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Fumiko Kawazoe, Shuichi Sato, Volker Leonhardt, Osamu Miyakawa

Experimental Demonstration of a control scheme for a tuned RSE interferometer for next-generation gravitational-wave detectors. Fumiko Kawazoe, Shuichi Sato, Volker Leonhardt, Osamu Miyakawa. Tomoko Morioka, Atsushi Nishizawa, Seiji Kawamura, Akio Sugamoto.

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Fumiko Kawazoe, Shuichi Sato, Volker Leonhardt, Osamu Miyakawa

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  1. Experimental Demonstration of a control scheme for a tuned RSE interferometer for next-generation gravitational-wave detectors Fumiko Kawazoe, Shuichi Sato, Volker Leonhardt, Osamu Miyakawa Tomoko Morioka, Atsushi Nishizawa, Seiji Kawamura, Akio Sugamoto Ochanomizu University NAOJ/Caltech Tokyo University Kyoto University LSC meeting, Hannover,10/24/2007

  2. Motivation • Plans to use an RSE interferometer in some of the next-generation interferometers for better sensitivities. • Adv.LIGO…Detuned RSE • LCGT…Tuned RSE ( = zero detuning or broadband ) • Controlling DOFs is vital for a detector • Control scheme developed for LCGT • Can be a back-up design for Adv.LIGO(detuned) • Prototype experiment to verify the control scheme LSC meeting, Hannover,10/24/2007

  3. Controlling the RSE LSC meeting, Hannover,10/24/2007

  4. Ｌｙ ｌｙ Ｌｘ ｌｘ ｌｓｘ ｌｓｙ 5 degrees of freedoms • L+ = (Lx + Ly) / 2 • L- = (Lx - Ly) / 2 Ｌｙ • l+ = (lx + ly) / 2 • l- = (lx - ly) / 2 Fabry-Perot cavity • ls = (lsx + lsy) / 2 Ｌｘ laser BS PRM Fabry-Perot cavity SEM A very complicated control system due to the increased number of DOFs LSC meeting, Hannover,10/24/2007

  5. Control scheme concepts • Fabry-Perot cavities’ control signal---beat between the carrier and PM sidebands • Central part of the RSE--- beat between the AM and PM sidebands • Fabry-Perot control signal are bigger by the high finesse • Can separate FP control signal and the central control signal by not using the carrier for the central part LSC meeting, Hannover,10/24/2007

  6. The central part control strategy --- Michelson Asymmetry For AM sidebands: 2δl = nλ (n = 1,2,3…) For PM sidebands: 2δl = (2m+1)/2 λ (m= 0,1,2…) Due to the Michelson Asymmetry AM all reflect from the Michelson part PM all transmit though the Michelson part Cavity length design AM resonant inside PRCPM resonant inside PRC+SEC Contrasting behavior in the Michelson part  as little as possible signal coupling LSC meeting, Hannover,10/24/2007

  7. The sensing signal matrix Theoretical signal matrix (DC) With the prototype parameters Fabry-Perot signals are clear from other signals. L+ L- l+ l- ls 1 8.0 e-6 -2.6 e-2 6.2 e-4 1.3 e-2 -2.2e-8 1 1.4 e-8 1.3 e-2 2.0 e-8 -4.9 e-2 -1.1 e-4 1 -8.6 e-3 -5.3 e-1 -1.0 e-4 7.6 e-2 1.4 e-3 1 1.1 e-5 -1.5 e-1 -1.2 e-2 1.1 -2.2 e-2 1 BP DP BP(DD) DP(DD) PO(DD) Linearly independent matrix. These 6 are small LSC meeting, Hannover,10/24/2007

  8. Prototype RSE experiment Built inside NAOJ’s campus in 2005 RSE locked in 2007 ITMp ETMi mm lens 3rd chamber LSC meeting, Hannover,10/24/2007

  9. Optical layout, and Parameters FP Finesse：～100 （specialized for lock demonstration） 4.34m PM：17.25MHz AM：103.5MHz ∞ 6.0m Stable cavities 5.7m ~90mW LSC meeting, Hannover,10/24/2007

  10. Mainly Input table, plus some detection ports TRp PD LASER MZ PD PBS OSA L- PD EOM(AM) EOM(PM) l+ PD ¼ λ LSC meeting, Hannover,10/24/2007

  11. Detection ports ls PD DP monitor PBS ¼ λ l- PD Tri PD L- PD To OSA LSC meeting, Hannover,10/24/2007

  12. Copper Upper mass Damping magnets Eddy current damping system Suspension system Double suspension system Single loop Two loop 30cm Qpitch:3 Qyaw:7 LSC meeting, Hannover,10/24/2007

  13. Test mass Current in Actuator coils x4 Actuator magnets x4 Suspension systemDC alignment LSC meeting, Hannover,10/24/2007

  14. Lock of the tuned RSE: Lock state State2: l- & l+ locked State3: l-, l+, & ls locked State4:RSE locked State1: l- locked State0: Nothing is locked PM AM LASER BP DP LSC meeting, Hannover,10/24/2007

  15. Lock of the tuned RSEDC power at various detection ports l+ locked ls locked L+ & L- locked l- locked DP Power（AU） BP PRCgain FPi Power（AU） FPp 10sec Time(sec) 4 0 0&1 2 3 state 0: not controlled1: l- locked 2 : l-, l+ locked 3: l-, l+, ls (central part) locked 4:RSE locked (longest ~15min. disturbed by human activity) LSC meeting, Hannover,10/24/2007

  16. 2 3 Lock of the tuned RSE:Evaluation of lock PM AM Optical Spectrum Analyzed at PO, and DP PO DP AM PM 0&1 ( 1: l-2: l-, l+3: central part )

  17. Measured signal matrix（preliminary） L+ L- l+ l- ls BP 1 5.6 e-2 -5.0 e-2 3.5 e-2 1.1 e-2 4.5e-2 1 1.3 e-2 -8.3 e-2 9.7 e-3 -2.8 e-1 -7.1 e-2 1 -3.6 e-1 -1.5 e-1 4.6 e-2 -1.6 e-1 1.6 e-1 1 6.2 e-2 -6.5 e-1 3.3 e-1 9.2 e-1 -3.6 1 DP L+ L- l+ l- ls BP(DD) DP(DD) PO(DD) • Dem. phase set to maximize the desired signal • Source:3.3kHz Needs better lock quality for further discussion.. LSC meeting, Hannover,10/24/2007

  18. Results and future work Control of a tuned RSE interferometer was successfully demonstrated. • FP cavities with L+, and L-. • Central part with double mod-demod. Lock acquisition scheme for LCGT is verified with this control scheme. • Future work: • Further investigation of the signal matrix (further diagnolazation, possible application of the delocation scheme, shot noise sensitivity as a detector after the lock is acquired) • Measurement of the optical gain matrix with better lock quality.

  19. Delocation scheme LSC meeting, Hannover,10/24/2007

  20. Diagnolized signal matrix LSC meeting, Hannover,10/24/2007

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