


LIGObeam tube

LIGO beam tube under construction in January 1998

65 ft spiral welded sections

girth welded in portable clean room in the field

1.2 m diameter - 3mm stainless50 km of weld

NO LEAKS !!


LIGOvacuum equipment


Core Opticsfused silica

LIGO requirements Surface uniformity < 1 nm rms Scatter < 50 ppm Absorption < 2 ppm ROC matched < 3% Internal mode Q’s > 2 x 106

LIGO measurements• central 80 mm of 4ITM06 (Hanford 4K) • rms = 0.16 nm• optic far exceeds specification.

Surface figure = / 6000


Core Optics installation and alignment


Interferometerlocking

Laser

end test mass

Light bounces back and forth along arms about 150 times

input test massLight is “recycled” about 50 times

signal

Requires test masses to be held in position to 10-10-10-13 meter:“Locking the interferometer”


Lock Acquisition


LIGOwatching the interferometer lock

signal

LaserX Arm

Y Arm

Composite Video


LIGOwatching the interferometer lock

signal

X Arm

Y Arm

Laser

X arm

Anti-symmetricport

Y arm

Reflected light

2 min


An earthquake occurred, starting at UTC 17:38.

The plot shows the band limited rms output in counts over the 0.1- 0.3Hz band for four seismometer channels. We turned off lock acquisition and are waiting for the ground motion to calm down.

From electronic logbook 2-Jan-02

Engineering Rundetecting earthquakes


17:03:03

01/02/2002

=========================================================================

Seismo-Watch

Earthquake Alert Bulletin No. 02-64441

=========================================================================

Preliminary data indicates a significant earthquake has occurred:

Regional Location: VANUATU ISLANDS

Magnitude: 7.3M

Greenwich Mean Date: 2002/01/02

Greenwich Mean Time: 17:22:50

Latitude: 17.78S

Longitude: 167.83E

Focal depth: 33.0km

Analysis Quality: A

Source: National Earthquake Information Center (USGS-NEIC)

Seismo-Watch, Your Source for Earthquake News and Information.

Visit http://www.seismo-watch.com

=========================================================================

All data are preliminary and subject to change.

Analysis Quality: A (good), B (fair), C (poor), D (bad)

Magnitude: Ml (local or Richter magnitude), Lg (mblg), Md (duration),

=========================================================================


Detecting the Earth Tides Sun and Moon


LIGO Goals and Priorities Interferometer performance

» Integrate commissioning and data taking consistent with obtaining one year of integrated data at h = 10-21 by end of 2006

Physics results from LIGO I» Initial upper limit results by early 2003

» First search results in 2004

» Reach LIGO I goals by 2007

Advanced LIGO» Prepare advanced LIGO proposal this fall

» International collaboration and broad LSC participation

» Advanced LIGO installation beginning by 2007


Preliminary


Astrophysical Sources the search for gravitational waves

Compact binary inspiral: “chirps”» NS-NS waveforms are well described» BH-BH need better waveforms » search technique: matched templates

Supernovae / GRBs: “bursts” » burst signals in coincidence with signals in

electromagnetic radiation » prompt alarm (~ one hour) with neutrino detectors

Pulsars in our galaxy: “periodic”» search for observed neutron stars (frequency,

doppler shift)» all sky search (computing challenge)» r-modes

Cosmological Signals“stochastic background”


“Stochastic Background”cosmological signals

‘Murmurs’ from the Big Bangsignals from the early universe

Cosmic microwave background


Stochastic Backgroundcoherence plot LHO 2K & LLO 4K


Stochastic Backgroundprojected sensitivities


Advanced LIGO

Active Seismic

Multiple Suspension

Saphire Optics

Higher Power Laser


Advanced LIGO

Enhanced Systems

• improved laser• suspension• seismic isolation• test mass material

• narrow band optics

Improvement factor

~ 104


Gravitational-wave Astronomyfrequency range

EM waves are studied over ~20 orders of magnitude» (ULF radio HE -rays)

Gravitational Waves over ~10 orders of magnitude

» (terrestrial + space)

Audio band

LIGO I (2003-06)Adv LIGO (2008 -)

LISA 2011-

LIGO Update ------------ “ The Search for Gravitational Waves”

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