1. Stefan Hild 1Ilias WG1 meeting, Sep 2005, Perugia Title GEO 600 Commissioning progress Max-Planck-Institut für Gravitationsphysik (Albert-Einstein-Institut) Stefan Hild Ilias WG1 meeting, Sep 2005

2. Stefan Hild 2Ilias WG1 meeting, Sep 2005, Perugia GEO 600 layout 1.5-2 kW 0.09

3. Stefan Hild 3Ilias WG1 meeting, Sep 2005, Perugia Tuning signal recycling to 300 Hz Better knowledge of IFO parameters:  more accurate prediction from simulations  downtuning to 200 Hz realized Fixed instability of MI auto- alignment by setting up a new telescope for DWS. We will stay at 330 Hz !

4. Stefan Hild 4Ilias WG1 meeting, Sep 2005, Perugia GEO 600 design sensitivity

5. Stefan Hild 5Ilias WG1 meeting, Sep 2005, Perugia Calibration and demod phase @ 300 Hz Using signal recycling  GW signal is split in P and Q quadrature P-response independant of demod phase Q-response only for larger than 20 to 30 deg demod phase compatible with current calibration (zero + complex pole) Decided to use 40 deg for time being. Drawback: ‚P‘ used for MI servo is not really only ‚P‘

6. Stefan Hild 6Ilias WG1 meeting, Sep 2005, Perugia High RF on HPD / Q-compensation Observations: Found huge RF level after MI diode (1 Volt) Large DC level in Q after mixing. Q-compensation: Injected RF directly into resonance circuit of the HPD to make Q DC level zero. Improved sensitivity above 700 Hz Q-comp OFF Q-comp ON

7. Stefan Hild 7Ilias WG1 meeting, Sep 2005, Perugia RF setup OLD setup New setup: Using a less noisy splitter(0/90°) Using a cable as phaseshifter NEW setup Old setup: Dominated by phase noise in the LO path (phaseshifter and splitter(0/90°) Due to this noise from Q was mixed into P quadrature. That is why Q- compensation worked.

8. Stefan Hild 8Ilias WG1 meeting, Sep 2005, Perugia Shot noise Green line is the shot noise level calculated from the DC current of the photodiode. We are within a factor sqrt(2) shot noise limited above 1kHz !

9. Stefan Hild 9Ilias WG1 meeting, Sep 2005, Perugia Future RF setup Proposed by Rana and others GOALS: Using only high quality hardware Guaranteeing high RF levels in all components

10. Stefan Hild 10Ilias WG1 meeting, Sep 2005, Perugia Noise projections 21 st of july

11. Stefan Hild 11Ilias WG1 meeting, Sep 2005, Perugia Noise in the SR-long loop Noise in the detection band is entirely limited by front-end- noise (shot noise from the detector). Limits sensitivity from 100 to 500 Hz PROBLEM Large locking range OLG of 10^6 at 0.1 Hz No feedback noise above100 Hz Requirements 1.Servo has a locking mode and a running mode 2.Lowering UGF to get less gain in detection band 3.Using lowpass filter with very steep roll off above UGF (implemeted using a dSPACE system) Solutions

12. Stefan Hild 12Ilias WG1 meeting, Sep 2005, Perugia Analog SR electronics Red = acq amp, green = acq pha Dark blue = run amp, brown = run phase Light blue = run2 amp, pink = run2 pha

13. Stefan Hild 13Ilias WG1 meeting, Sep 2005, Perugia Signal Recycling digital Phase @18 Hz = -147 deg

14. Stefan Hild 14Ilias WG1 meeting, Sep 2005, Perugia SR feedback: analog vs. digital

15. Stefan Hild 15Ilias WG1 meeting, Sep 2005, Perugia SR loop filter future design Filter not used at the moment. Can be implemented when more gain is needed around pendulum resonances Four complex integrators: 2.25 (2x),1.3, 0.56 Hz

16. Stefan Hild 16Ilias WG1 meeting, Sep 2005, Perugia Sensitivity improvement July to August High frequency improvements: reduction of RF phase noise Low frequency improvements: reduction of Signal recycling feedback noise

17. Stefan Hild 17Ilias WG1 meeting, Sep 2005, Perugia PR-bench Historically grown layout of PR-bench not optimal ! beam clipping too many transmissive optical components too many polarizing components acoustic coupling Goal: Shorten and simplify the HPD path

18. Stefan Hild 18Ilias WG1 meeting, Sep 2005, Perugia Sensitivity after PR bench work Removed resonance structures between 100 and 200 Hz.

19. Stefan Hild 19Ilias WG1 meeting, Sep 2005, Perugia Noise projections 21 st of july

20. Stefan Hild 20Ilias WG1 meeting, Sep 2005, Perugia Michelson length control < 0.1Hz

21. Stefan Hild 21Ilias WG1 meeting, Sep 2005, Perugia < 10 Hz < 0.1Hz Michelson length control Reaction Pendulum: 3 coil-magnet actuators at intermediate mass, range ~ 100µm

22. Stefan Hild 22Ilias WG1 meeting, Sep 2005, Perugia < 10 Hz > 10 Hz < 0.1Hz Michelson length control Reaction Pendulum: 3 coil-magnet actuators at intermediate mass, range ~ 100µm Electrostatic actuation on test mass bias 630V, range 0-900V= 3.5µm

23. Stefan Hild 23Ilias WG1 meeting, Sep 2005, Perugia Using ESD as actuator Force is proportional to square of applied voltage. high voltages are needed for bipolar acting a bias voltage needs to be applied Noise is introduced: loop electronics sqrt circuits intrinsic HV amplifier noise

24. Stefan Hild 24Ilias WG1 meeting, Sep 2005, Perugia Sqrt circuits in MI loop ESD: F  U^2 Sqrt circuits are necessary to give full linear force range for acquisition. Drawback: sqrt circuits are noisy 1µV/sqrt(Hz) (=100µV/sqrt(Hz) @ ESD)

25. Stefan Hild 25Ilias WG1 meeting, Sep 2005, Perugia ESD: F  U^2 Sqrt circuits are necessary to give full linear force range for acquisition. Drawback: sqrt circuits are noisy 1µV/sqrt(Hz) (=100µV/sqrt(Hz) @ ESD) Bypassing sqrt circuits after lock is acquired. Sqrt circuits in MI loop

26. Stefan Hild 26Ilias WG1 meeting, Sep 2005, Perugia Noise in MI loop HVA noise = 100nV/sqrt(Hz) (=10µV/sqrt(Hz) @ ESD) HV-amplifier noise can be reduced by decreasing bias voltage or active noise suppression. Suppressing noise introduced by loop electronics needs whitening

27. Stefan Hild 27Ilias WG1 meeting, Sep 2005, Perugia MI loop whitening / dewhitening dewhiten Whiten Whitening right after mixer: zero 3.5 Hz pole 35 Hz Dewhitening for both split passes Passive dewhit- ening done in HV path (0-1kV)

28. Stefan Hild 28Ilias WG1 meeting, Sep 2005, Perugia Sensitivity after fixing noise from MI loop

29. Stefan Hild 29Ilias WG1 meeting, Sep 2005, Perugia Michelson servo design

30. Stefan Hild 30Ilias WG1 meeting, Sep 2005, Perugia MI loop gain problem Strange observations: We are not able to increase the low frequency loop gain, even though it should work from loop model (oscillation around 8 Hz) OLG measurements show that there is nearly no gain around 8 to 10 Hz. We needed to turn down the MI crossover gain continiously for the last few months Findings: Influence of MI AA gain on maximum cross over frequency (AA-tilt ,  cross over possible.  phase margin of crossover, can  crossover frequency, but adding integrator still causes 8Hz oscillation  IM gain (  crossover frequency),  less noise in servo 4 to 8 Hz.  IM gain, still low gain around 8 to 10 Hz (low gain can‘t be caused by IM)

31. Stefan Hild 31Ilias WG1 meeting, Sep 2005, Perugia Injecting LF noise in MI loop Injected noise from 5 to 11 Hz Between 6 and 7 Hz the noise is not suppressed !

32. Stefan Hild 32Ilias WG1 meeting, Sep 2005, Perugia Measurement of open loop gain (PRMI) Resonance structure is clearly visible Very low gain around 9 Hz Design gain:  7 @ 15 Hz  20 @ 10 Hz  80 @ 6 Hz

33. Stefan Hild 33Ilias WG1 meeting, Sep 2005, Perugia Mi servo design detail

34. Stefan Hild 34Ilias WG1 meeting, Sep 2005, Perugia TF: Alignment to longitudinal Tilt couples a factor of 10 stronger than rot @ 10 Hz. (IM-FF tilt2long) Why are the two rot-TF so different?

35. Stefan Hild 35Ilias WG1 meeting, Sep 2005, Perugia How to go on with the MI loop gain problem Measure MI loop gain for various conditions to decouple crossover and AA-tilt. Implementing digital AA control to be more flexible (nearly done). Measure tilt2long for single suspensions, with the goal of setting up a FF system. Investigate possible advantages of using the ESDs for angular alignment.....

36. Stefan Hild 36Ilias WG1 meeting, Sep 2005, Perugia Segmented ESD for alignment

37. Stefan Hild 37Ilias WG1 meeting, Sep 2005, Perugia Sensitivity improvement of GEO

38. Stefan Hild 38Ilias WG1 meeting, Sep 2005, Perugia Latest noise projections

39. Stefan Hild 39Ilias WG1 meeting, Sep 2005, Perugia Current sensitivity vs. Design sensitivity

40. Stefan Hild 40Ilias WG1 meeting, Sep 2005, Perugia Discussion Michelson loop gain problem: What experience exists in VIRGO with angular to longitudinal and longitudinal to angular couplings ? Is somewhere gain lost ?... Digital filtering: What kind of filters are used within VIRGO for steep roll off?

41. Stefan Hild 41Ilias WG1 meeting, Sep 2005, Perugia E n d