1 1.ISC scope and activities 2.Initial Virgo status 3.Design requirements 4.Reference solution and design status 5.Plans toward completion 6.Technical risks Outline AdV ISC subsystem François BONDU for ISC group

2 ISC scope and activities Bring the interferometer to its operating point and keep it here reliably Lock acquisition F. Cavalier (LAL-Orsay), G. Vajente (INFN Pisa – Pisa U) Steady state length control G. Vajente (INFN Pisa – Pisa U) Angular control M. Mantovani (EGO) Parametric instabilities P.-F. Cohadon (LKB - Paris) Scope details, task list, interactions with other systems: VIR-085A-08

3 ISC scope and activities Longitudinal control

4 Initial Virgo control

5 8MHz MICH 6MHz PRCL 6MHz DARM 6MHz CARM FREQ Initial Virgo length control

6 Feed-forward techniques: VIR-050A-08

7 Initial Virgo angular control reconstruction matrix

8 Initial Virgo angular control reconstruction matrix

9 Lock acquisition: Reliability of lock acquisition transients, bandwidth high speed mirrors when bad weather Actuation compatible with a low-noise “science mode” operation reduced sensitivity to magnetic noises Deterministic lock acquisition Design requirements (1/4) Ex. v mir = 1  m/s Initial virgo: T res / T sto = / >> 1 AdV: T res / T sto = / << 1

10 Steady state length control: No noise from auxiliary degrees of freedom Design with radiation pressure effects Additional signal recycling cavity Multiple inputs multiple outputs system observability robustness Design requirements (2/4)

11 Alignment: Alignment lock acquisition compatible with local controls performances No noise in gravitational wave channel from alignment signals Design with radiation pressure effects Multiple inputs multiple outputs system (18 d.o.f.s) observability; robustness Design requirements (3/4) LIGO P030055

12 Parametric instabilities: Should not affect interferometer performances Evaluation of PIs in AdV configuration Passive or active mitigations Design requirements (4/4)

13 Reference solution (1/4) Lock acquisition Arm cavity lock acquisition first, with auxiliary lasers CALVA experiment at LAL Sensing: laser with 3 modulations Driving: Variable finesse

14 Reference solution (1/4)Lock acquisition CALVA experiment EGO-PRE-STAC-102

15 Reference solution (2/4) Steady state length control Simulation of transfer function with radiation pressure: Optickle (LIGO) Increased complexity  (almost) diagonal sensing matrix laser with 3 modulations Driving: low noise operation Feed-forward techniques Suspension hierarchical control Robust operation of a multiple inputs multiple outputs system Without radiation pressure effects With radiation pressure effects VIR-068B-08

16 Reference solution (2/4)Steady state length control Carrier SB1 9.4 MHz SB MHz SB3 8.3 MHz VIR-068B-08 D.O.F.Single demod.Double demod. DARMAP_DC CARMSP_SB1_P PRCLSP_SB3_PSP_3+1_P MICHSP_SB2_PSP_2-1_Q SRECSP_SB1_PSP_2-1_Q displacement of towers

17 Reference solution (2/4)Steady state length control Schnupp asymmetry and Tower displacements: Virgo Schnupp asymmetry (80 cm) + low SB2 transmission to SREC (diagonalization)  Modulation frequency for SB1 ~ 170 MHz NOT compatible with high-power, high efficiency photodiode response (DET) Small Schnupp asymmetry  This reference solution  Tower displacement and infrastructure modifications VIR-049A-08

18 Double demodulationSingle demodulation Use of initial Virgo feed-forwad techniques VIR-050A-08 Reference solution (2/4)Steady state length control

19 Reference solution (2/4)Steady state length control R.M.S. (m) 10 Hz (m/√Hz) DARM CARM MICH PRCL SREC VIR-080A-08

20 Reference solution (3/4) Alignment Sensing: same modulation frequencies as for the length control Ward technique for arm cavity alignment completeness of sensing matrix (NDRC) pick-off beams reflected by arm cavities Robust operation of a multiple inputs multiple outputs system

21 Reference solution (4/4) Parametric instabilities Study: Parameters with AdV case Table-top experiment at LKB, active control? LIGO developments (passive / active control)

22 Plans towards completion (1/2) Documents ISC Design Requirement Document missing: lock acquisition: comparison of auxiliary laser / mirror decelerators ISC Preliminary Design Document actuation (force) excursion range / noise sensitivity stability & robustness of MIMOS for lengths and alignment specifications for pre-stabilized laser linewidth and arm cavity asymmetry alignment design: parameter tuning, negative torque mitigation Planning TBD

23 Plans towards completion (2/2) Decisions Alignment: give up Anderson-Giordano technique Steady state length control: single vs. double demodulation schemes Steady state length control: modulation frequencies and macroscopic lengths Lock acquisition: Combination of auxiliary laser / variable finesse technique

24 Risks Alignment: Manpower: 18 dofs, tuning of telescope Gouy phases and demodulation phases, noises negative torque mitigation Parametric instabilities: Mitigation TBD

25 ISC scope and activities PAY/DET DAQ VAC/IME INJ/LAS PAY OSD PAY DAQ Lock acquisition Arm locking with auxiliary laser Procedure for full interferometer locking with “variable finesse” (from dark to bright fringe) Steady state length control Linear locking design: modulation frequencies, macroscopic lengths, couplings, photodiode signals Feed-forward techniques Laser frequency stabilization Specifications on core mirror seismic isolation Angular control Ward technique (New for arm cavities) Parameter tuning for 18 degrees of freedom Noise specifications Modes with effective negative torque Parametric instabilities Case for AdV mirrors Active control?