1 Commissioning status and plans ILIAS - June 14 th 2005 Matteo Barsuglia 1/ what happened in the last month 2/ New sensitivity: a preliminary noise budged and next steps 3/ Jumps investigations 4/ Plans for the next 6 months

2 1/ What happened in the last month

3 C5 sensitivity (Dec 2004) C4, recombined 7W input power C5, Recycled 0.7 W input power

4 Laser frequency refl_3f_phase ref rec_quad rec_phase Asy_phase ‘detection’ mode DARM controlled with Asy_phase CARM with rec_phase MICH with rec_quad PRC with refl_3f_phase May 17 th : realignment of B5 (rec beam photodiode) B5 photodiode (rec beam)

5 Minirun M3 – may 19 th Proper minirun M3 Restoring C5 science mode

6 Comparison with M2 – May 5 th

7 Jumps during M3 ~5 jumps

8 Sensitivity on May 20 th Roll-off Michelson at 50 Hz (100 Hz during C5) LO board upgraded Local control upgraded C5 sensitivity

9 Michelson 50 Hz 1/ Elliptic roll-off at 50 Hz unity gain frequency at 6-7 Hz

10 May 19 th -26 th : a good week ‘ no jumps’

11 May 23 rd sensitivity Low noise coil drivers on arm mirrors (1/25)

12 Marionetta and tidal control f < 10 mHz 10 mHz < f < 10 Hz f > 10 Hz Recycled ITF internal power Force on marionetta Force on mirror Marionetta and tidal control tested with recycled interferometer Residual correction seems to be compatible with Virgo specifications

13 May 27 th, Jumps again Injection realignment ITF relocked 50’ Some locks with jumps some locks without jumps realignment quadrant mode- cleaner Work on NI vertical damping

14 50’ lock on Thursday evening No evident jumps Power fluctuations maybe higher than normal

15 May 27 th, Jumps again Injection realignment ITF relocked 50’ Some locks with jumps some locks without jumps Only work: realignment quadrant mode- cleaner Work on NI vertical damping

16 Friday May 27 th, the bad Zoom on a jump bench of the first plot

17 Friday 27 th, the good

18 Friday 27 th, the good New sensitivity curve (with BS coils drivers x4 resistors) – obtained during one of the “good” locks Zoom on the Hz region with resistors x4  BS and arm mirrors should contribute at the same level

19 Sensitivity evolution May 27 th

20 Last week

21 photodiode centering checks May 30 th - June 1 st Photodiodes B1p, B5, B5_2f, B2_3f PR-NI configuration other mirrors misaligned by 10 mRad maximize AC or DC signal Photodiodes B8 North cavity configuaration other mirrors misaligned by 10 mRad maximize DC signal All photodiodes were found centered

22 June 1 st : demod phases checks Demod phases (with respect to May 17 th ) B2_3f –170  -150 (maximizing P/Q for a line on PR using the CITF) B5_2f –43  -23 (maximizing sideband crossing, using the CITF) B5 –34  -28 (minimizing frequency noise on Acq, using north cavity only) B8 OK (minimizing frequency noise on Acq, using north cavity) - Are the tuning criterions right ? - Why these phases changes?

23 M4 – changes in B2_3f_phase -150 (“good” phase) -110

24 M4 – new BS local controls

25 Improvements in low frequency sensitivity – june 3 rd - Black = may 27th (+ x4 resistors on BS) - red = June 3 rd (+ new controls on BS and gain decreased by factor 2 on WI and NI)

26 Sensitivity evolution – low freq C5 June 3rd

27 2/ Sensitivity: a preliminary noise budget and the next actions

28 C5 May 2005 sensitivity curve electronic noise (shutter closed) shot noise Virgo nominal sensitivity x 40 x 4 Phase noise Sensitivity – high frequency (Input power = 0.7 W)

29 Volts/sqrt(Hz) ACp noise (>5000 Hz) ACq signal (0-100Hz)  = 0.39  rad/  Hz Volts During C5:  = 0.48 rad/Hz Now:  = 0.39 rad/Hz No big improvement on  But a big reduction of B1_ACq!  Improvement of local controls? C5 May 27, M3 data Phase noise measurements

30 Power fluctuations Contrast 1 mW / 20 W ~ 5e-5 Internal power (rescaled)Dark fringe power (W)

31 What is the bump? Volts/sqrt(Hz) ACp noise ( Hz) ACq signal (0-100Hz) => The amplitude of the bump does not vary with B1_ACq like phase noise Volts ? 31

32 High frequency: actions Oscillator phase noise Several parallel solutions: Local oscillator distribution electronics replaced Main oscillator to be replaced market evaluation on going Prototype for active compensation of the ‘wrong’ quadrature (ASI servo a la LIGO) ready to be tested Linear alignment should help to reduce the ‘wrong’ quadrature When oscillator phase noise is killed  limit will be (?) by electronic and shot noise  change injection bench  power x10 Electronic noise constant Shot noise scales as Still factor 5 missing with respect to the design (1 kW on BS) Increase transmission of the mode-cleaner (now 50%) Increase PR reflectivity planned 0.92  0.95

33 Sensitivity: low frequency May 23rd and 25th Coherence with auxiliary degrees of freedom control noises (PRC and MICH) Coherence with BS angular control signals The signals are coherence each others: need cross-coherence computation to identify the individual components

34 Sensitivity: low frequency BS_zCorr BS_txCorr PR_zCorr Individual contributions 20 Hz 4050 BS_zCorr

35 June 01 (M4) & May 25 The coherence between B1_ACp and BS (tx, z), PR (z) correction is reduced  the 3 channels are coupled and BS_txCorr was the main source of the noise Now, B1_ACp coherent with WI_txCorr 35 Sensitivity: decrease angular noises

36 Low frequency: actions Local controls: They will be switched off when automatic alignment will work : wait to commission the automatic alignment Small improvements on going Actuators noise: Low noise coils driver (1/25) don’t limit the sensitivity on BS (1/4)  same level that the arm mirrors Auxiliary degrees of freedom Roll-off optimization (now at 50 Hz) Analysis of the noise source and propagation Non diagonal driving matrix elements

37 Reduce the control noises

38 Reduce the control noises Alreay tested in LIGO

39 Reduce the control noises: simulation Siesta simulation Influence of the BS noise in the low frequency part of the spectrum Tentative of suppression through addiction of non- diagonal terms in the driving matrix No reduction Perfect TF 15% error in the TF

40 3/ Jumps investigations: ideas and next actions

41 Jumps – some ideas Optical defect: Clipping from IB mirrors Beam quality not enough Bad management of the secondary beams from BS at the injection level Clipping, stry light from BS … Coupling with global alignment (I.e. Anderson effect) Locking problem (I.e.bad setting of the demodulation phases) Electronic hidden problem Problem related with the ITF parameters (I.e. recycling cavity flat-flat) Why sometimes (~ week) it works very well?

42 0/ What was done in the last month Stray light hunting widely done on the reflected beam Realignment of photodiodes: Establishment of a check procedure based on simple optical configuations (power recycling – north input cavity, north cavity) Monitoring of the photodiode position through CCD cameras (not on all the beams) Experiments to understand the relationships between jumps and mirror misalignments put low frequency lines on all the mirrors, at 8% (lock more robust)

43 Jumps vs mirrors alignment Mirrors angle combination “jumped” state Standard state May 20th data, 8 % If confirmed at the dark fringe can be an indication of an optics defects (clipping, stray light..)

44 1/Injection realignment: may 26 th Injection realignment ITF relocked by Vincenzo 50’ Some locks with jumps some locks without jumps Only work: realignment quadrant mode- cleaner Work on NI vertical damping

45 1/Injection re-alignment: history One of the local control laser of the injection system was almost dead (power 40% less than normal) This laser is one of the angular references of the bench (the “fine” mode) During the replacement the reference becomes a CCD camera (the so called “rough mode”) Differences between the rough mode and the fine mode can makes differences in the injection bench position Once the new laser is installed the beam is aligned with respect to the reference cavity, attached at the bench The mode-cleaner is re-locked, and the beam incoming in the interferometer is realigned through picomotors after the mode-cleaner

46 1/Injection re-alignment: actions Find some indications of how the injection bench has moved with respect to the original position (I.e.how much we should move the picomotors after the mode- cleaner to realign the beam at 3 km) Try to reconstruct the injection bench rotation (300 microrad in the interferomter plane) Move the injection bench in the inverse direction (today) and re-align the beam consequently Re-lock the interferometer If necessary, make a further scan

47 1/Injection re-alignment: future 2 new features: BMS: beam monitoring system: a reference (on the ground) for the beam alignment The beam is aligned with respect to the mode-cleaner dihedron

48 2/ Beam splitter stray light

49 2/ Beam splitter stray light

50 3/ Fringes on the north&west cavity reflected beams North cavity well aligned (PR, WI misaligned by 10 millirad, WE misaligned by 500 microrad) seen also on west cavity (same fringes) - from the input beam ? - from input mirrors AR ?

51 Laser frequency refl_3f_phase ref rec_quad rec_phase transW_phase 4/ Change the locking scheme: the standard scheme ‘acquisition’ mode DARM controlled with transW_phase CARM with rec_phase MICH with rec_quad PRC with refl_3f_phase

52 Laser frequency refl_3f_phase ref rec_quad rec_phase Asy_phase ‘detection’ mode DARM controlled with Asy_phase CARM with rec_phase MICH with rec_quad PRC with refl_3f_phase 4/ Change the locking scheme: the standard scheme

53 refl_3f_quad Ref_phase Asy_phase ‘detection’ mode DARM controlled with Asy_phase CARM with rec_phase  ref phase MICH with rec_quad  refl_3f_quad PRC with refl_3f_phase 4/ Change the locking scheme: the new scheme Laser frequency refl_3f_phase

54 4/ Change the locking scheme Idea : eliminate the suspect of spurious effect on the beam REC (B5) eliminate the suspect of some not understood coupling between locking signals Planning: 2 steps 1/ MICH: rec_quad  ref_3f_quad Measurement and software this week 2/ CARM (laser freq.): rec_phase  ref_phase Measurements next week

55 Laser frequency refl_3f_phase ref rec_quad rec_phase Asy_phase ‘detection’ mode DARM controlled with Asy_phase CARM with rec_phase MICH with rec_quad PRC with refl_3f_phase  refl_phase 5/ Change the locking scheme: eliminate the 3f photodiode

56 5/ Change the locking scheme: eliminate the 3f photodiode Idea : Problems with the 3f photodiode (signals generation, electronics, demod phase tuningm,…) Move the control on a standard photodiode (ref_phase) Results: Already tried (jumps still present) To repeat : was done when B5 photodiode (rec beam) was misaligned Problems Offset in the ref beam (B2 beam) Planning Try again, with offset compensation – see what happens to the offset changing the CARM/frequency control error signal

57 6/ B2 offset Interferometer locked in detection mode PRC controlled with ref_3f_phase photodiode (B2_3f_phase) mW offset present since the beginning (even in the periods with no jumps)

58 6/ B2 offset: simulation Offset constant versus misalignement up to 1 microrad

59 6/ B2 offset vs beam shape: simulation Suspended bench External bench Standard input file PRC ‚flat‘ surface with RC (vertical)=-10km Reflected beam shapes computed with finesse

60 Laser frequency refl_3f_phase ref rec_quad rec_phase transW_phase ‘acquisition’ mode DARM controlled with transW_phase CARM with rec_phase MICH with rec_quad PRC with refl_3f_phase 7/ Better decouple the locking matrix Driving and sensing coupling

61 changes in B2_3f_phase -150 (“good” phase) -110

62 7/ Better decouple the locking matrix Planning: Driving matrix already decoupled Experiment to decouple better the sensing matrix started

63 8/ Close the automatic alignment Status: 7/10 loops closed Optical offsets found in the quadrant Reconstructed offsets can be also microrad Offset from working point Loop engaged

64 8/ Multiple-zeros in the error signals with misalignments The PRC signal approaches a multiple zeros behavior by setting the demodulation phase tens of degree off the nominal value (41°)

65 Jumps: actions summary Scan the injection system alignment Change locking scheme Continue work on linear alignment Understand better the BS centering simulation work with Finesse and Siesta

66 4 / Plans for the next 6 months

67 Planning – 6 months June-July 2005 Close linear alignment Investigate bistabilities July 29 th - August 12 th C6 run September-October Injection bench and power recycling mirror replacement Sub-systems upgrades November - December Injection bench commissioning Restart of the interferometer Noise hunting

68 Benefits to replace IB and PR Benefits to change IB: mirrors clip the beam beam is astigmatic secondary beam BS not separated ISYS alignment is not stabe - Jumps can be related with IB - Even if jumps are not related with IB  more clean status - Present IB: power reduced  situation can change with x10 power Benefits to change PR: Resonances ~ 100 Hz region removed, better control Lens removed: ITF alignment simpler

69 Activities during the injection bench stop Suspensions upgrades Modification of the accelerometer electronics Vertical inertial damping Replacement of the local control lasers Software upgrades Documentation effort

70 Inertial damping upgrade/1 Motivation: Interferometer operation is critical with strong winds or earthquakes Seismic noise is re-injected via position control (LVDT) Crossover LVDT/accelerometers~ 70 mHz  too high The reduction of the LVDT control bandwidth is prevented by the low frequency response of the accelerometers

71 Inertial damping upgrade/2 If IP legs are not parallel the top table tilts as it translates Non-parallelism can be obtained in two ways 1/ Mechanical imperfections 2/ Twist by rotational offset (dominant)  Tilt induces a “fake” low frequency signal in the accelerometers the “cradle” effect

72 Inertial damping upgrade/3 Non parallelism eliminated by signal processing techniques Allows to reduce crossover 70  50 mHz an reduce the reintroduction of seismic noise by a factor 3 implemented on all the long suspensions To reduce further the crossover we need to amplify the accelerometer electronics to beat the ADC noise tested succesfully on a suspension: reduction of a factor 10 of the seismic noise with respect to standard crossover (70 mHz) Plan to extend the result to all the suspensions during the injection bench stop

73 Injection bench commissioning/ restart of the interferometer Close injection bench local controls Re-Lock the input mode-cleaner Align the beam into the interferometer (x10 power) Re-measure locking paramters Re-lock the recycling interferometer

74 Summary Problem of jumps not yet solved Many possibilities but not clear indications Sensitivity improvements in the short windows without jumps h~ 2e-21, factor 4 from dark (and shot) noise of B1 photodiode spectrum non stationnary – need automatic alignment Noise hunting preparation on going Plan to make a 2 weeks run during summer, if jumps problem is solved Injection bench change scheduled for early september (2 months stop)