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Virgo Commissioning Status WG1 meeting Potsdam, 21st July 2006 1 Full ITF re-lock Mid of March: 7 Watts entering the ITF Recycling Cavity Power (1 day) Recycling gain = 25 (instead of 45) Locks not longer than a few minutes Recycling gain lower than expected 2 Other problems observed Clipping of the beam discovered at the level of the output telscope Suspended detection bench 3 Other problems observed Clipping of the beam discovered at the level of the output telscope Matching of the beam with the cavities only 88% Reflected beam shape very bad ITF locked 4 Tring to fix problems Centering of the beam on the mirrors Improvement of the matching Matching improved (88%96%) Clipping disappeared 5 Interferometer powers 1 month Recycling gain from 25 to 40 280 W on the BS 10 times more power than C7 (25 W) 6 Re-lock of the ITF End of May Lock still not stable Oscillations around 30-50 Hz Present “everywhere” Not clearly connected with any longitudinal loop oscillation Quite often they caused the unlock of the ITF 7 Locks long enough to see thermal effects see Julien’s talk Sideband power 8 Locks long enough to see thermal effects dramatic change of the locking parameters in the firts minutes of lock acquisition quite challenging to keep the ITF locked 9 Coupling with alignment fluctuations 0.4 mrad 10 Coupling with alignment fluctuations locking parameters very sensitive to alignment fluctuations (Locking/Alignment shifts) small window in which the locking parameters make the ITF more stable 11 Useful tools On-line monitor: ugf of the longitudinal loops P\Q of the error signals Automatic gain adjustment (Differential ARM loop) 12 Useful tools Scanning Fabry-Perot on the dark fringe beam Sidebands always unbalanced, instabilities clearly correlated with one sideband vanishing 13 Improvements Easier to identify possible sources of instabilities Help in tuning locking parameters 14 Results 1- Lock acquisition reliable W 15 Once the lock was stable enough.. … it was possible to close the automatic alignment: further improvement of the locking stability ITF conditions more repeatable * new alignment procedure tested and implemented relaxed constraints on the locking parameters 16 Results 2- Typical locking periods of hours Automatic alignment ON: 10 loops closed 17 Results 3- Start of low noise operations as in C7 Dark fringe controlled with B1 (OMC on resonance) Re-allocation to the marionette + low noise coil drivers More aggressive filters in the longitudinal loops 18 Presented by Romain at the last collaboration meeting Noise Budget Sensitivity BS length control noise PR length control noise (direct coupling) Arm mirror actuator noise BS actuator noise B1 shot noise Sensitivity B1 electronic noise Oscillator phase noise B5_ACp (freq. servo error signal) Laser frequency noise ? Yes! 19 19 PRCL sensing noise reduction Increasing of the light impinging the photodiode (just done) Current sensitivity B2_3f readout noise (4 mW) B2_3f readout noise with 100 mW Expectations, no direct measurement yet Further noise reduction by switching on B2 20 Noise Reduction: near future Length control noise: Improvement of MICH-PRCL longitudinal loop decoupling Optimization of the automatic alignment loops (see Maddalena’s talk) Frequency noise reduction 21 Noise Reduction: already planned actions Vibration isolation of external detection bench DONE Actuators noise: plans for new coil drivers Acoustic noise: plans ready for installation of acoustic enclosure in the laser Diffused light mitigation: optimization of the benches optical set-up started, need few iterations 22 Conclusions It seems that we can survive to the thermal effects, but studies are in progress Short term plans: complete automatic alignment, increase locking robustness (difficult to recover a stable lock after changes in the system, see last week) Noise hunting just started 23 Matching and beam centering Parabolic telescope Beam centering (clipping removal) and matching imply to act on injection bench telescopes Spherical telescope Iterative procedure: Beam-mirror centering Astigmatism removal 24 Centering techniques methods: Image analysis using camera local control (only for beam splitter) Angle to length coupling 25 What has been intentionally changed? 26 Scan of the B2_3f demdoulation phase (automatic alignment closed, thermal drift over) 27 Laser frequency noise ? Dark fringe signal coherent with B5_ACp between 240 Hz and 6 kHz B5_ACp = error signal of the laser frequency stabilization loop (SSFS) Also coherent with the angular error signals of IMC automatic alignment B5_ACp superimposed on Dark Fringe Signal using the 444 and 1111 Hz lines See logbook entry 12603 by M. Evans Sensitivity B5_ACp Conclusion : B1_ACp and B5_ACp see the same noise (presumably laser frequency noise) 28 Global view for 2006 Main task Duration (weeks) In parallel/remarks Completion of recycled interferometer commissioning 8 High frequency noise hunting robustness increase locking loops Noise hunting: already planned 6 operations (actuators noise reduction, acoustic enclosure, feet detection lab) High frequency noise huntung Noise hunting: control noises “first reduction” (angular and longitudinal) 6 High and intermediated frequency noise hunting Noise hunting: scattered light reduction 4 High and intermediated frequency noise hunting Total: 6 months (end of 2006) Start data taking during long week-end as soon as the interferometer is stable and sensitivity better than C7 (september?) Priority to the high-intermediate frequency range Goal: factor 10 in the inspiral range 29 Plans for 2007 Science data taking Shutdown with upgrades to be defined: Eddy current removal Thermal compensation implementation Acoustic mitigation 2nd generation? Optical table re-shuffling and diffused light mitigation 2nd generation ? Mode-cleaner mirror replacement ? Re-commissioning Noise hunting 2nd phase 30