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Advanced LIGOResearch and Development

Update

Dennis Coyne

LSC Meeting at LLO

16 March 2004

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Recent Progress

Lots of research reported at the August, Hannover LSC meeting and some at the November, Hanford LSC meeting

Wish only to give highlights on what’s happened in the interim

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Pre-stabilized Laser

LZH/MPQ studying the two head configuration » optimizing birefringence

compensation Four Head Ring Laser

» Tested new fiber-bundle design

» Demonstrated >165 W

H R

TR

BP

Q R

f

f2 f

Q R

f

f

f Q R f

M aster-Laser

BP

H igh Pow er S lave

output

NPRO

BP

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Input Optics

High Power Test Lab at LLO» 100W, good mode quality, single polarization,

1.06 um laser is non-trivial. ELS failed» IPG Photonics is de-rating one of their high

power commercial systems. Delivery in ~3 months

Low absorption, large aperture Faraday Isolator» Preparing a FI assembly with low loss TGG

crystal for LHO (not thermally compensated) Electro-Optic Modulators (EOM)

» New Focus to build EOMs on an OEM scale based on RTP-crystals

» Expect to get one in a few weeks & tests Laser adaptive optics for mode matching

» Preliminary measurements of lens power and modal contamination

2000

2100

2200

2300

2400

2500

2600

-30 -20 -10 0 10 20 30

Distance from OG515 (inch)

Bea

m D

iam

eter

(u

m)

0W

4W

6W

8W

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Core Optics Components

Held COC design requirements review Substrates

» Absorption measured on two more, ~full size sapphire pieces confirm the first large sapphire measurements of ~60 ppm/cm average (~30 to 130 range)

» Setting up further diagnostics and development of sapphire:

– Annealing tests on large pieces at Crystal Systems has been delayed by funding

– Annealing tests on small pieces at Stanford are proceeding

– Parts for direct measurement of thermoelastic noise in Japan

– Test piece to measure Q at low frequencies (~4 kHz) – results expected March

– Caltech absorption measurements on intermediate size pieces match LMA-Lyon pattern (relative); calibration still uncertain

– Annealing oven at Hobart and William Smith in operation – results expected soon

» Downselect: June 2004

LIGO Lab (Caltech)

VIRGO (LMA-Lyon)

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Core Optics Components

Coatings» Low loss coatings program with LMA-Lyon and CSIRO

– 1st Q results for CSIRO tantala/silica REO/Lyon/MLD (despite questions/problems with absorption and uniformity)

– Hafnia/silica sample from Lyon are expected in ~ a week Absorption is ~ 5-6 ppm; will never reach the 0.5 ppm req’d Scatter is also higher, 20-40 ppm

» High coating scatter loss– LHO ITM HR coating scatter loss >> entire loss budget for the

nominal AdL design– Scatter loss from LLO ITM measurements planned– Plan lab surface measurement via focused surface scan/scatter

detection use of the RTS instrument (Caltech) TNI

» Working on reducing and understanding the noise floor repeatability and the effect of coating loss

» Fused Silica (FS)– Reinstalled FS optics and obtained the same sensitivity!

» Sapphire– Very recently installed sapphire test masses and locked the

interferometer

High Resolution Image of Scatter from the ITMx,2k HR Coating

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Active Thermal Compensation(ATC)

ATC» AdL “working” baseline has the compensation

plate in the ITM reaction chain; Final review/decision in April

» ‘Staring configuration’ implemented at LHO; could also have AdL application in this form

Gin Gin Experiment» Emphasis for Gin Gin experimental plan is

radiation pressure effects and instabilities» Completed calculations of thermal lensing and

residual power in higher order modes» Compensation plate (Ø160 mm fused silica

Heraeus 311SV) being polished & coated» Initial (in air) Mach Zehnder interferometer

measurements for small compensation plate are encouraging and confirm simulations

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Seismic Isolation:In-chamber, Active, Two-Stage System

ETF testing continues (sensor characterization, electronics noise reduction, transfer function measurements, damping & isolation controls, …)

In-vacuum actuator development RFQ HAM & BSC Prototype mechanical design

» Have held a few in-process design reviews» Difficult to meet stiffness requirements and extremes in payload mass

properties» Design review late March

stage 1-2 actuator

stage 0-1 actuators

stage 0-1 actuator stage 0-1

actuator

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Suspensions

Triple, mode cleaner “controls” prototype to be tested at LASTI this summer Quadruple “controls prototype” development emphasis by US & UK team members OSEM design concept proposal/review/decision in April

» SUS/UK team investigated interferometric & geometric sensors

» Preliminary recommendation: use of the interferometric sensor where high sensitivity is required, shadow sensors elsewhere

Eddy current damping demonstrated as viable alternative/supplement to active damping

BS & FM to have same triple suspension ‘chains’

Set BSC chamber pendulum lengths Univ. of Glasgow is developing a ~100W

CO2 laser pulling/welding machine for silica ribbons/fibers

» EGO funded» Optical thickness profiling device to be

developed Ear design / ear bond thermal noise

» Finite element analysis of bond loss» Alternate geometries studied

QUAD SUSPENSION TRIPLE SUSPENSION

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Systems

Systems» Layouts

– Improvements in the vertical wedged optics layout & calculation of all vertical coupling

– Progress on horizontal wedged optics layout– Payload mass properties estimates for each

chamber (for SEI design)

» Requirements– Records Of Decisions/Agreements (RODA)– AdL Vacuum Outgassing requirements &

Subsystem budget– Subsystems required to have email forums &

web pages System Tests

» LASTI– Completing HEPI– Revised plan for AdL testing– MC Triple suspension this summer

» 40m– SR soon!

Power & Signal Recycling Cavity Layout(non-folded interferometer)

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Systems -- Interferometer Sensing & Controls (ISC):

40m Lab Fabry-Perot Michelson Configuration

» Robust locking (Michelson, common-mode arm and differential mode arm cavities)

» Improved sensitivity Dual Recycled Configuration

» All installation has been completed!» The mode cleaner and Fabry-Perot

Michelson have locked!» Efforts to lock the dual-recycled

Michelson are underway!

Thermal noise

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Advanced LIGO R&D

Significant progress!

LIGO Management» getting detailed cost and schedule model updated» using to make revised R&D plan from the ground up that fits

constraints, has needed flexibility

NSF studying the Advanced LIGO Proposal

…meanwhile, lots of good science and engineering going on!