Advanced LIGO Design and Simulation T ools
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Transcript of Advanced LIGO Design and Simulation T ools
Advanced LIGO Design and Simulation Tools
Lisa Barsotti (MIT)
GWDAW 2010, Kyoto
Historical Context
1st generation
1st generation +
2nd generation
3rd generation
2nd generation +
Historical Context
1st generation
1st generation +
2nd generation
3rd generation
2nd generation +
4th generation !!
Outline
Design Process Questions we asked ourselves Some of the answers we found by means of simulations
Thoughts on simulation tools Conclusions
(Naive) Design Process
Simulations can’t help you anymore….
Parametric Instabilities
Gas Damping Noise
aLIGO Design Fundamental Noises:
SEISMIC NOISE THERMAL NOISE SHOT NOISE
GWINC (Matlab)
Arm cavities: 4 kmMax Power: 125W
Can we control our IFO?
New optical configuration: Signal Recycling Stable cavities
High Power More (coupled) DOFs Noise performance down to 10 Hz New suspensions and actuators
Can we control our IFO? Arm cavities: 4km Max Power: 125W Arm Finesse: 450 ITM T: 1.4%, PRM T:3%, SRM T=20% Schnupp asymmetry: 5cm Modulation Frequencies: 9 & 45 MHz Recycling cavities: 57m
Length sensing and control scheme (LSC): Modulation Frequencies
Error signals Control loops (Looptickle, now Lentickle)
OPTICKLE
Can we align our IFO?
High Power: radiation pressure effects
Stable cavities are good, but: alignment signals smaller more mirrors to control
Physics Letters A 354 (2006) 167–172
2
121 ),,,(ˆ
PLggkoptkpend kpendkopt
Can we align our IFO? Optickle model of angular DOFs (PICKLE) Complete Matlab model of the aLIGO suspension + seismic isolation
system performance
Are the control noises compatible with the design sensitivity?
OPTICKLE
How do we deal with thermal effects?Stationary Interferometer Simulation
Mode matching stability vs input power: optimal Gouy phases Compromise with alignment sensing
Arain, Mueller ROCs (m):Rprm = -11.45Rpr2 = -4.516Rpr3 = 36.00
Rsrm = -5.250Rsr2 = -6.455Rsr3 = 36.00
vGouyPRC = 24.803vGouySRC = 20.342
Beam Sizes (mm): PRM 2.3 PR2 6.1 PR3 54
SRM 1.9 SR2 8.23 SR3 54
Can we robustly lock our IFO?
Hierarchical Control of the Quadruple Suspension (SIMULINK)
John, Bram (ANU)
The 40m will experimentally study lock acquisition for aLIGO this year
Work on Hierarchical Control on the Quad Prototype at MIT
Yes, but extra hardware is needed ALS (green beams)
End2End (C++)
Do we know our main actuator?
(John Miller)
Electro-Static Drive (ESD)
5mm GAP between the Test Masses and the ESDs:Gas Damping Noise (Rai)
(Matt Evans)
COMSOL
MONTECARLO
Questions not answered (yet)
Locking signals vs static mirror misalignments (asked by Hartmut 2 years ago): FINESSE can do it…lazy simulator
Model for OMC alignment Full signal chain with electronic noise, ADC/
DAC, whitening filters, saturations, etc.. Add your own
Some Thoughts on Simulation Tools It can be hard to find answers, but it is also hard
to ask the right questions
Which questions are the right ones is not obvious
You might already know the answer. You might be able to write it on an envelope, but you might be wrong…that’s why good simulation tools are needed!
Conclusions
aLIGO design phase is ending..we are actually building it!
Massive use of simulation in the design process
Hard to find optimal solutions: trade offs Models will be useful to understand the as
built IFO as well….keep simulations handy!
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Sidles-Sigg InstabilitiesPhysics Letters A 354 (2006) 167–172
2
121 ),,,(ˆ
PLggkopt
Torque induced by radiation pressure
Ikk
f
Ikk
f
pendSoftSoft
pendHardHard
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21
Modification of the pendulum resonance frequencies:
x1
x1
x2
x2
2
21
1c2
c2c1
c1
kpend kpendkopt
HARD
SOFT