Virgo commissioning update-

VSR1 first month summary

E. Tournefier

WG1 meeting, Cascina June 20th ,2007

Activities since last WG1 meeting (March 28th)

• Virgo complete electrical shutdown (April 6th -> 18th)Infrastructure works:– Electrical works: UPS replacement, reorganisation,…– Computing: civil work, re-organisation, new file server,…Detector improvements- Acoustic enclosure around external detection bench- Replacement of Brewster window with a larger oneRestart went ok: ITF relocked within ~2days

• 1 month of commissioning before the run– Acoustic enclosures at end benches– Diffused light investigations + some noise reduction– Improvements of controls (longitudinal, angular, suspensions)– Change of naming convention (V1:channel_name)for easier data exchange

with LSC

• VSR1 started on May 18th as planned– Short commissioning breaks for improvements / problem fixing

Acoustic enclosures

• External detection bench:– Displace bench from the tower (~50cm)– Install acoustic panels (a room into the room)

• End benches:– Simpler: build a room around the benches

DetectionEnd buildings

Acoustic noise reduction: end benches

Tentative acoustic noise projection before

Tentative acoustic noise projection with acoustic enclosureSeismic noise on the optical bench

- No acoustic enclosure- With acoustic enclosure

- Previous actions: Improvement of the optical setupBut: projection of acoustic noise of end benches was still close to themeasured sensitivity

Acoustic enclosure needed

Result: impact reduced above 100 Hz

New Brewster window

Why change the detection Brewster window:- Brewster-detection tower was shown to be an area very sensitive to acoustic noise- tentative noise projections: Brewster could be a limiting factor- old Brewster didn’t respect the rule: diameter > 5 x beam waist

Brewster link

Detection tower

Tentative projection of ‘Brewster noise’

Replace Brewster with a larger one (April shutdown)

Followed by diffused light investigationsNo obvious improvement in sensitivity

See Raffaele’s talk

Other actions for noise reductions

Replaced pump of SR tower with a smaller one(noise reduced but path is unclear)

BS actuator noise reduced

(last WG1 meeting)

Mirror actuator noise reduction

• Electronic noise of the coil drivers + DAC Shaping filters, more gain to reduce its impact

zCorr

I (A) to mirror coil

BS actuator noise reduced in May

The arm mirrors actuators need to be improved can be done during VSR1

Actuators calibration

Actuation TFs Simple pendulum

Simple cavity filtering(500 Hz pole)

More precise measurement of the actuators response frequency dependence could be due to Eddy current effects Change of 20% at high frequencies

10%

Longitudinal controls

PRCL

MICH

B2_ACpmix

Usual noise subtraction (online): -MICH and PRCL corrections sent to the end mirrors tosubtract the noise reintroduced by these loops into thedark fringe- coefficient is frequency dependent

MICH noise reduction ~ 50

- with =0 - with measured (f)

See Bastian’s talk

Longitudinal controls: noise budget

BS control noise limits the sensitivity below 40 Hz=> What is the origin of this noise?

- B1_ACp - BS control noise- PR control noise

Origin of BS control noise ?

• Related with acoustic noise inside the laser lab Beam jitter seen by B2 photodiode (used for PR & BS)?• Sometimes disappears … but acoustic noise does not

change

Input beam jitter Acoustic noise in laser lab

Beam jitter vs acoustic noiseBeam jitter vs dark fringe

dark fringe

Angular controls

• Second modulation frequency (8MHz) now used for Q22

=> Get rid of DC signal• Control loops improvements• Mirror centering ~ 1mm

Angular noise budget

-Angular controls do not limit thesensitivity- Reduction of electronic/shot

noisein error signal still possible

Suspension control: z -> couplings

Compensation of non-linear coupling:Large seismic activity large correction sent to marionetta (zM) y motion of F7 and payload Side effects on alignment

Solution: compensate for z -> y coupling

Need a quadratic compensation:

Dark fringe

-No quadratic compensation-With quadratic compensation

y=c*zM +d*zM2

Suspension control: top stage control

Old problem: environmental noise (seism) reintroduced by Lvdt used for top stage control

=> Use the ITF longitudinal error signal instead (Global Inverted Pendulum Control)

=> z correction to the mirror well reduced

GC (reconstructed z)

LVDT

LVDTLVDTLVDT

VSR1: enabled only for NE-WE

No GIPCWith GIPC

Sensitivity vs wind and sea activity

Matteo’s empirical formula: Horizon = H0(1 - a x seism – b x wind)

WSR1 (Sept 2006)VSR1 (May 2007)

a= 0.37, b= 0.37 a= 0.07, b= 0.04

=> Sensitivity to bad weather conditions is well reduced

Lock acquisition: thermal transient troubles

• Variations in the thermal transient : seems related to activities in laser labSometimes need to wait few hours before being able to lock

Thermal effects: sidebands image

• Image of the sidebands (first step of phase camera):scanning system on B5 beam: - the beam is scanned on a pin-hole + photodiode - demodulated signal is used to reconstruct the sidebands shape

Waiting for thermal compensation system + complete phase camera

VSR1 noise budget

Still magnetic noise?

Mystery noise

Mystery noise

• Some observations:– Coupling to DF increases with misalignments– Sudden decreases/increases (also seen in frequency noise)– Structures not excited with noise injections/tapping tests around

benches/towers

Keep searching…

VSR1: first month summary

Thanks to Roberto for the material

Run organisation

• Goal: – Take science data for a minimum period of 4 months starting from

the 18th May 2007 at 23:00 (LT)

• Shifts have been planned until 20th September 2007:• 18 weeks, 378shifts.

– Shift team and time schedule:• Team: 1 operator + 1 physicist,• Shift period: 8 hours • Shift start times: 07:00 – 15:00 – 23:00

• Permanent ON Call:– 11 Virgo ITF Sub-systems:

(Alignment, DAQ, Detection, Electronics, Locking, Global Control, Laser &Injection, MSC, On line Computing &Network, Software, Suspension Electronics & Software)

– 4 EGO Site Services:(Network & Global Security System, Site Infrastructure-Conditioning, Site Infrastructure-Electricity, Vacuum)

Duty cycle

– Duty cycle in science mode ~ 85%– 42 unlocks from “Science Mode” registered up to 17/06/07– Longest Lock: about 58.5 hours , Longest Unlock: about 16.1 hours

Science mod recovery time

Science Mode Unlock Time Periods (18th May - 16th June: 42 Unlocks)

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Days

Ho

urs

– Longest unlock: 16 hours– Smallest ~ 30mn (time needed for lock acquisition)

Lock duration

VSR1 Locking Step Time Periods (18th May - 16th June: 42 Locking periods)

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Date

Ho

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of

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ckin

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– Longest lock: 58 hours

Unlocks

VSR1 Unlocks Type Distribution (18th May - 16th June: 42 Unlocks)

Commissioning4,8%

Unknown14,3%

Maintenance9,5%

Manual-Adjusting2,4% Thunderstorms

2,4%

SSFS2,4%

Earthquakes16,7%

Bad Weather4,8%

GxOB crash2,4%

GC Crash11,9%

WI_LC Glitches4,8%

12Hz Long. Oscill.4,8%

ISYS 2,4%

Fast Unlocks16,7%

• Analysis of unlocks ongoing (preliminary statistics)

Main unlock reasons:- IMC fast unlocks Partially cured (loop gain reduced) - Global control crashes Pb = longer recovery (susp excited)- Earthquakes

Manual unlocks for:- Weekly maintenance- Commissioning breaks

Only 3 unlocks due to bad weather

Commissioning breaks

Alignment drifts observed during long locks: related to Q81 quadrant mis-centering (used for BS control) => spoils error signal (AC)

Temporary solution: realign quadrant from time to time Improvement: include Q81 asymmetry in the error signal for BS control

Small drifts still there Try to use another error signal (B1p?)or Install galvanometer to keep centering in science mode

realignment

Dark fringe

Q81 asymmetry IMC Fast unlocks

- Reduction of IMC loop gain 1 unlock per couple of day => ~ 1 per week - more investigations ongoing (electronics)

Suspension controls: some improvements /tests

Long term observations: Etalon effect!

• Etalon effect: small FP cavity inside input mirrors (due to AR face)=> effective reflectivity modulated with mirror thickness (temperature)

AR HR HR

r1 r2 r3LA

LB

AR HR HR

r1 r2 r3LA

LB

B7/B8 phd

-FP transmitted power-Input mirror temperature

Temperature variation

FP

Tra

nsm

itte

d po

wer

Some short term plans

• Continue noise investigations– ‘Mystery noise’ ( 200Hz)– Magnetic noise (50 - 100 Hz)– Low frequency noise in laser lab (=> BS error signal)– Reduce mirror actuator noise (cavity mirrors)

• Controls:– Alignment drifts: get rid of Q81 or use galvanometer– Suspension control improvements in preparation