LIGO-G040541-00-D

LIGO calibration during the S3 science run

Michael Landry

LIGO Hanford Observatory

Justin Garofoli, Luca Matone, Hugh Radkins (LHO), Rana Adhikari, Peter Fritschel (MIT),

Patrick Sutton (Caltech), Brian O’Reilly (LLO), Xavier Siemens (UWM), Gabriela González, Andres Rodriguez (LSU), Martin Hewitson (GEO)

GWDAW9December 19, 2004

Annecy, France

GWDAW9, 19 Dec 2004 2LIGO-G040541-00-D

Overview

1. Calibration basics

2. Calibration improvements for S31. Line strengths in all IFOs

2. Accurate DC calibrations

3. Checks on systematics

3. S4 photon calibrator

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IFO review

1 ( ) ( ) ( )( , ) ( , ) ( , ) ( , )

( ) ( )

t t G fh f t R f t ASQ f t ASQ f t

t C f

)()()()()(),( fDtfCtfAtfG

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Calibration method

• Measure open loop gain G, input unity gain to model• Extract sensing function C=G/AD from the model• Produce response function at time of the calibration, R=(1+G)/C• Now, to extrapolate for future times, monitor single calibration

line in AS_Q error signal, plus any changes in gain beta, and form alphas

• Can then produce R at any later time t, given alpha and beta at t• Independent time-domain method (spearheaded by Xavier

Siemens with input from Martin Hewitson) uses frequency domain filters as input. Calibrated frames available for use by analysis groups

• Xavi also demodulates lines, which allows for a nice check on alphas and betas (frequency domain method assumes alpha and beta real, whereas demodulated lines are complex)

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Sample error budget: S2 H1

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Calibration improvements I

Effect of lineamplitude on

error in productof alpha and beta

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S3 V3 , coefficients: L1

Error:0.5%

Over all of S3:

variation: 15% variation: 4%

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S3 Calibration errors

• Errors from reference models in S3 ~ errors in S2 (5-10%)• Random variations, errors in alpha, beta (60 sec integration time):

error

S3 variation

S3 variation

L1 0.5% 15% 4%

H1 0.3% 4% 1%

H2 0.7% 6% 2%

In S2: 0.7% (L1), ~3% (H1, H2).

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Calibration improvements IIDC calibration

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Calibration improvements II

ETMx

Asymmetric Michelson

Lock configuration by feedingBack to ETM

Instead of ~6% error on theETM calibration, ~2%

Lots of checks on actuationstrength calibration: toggling,Michelson swinging, freeswinging AS_Q, tidal actuators

Important for hardware injections

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Calibration improvements IIIunderstanding systematics

• Use of true dc calibration requires good understanding of systematics

• Assess systematic error in digital filter compensation, e.g. dewhitening filters

DigitalControl signal

Digital Anti-dewhitening

filter DAC

Analogdewhitening

filter

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S3 response function R comparison

• V2: assumes digital compensation is perfect• V3: uses hardware measurement

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S4: Photon calibrator

• previously installed and tested – laser troubles with rotating polarization• recently reinstalled, awaiting laser safety approval• expect limited test for S4: independent check on magnitude of calibration (and timing, too)

Oddvar Spjeld, LLO

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Conclusions

• LIGO frequency domain calibration improving in accuracy with each science run

• S3 calibration makes use of several new measurements• Anticipate independent check with photon calibrator for S4

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Contributions to the Error

Magnitude: 2

4

22

4

22

4

2222

1

1

1

1

1

1G

G

G

G

G

G

G

G

G

D

D

A

A

R

R

Phase: 2

4

22222

4

2222

1

1

1

1GDAR

G

GGG

G

G

R(fi,t) = 1 + (t) (t) G(fi)

(t) C(fi)

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News on calibrationsince Aug LSC meeting

Not enough!…• Coefficients: validation studies of “new” method (using

demodulated line)• Models:

» Codes were succesfully reviewed (P. Fritschel), no errors found. – V2 model version reviewed; V3 mods will need to be assessed

» Work in progress on LHO models (to incorporate hardware/digital filters)» Work in progress: systematic model/measurement comparison for different

calibration runs in L1. • Validation (use of!) X. Siemen’s h(t) frames has started…

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Hardware measurements

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S3 V3 , coefficients

• V2 (from P. Sutton’s SenseMon)» from SenseMon averaging input matrix» from SenseMon’s line amp, , and G0(f0)

• V3: use Xavier Siemens’s code to generate demodulated lines in ASQ, DARM, EXC

» Complex = ( 1/D0)*(DARM-EXC)/ASQ» Complex = -(D0/G0)*ASQ/DARM» Complex = -(1/G0)*(DARM-EXC)/DARM» Non-zero mean of imaginary part indicates errors in reference functions D0,G0 (at cal

freq).» Standard deviations of imaginary parts are error estimates in real part (and depend on

sampling frequency).

• Compare consistency of Xavi’s output and existing model

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“New” method: validation steps

H1, reference time

G0 phase “error”:1.5 deg

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S3 V3 coefficient: H1

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S3 V3 coefficient: L1

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S3 V3 , coefficients: H1

Error:0.3%

Over all of S3:

variation: 4% variation: 1%

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H1