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First light AO WFS Laboratory closed loop test E. PINNA, A. PUGLISI, A. TOZZI, S. ESPOSITO

First light AO WFS Laboratory closed loop test E. PINNA, A. PUGLISI, A. TOZZI, S. ESPOSITO. Contents. C-loop test set-up Interaction and reconstruction matrix Closing the loop Some preliminary loop performances Conclusion. Laboratory set-up. P yramyd W ave F ront S ensor. B asic

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First light AO WFS Laboratory closed loop test E. PINNA, A. PUGLISI, A. TOZZI, S. ESPOSITO

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  1. First light AO WFSLaboratoryclosed loop testE. PINNA, A. PUGLISI, A. TOZZI, S. ESPOSITO

  2. Contents • C-loop test set-up • Interaction and reconstruction matrix • Closing the loop • Some preliminary loop performances • Conclusion

  3. Laboratory set-up Pyramyd Wave Front Sensor Basic Computational Unit TTM Wave forms Optical coupling PIXEL DATA SYSTEM PUPIL 8mm diafragm in front of the OKO DM ACTUATORS COMMANDS To TTM CCD 39 PIXELS TIP TILT MIRROR Set-up window DM actuators monitor CLOSED LOOP SYSTEM TELECENTRIC LENS Focusing the f/15 beam SUPERVISOR PC WHITE LIGHT SOURCE 2micron fiber to OKO DM ETHERNET LINK To supervisor PC DM OKO 37 act

  4. Interaction matrix Sx(i) Sy(i) Acting act(i) S(i) Generated on the PWFS Computed and recorded on the BCU S(i) = [ Sx(i) , Sy(i) ] (dim= 2Nsubap) Nact Measurement of zonal INT MAT INT MAT = [ S(1) , S(2) , ... , S(Nact) ]

  5. Reconstruction matrix Nact Sd x Rec =C Vector of differential mirror commands Sd= Sm – S0 Differential S from a slopes reference S0 Zonal Reconstructor 2Nsubap Inverting the INT MAT with the SVD method:REC MAT

  6. Closing the loop BCU Sd slopes Start from an aberrration introduced by the DM itself, mainly a defocus. WFS CCD FRAMES Binning 1 30X30sub ap

  7. Closing the loop C-LOOP STARTS Starting aberration Factor 10 slopes rms reduction (in 6-7 steps) rms(Sd) (a.u.) Loop stability Closed loop (slopes mean ~ 10-3) Residual RMS due to photon noise Iteration number Interesting number! This, in principle, can give an information about the LBT AO system behavior for these modes Start from an aberrration introduced by the DM itself, mainly a defocus.

  8. Wavefront RMS 300 phot / subap 30 phot / subap 5000 phot / subap 1000 phot / subap 100 phot / subap WF RMS (nm) Residual WF Scaling like 1/ sqrt(N) Iteration number Signal to wavefront matrix: S2WF = REC x INFMAT • Knowing: • OKO37 • INFLUENCE MATRIX • (interferometer) • REC Sd x S2WF = residual WF

  9. Wf rms vs R-mag Mag equivalent estimation: Mirror surface = 48m2 Bandwidth = 0.3 mm topt = 0.5 (telescope+wfs) <Q.E.>=0.8 Bin1 = 707 Subap

  10. Conclusion • This preliminary closed loop tested: • PWFS HW • BCU slopes computer HW • BCU Real Time SW • AO supervisor SW • Loop closed @1kHz, 300Hz saving diagnostic • We obtain also a first estimation of PN propagation in closed loop. Ready to start the P45 closed loop TEST

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