paolo la penna ilias n5-wp1 meeting noise analysis in virgo cascina, 7-8 july 2004 analysis of noise...

Paolo La PennaILIAS N5-WP1 meetingNoise analysis in Virgo

Cascina, 7-8 July 2004

Analysis of noise in VIRGO



What we mean for “noise analysis” How is the noise analysis work organized in Virgo Which tools Noise and data analysis groups What has been done Some results in noise identification Sensitivity curve debugging (noise understanding)



What we mean for noise analysis

VIRGO commissioning: interferometer still in a development phase the Interferometer’s configuration is progressively upgraded

The sensitivity is measured through the output signal calibration

We try to identify the different sources of the noises

We try to upgrade things in order to reduce the identified noise source



Work organization

Engineering runs: allow collection of data (3-5 days every 2 months)

Data Analysis: division in investigation groups (normally 3-4 persons with a coordinator)

Discussion of the results in data analysis meetings

Depending on the results, the further activity is decided (implementations, modifications, etc.)



Summary of the performed activity

CITF (2000-2002): Five engineering runs (E0-E4)About 5-10 investigation groupsAbout two meetings after each run

VIRGO (2003-now):Four Virgo runs up to now (the last at the end of June)About 10 investigation groupsNormally one preliminary meeting short after the run, then a

more detailed one

http://wwwcascina.virgo.infn.it/commissioning/Eruns.html



Engineering runs

4 VIRGO Engineering runs (C1-C4, now five days each)

C1 (14-17 November 2003): North Arm locked

C2 (20-23 February 2004) : North Arm locked+linear alignment; West Arm locked

C3 (23-27 April 2004) : North Arm locked+linear alignment+second stage frequency stabilization; Recombined locked (lock acquisition mode, no linear alignment)

C4 (24-29 June 2004): Recombined+linear alignment on both arms+second stage frequency stabilization



VIRGO sensitivity curve



Progress in sensitivity

10 100 1000 1000010-20

10-19

10-18

10-17

10-16

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

C1 (North Arm) C2 (North Arm) C3 (North Arm) C3 (recombined) C4 (recombined) Design

m/s

qrt(

Hz)

Hz



Investigation groups

Individuated investigation groups:(http://wwwcascina.virgo.infn.it/DataAnalysis/Noise/)

Present list of the groups:

– Calibration– Locking performances and noise – Alignment performances and noise – Suspension control performances and noise – Environmental noise – Laser noise – Glitches search and identification – Lines identification – Quantify noise stationarity/gaussianity – Readout noise



Tools

Data are in the Common Data Frame Format for Interferometric Gravitational Wave Detectors

Mostly handled with:

dataDisplay: data visualization and analysis Siesta: simulation vs data Vega: data visualization and analysis Other (personal) softwares and/or libraries



dataDisplay

dataDisplay: Virgo software for visualizing and analyze data

It is the most commonly tool used by commissioning people.

It allows on-line (in-time) data analysis and visualization It allows visualization of measured and simulated data It has ist own routines for analysis (FrVect: offsets, sum,

multiplication, FFT, coherence,TF, etc.)



Siesta

Siesta: Virgo software for simulation

C written code with C input cards It allows the simulation of the whole interferometer (optics,

mechanics, etc.) in the time domain It has its own routines for analysis (FFT, coherence, TF,

…) It allows simulation of control loops: simulated data in

frame format can be compared with the measured ones (e.g. with dataDisplay)



VEGA

VEGA:

Graphical software, based on ROOT (Cern), modified to handle data in the Frame format (Frame library and FrVect)

Allows off-line data visualization and analysis

Less used by commissioning people than dataDisplay

It is linked to the Cernlib libraries for data analysis



Others

Many people working in noise analysis have developed their own routines and libraries (Matlab, C and C++ software).

Some examples:

Lines identification: Florence-UrbinoNon-linear, non-stationary: Nice, UrbinoLines removal: LAPPWhitening: EGO



Common library

Since there is much dispersion, discussion is going on in Virgo in order to create a common library for noise (and data) analysis.

For the moment no final common reference software has been established yet



Examples of noise investigation



Environmental sensors

3km

3km

Central building

MC End b.

West End b.

North End b.Low Frequency Accelerometers

Tri-axial, 0.2-200 Hz

(Kinemetrics - “Episensors”)

High Frequency Accelerometers

Vertical Piezo, 10-10000 Hz

(Bruel&Kjaer)

Other Environmental probes:

• Microphones• Magnetometers• Pressure probes• Humidity • Temperature • Weather station



LF seismic activity monitoring

Episensor (tri-axial accelerometer) in the central Building

Updated on web each 10 minutes

Sea activity

Human activity(road traffic on highway bridges)

Human activity around the site



Acoustic noise in the detection laboratory



C1 (North Arm)

Electronic noise

Shot noise

MC length control noise

MC length noise

Mirror control noise



C2 (North Arm)

Shot noise

ADC noise

MC length control noise

MC length noise



C2: spectrogram 150 Hz-3 kHz

Decrease of noise Noise is higher than it was before the decreasing period

Noise at beginning

of C2

ZOOM



Effect of the pump

Between 13h22 (UTC) and 14h40, all pumps are progressively switched off

At 13h59, IB pump switched off

ZOOM

Between 14h40 and 15h00, original conditions are restored



C3 : scroll pumps OFF (IB), except 5min/day

C2

C3

Residual env. noise dominates mainly in [1500, 3000]Hz Turbo pump (mainly IB) ?

IB tower accelerometer

Coherence with dark

fringe



C2: Mirror internal modes identification

Coloured noise injected at the RM actuators of each mirror

ANSYS mirror simulation Calibration software (CaRT) One period at the NA and another at the WE Mirror internal lines and quality factors measured



C2: North mirror internal modes identification

NI:3917.2 Hz5584.7 Hz

NE:3883.0 Hz5542.2 Hz



C2: Mirror Internal modes measurement



C4: Thermal noise

5542 5543 5544 5545 5546 5547 554810-12

10-11

10-10

Am

plitu

de

Frequency [Hz]

PrB1ACp

End mirrors

Internal modes are now visible in the ITF output(recombined ITF)

NE at 5543 Hz WE at 5545 Hz



C3 (North Arm)

With SSFS :

RFC noise contribution is reduced

C3 sensitivity now limited by another

kind of noise

FFT(Sc_NE_zGc) x Mechanical TF(NE)

C2 sensitivity limited by RFC

noise



C3 (North Arm)

Pr_B1_ACp spectrum (April 23rd, 20:00:00 UTC )

Electronic Noise

Shot Noise



C3: Injection Bench lines (10 Hz< f < 100Hz)

Input Bench resonances

Good coherence around the IB resonances

introduced in the sensitivity by the IMC AA loop

Sc_MC_txCorrM Sc_MC_txCorrR

Sc_MC_tyCorrM Sc_MC_tyCorrR



C3-Recombined: Electronic Noise

Pr_B1_ACp spectrum (April 27th, 12:20:00 UTC )

Electronic Noise (measured with shutter closed)

Shot Noise

Additional noise



C3-Recombined: West terminal photodiode (B8) noise

Hz

Gain

frequency

Transfer function of the standard filter

Static gain = 1.727 x 10ˆ9

West arm

B8_phase/B8_DC

Sc_WE_zCorr

Filter

Pr_B8_ACp limited by electronic

noise above 200 Hz

injected in sensitivity by

the control loop

Pr_B8_ACp used to acquire the lock of the

West Cavity

Coherence between B1_ACp & B8 _ACp

sensitivity limited by B8 electronic noise between 200 Hz & 1

kHz



C3-Recombined: West terminal photodiode (B8) noise

Standard filter

New filter

frequency

Phase

|gain|

Roll off @ 300 Hz

B8 noise model suits to sensitivity curve

between 200 & 1000 Hz

New noise structures



C3 Noise limitation to the sensitivity curve

1 - North arm

High frequencies : Electronic noise(?) or noise coming from the ITF (?) Above 250 Hz : not well understood Between 10 & 250 Hz : coherence with the correction signals used by the IMC RFC noise (NA length control loop): does not limit C3 sensitivity, but could

limit the sensitivity below 50 Hz for full VIRGO

2 - Recombined configuration

High frequencies : electronic noise 200-1000 Hz : noise due to B8 10-100 Hz : “laser frequency noise” but is reduced at the end of the run



C4 General results about sensitivity (C4 data still to be discussed)



Summary

Virgo is not in its final configuration: Noise identification means debugging the progress of the activity

The commissiong activity for noise analysis is mainly concentrated on the data from the runs, in identifying the noise sources in the sensitivity curve

Many tools for analysing noise are present, discussion is going on for establishing a common library

paolo la penna ilias n5-wp1 meeting noise analysis in virgo cascina, 7-8 july 2004 analysis of noise...

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