SIESTA for Virgo locking experience

1
SIESTA for Virgo locking experience

• L. Barsotti
• University of Pisa INFN Pisa
• on behalf of the
• Virgo Locking Group

Simulation Workshop
Cascina, March 16th 2004
2
Outlines

• Commissioning of the first 3km cavity
• Recombined mode
• Full Virgo
• Other activities in parallel

3
North Cavity Optical Scheme
PR, WI, WE mirrors misaligned
WE
WI
T8
NE
NI
6 W
BS
B7
T50 ppm
T12
PR
B5
B1p
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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

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North Cavity Control Scheme
Lock Acquisition

• Linearized error signal

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Optical Gain

• Measured

• Simulated

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Transfer Function Open Loop
Gain
simulated
measured
Phase
8
Lock Algorithm Efficiency
C1 run data Several lock events collected
locking and delocking the cavity
linearized error signal

• Lock almost always acquired at the first trial

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Lock Algorithm Efficiency
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Lock Algorithm Efficiency

• Sweep at 12 mm/s

Lock event
Lock failed
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Lock Algorithm Efficiency
not linearized error signal
C1 data
Simulation
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SIESTA link to real time control
SIESTA
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SIESTA link to real time control
VIRGO
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Recombined Optical Scheme
PR mirror misaligned
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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

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Reconbined 2 Steps Control Scheme
17

• Michelson and West cavity controlled with the
  symmetric (B2_quad) and the antysimmetric signal
  (B1p_quad)
• Sensing matrix

• Theorical optical matrix

• Optical matrix measured by Siesta

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Locking simulation North cavity
Locking
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Locking simulation Mich West
Powers
Lengths
Triggers
Corrections
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Recombined 3Steps Control Scheme

• switch from B1p to B1 after the lock acquisition

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Lock acquisition - simulation
Simple simulation real suspensions and
actuators
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Lock acquisition - simulation
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First lock acquisition
27th February
Locking event At 3.25 am
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Sensitivity - simulation
Improvement real photodiodes (electronic noise,
shot noise)
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Sensitivity
Simulated
Measured
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Switch to the linear locking state

• Optical matrix

• Inverse optical matrix

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Linear Locking Control Scheme
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Linear lock of the recombined
Simulation
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Full Virgo Optical Scheme
B8
WE
WI
NI
PR
NE
BS
B7
B5
B2
B1
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Lock acquisition of full Virgo

• Multistates approach (LIGO scheme)

• Dynamical inversion of the optical matrix

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Lock acquisition of full Virgo
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Something more

• Modal simulation
• Longitudinal local control optimization
• Spikes removal

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Modal simulation

• High order modes (n m 5 )
• compromise with the computational time
  1 sec _at_ 20 kHz ? 45 sec

• misalignment of 2 mrad in qy of the curve mirror

• Check with other codes in progress

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Something more

• Modal simulation
• Longitudinal local control optimization
• Spikes removal

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Optimization of the z damping loop I

• measured

zCorr
zMirror
mm

• Damping time 10 sec

t10 sec
Open loop transfer function
Unity gain _at_ 0.65 Hz
Hz
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Optimization of the z damping loop II

• simulated

zCorr
zMirror
V
m
t2 sec
Open loop transfer function
Critical damping _at_ 1.45 Hz
Hz
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Optimization of the z damping loop III

• measured after the optimization

Critical damping _at_ 1.45 Hz
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Something more

• Modal simulation
• Longitudinal local control optimization
• Spikes removal

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Spikes removal
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Spikes removal
Rearrange the algo Error signal ? derivative ?
window ? integrator? window
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Other activity Hierarchical control

• preliminary results

wwwcascina.virgo.infn.it/collmeetings/presentation
s/Mar2004/Fiori_11Mar04_MarioLockSim.ppt
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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