1. 1 Virgo Commissioning progress and plans ILIAS, Jan 23 rd 2007 Matteo Barsuglia on behalf of the Commissioning Team

2. 2 Outline  Status at the last meeting, November 13 th  Commissioning progress during last 2 months  Future steps  Related talks:  Noise hunting issues in Virgo (Gabriele)  Use of a second modulation (Maddalena, Henrich)  Some considerations on Virgo design sensitivity (Matt)

3. 3 Thermal lensing: power decrease needed Laser power reduction (25%) Stored power reduction ~ 10% wrs WSR-1 20 min 100 sec Matching activity: 10% power increase

4. 4 WSR5 noise budget  Unknown noise in the 100 Hz region (suspect: diffused light)  Longitudinal control near the sensitivity – sometimes limiting

5. 5 Sensitivity to weather conditions Red curve: 2.7 Mpc -(wind+sea) Red curve = 2.7 Mpc-(wind+sea)

6. 6 Progress since last meeting  Calibration uncertainty fixed  Noise hunting  Diffused light investigations  Longitudinal control noise  Increase ITF robustness  Automatic alignment  Mirror suspension control  2 WSR’s performed  WSR-6 in December  WSR-7+ commissioning run in January

7. 7 Calibration fixed – end of November  Discrepancy of 40% between calibrations with north-end and west-end  Conservative value taken so far  Problem discovered in a DAC of one of the end test masses  New value gives “improvement” in sensitivity  1.4 above 100 Hz  Present uncertainty ~ 10%

8. 8 Diffused light investigations

9. 9 Detection port  Dump spurious beam on vacuum (half of December)  Simplify optical scheme of the external bench (beginning of January)

10. 10 B1b B5b Optics centering checks: - Realignment of M9 (on B1s) In vacuum beam dumps

11. 11 In vacuum beam dumps/2 No significant results from the mitigations in and out vacuum

12. 12 Big work on alignment  Increase the gain in the alignment filters, in order to:  Improve the quality of the data  Increase ITF robustness  deal with bad weather conditions  Gain increase already done, further increase planned  Re-design of the alignment control chain  Filters migration to the global control (not the DSP)  more flexible  Possibility to change between acquisition/detection filters  Possibility to inject noise on error points and measure open loop TF  Second modulation at 8 Hz, control the “common-end” mode

13. 13 New alignment filters ty (yaw) tx (pitch)

14. 14 Quality of the data: WSR5 vs WSR7 WSR5 (nov 10-13) WSR7 (Jan 12-15) Coalescing binaries analysis

15. 15 WSR’s program  1 (Sept 8 th -11 th ) ~ 90% duty cycle  2 (Sept 22 nd -25 th ), ~ 65% due to infrastructure failure, >90% after  3 (Oct 6 th -9 th ) - cancelled  4 (Oct 13 th -16 th ) – cancelled  5 (Nov 10th-13th), ~ 65%  6 (Dec 1 st -4 th ), ~ 80%  7 (Jan 12 th -15 th ), ~ 76% + commissioning run 2.5 days  Tests (noise injections, change of some parameters,…) in stable and homogeneous conditions  8 (Feb 9 th -12 th ) planned

16. 16 Earthquake during WSR7 From Hanford e-log

17. 17 Noise budget – WSR7  Unknown noise in the 100 Hz region (suspect: diffused light)  Power recycling control near the sensitivity – sometimes limiting

18. 18 Structures around 100 Hz

19. 19 Longitudinal control noise  Switch to B2  “Beta” technique  Change completely control scheme

20. 20 Locking scheme

21. 21 Switch to B2  PR is currently controlled with B2_3f (third harmonics)  B2 (first harmonics) gives better SNR, about 1 order of mag  Transition B2_3f  B2 works  B2 contains an offset  Not understood  Manually compensated  ITF controlled with B2 works for hours but still not convincing (instabilities), more test are needed

22. 22 Noise budget – B2

23. 23 Beta technique MICH and PRCL corrections sent to the end mirrors to subtract the noise reintroduced by these loops to the dark fringe

24. 24 Change the control strategy  beta technique is not sufficient to decrease enough the control noise  Fluctuations of the coupling  Second modulation (not resonant in the recycling cavity) already in preparation to control the angular common end mode  If transition to B2 does not work ina reliable way  Lock the SSFS with the second modulation  Move the power recycling control from B2_3f to B5 (pick-off)

25. 25 Plans before next meeting  Noise hunting  Diffused light investigations  Control noise  SSFS new board  Continue work on alignment  Increase filter gain  Second modulation – common end  Continue work on mirror suspension control  WSR8 (mid February) + 1-2 WSR’s to be decided

26. 26 Noise hunting: terminal benches  Diffused light mitigation end benches (next week)

27. 27 Noise hunting: detection port  Further diffused light mitigation suspended injection bench (half February)  Further diffused light mitigation external injection bench (February)  Acoustic mitigation detection laboratory (end of March)  New (larger) Brewster (April?)

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