SIESTA for Virgo locking experience L. Barsotti University of Pisa – INFN Pisa on behalf of the Virgo Locking Group Cascina, March 16th 2004 Simulation Workshop

Outlines   Commissioning of the first 3–km cavity   Recombined mode   Full Virgo   Other activities in parallel

North Cavity Optical Scheme B1p T=8% T=50 ppmT=12% 6 W B5B5 B7B7 PR, WI, WE mirrors misaligned WE WI NENI BS PR

Commissioning of the North Cavity Feedback characterization: optical gain open loop transfer function Analysis of the lock algorithm efficiency linearized error signal no linearized error signal Comparison with real data (C1, C2 runs)   Real suspensions, real actuators, real photodiodes, computational delays included in the simulation

North Cavity Control Scheme B1p T=8% B7B7 NE NI BS PR Hz |Gain| frequency Lock Acquisition Linearized error signal:

Optical Gain:   Measured   Simulated

Transfer Function Open Loop simulated measured Gain Phase M G zErrzCorr noise

Lock Algorithm Efficiency   Lock almost always acquired at the first trial C1 run data : Several lock events collected locking and delocking the cavity linearized error signal

Lock Algorithm Efficiency Failed locking attempt v ~ 12.5  m/s 8  m/s: maximum velocity for the lock acquisition success   Constraints on the velocity according to the theory: Gain due to the linearization:  ~ 10

Lock Algorithm Efficiency With velocity lower than 10  m/s lock at the first attempt With velocity higher than 10  m/s lock at the second attempt Lock failed   Sweep at 12  m/s : Lock event

Lock Algorithm Efficiency Failed locking attempts not linearized error signal C1 data Simulation

SIESTA link to real time control SIESTA Control signals Photodiodes signals Algorithms running in the global control

SIESTA link to real time control Control signals Photodiodes signals Algorithms running in the global control VIRGO

Recombined Optical Scheme B1B1 T=8% B5B5 B7B7 B8B8 B2B2 WE NE NI WI BS PR PR mirror misaligned

Recombined mode 2 Steps locking strategy: sensing matrix procedure to find experimentally the algorithm parameters from simple optical systems 3 Steps locking strategy sensitivity curve comparison with real data Linear locking

Reconbined 2 Steps Control Scheme B1B1 B5B5 B7B7 B8B8 B2B2 north cavity controlled with B5 west cavity and michelson controlled at the sime time

  Theorical optical matrix:   Optical matrix measured by Siesta:   Michelson and West cavity controlled with the symmetric (B2_quad) and the antysimmetric signal (B1p_quad)   Sensing matrix

Locking simulation – North cavity Locking

Locking simulation – Mich & West PowersLengths Triggers Corrections

B7_demod B1p_demod B2B2 North arm West arm B5B5 B8_demod   switch from B1p to B1 after the lock acquisition Recombined 3Steps Control Scheme

Lock acquisition - simulation “Simple” simulation: real suspensions and actuators

Lock acquisition - simulation

First lock acquisition 27th February Locking event At 3.25 am

Sensitivity - simulation Improvement: real photodiodes (electronic noise, shot noise)

Sensitivity Simulated Measured

Switch to the linear locking state   Optical matrix: d2_quad d2_phase d1p_quad MICH CARM DARM   Inverse optical matrix:

⊗ B1p_quad B2_quad North arm West arm B2_phase Linear Locking Control Scheme

Linear lock of the recombined Simulation

Full Virgo Optical Scheme B1B1 B5B5 B7B7 B8B8 B2B2 WE NE NI WI BS PR

Multi–states approach (LIGO scheme) Dynamical inversion of the optical matrix Lock acquisition of full Virgo

Something more…  Modal simulation  Longitudinal local control optimization  Spikes removal

Modal simulation   High order modes (n + m ≤ 5 ) compromise with the computational time 1 20 kHz ⇒ 45 sec   Check with other codes in progress misalignment of 2  rad in  y of the curve mirror

Something more…  Modal simulation  Longitudinal local control optimization  Spikes removal

Optimization of the z damping loop – I   10 sec zCorr zMirror mm Hz Unity 0.65 Hz measured Open loop transfer function   Damping time  sec

Optimization of the z damping loop – II simulated Open loop transfer function Critical 1.45 Hz Hz m VV zCorrzMirror   2 sec

Optimization of the z damping loop – III measured after the optimization mm VV  ~ 2 sec zCorrzMirror Guadagno open loop Hz Critical 1.45 Hz

Something more…  Modal simulation  Longitudinal local control optimization  Spikes removal

Spikes removal

Rearrange the algo: Error signal  derivative  window  integrator  window

Hierarchical control Other activity: Hierarchical control marionetta reference mass mirror z Control from the reference mass Control from the marionetta Transfer function betweeen force on steering filter and z movement of the mirror preliminary results wwwcascina.virgo.infn.it/collmeetings/presentations/Mar2004/Fiori_11Mar04_MarioLockSim.ppt

Conclusions   Siesta: fundamental tool for locking studies   Link to the real time control system   Work in parallel with other groups to improve the simulation (suspensions, alignment)   Noise analysis