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![Page 1: 1 Commissioning status and plans ILIAS - June 14 th 2005 Matteo Barsuglia 1/ what happened in the last month 2/ New sensitivity: a preliminary noise budged.](https://reader036.fdocuments.us/reader036/viewer/2022062714/56649d145503460f949e81c9/html5/thumbnails/1.jpg)
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
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1/ What happened in the last month
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C5 sensitivity (Dec 2004)
C4, recombined 7W input power
C5, Recycled 0.7 W input power
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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)
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5
Minirun M3 – may 19th
Proper minirun M3 Restoring C5 science mode
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Comparison with M2 – May 5th
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Jumps during M3
~5 jumps
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Sensitivity on May 20th
• Roll-off Michelson at 50 Hz (100 Hz during C5)
• LO board upgraded
• Local control upgraded
C5 sensitivity
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Michelson roll-off @ 50 Hz
1/ Elliptic roll-off at 50 Hz
unity gain frequency at 6-7 Hz
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May 19th-26th: a good week
‘ no jumps’
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May 23rd sensitivity
• Low noise coil drivers on arm mirrors (1/25)
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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
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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
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50’ lock on Thursday evening
No evident jumps
Power fluctuations maybe higher than normal
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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
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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
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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
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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?
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M4 – changes in B2_3f_phase
-150 (“good” phase)
-110
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M4 – new BS local controls
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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)
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Sensitivity evolution – low freq
C5
June 3rd
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2/ Sensitivity: a preliminary noise budget and the next actions
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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)
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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
29
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
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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
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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
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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?
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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)
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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
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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
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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 ?
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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
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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
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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
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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
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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
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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
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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
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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)