Online Veto Analysis of Online Veto Analysis of TAMA300TAMA300

Daisuke TatsumiDaisuke TatsumiNational Astronomical Observatory of JapanNational Astronomical Observatory of Japan

The TAMA CollaborationThe TAMA Collaboration

8th GWDAW 19 Dec 2003 @ Milwaukee, UWM, USA

IntroductionIntroduction<Veto Analysis><Veto Analysis>To distinguish GW signals from noises, To distinguish GW signals from noises, we should identify the noise sources. we should identify the noise sources.

In TAMA case, several noise contributions were already evaluated in the frequency domain as shown in this figure.

<Online Veto Analysis><Online Veto Analysis>Because detector conditions will be changed, we need to Because detector conditions will be changed, we need to monitor all of noises continuously and in time.monitor all of noises continuously and in time. For example, a mean level of some noise do not contaminateFor example, a mean level of some noise do not contaminatethe displacement noise. But non-stationary noises may the displacement noise. But non-stationary noises may influence. Even in such case, if we monitor the noise influence. Even in such case, if we monitor the noise contamination continuously, we can distinguish the noise contamination continuously, we can distinguish the noise from GW signals.from GW signals.

For the veto analysis, it is very important to evaluate For the veto analysis, it is very important to evaluate noise contamination continuously. noise contamination continuously.

IntroductionIntroduction

ContentsContents

We began to study Veto Analysis intended to We began to study Veto Analysis intended to the following noises:the following noises:

1.1. Differential motion of Power Recycled Michelson Differential motion of Power Recycled Michelson (Hereafter it is called (Hereafter it is called slmslm: small l minus): small l minus)

2.2. Laser Intensity NoiseLaser Intensity Noise 　　 (int)(int)

By focusing on these, I talk about current status ofBy focusing on these, I talk about current status of

• Checking of the noise contaminationChecking of the noise contamination mechanism mechanism

• Online evaluation of these noise contaminationsOnline evaluation of these noise contaminations

This is a schematic view of noise contamination mechanism on slm. Slm is controlled at low frequency region below 20 Hz. In other words, at the observation band, it is not controlled. So we can consider that the noise contaminate via this path with a coupling constant of epsilon.

Noise Transfer Function = V4 / V2Noise Transfer Function = V4 / V2To confirm this model, we measured noise transfer function from slm to the displacement noise.

Noise Contamination MechanismNoise Contamination Mechanism(slm noise)(slm noise)

slm

Hslm

Dslm

Fslm

Aslm(slm) -

WFslm

H

D

F

A(llm) -

WFer

L l

V2V4

UGF: 20Hzcoupling constant

Noise Transfer FunctionNoise Transfer Function (slm noise)(slm noise)

Inconsistent with measurement.

Inconsistent with measurement.

But the model is not consistent with measurement.

Laser

l1

l2

slm = l1 - l2

Laser

l1

l2

slm = l1 - l2

Compound mirror

Simple Power-Recycled MichelsonSimple Power-Recycled Michelson

The origin of the differenceThe origin of the difference

This difference come from our incorrect assumption.We could not consider the slm to such a simple Power-Recycled Michelson.

We should consider the slm to Power-Recycled Michelson with compound end mirrors. It means its reflectivityhas frequency dependence.

Noise Contamination MechanismNoise Contamination Mechanism(slm noise)(slm noise)

slm

Hslm

Dslm

Fslm

Aslm(slm) -

WFslm

H

D

F

A(llm) -

WFer

L l

V2V4

UGF: 20HzH

coupling constant

We modified the model by taking into account such compound mirror effect as H.

Noise Transfer FunctionNoise Transfer Function (slm noise)(slm noise)

We confirmed that the modified model is consistent with measurement.

Noise Contamination MechanismNoise Contamination Mechanism(Intensity Noise)(Intensity Noise)

L

INT

HINT

DINT

FINT

AINT(INT) -

WFINT

H

D

F

A(llm) -

WFer

Intensity NoiseIntensity Noise

DINT

V4V3

UGF: 50kHzcoupling constant

Next is intensity noise. It is also modeled in a similar way.But, because the intensity noise is controlled at observation band, only the suppressed intensity noise contaminate to the displacement noise with a coupling constant of epsilon.

Noise Transfer Function = V4 / V3Noise Transfer Function = V4 / V3 To confirm this model, we measured transfer function.

Noise Transfer FunctionNoise Transfer Function (Intensity Noise)(Intensity Noise)

Inconsistent with measurement.

Inconsistent with measurement.

The amplitude is consistent, but the phase is not consistent.

Transfer Function (Transfer Function (T)T)

The difference suggests us that this kind of all-path filter is necessary. But unfortunately we cannot understand why this filter is needed.Now numerical approach on this program is going on in our group.

Noise Contamination MechanismNoise Contamination Mechanism(Intensity Noise)(Intensity Noise)

L

INT

HINT

DINT

FINT

AINT(INT) -

WFINT

H

D

F

A(llm) -

WFer

T

Intensity NoiseIntensity Noise

DINT

V4V3

UGF: 50kHzcoupling constant

Anyway we constructed model of noise contamination experimentally.

Noise Transfer Function Noise Transfer Function (Intensity Noise)(Intensity Noise)

And we confirm the model is consistent with measurement.

Online evaluation of noise contaminationOnline evaluation of noise contamination

Noise contamination mechanisms were modeledNoise contamination mechanisms were modeledand were measured as and were measured as transfer functiontransfer function. . So we can evaluate noise contamination by using So we can evaluate noise contamination by using auxiliary noise spectrumauxiliary noise spectrum. .

Moreover, in the online evaluation, Moreover, in the online evaluation, coupling coupling constants are also monitoredconstants are also monitored by using calibration by using calibrationpeaks to follow changing of the detector condition. peaks to follow changing of the detector condition.

Calibration Peaks forCalibration Peaks forNoise CalibrationNoise Calibration

slm noise Intensity noise

To monitor the coupling constant, sinusoidal wave signals were injected into each control system.

Noise ContaminationNoise Contamination(displacement L-, slm, Intensity)(displacement L-, slm, Intensity)

This figure shows displacement noise spectrum, black is total noise.And green and purple are slm and intensity noise contamination, respectively.

Noise ContaminationNoise Contamination(displacement L-, slm, Intensity)(displacement L-, slm, Intensity)

To enhance theTo enhance theIntensity Noise Intensity Noise

1. Intensity 1. Intensity Servo vary OFFServo vary OFF

2. Add offset on l-2. Add offset on l-

ContaminationContaminationof Intensity noiseof Intensity noiseis well consistent is well consistent with displacement with displacement noisenoise

SummarySummaryTo realize online veto analysis,

1. We check the noise contamination mechanisms of slm and intensity noises.

2. We demonstrate online evaluation of the noise contaminations.

In progress,

1. Increasing the number of monitored noise:alignment, frequency noise and so on.

2. Noise reduction by using this system.

Checking Transfer Function Checking Transfer Function

HINT

DINT

FINT

AINT-

WFINT

DINT

V3

Vs

V3 / Vs