Status of Advanced LIGO: We are listening! · Michelson interferometer ... Currently Engaged in O1! Dec 16 2015, CGC Conference in Ft. Lauderdale, FL Johannes Eichholz for the LIGO

LIGO-G1501517

Status of Advanced LIGO: We are listening!

Johannes Eichholzfor the

LIGO Scientific Collaboration

16th December 2015Miami 2015 CGC Conference in Ft Lauderdale, FL

Overview

2 Johannes Eichholz for the LIGO Scientific Collaboration Dec 16 2015, CGC Conference in Ft. Lauderdale, FL

● Gravitational waves and laser interferometers

● Advanced LIGO topology

● Current status

● Data challenge

● Future efforts

99 Years of Gravitational Waves


● Perturbed Einstein equations

● Quadrupole pattern

● Two polarizations

● Precise measurement of change in orbital period● Energy loss mechanism: Gravitational Waves!

Best indicator this far: PSR B1913+16 (Hulse-Taylor)

GW Strain and Detector Sensitivities


Supernovae

BinaryInspirals

Pulsar Timing

Long BaselineSpace Interferometers

SupermassiveBinaries

PrimordialGWs

Extreme Mass-Ratio Inspirals

BinarySystems

LIGO

aLIG

O

Ground-basedInterferometers

Spinning NS

Interferometric Detectors


● Changing distance affects laser phase● Michelson topology suppresses laser noise● Passing waves modulate IFO output● Interferometers are antennas

● Little to no directional resolution● Polarization and direction dependance

Antenna patterns

Several enhancing key technologies

First Generation Detector Sites


LIGO Hanford (x2)

Virgo (Italy)

GEO600 (Germany)

LIGO Livingston

● Large Scientific Collaboration● Technology transfer● Joint science runs● Coordinated upgrade schedule● Advanced LIGO approved in 2004

● Transition to second generation

List of publications: https://www.lsc-group.phys.uwm.edu/ppcomm/Papers.html

4 km + 2 km

4 km3 km

1.2 km (folded 600 m)

Duty Cycle Over the past 10 Years


https://losc.ligo.org/timeline/

Maintains up-time in case of events

Decommissioned

Beginning ofConstruction

Beginning ofinstallation

Installation complete;Commissioning starts

Advanced Virgois approved

Beginning ofconstruction

GEO

H1

H2

L1

V1

From Enhanced to Advanced LIGO


● Detectors sense amplitude of GW● Range scales with strain sensitivity● 10x sensitivity: 1000x volume

● Boosts event rates

● Better seismic isolation● Lower mechanical loss

● Increased laser power● Need to be aware:

● Thermal noise● Radiation pressure

Suspensions Laser Power

RadiationPressure Coating Brownian

Advanced LIGO Optical Layout


Cavity-enhanced dual-recycledMichelson interferometer

● High input power

Pre-Stabilized Laser

Phase Modulator

Input Mode Cleaner

Output Mode Cleaner

Faraday Isolator

Faraday Isolator

End Test Mass X-Arm

End Test Mass Y-Arm

Detector Readout

4 km

4 km

Beamsplitter

125 W


Phase Modulator

Input Mode Cleaner

Output Mode Cleaner

Faraday Isolator

Faraday Isolator

Input Test Mass X-Arm

End Test Mass X-Arm

End Test Mass Y-Arm

Input Test Mass Y-Arm

Detector Readout

4 km

4 km

Beamsplitter

125 W

18 kW

18 kW




● High input power● Arm cavities increase interaction time




● High input power● Arm cavities increase interaction time● Power recycling traps light in IFO


Phase Modulator

Input Mode Cleaner

Output Mode Cleaner

Faraday Isolator

Faraday Isolator


End Test Mass X-Arm

End Test Mass Y-Arm


Detector Readout

Power Recycling Mirror

4 km

4 km

Beamsplitter

125 W

5.2 kW

750 kW

750 kW




● High input power● Arm cavities increase interaction time● Power recycling traps light in IFO● Signal recycling enhances GW signals

● New in Advanced LIGO


Phase Modulator

Input Mode Cleaner

Output Mode Cleaner

Faraday Isolator

Faraday Isolator


End Test Mass X-Arm

End Test Mass Y-Arm


Detector Readout

Power Recycling Mirror

Signal Recycling Mirror

4 km

4 km

Beamsplitter

125 W

5.2 kW

750 kW

750 kW

Key Upgrades: Suspensions


● External hydraulic pre-isolation● Internal active stabilization● Quadruple suspensions for arm

cavity optics● Monolithic last stage

● Triple suspensions for other core optics

● Over ten orders of magnitude seismic isolation above 10 Hz

Picture credit: https://www.advancedligo.mit.edu

Key Upgrades: Laser and Optics


Picture credit: https://www.advancedligo.mit.eduP. Kwee et al.: Opt. Express 20 10 (2012)

● More laser power● Additional amplification stage

● New test masses● 4x heavier (40 kg each)● High purity fused silica substrates● Ti:Ta2O5-SiO2 multilayer coatings

Commissioning


● Installation complete as of August 2014● Formally accepted in March 2015

● Both detectors full lock capability● Since then: Commissioning

● Gradually improve sensitivity

● Detector characterization● 100k+ auxiliary channels

● Identify problems● Stray light● Channel cross-talk, feedback controls● ???

● Gradually increase laser powerAasi et al. (2013)

LIGO Document G1401390

Advanced LIGO Timeline


● Timeline as of December 2014 (presented at last year's CGC conference)● Intermittent engineering runs

● Extended periods of detector up-time for testing● First observation run (O1) started with only a few days delay

● Will lasts until mid-January● Second observation run planned for second half of 2016

We are here, according to plan!

Currently Engaged in O1!


● ~70 Mpc at beginning of O1● For binary neutron star inspirals

● Larger for heavier binaries● Merger frequency decreases

● Uncertain for SN or spinning NS

Laser power

Detector calibration

Brownian noise?

● Shot noise limit reached● Further increase laser power● Squeezed light

● Detector noise characterization● Coupling to environmental noise

● Brownian noise levels● First-time limitation

The Data Challenge


● Main channel: differential arm● Projection into plane of detector● GW signals will be weak

● Only few cycles for integration● Buried in noise● Require complex extraction techniques

How exactly do we look for gravitational waves in the data stream?

Modeled Searches


Continuous wave

Inspiral

Ringdown

● Simulate waveforms with GR and PN methods● Create template bank

● Large parameter space for binary inspirals● Masses, separation, spins● Orientation, distance and sky location

● Correlate datastream with template bank

Example: Matched Filtering

Compact BinaryCoalescences

● Online or offline searches● Can be turned into a test of GR!

● Merger and ringdown modeled with numerical relativity

Unmodeled Searches


Example: Coherent Wave Burst (CWB)

LIGO Livingston

LIGO Hanford

Reconstructed waveform

● Trigger from excess power in frequency bins● Coincident in different detectors?● Find timing offsets

● Identical phase progression● Correlate detector data for waveform

INJE

CTED

EVE

NT

Time-frequency traces

Problems with blind searches


● Ground-based detector sources are all transient in nature● Cannot simply “look again”

● Detectors can glitch and produce output that looks like a GW● Detection statistics for ranking of significance● Vetos from auxiliary channels

● Glitches are caused locally● Uncorrelated between different detectors● Can still be coincident

● The more independent data streams, the better!!!

More detectors are coming!


LIGO Hanford

Virgo (Italy)

GEO600 (Germany)

LIGO Livingston

KAGRA

LIGO-India

Advanced Virgo


● Advanced Virgo approved in 2009 ● Construction began in fall 2011● Installation expected to finish soon● Joint observation run with LIGO

planned for 2016

● Input laser noise to specs● Input test masses suspensions installed

● Quads were pioneered by Virgo● All large mirrors have been produced

LIGO-India


● Awaiting “in principal” approval from government (very soon)● Will use parts of decommissioned Hanford-2 LIGO detector● Far into site selection process (from 20 down to 2-3)

Cooperation between LIGO and Indigo(Indian Initiative in Gravitational-wave Observations)

Would improve sky localization immensely!

Without LIGO India With LIGO IndiaAasi et al. (2013)

KAGRA


● Third large Japanese detector● TAMA 300, CLIO

● First underground observatory● Located in Kamioka mine with other experiments

(Super-Kamiokande, XMASS, KamLand)● Pioneering cryogenics in interferometric detectors

● May start observing as early as 2018!

Summary


● Advanced LIGO completed upgrades● Outperforms previous sensitivity by factor of 3 and improving

● Currently engaged in first observation run● Advanced Virgo is expected to join observations in 2016● KAGRA may start observing as early as 2018● LIGO-India could reach astrophysical sensitivities by 2022

● Six 2nd generation interferometric detectors on the horizon● LISA Pathfinder launched successfully

In the meantime,LIGO is staying tuned

LIGO Scientific Collaboration

Documents

Status of Advanced LIGO: We are listening! · Michelson interferometer ... Currently Engaged in O1! Dec 16 2015, CGC Conference in Ft. Lauderdale, FL Johannes Eichholz for the LIGO