1. 1 Virgo Commissioning progress ILIAS, Nov 13 th 2006 Matteo Barsuglia on behalf of the Commissioning Team

2. 2 Outline  July-August  Main problem: thermal lensing  Main activities:  Lock acquisition improvements & automatic alignment  Noise hunting: recover good sensitivity after the shutdown  Thermal lensing  Data takings: WSR-1 (Sept 8 th -11 th )  Upgrades (September-October)  Faraday isolation optimization  Acoustic isolation laser laboratory  Matching improvements  Actuators noise reduction  Detection Brewster replacement  Frequency noise  see Matt’s talk  WSR-5 (last week-end)  Future steps

3. 3 Thermal lensing 20 min Still the main concern (Lock acquisition long and more difficult / Noise couplings?)  Why?  Absorption in the input mirrors seems to be part of the problem (x4-x10 with respect to the design)  Also thermal lensing in the Faraday?  Dynamics of the fields inside the interferometer not understood  Simulation ongoing (Finesse, darkF, Matlab)  Diagnostics through optical spectrum analyzer  Phase camera in a few months  Thermal compensation in > 1 year

4. 4 Thermal lensing: last week results/1

5. 5 Thermal sensing: last week results/2 20 min 6.7 W input: old matching

6. 6 Thermal sensing: last week results/2 20 min 100 sec 6.7 W input 6.7 W input: old matching Matching activity Stored power increase ~ 10%

7. 7 Thermal sensing: last week results/2 20 min 100 sec 6.7 W input 5.4 W input 6.7 W input: old matching Matching activity Stored power increase ~ 10% Laser power reduction (19%)

8. 8 Thermal sensing: last week results/2 20 min 100 sec 6.7 W input 5.4 W input 5 W input 6.7 W input: old matching Matching activity Stored power increase ~ 10% Laser power reduction (19%) Laser power reduction (25%) Stored power reduction ~ 10%

9. 9 Automatic alignment  14 d.o.f. controlled  8 with high gain (~3 Hz), 6 with low gain (~10 mHz)  Power recycling automatic alignment critical during lock acquisition  8 wavefront signals, 6 DC signals (common end mirrors, NI, WI)  Future steps: better filtering, enlarge BW, find demodulated signal for common end

10. 10 WSR-1 sensitivity C7 WSR-1

11. 11 WSR-1 noise budget

12. 12 Faraday isolation optimization  Faraday isolation ~ 100, expected 10,000  Small key Allen found attached to the rotator  isolation 10,000 in air  In vacuum isolation ~ 1000  Remote adjustment planned  Some signals improved – no clear improvements in the sensitivity Power recycling alignment

13. 13 Brewster detection replacement Detection Brewster window  B1 sensitive to detection Brewster vibrations  Wrong Brewster – too small (80 mm instead 110 mm)  New window installed in October  New tests on going

14. 14 Acoustic enclosure laser lab to the vacuum chamber

15. 15 Acoustic enclosure laser lab  Actenuation 3-4 for both benches  Less than expected  try to find shortcuts  Problems with turbulent air flux  Temporary solved using apertures (final solution: silenced door)

16. 16 Clapping tests detection lab  Actions planned for detection bench and end benches

17. 17 Noise at high frequency  Oscillator phase noise OK  Shot noise  Almost at the measured value  Difference with design  Stored power 300 W (500W design)  T_OMC = 0.8 (1 design)  Calibration: ~ 40% uncertainty  Frequency noise  See Matt’s talk

18. 18 Control noises

19. 19 Power recycling noise  BW ~ 40 Hz, cut-off 200 Hz  Power recycling coupling changes by factor 10  Mechanism not understood Actions:  Understand the coupling mechanism  Switch to B2  Understand the noise of the error signal (B2_3f_ACp)

20. 20 B2_3f error signal / switch to B2  B2_3f limited by read-out noise from ~ 50-100 Hz  ~50 mW when ITF locked ~70 mW during lock acquisition - max power  B2_3f signals strongly depressed by the use of the 3 rd harmonics demodulation  B2 gives a better SNR (1 st harmonic demodulation)  Switch already tried but never worked for long time periods

21. 21 Actuators noise DAC DSP CoilDriver G EmphasisDeEmphasis

22. 22 Detection bench noise/2 C7  Transfer function zBench  ITF output  Several structures already present in the ITF output excited

23. 23 Detection bench noise C7 Actuators noise

24. 24 WSR-5 sensitivity C7

25. 25 Sensitivity to weather conditions Red curve: 2.7 Mpc -(wind+sea) Red curve = 2.7 Mpc-(wind+sea)

26. 26 Suspension improvements LVDT ACC + NINE WE WI BS PR 3f I f I,Q CARM MICH PRCL f I DARM Use 4 locking signals for the position control of 4 mirrors in the beam direction GOALS: 1.reduce use of noisy sensors 2.do not use ACC where tilt dominates with no reinjection of seismic noise

27. 27 Future steps  Noise hunting  B2 switch – power recycling control noise improvements  Detection bench actuators noise reduction  Diffused light mitigation  Detection bench  External injection bench  Mirror centering/coils balancing  Suspension control improvements  Global inverted pendulum suspension control  Vertical inertial damping  New SSFS (common mode servo) board  Acoustic isolation detection laboratory and end benches  Continue WSR program (data taking each ~3 weeks)  Long run (a few months) before end of S5