40m TAC, 10/13/05 1

Report to the 40m Technical Advisory Committee

February 9, 2006

The 40m TeamBen Abbott, Rana Adhikari, Dan Busby, Jay Heefner, Osamu

Miyakawa, Mike Smith, Bob Taylor, Monica Varvella, Steve Vass, Rob Ward, Alan Weinstein

with lots of help from: Matt Evans, Helena Armandula, Rolf Bork, Alex Ivanov, SURF students, etc…

40m TAC, 10/13/05 2

October: RSE The last meeting of our TAC was October 13, 2005. On October 14, Osamu brought the interferometer into full

lock, with RSE, and the arms at full resonance (negligible CARM or DARM offsets). » He was able to hold lock for many minutes, and regain lock when lost.

Working independently and with somewhat different strategy, Rob, Rana and Matt brought the interferometer into full lock» used the POX RF signal to control the analog common mode servo» holding for hours, regaining lock easily. » Rob and Matt automated the lock acquisition procedure.

Both Osamu and Rob/Rana/Matt took CARM and DARM transfer functions, noise spectra, etc. » There was a clear RSE peak in DARM, no optical spring peak.

40m TAC, 10/13/05 3

RSE and optical spring Osamu realized that we aren't seeing the optical

spring peak in the DARM transfer function because we were locking the signal recycling cavity in the wrong place, on the "other side" of the spring (so that it's an anti-spring).

He flipped the sign of the SRC servo loop, then flipped the sign of several more loops before he was able to regain full lock in the AdLIGO configuration. And there, in addition to the clear RSE peak at ~ 4 kHz, was a beautiful optical spring peak at ~ 40 Hz!

Rob, independently, arrived at exactly the same set of sign flips to achieve lock in the optical spring configuration.

40m TAC, 10/13/05 4

Optical response (correcting for pendulum, filtering), with fit to Buonanno & Chen formula

Description of data, fit:http://www.ligo.caltech.edu/~cit40m/Docs/40mTF_060207.pdf P060007-00-R. Where to publish?

DARMin1 / DARMout----------------------------XARMin1 / XARMout

times arm cavity pole.

Yields optical response,taking out pendulum,analog & digital filtering,etc.

XARM TF is understoodsemi-quantitatively.

Offset-locked CARM also has optical spring peak,also well modeled.

Anti-spring TF also well modeled.

40m TAC, 10/13/05 5

CARM optical springs

102

103

80

90

100

110

120

130

140CARM optical springs at different CARM offsets

f (Hz)

CA

RM

opt

ical

res

pons

e (d

B)

Arm power = 6

Arm power = 8Arm power = 10•Solid lines are from TCST

•Stars are 40m data•Max Arm Power is ~80•Also saw CARM anti-springs

40m TAC, 10/13/05 6

Optical spring in E2E

• Calculated by time domain simulation

• Demod phase of 10 is a guess; needs tweaking

• Calculation time ~5min using DRMI summation cavity

40m TAC, 10/13/05 7

a :input vacuumb :outputD :input carrierM :constanth :gravitational wave

Measurement of optical transfer function

hSQL:standard quantum limit: transmissivity of SRM: coupling constant: GW sideband phase shift in SRC: GW sideband phase shift in IFO

a<<h; non-quantum measurement

Mathematical description for optical spring in detuned RSE

SQL

)()(2 2 1

h

hee

Mii DaCb

SQL

)( 1 2

1

he

Mhi D

b

a b

D arm cavity

arm

ca

vity

laser

Signal recyclingmirror

Beam

splitt

er

h

h

40m TAC, 10/13/05 8

Simple picture of optical resonance

Car

rier

fre

quen

cy

-10000 -5000 0 5000 10000

50

100

200

500

1000

Fdet (=4kHz at 40m)

Signal sideband frequency offset from carrier [Hz]

Sid

eban

d am

plit

ude

at o

utpu

t [a.

u.]

FWHM

USBLSB

fsig

•Response between GW USB and GW LSB is different due to the detuned signal recycling cavity.

•the resonance of the SR cavity and is maximally enhanced for

fsig = fdet

40m TAC, 10/13/05 9

Simple picture of optical spring in detuned RSE

Let’s move arm differentially, X arm longer, Y arm shorter from full RSE

PowerX arm down, Y arm up X arm down, Y arm down X arm up, Y arm down

Radiation pressureX arm down, Y arm up X arm down, Y arm down X arm up, Y arm down

Spring constantNegative(optical spring) N/A Positive(no optical spring)

DARM (Lx-Ly) DARM (Lx-Ly)

DARM (Lx-Ly)

Pow

er(W

)

Pow

er(W

)

Pow

er(W

)

BRSECorrect SRM position Wrong SRM position

X arm X armY arm Y arm

40m TAC, 10/13/05 10

Darker AP In this correct locking point, the spot at AP is now much nicer: rounder, and the

optical spectrum analyzer shows that the carrier is now nearly dark. It looks like the correct locking point exhibits "mode healing", while the wrong locking point exhibits "mode damaging". Repeatable.

anti-spring spring

Osamu gave a LIGO/Caltech seminar on the Optical spring and optical resonance in the 40m Detuned RSE interferometer, on November 1. G050568

40m TAC, 10/13/05 11

MOPA changes On November 6, in response to a plea from Mike Zucker, we packed up our 10 Watt

MOPA # 118 (“Asissi”) and shipped it to LLO. By November 8, it was installed, delivering 8.9 W,

and L1 had an inspiral range of 10.4 Mpc. Replacement laser (old H2, MOPA #102 ) arrived November 28. There were a

variety of differences, requiring some reworking » water cooling re-plumbing and leak fixing.» NPRO temperature scan.» 5.4W with the calorimeter at the exit of the MOPA. » Implement SLOW loop actuator, and servo.» We installed a phase-correcting EOM external to the MOPA, as at the sites.» Rearranged some optics for easy steering into PMC.» Mode matched into the PMC.» Replaced old FSS with new TT FSS.» More light on PMCR RFPD, ISS DCPDs.» Tuned up FSS, PMC and ISS servos.» PMC transmission is significantly lower than before, not sure why.» Re-aligned beam through Mach Zehnder, IOO, periscope, mode cleaner.

Finally back up with locked mode cleaner and arms by December 20. Full lock, once again, by Jan 5.

40m TAC, 10/13/05 12

While we were laser-less (1)

Osamu re-measures seismic noise at 40m, builds new model of stack TF, and new noise prediction.

Osamu starts thinking about calibration with the more complex optical plant.

40m TAC, 10/13/05 13

While we were laser-less (2)

DAQ RAID array failed at end of November; replaced. » 3.7 years of minute trends feared lost.» Alex Ivanov recovers the minute trends after a month of heroic effort. » Now all minute trends (and EPICS snapshots, online code, etc) backed up nightly.

Rana evaluated our PMC, MC, and CM servo boards. All need to be updated / replaced. New boards are now in hand.

Many new DAQ channels added. Rob attended QND workshop at Hannover in December. He gave

talks on the optical spring as observed at the 40m, various modeling tools used to understand the AdvLIGO configuration, and his new modeling tool OpTickle.

Osamu, Dan, Ben take S5 shifts New coffee maker purchased. Productivity takes a leap.

40m TAC, 10/13/05 14

Deterministic Locking

Rob, Rana, Matt are developing schemes to lock the full IFO in a smooth, controlled, deterministic way (“no-bang locking”).

These steps involved mis-aligning and re-aligning the recycling mirrors. At each stage, more degrees of freedom are brought into lock in a controlled way.

Normalized DC signals are used to minimize interference between changing IFO state and LA control signals.

Real-time LSC code was cleaned up, and made more flexible for new LA approaches.

LSC rack got some re-cabling to get more DC signals into the system.

There is now a scheme to deterministically lock the PR-FPMI, with the carrier not fully resonant. The procedure is very repeatable and easy.

Attempts to add the SRC have so far failed. Work, and thinking, is in progress.

40m TAC, 10/13/05 15

DC readout progress

We have acquired almost all of the parts we need:» two in-vac PZT steering mirrors (SRM OMMT)» output mode-matching telescope (designed/built by Mike Smith)» in-vac folding mirrors» monolithic 4-mirror OMC, mirrors, UHV-PZT for length actuation» DC PD monolithic base, electronics in vacuum can» breadboard to pre-align in-vac optics» SR 830 Lock-In Amplifier to lock OMC

Still under development:» PZT driver for OMC» PZT drivers for in-vac steering mirrors» steering mirror ASC controls» Front-end wiring, EPICS wiring, DAQ channels

Plan to be ready to install by end of March

40m TAC, 10/13/05 16

Output mode cleaner, DC PD

OMC:Monolithic, copper, 4-mirror design.

DCPD:Monolithic, electronics invacuum nipple

40m TAC, 10/13/05 17

Coming milestones (1) re-establish robust lock of the dual-recycled FPMI, after the

replacement of our laser (just about done); re-measure and understand the detector response (one week); develop and implement more robust "deterministic” locking strategies

(open-ended, but one Feb-April is our plan); learn how to tune the detector response for optimal sensitivity and

control, by measuring and adjusting things like demod phases and offsets; (open-ended, but one Feb-April is our plan);

calibrate the detector and measure the displacement noise spectrum (Feb);

develop a "noise budget" to identify, and hopefully reduce, the dominant sources of technical noise (March, and on-going);

40m TAC, 10/13/05 18

Coming milestones (2)

assemble, install, commission and study the behavior of a DC readout system, including the tuning (offsets, etc) and the noise contributions (March-June);

Develop plans for injecting squeezed vacuum into the 40m asymmetric port, using a squeezer to be brought from MIT by Keisuke Goda and Nergis. Begin experiments by summer?

Continue development of e2e models and Optickle QN frequency-domain model.

Prototype ASC/WFS solutions» going to lower f2 RF ?

40m TAC, 10/13/05 19

Squeezed vacuum experiment

Vacuum squeezer apparatus developed by Nergis, Go and company at MIT

Go plans to bring his vacuum squeezer to the 40m lab this spring, with the goal of injecting squeezed vacuum into the 40m interferometer by this summer, and observe reduction in quantum (shot) noise… IF 40m is shot-noise limited at squeezing frequency.

OPTIMISTICALLY, the work could proceed in parallel with AdvLIGO goals (lock acquisition & control, DC readout).

Based on this optimistic assessment, it would be worthwhilefor Go to visit, starting in March.

Even if we aren't injecting squeezed vacuum by this summer, we will make good use of Go's visit, helping reduce noise.

40m TAC, 10/13/05 20

Go’s schedule

40m TAC, 10/13/05 21

Possible layout of squeezer, readout

40m TAC, 10/13/05 22

Two squeezing experiments

MHz squeezing test in the semi-Advanced LIGO configuration, meaning a detuned RSE with the power recycling mirror (PRM), but without the output mode cleaner (OMC)

“low-frequency” squeezing test in the Fabry-Perot Michelson (FPMI) configuration.

40m TAC, 10/13/05 23

What we need from TAC

Comments on paper on 40m response Advice on squeezing experiment Advice on replacing MZ with single EOM

» Paper on MZ for eliminating sidebands-on-sidebands in preparation by Bryan Barr

Words of encouragement

40m TAC, 10/13/05 24

Some optional slides on synthesizing Mach-Zehnder

40m TAC, 10/13/05 25

No sidebands on sidebands with Mach-Zehnder

With two EOMs in series to generate PM sidebands at f1 and f2, get “sidebands on sidebands” at f1 ± f2

We use MZ to generate sidebands in parallel

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

As)

PCs in series

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

Ap)

PCs in parallel

f1f2

40m TAC, 10/13/05 26

Synthesize MZ?

The MZ adds complexity and noise. Can we do it with one EOM?

The PM waveform that must be input to a single EOM to produce f1 and f2 with no f1 ± f2 :

required waveform: Synthesized:

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

Sp)

Phase signal for PCs in parallel

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

Sm

)

Synthesized phase signal for PCs in parallel

40m TAC, 10/13/05 27

The synthesized waveform does the job!

BUT it can’t be done with pure PM; it involves complex coefficients (AM).

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

Ap)

PCs in parallel

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

Am

)

Synthesized MZ

40m TAC, 10/13/05 28

Can it be done with pure PM?

Using only real sines and cosines:

Doesn't work: -4f and -6f are suppressed, but +4f and +6f are not.

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

Sm

)

Synthesized phase signal TRY

-10 -8 -6 -4 -2 0 2 4 6 8 1010

-2

10-1

100

101

102

103

104

frequency (Hz)

fft(

Am

)

Synthesized MZ TRY

40m TAC, 10/13/05 29

Extra, older slides

40m TAC, 10/13/05 30

Noise investigation in DRMI+single arm (no CM servo)

Requirement of RMS noise for full lock(10% of FWHM of RSE)

40m TAC, 10/13/05 31

DC Readout at the 40m DC Readout eliminates several sources of technical noise (mainly due to the RF

sidebands): – Oscillator phase noise – Effects of unstable recycling cavity. – The arm-filtered carrier light will serve as a heavily stabilized local

oscillator. – Perfect spatial overlap of LO and GW signal at PD.

DC Readout has the potential for QND measurements, without major modifications to the IFO.

We may not be able to see shot noise at low frequency, given our noise environment. We may not even see any noise improvements, but we might!

The most important thing we will learn is : How to do it » How to lock it?» How best to control the DARM offset?» What are the unforeseen noise sources associated with an in-vacuum OMC?» How do we make a good in-vac photodiode? What unforeseen noise

sources are associated with it?

40m TAC, 10/13/05 32

DC readout equipment

Most in-vac optics and opto-mechanics have been ordered» Most mirror mounts and mirrors» Output mode-matching telescope with picomotor focus» two Piezo-Jena steering mirrors» The PZT drivers are under design by Jay Heefner (also maybe needed at sites

for RBS system); based on IO PZT drivers. Need strain gauge readback.

OMC design from Mike Smith» 4-mirror design» super-mirrors with REO coatings coming from LIGO Lab spares

DC PD assembly and electronics under design (Abbott, Adhikari) OMC control, DC PD readout, and monitoring electro-optics and

readout, under design (Heefner), mostly using existing infrastructure and equipment.

Alignment on bench, in air, and in vacuum seems feasible. Mount everything on breadboards, install into vacuum chamber as a unit.

40m TAC, 10/13/05 33

Output Optical Train

Mike Smith

SRM

1st PZT steering mirror

2nd PZT steering mirror

gets a little tightaround IMMT

OOC IOC

BSC

40m TAC, 10/13/05 34

Output Optic Chamber

Mike Smith

from SRM

to AS RF beamline(roughly 1/3 of AS power)

also a convenient path for autocollimator beam, for initial alignment in air

to OMCR beamline

to OMCT beamline

from PSL to IMC

IMCR, IMCT, and SP beamlines

2nd PZT steering mirror

PZT steering mirrors and their controls are duplicates of a pair that we have

already installed and commissioned for steering from IMC to main IFO (in-vac);

controls are fully implemented in the ASC system (by Rolf). Similar systems

can be used for “LIGO I.V”.

Piezosystem Jena PSH 5/2 SG-V, PZT tilting mirror mount with strain gauge, and associated drivers and

power supplies

Existing in-vac seismically isolated

optical table (OOC)Mike Smith has designed a

compact, monolithic MMT, similar to our input MMT, using spherical

mirrors.

4-mirror monolithic OMC.Pair of DC PDswith in-vac electronics

on monolithic base.

40m TAC, 10/13/05 36

OMC design in SolidWorks Small number of pieces HV compatible

» a bit of glue on the PZT mirror Mirrors mounted mechanically,

on silver washers (no glue) ALGOR FEA: lowest mech

resonance at ~770 Hz Construct out of well-damped

material, to minimize effect of resonances

» Brass? Copper?» Or just stick with aluminum?

All high-quality (REO super-polished and coated) mirrors available from LIGO lab spares (well, the 4th HR mirror, 0o incidence, may need to come from Newport)

Mike Smith

From MMT

to DCPD

PZT mirror

SS fixed spacer

~ 20 cm

reflected beam

mechanical clamps

(no glue)

40m TAC, 10/13/05 37

Low-loss mirrors The TAC encouraged us to consider low-loss mirrors for our OMC (eg, super-polished, REO coatings, etc). The PZT-mounted curved mirror will be supplied by Peter King, out of PMC spares. Helena worked with REO for the remaining required mirrors + spares: ~$7K, 6 weeks. Peter F asked around: LHO has spare PMC mirrors with T=1.4%, and HR mirrors (43.5o incidence P-pol). Our “4th” mirror needs to be HR at ~10o incidence P-pol. We will test the HR mirrors to see if they work.

Else, we can get Newport “super-polished” broadband mirrors for ~$475, with R~99.95%.

Mirror Diameter Thickness Side 1 Side 2 wedge Radius of curvature

M1 7.75 mm 4 mm R > 99.95%, 0° inc AR < 30 amin 1 m, CC/PL

M2 1” 0.25” R 99.95%, 10° inc AR < 30 amin Flat PL/PL

M3 1” 0.25” T ~ 1.4% , 45° inc, P-pol R < 0.2% 30 amin Flat PL/PL

M4 1” 0.25” T ~ 1.4% , 45° inc, P-pol R < 0.2% 30 amin Flat PL/PL

40m TAC, 10/13/05 38

In-vac DC photodiodes

In-vacuum DC PD assembly, showing a 50% beamsplitter, two photodiodes, a beam-dump, and a vacuum can to hold electronics. Electronics under design (Abbott, Adhikari)

Ben Abbott

40m TAC, 10/13/05 39

Development of e2e simulation: 4Om/AdvLIGO package

Monica Varvella (visitor from LAL/Orsay) has developed a 4Om/AdvLIGO package with a DRFPMI optical plant, and is developing the control plant with help from Matt Evans and Hiro Yamamoto

Tests include a careful comparison with Twiddle, as well as comparison of error signal sweeps between simulation and 40m data.

Can be used to extract the velocity of the mirrors in the 40m under controlled circumstances: lock all degrees of freedom, CARM offset, and then HOLD the CARM servo and watch error signal as mirrors sweep through arm resonance.

40m TAC, 10/13/05 40

Error signal sweeps at 10-9 m/s for the 40m IFO obtained in

E2E framework and compared with TWIDDLE predictions

Example:DARM @ AP 166 MHz

TWIDDLE and E2E comparison

e2e SIMULATION:4Om/AdvLIGO package

TWIDDLE

E2E

40m TAC, 10/13/05 41

e2e SIMULATION: 4Om/AdvLIGO package

Comparison between real data (black) and e2e simulated data (red) of the transmitted light for both the arms (full IFO): the mirror velocities used in

E2E simulation are the values obtained fitting the real data

Real data have been used to estimate relative mirror velocity for

both the arms:

Vxarm= (0.35 ± 0.13) μm/s

Vyarm= (0.26 ± 0.13) μm/s

E2E

E2E

real data

real data

Tr X

Tr Y

40m TAC, 10/13/05 42

e2e SIMULATION: 4Om/AdvLIGO package

Comparison between real data , e2e simulated data and the

theoretical prediction V(t) of the SP error signal @ 166 MHz

The τ and the velocity v is the value obtained fitting real data

τ = 0.7 msv = 0.26 μm/s

V(t) ~ exp(-t/τ) sin( a t2)

with a = -(k v) / (2 T)