1. 1 Virgo Commissioning Status WG1 meeting Potsdam, 21 st July 2006

2. 2 Full ITF re-lock  Locks not longer than a few minutes  Mid of March: 7 Watts entering the ITF Recycling Cavity Power (1 day)  Recycling gain lower than expected Recycling gain = 25 (instead of 45)

3. 3 Other problems observed  Clipping of the beam discovered at the level of the output telscope Suspended detection bench

4. 4 Other problems observed  Reflected beam shape very bad  Matching of the beam with the cavities only 88%  Clipping of the beam discovered at the level of the output telscope ITF locked

5. 5 Tring to fix problems  Centering of the beam on the mirrors  Improvement of the matching  Clipping disappeared  Matching improved (88%  96%)

6. 6  Recycling gain from 25 to 40 1 month Interferometer powers  280 W on the BS  10 times more power than C7 (25 W)

7. 7 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

8. 8 Locks long enough to see thermal effects Sideband power see Julien’s talk

9. 9  dramatic change of the locking parameters in the firts minutes of lock acquisition  quite challenging to keep the ITF locked Locks long enough to see thermal effects

10. 10 Coupling with alignment fluctuations 0.4 rad

11. 11  locking parameters very sensitive to alignment fluctuations ( Locking/Alignment shifts )  small window in which the locking parameters make the ITF more stable Coupling with alignment fluctuations

12. 12 Useful tools  On-line monitor:  ugf of the longitudinal loops  P\Q of the error signals  Automatic gain adjustment (Differential ARM loop)

13. 13 Useful tools  Scanning Fabry-Perot on the dark fringe beam  Sidebands always unbalanced, instabilities clearly correlated with one sideband vanishing

14. 14  Easier to identify possible sources of instabilities  Help in tuning locking parameters Improvements

15. 15 Results 1- Lock acquisition reliable W

16. 16 Once the lock was stable enough..  further improvement of the locking stability  ITF conditions more repeatable * new alignment procedure tested and implemented  relaxed constraints on the locking parameters … it was possible to close the automatic alignment:

17. 17 Results 2- Typical locking periods of hours Automatic alignment ON: 10 loops closed

18. 18 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

19. 19 Sensitivity BS length control noise PR length control noise (direct coupling) Arm mirror actuator noise BS actuator noise B1 shot noise B1 electronic noise Oscillator phase noise Laser frequency noise ? 19 Presented by Romain at the last collaboration meeting Yes! Noise Budget Sensitivity B5_ACp (freq. servo error signal)

20. 20 PRCL sensing noise reduction Further noise reduction by switching on B2 Current sensitivity B2_3f readout noise (4 mW) B2_3f readout noise with 100 mW  Increasing of the light impinging the photodiode (just done) Expectations, no direct measurement yet

21. 21 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

22. 22 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

23. 23 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

24. 24 Matching and beam centering Spherical telescope Parabolic telescope Iterative procedure: Beam-mirror centering Astigmatism removal  Beam centering (clipping removal) and matching imply to act on injection bench telescopes

25. 25 Centering techniques methods:  Image analysis using camera local control (only for beam splitter)  Angle to length coupling

26. 26 What has been intentionally changed?

27. 27 Scan of the B2_3f demdoulation phase (automatic alignment closed, thermal drift over)

28. 28 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)

29. 29 Global view for 2006 Main taskDuration (weeks)In parallel/remarks Completion of recycled interferometer commissioning 8High frequency noise hunting robustness increase locking loops Noise hunting: already planned operations (actuators noise reduction, acoustic enclosure, feet detection lab) 6High frequency noise huntung Noise hunting: control noises “first reduction” (angular and longitudinal) 6High and intermediated frequency noise hunting Noise hunting: scattered light reduction 4High 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

30. 30 Plans for 2007  Science data taking  Shutdown with upgrades to be defined:  Eddy current removal  Thermal compensation implementation  Acoustic mitigation 2 nd generation?  Optical table re-shuffling and diffused light mitigation 2 nd generation ?  Mode-cleaner mirror replacement ?  Re-commissioning  Noise hunting 2 nd phase