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VIRGO commissioning progress

VIRGO commissioning progress. Paolo La Penna for the VIRGO collaboration European Gravitational Observatory. Virgo shutdown had started after C7 (19 September 2005) The new IB had been installed in the IB tower (end November 2005 The fake dihedron was still mounted on the bench

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VIRGO commissioning progress

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  1. VIRGO commissioning progress Paolo La Penna for the VIRGO collaboration European Gravitational Observatory

  2. Virgo shutdown had started after C7 (19 September 2005) The new IB had been installed in the IB tower (end November 2005 The fake dihedron was still mounted on the bench The Nd:YAG beam (up to 5 W for the moment) had been sent into the bench: some light (with even some interference) was visible at the end of the MC The optics on the bench were being realigned using the IB actuators: this operation was performed staying inside the tower, with the laminar flux on and the LC closed The alignment of the IMC was going on (http://www.ego-gw.it/ILIAS-GW/WP1docs/lapenna_121205.ppt) Status in December 2005

  3. The IMC was fully aligned in vacuum at about mid December. IMC locked at end of 2005. Beam at the end of the ITF at begin of January 2006. ITF alignment at mid of January. First ITF cavities lockings at end of January. Full RFC alignment at end of February. Full locking of the ITF going on now (mid of March). Since then: The full restart of the ITF, after IB installation, took about three months

  4. I – Injection system restart

  5. Alignment and locking of the IMC in vacuum Alignment of the IB optics in vacuum Alignment of the beam on the ITF and telescopes tuning Alignment and locking of the RFC Setup and alignment of the EIB BMS IMC matching improvement IMC automatic alignment Power stabilization RFC automatic alignment Operation performed on the Injection System

  6. Changes in Virgo after September shutdown PR mirror IB+RFC EIB

  7. Injection system Lower stage Upper stage

  8. Difference old-new IB Old IB New IB

  9. IMC alignment: december 2005 HeNe autocollimation on the MC mirror Acting on the IB alignment (checked with a ccd)

  10. IMC alignment: december 2005 laser YAG beam direct beam centering on the MC mirror acting on the external steering mirrors

  11. IMC alignment: december 2005 laser MC mirror alignment until IMC resonances are visible

  12. IMC locking: december 2005 laser Pout 8 W IMC locking Feedback on laser pzt using the reflection as a trigger

  13. ITF alignment: 13 january 2006

  14. The Reference Cavity alignment has taken more time than expected A first attempt to align it using the 20 W beam failed A second attempt after having aligned a probe beam coming from the opposite direction, and looking at the RFC transmission, led to a poor RFC alignment (but it allowed to lock and start working on the ITF) A third attempt overlapping the probe beam and the 20 W beam was successful From the beginning to the end almost one month was necessary RFC alignment and locking: february 2006

  15. YAG from inverse path: fringes • Probe beam from the inverse path • Probe beam superposed to a HeNe passing through the RFC in the lower part • Camera looking at the coils frame (hit by the RFC transmission): mode flashing visible Secondary YAG beam 1 V @ 25 Hz pzt scanning ccd • CCD and PhD looking at RFC reflection ccd photodiode

  16. Contrast improvement and alignment YAG probe Reflected beam Contrast = 0.7

  17. RFC alignment using PR alignment

  18. RFC alignment using PR alignment

  19. Near Field of M13 and Far Field 1m-f FF NF Screens

  20. M14 movement 1m-f FF Move M14 and observe overlapping with NF ccd NF

  21. M13 movement 1m-f FF Correct with M13 to overlap on the FF ccd Move M14 and observe overlapping with NF ccd NF

  22. After alignment: the 20 W beam resonates in the RFC ccd PhD

  23. The RFC transmission is not visible with the RFC aligned • Inverse path beam and direct beam are being superposed below acting on M13 and M4 mirrors • When superimposed both beams should resonate ccd PhD

  24. RFC locked, reflected 20 W YAG beam: 1 March 2006 Good alignment + longitudinal mismatching Contrast = 54 % (it was 80% before the shutdown)

  25. The RFC alignment was more difficult than expected: the cavity axis was not where it was expected, maybe the RFC was not aligned inside its tank, or it had moved slightly during new IB assembling The RFC is locked in a stable way, with the beam transmitted by the IMC: more stable with the alignment with respect to the previous setup We cannot see the RFC transmission RFC alignment: conclusion

  26. RFC locking filter change: a new filter has been implemented, which allows a reduction of the frequency noise of the prestabilized beam RFC automatic alignment: this activity is going on; it will allow to keep the beam aligned on the RFC using the two closed loop pzt placed before the RFC. This allows shifts of the beam on the upper part, in order to better align the upper part optics, without losing the RFC alignment Further activities on RFC

  27. Problems encountered Several problems/failure have occurred: it has been necessary to open the IB tower twice Wrong PSD electronics DPS misaligned TS damaged Beam clipped PM stuck RFC_trans clipped

  28. Beam Steering System IMC matching improvement IMC automatic alignment restarted Input power stabilization (the photodiode measuring the IMC transmission has been changed) RFC automatic alignment PSD on the IB working (new homemade electronics) Further activities involving the injection system After the restart of the IB, some new features and other activities have been performed:

  29. BMS: DC quadrants, ABP actuation • BMS allows to keep beam aligned with respect to DC_quadrants placed on the External Injection Bench. • The signal from the DC quadrants is sent to the ABP (Automatic Beam Positioning) mirrors (pzt steered mirrors). • It allows a stable and repetitive positioning of the beam entering into the IMC; • It allows performing pure translations and angle of the beam. ABPs NF QF FF QF (on laser bench)

  30. With the help of BMS, IMC matching has been improved: 96% matching (it was 82%), 91% contrast (should correspond to about 1500 ppm losses in the IMC). IMC transmission is now about 8 W (at about the same level as before the shutdown) This power is entering into the ITF (we had 0.7 W entering into the ITF before the shutdown) IMC matching

  31. The AA of the MC is working again as before the shutdown (for the moment acting only on the MC mirror, correcting the FF_vert and the NF_horiz degrees of freedom. The (new) AA of the IB is ready to be implemented: it should replace the LC of the IB IMC automatic alignment

  32. Power Stabilization IMC_trans HF Master laser Diode current Data from spectrum analyser is 50 times lower in the 100Hz region than dataDisplay measurent (above) (to be investigated)

  33. Closed on the vertical DOF (1 Hz bandwidth) Horizontal DOF not working (M16_PZT horiz. not working properly) RFC automatic alignment M15 RFC AA now separated from IMC AA M16 Wavefront sensing quadrants on the EIB

  34. New PR mirror: monolithic and higher R (0.95 vs 0.925) Comparison between the old (black) and new monolithic (red) PR mirror

  35. II- ITF restart

  36. IB LC after RFC locking The IB LC filters were changed after restart: frequency noise was reintroduced

  37. Frequency noise after RFC locking (ITF misaligned) IB transfer function Frequency noise

  38. IB LC filter upgrade IB in high noise control IB in low noise control Blue curves: MC in high/low noise (factor 100 G difference) Red curves: MC in high/low noise (factor 100 G difference)

  39. MC-RFC locking filter: after restart Too small G  SSFS couldn’t engage

  40. Frequency noise after RFC locking (ITF misaligned) Purple: C7 Black: after new IB RFC locking

  41. New MC-RFC locking filter upgrade

  42. New frequency noise: SSFS can engage

  43. Frequency noise: C7 (beam attenuated) vs now Now C7

  44. Photodiodes gains readjusted for the higher power (10 times more than before shutdown) Automatic alignment restarted: Tested the drift control of the two cavities Quadrant photodiodes gains adjusted Not gone further because it needs the full locking of the ITF PR-NI PR-NE CITF NE-WE-BS NA WA Recombined SSFS Variable Finesse with PR misaligned …. Now the full recycled ITF is being locked ITF restart: locking Since end of January:

  45. SSFS L1 L2 B2_3f_ACp B5_ACp SSFS using CARM for the Beam Frequency stabilization B1p_DC B8p B2_3f_ACp  PR (PRCL) B1p_DC  BS (MICH) B5_ACp  SSFS (CARM) B8_ACp NE-WE (DARM) l1 l2 l0

  46. The restart of SSFS required some gain tuning because: RFC locking filter was different Frequency noise was different RFC gains are different SSFS restart After tuning readjustment, IB LC filters and RFC locking filter SSFS is now working properly

  47. Towards the dark fringe B8p L1 L2 B2_3f_ACp B5_ACp SSFS using CARM STEP 7 B2_3f_ACp  PR (PRCL) B1p_DC  BS (MICH) B5_ACp  SSFS (CARM) B8_ACp NE-WE (DARM) l1 l2 l0 B1p_DC DF 0.05

  48. Status on 16th March: ITF locked up to step 7 (0.05 of the dark fringe) ITF locking Here we are

  49. Parabolic telescope T2: M6 mirror misalignment 3 closed loop picomotors Tilted: tx (650 mrad) and ty (850 mrad)

  50. Effect of M6 misalignment M6 aligned (beam at 3 km) M6 misaligned (beam at 3 km) (Qx=650 mrad Qy=850 mrad)

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