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 Advanced LIGO Design and Simulation T ools

 Advanced LIGO Design and Simulation T ools. Lisa Barsotti (MIT). GWDAW 2010, Kyoto. Historical Context. 1 st generation. 1 st generation +. 2 nd generation . 2 nd generation +. 3 rd generation . Historical Context. 1 st generation. 1 st generation +. 2 nd generation .

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 Advanced LIGO Design and Simulation T ools

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  1.  Advanced LIGO Design and Simulation Tools Lisa Barsotti (MIT) GWDAW 2010, Kyoto

  2. Historical Context 1st generation 1st generation + 2nd generation 2nd generation + 3rd generation

  3. Historical Context 1st generation 1st generation + 2nd generation 2nd generation + 3rd generation 4th generation !!

  4. Outline • Design Process • Questions we asked ourselves • Some of the answers we found by means of simulations • Thoughts on simulation tools • Conclusions

  5. (Naive) Design Process • Parametric Instabilities • Gas Damping Noise Simulations can’t help you anymore….

  6. aLIGO Design • Fundamental Noises: • SEISMIC NOISE • THERMAL NOISE • SHOT NOISE • Arm cavities: 4 km • Max Power: 125W GWINC (Matlab)

  7. Can we control our IFO? • New opticalconfiguration: • Signal Recycling • Stable cavities • High Power • More (coupled) DOFs • Noise performance down to 10 Hz • New suspensions and actuators

  8. 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

  9. kpend kpend kopt 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

  10. Can we align our IFO? • Optickle model of angular DOFs (PICKLE) • Complete Matlabmodel of the aLIGO suspension + seismic isolation system performance

  11. Are the control noises compatible with the design sensitivity? OPTICKLE

  12. How do we deal with thermal effects? Stationary Interferometer Simulation • Mode matching stability vs input power: optimal Gouy phases • Compromise with alignment sensing ROCs (m): Rprm = -11.45 Rpr2 = -4.516 Rpr3 = 36.00 Rsrm = -5.250 Rsr2 = -6.455 Rsr3 = 36.00 vGouyPRC = 24.803 vGouySRC = 20.342 Beam Sizes (mm): PRM 2.3 PR2 6.1 PR3 54 SRM 1.9 SR2 8.23 SR3 54 Arain, Mueller

  13. Can we robustly lock our IFO? • Yes, but extra hardware is needed ALS (green beams) End2End (C++) Hierarchical Control of the Quadruple Suspension (SIMULINK) John, Bram (ANU) Work on Hierarchical Control on the Quad Prototype at MIT The 40m will experimentally study lock acquisition for aLIGO this year

  14. Do we know our main actuator? 5mm GAP between the Test Masses and the ESDs: Gas Damping Noise (Rai) COMSOL (John Miller) MONTECARLO (Matt Evans) Electro-Static Drive (ESD)

  15. 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

  16. 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! 

  17. 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!

  18. kpend kpend kopt Sidles-Sigg Instabilities c1 Physics Letters A 354 (2006) 167–172 HARD x2 x1 Torque induced by radiation pressure c2 c1 c2 x1 x2 SOFT • Modification of the pendulum resonance frequencies:

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