1

Commissioning status and plans

ILIAS - June 14th 2005Matteo Barsuglia

1/ what happened in the last month

2/ New sensitivity: a preliminary noise budged and next steps

3/ Jumps investigations

4/ Plans for the next 6 months

2

1/ What happened in the last month

3

C5 sensitivity (Dec 2004)

C4, recombined 7W input power

C5, Recycled 0.7 W input power

4Laser frequency

refl_3f_phaseref

rec_quad

rec_phase

Asy_phase

‘detection’ mode

• DARM controlled with Asy_phase

• CARM with rec_phase

• MICH with rec_quad

• PRC with refl_3f_phase

May 17th: realignment of B5 (rec beam photodiode)

B5 photodiode (rec beam)

5

Minirun M3 – may 19th

Proper minirun M3 Restoring C5 science mode

6

Comparison with M2 – May 5th

7

Jumps during M3

~5 jumps

8

Sensitivity on May 20th

• Roll-off Michelson at 50 Hz (100 Hz during C5)

• LO board upgraded

• Local control upgraded

C5 sensitivity

9

Michelson roll-off @ 50 Hz

1/ Elliptic roll-off at 50 Hz

unity gain frequency at 6-7 Hz

10

May 19th-26th: a good week

‘ no jumps’

11

May 23rd sensitivity

• Low noise coil drivers on arm mirrors (1/25)

12

Marionetta and tidal control f < 10 mHz

10 mHz < f < 10 Hz

f > 10 Hz

Recycled ITF

internal power

Force on marionetta

Force on mirror

• Marionetta and tidal control tested with recycled interferometer

• Residual correction seems to be compatible with Virgo specifications

13

May 27th, Jumps again

Injection realignment

ITF relocked 50’

Some locks with jumps some locks without jumps

realignment quadrant mode-cleaner

Work on NI vertical damping

14

50’ lock on Thursday evening

No evident jumps

Power fluctuations maybe higher than normal

15

May 27th, Jumps again

Injection realignment

ITF relocked 50’

Some locks with jumps some locks without jumps Only work:

realignment quadrant mode-cleaner

Work on NI vertical damping

16

Friday May 27th , the bad

Zoom on a jump bench of the first plot

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Friday 27th, the good

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Friday 27th , the good

New sensitivity curve (with BS coils drivers x4 resistors) – obtained during one of the “good” locks

Zoom on the 50-100 Hz region

• with resistors x4 BS and arm mirrors should contribute at the same level

19

Sensitivity evolution

May 27th

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Last week

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photodiode centering checks May 30th - June 1st

Photodiodes B1p, B5, B5_2f, B2_3f

• PR-NI configuration

• other mirrors misaligned by 10 mRad

• maximize AC or DC signal

Photodiodes B8

• North cavity configuaration

• other mirrors misaligned by 10 mRad

• maximize DC signal

All photodiodes were found centered

22

June 1st: demod phases checks

Demod phases (with respect to May 17th)

• B2_3f –170-150 (maximizing P/Q for a line on PR using the CITF)

• B5_2f –43-23 (maximizing sideband crossing, using the CITF)

• B5 –34-28 (minimizing frequency noise on Acq, using north cavity only)

• B8 OK (minimizing frequency noise on Acq, using north cavity)

- Are the tuning criterions right ?

- Why these phases changes?

23

M4 – changes in B2_3f_phase

-150 (“good” phase)

-110

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M4 – new BS local controls

25

Improvements in low frequency sensitivity – june 3rd

- Black = may 27th (+ x4 resistors on BS)

- red = June 3rd (+ new controls on BS and gain decreased by factor 2 on WI and NI)

26

Sensitivity evolution – low freq

C5

June 3rd

27

2/ Sensitivity: a preliminary noise budget and the next actions

28

C5 May 2005

sensitivity curve

electronic noise (shutter closed)

shot noise

Virgo nominal sensitivity

x 40

x 4Phase noise

Sensitivity – high frequency

(Input power = 0.7 W)

29

Volts/sqrt(Hz)

ACp noise (>5000 Hz)

ACq signal (0-100Hz)

= 0.39 rad/Hz

Volts

During C5:

= 0.48 rad/Hz

Now:

= 0.39 rad/HzNo big improvement on

But a big reduction of B1_ACq! Improvement of local controls?

C5

May 27, 2005

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M3 data

Phase noise measurements

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Power fluctuations

Contrast

1 mW / 20 W ~ 5e-5

Internal power (rescaled) Dark fringe power (W)

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What is the bump?

Volts/sqrt(Hz)

ACp noise (1600-3000 Hz)

ACq signal (0-100Hz)

=> The amplitude of the bump does not vary with B1_ACq like phase noise

Volts

?

31

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High frequency: actions • Oscillator phase noise

Several parallel solutions:

• Local oscillator distribution electronics replaced

• Main oscillator to be replaced market evaluation on going

• Prototype for active compensation of the ‘wrong’ quadrature (ASI servo a la LIGO) ready to be tested

• Linear alignment should help to reduce the ‘wrong’ quadrature

When oscillator phase noise is killed

limit will be (?) by electronic and shot noise change injection bench power x10

• Electronic noise constant

• Shot noise scales as

• Still factor 5 missing with respect to the design (1 kW on BS)

• Increase transmission of the mode-cleaner (now 50%)

• Increase PR reflectivity planned 0.920.95

P

33

Sensitivity: low frequency

May 23rd and 25th

• Coherence with auxiliary degrees of freedom control noises (PRC and MICH)

• Coherence with BS angular control signals

• The signals are coherence each others: need cross-coherence computation to identify the individual components

34

Sensitivity: low frequency

BS_zCorr

BS_txCorr

PR_zCorr

Individual contributions

20 Hz40 50

BS_zCorr

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June 01 (M4) & May 25

The coherence between B1_ACp and BS (tx, z), PR (z) correction is reduced

the 3 channels are coupled and BS_txCorr was the main source of the noise

Now, B1_ACp coherent with WI_txCorr

35

Sensitivity: decrease angular noises

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Low frequency: actions

• Local controls:

• They will be switched off when automatic alignment will work : wait to commission the automatic alignment

• Small improvements on going

• Actuators noise:

• Low noise coils driver (1/25) don’t limit the sensitivity

• on BS (1/4) same level that the arm mirrors

• Auxiliary degrees of freedom

• Roll-off optimization (now at 50 Hz)

• Analysis of the noise source and propagation

• Non diagonal driving matrix elements

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Reduce the control noises

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Reduce the control noises

• Alreay tested in LIGO

39

Reduce the control noises: simulation

• Siesta simulation

• Influence of the BS noise in the low frequency part of the spectrum

• Tentative of suppression through addiction of non-diagonal terms in the driving matrix

No reduction

Perfect TF

15% error in the TF

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3/ Jumps investigations: ideas and next actions

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Jumps – some ideas

• Optical defect:

• Clipping from IB mirrors

• Beam quality not enough

• Bad management of the secondary beams from BS at the injection level

• Clipping, stry light from BS

• …

• Coupling with global alignment (I.e. Anderson effect)

• Locking problem (I.e.bad setting of the demodulation phases)

• Electronic hidden problem

• Problem related with the ITF parameters (I.e. recycling cavity flat-flat)

Why sometimes (~ week) it works very well?

42

0/ What was done in the last month

• Stray light hunting widely done on the reflected beam

• Realignment of photodiodes:

• Establishment of a check procedure based on simple optical configuations (power recycling – north input cavity, north cavity)

• Monitoring of the photodiode position through CCD cameras (not on all the beams)

• Experiments to understand the relationships between jumps and mirror misalignments

• put low frequency lines on all the mirrors, at 8% (lock more robust)

43

Jumps vs mirrors alignment

Mirrors angle combination

“jumped” state

Standard state

May 20th data, 8 %

• If confirmed at the dark fringe can be an indication of an optics defects (clipping, stray light..)

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1/Injection realignment: may 26th

Injection realignment

ITF relocked by Vincenzo 50’

Some locks with jumps some locks without jumps Only work:

realignment quadrant mode-cleaner

Work on NI vertical damping

45

1/Injection re-alignment: history

• One of the local control laser of the injection system was almost dead (power 40% less than normal)

• This laser is one of the angular references of the bench (the “fine” mode)

• During the replacement the reference becomes a CCD camera (the so called “rough mode”)

• Differences between the rough mode and the fine mode can makes differences in the injection bench position

• Once the new laser is installed the beam is aligned with respect to the reference cavity, attached at the bench

• The mode-cleaner is re-locked, and the beam incoming in the interferometer is realigned through picomotors after the mode-cleaner

46

1/Injection re-alignment: actions

• Find some indications of how the injection bench has moved with respect to the original position (I.e.how much we should move the picomotors after the mode-cleaner to realign the beam at 3 km)

• Try to reconstruct the injection bench rotation (300 microrad in the interferomter plane)

• Move the injection bench in the inverse direction (today) and re-align the beam consequently

• Re-lock the interferometer

• If necessary, make a further scan

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1/Injection re-alignment: future

• 2 new features:

• BMS: beam monitoring system: a reference (on the ground) for the beam alignment

• The beam is aligned with respect to the mode-cleaner dihedron

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2/ Beam splitter stray light

The BS “front” view

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2/ Beam splitter stray light

Image sequence

ITF unlocked Step 7 (8%)

Dark fringeITF unlocked

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3/ Fringes on the north&west cavity reflected beams

North cavity well aligned

(PR, WI misaligned by 10 millirad, WE misaligned by 500 microrad)

• seen also on west cavity (same fringes)

- from the input beam ?

- from input mirrors AR ?

51Laser frequency

refl_3f_phaseref

rec_quad

rec_phase

transW_phase

4/ Change the locking scheme: the standard scheme

‘acquisition’ mode

• DARM controlled with transW_phase

• CARM with rec_phase

• MICH with rec_quad

• PRC with refl_3f_phase

52Laser frequency

refl_3f_phaseref

rec_quad

rec_phase

Asy_phase

‘detection’ mode

• DARM controlled with Asy_phase

• CARM with rec_phase

• MICH with rec_quad

• PRC with refl_3f_phase

4/ Change the locking scheme: the standard scheme

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refl_3f_quad

Ref_phase

Asy_phase

‘detection’ mode

• DARM controlled with Asy_phase

• CARM with rec_phase ref phase

• MICH with rec_quad refl_3f_quad

• PRC with refl_3f_phase

4/ Change the locking scheme: the new scheme

Laser frequency

refl_3f_phase

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4/ Change the locking scheme

• Idea :

• eliminate the suspect of spurious effect on the beam REC (B5)

• eliminate the suspect of some not understood coupling between locking signals

• Planning: 2 steps

1/ MICH: rec_quad ref_3f_quad Measurement and software this week

2/ CARM (laser freq.): rec_phase ref_phase Measurements next week

55Laser frequency

refl_3f_phaseref

rec_quad

rec_phase

Asy_phase

‘detection’ mode

• DARM controlled with Asy_phase

• CARM with rec_phase

• MICH with rec_quad

• PRC with refl_3f_phase refl_phase

5/ Change the locking scheme: eliminate the 3f photodiode

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5/ Change the locking scheme: eliminate the 3f photodiode

• Idea :

• Problems with the 3f photodiode (signals generation, electronics, demod phase tuningm,…)

• Move the control on a standard photodiode (ref_phase)

• Results:

• Already tried (jumps still present)

• To repeat : was done when B5 photodiode (rec beam) was misaligned

• Problems

• Offset in the ref beam (B2 beam)

• Planning

• Try again, with offset compensation – see what happens to the offset changing the CARM/frequency control error signal

57

6/ B2 offset

• Interferometer locked in detection mode

• PRC controlled with ref_3f_phase photodiode (B2_3f_phase)

40-50 mW offset present since the beginning (even in the periods with no jumps)

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6/ B2 offset: simulation

Offset constant versus misalignement up to 1 microrad

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6/ B2 offset vs beam shape: simulation

Suspended bench External bench

Standard inputfile

PRC ‚flat‘ surface withRC (vertical)=-10km

Reflected beam shapes computed with finesse

60Laser frequency

refl_3f_phaseref

rec_quad

rec_phase

transW_phase

‘acquisition’ mode

• DARM controlled with transW_phase

• CARM with rec_phase

• MICH with rec_quad

• PRC with refl_3f_phase

7/ Better decouple the locking matrix

Driving and sensing coupling

61

changes in B2_3f_phase

-150 (“good” phase)

-110

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7/ Better decouple the locking matrix

• Planning:

• Driving matrix already decoupled

• Experiment to decouple better the sensing matrix started

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8/ Close the automatic alignment

• Status:

• 7/10 loops closed

• Optical offsets found in the quadrant

• Reconstructed offsets can be also 10-15 microrad

Offset from working point

Loop engaged

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8/ Multiple-zeros in the error signals with misalignments

The PRC signal approaches a multiple zeros behavior by setting the demodulation phase tens of degree off the nominal value (41°)

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Jumps: actions summary

• Scan the injection system alignment

• Change locking scheme

• Continue work on linear alignment

• Understand better the BS centering

• simulation work with Finesse and Siesta

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4 / Plans for the next 6 months

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Planning – 6 months • June-July 2005

• Close linear alignment

• Investigate bistabilities

• July 29th- August 12th

• C6 run

• September-October

• Injection bench and power recycling mirror replacement

• Sub-systems upgrades

• November - December

• Injection bench commissioning

• Restart of the interferometer

• Noise hunting

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Benefits to replace IB and PR

• Benefits to change IB:

• mirrors clip the beam

• beam is astigmatic

• secondary beam BS not separated

•ISYS alignment is not stabe

- Jumps can be related with IB

- Even if jumps are not related with IB more clean status

- Present IB: power reduced situation can change with x10 power

• Benefits to change PR:

• Resonances ~ 100 Hz region removed, better control

• Lens removed: ITF alignment simpler

69

Activities during the injection bench stop

• Suspensions upgrades

• Modification of the accelerometer electronics

• Vertical inertial damping

• Replacement of the local control lasers

• Software upgrades

• Documentation effort

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Inertial damping upgrade/1

Motivation: Interferometer operation is critical with strong winds or earthquakes

• Seismic noise is re-injected via position control (LVDT)

• Crossover LVDT/accelerometers~ 70 mHz too high

• The reduction of the LVDT control bandwidth is prevented by the low frequency response of the accelerometers

71

Inertial damping upgrade/2

If IP legs are not parallel the top table tilts as it translates

Non-parallelism can be obtained in two ways

1/ Mechanical imperfections

2/ Twist by rotational offset (dominant)

Tilt induces a “fake” low frequency signal in the accelerometers the “cradle” effect

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Inertial damping upgrade/3

• Non parallelism eliminated by signal processing techniques

• Allows to reduce crossover 7050 mHz an reduce the reintroduction of seismic noise by a factor 3

• implemented on all the long suspensions

• To reduce further the crossover we need to amplify the accelerometer electronics to beat the ADC noise

• tested succesfully on a suspension: reduction of a factor 10 of the seismic noise with respect to standard crossover (70 mHz)

• Plan to extend the result to all the suspensions during the injection bench stop

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Injection bench commissioning/ restart of the interferometer

• Close injection bench local controls

• Re-Lock the input mode-cleaner

• Align the beam into the interferometer (x10 power)

• Re-measure locking paramters

• Re-lock the recycling interferometer

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Summary

• Problem of jumps not yet solved

• Many possibilities but not clear indications

• Sensitivity improvements in the short windows without jumps

• h~ 2e-21, factor 4 from dark (and shot) noise of B1 photodiode

• spectrum non stationnary – need automatic alignment

• Noise hunting preparation on going

• Plan to make a 2 weeks run during summer , if jumps problem is solved

• Injection bench change scheduled for early september (2 months stop)