Advanced LIGO optical configuration investigated in 40meter prototype

Transcription

1 Advanced LIGO optical configuration investigated in 4meter prototype LSC meeting at LLO Mar. 22, 25 O. Miyakawa, Caltech and the 4m collaboration LIGO- G5195--R LSC meeting at LLO, March 25 1

2 Caltech 4 meter prototype interferometer Objectives Develop lock acquisition procedure of detuned Resonant Sideband Extraction (RSE) interferometer, as close as possible to Advanced LIGO optical design Characterize noise mechanisms Verify optical spring and optical resonance effects Develop DC readout scheme Next Rob s talk Bright port PRM BS SRM Dark port Extrapolate to AdLIGO via simulation X arm etc. Y arm LIGO- G5195--R LSC meeting at LLO, March 25 2

3 Important Milestones 23 Installation of Four TMs and BS:done Lock of FP Michelson :done 24 Installation of Power Recycling Mirror (PRM),Signal Recycling Mirror (SRM) :done Installation Mach-Zehnder to eliminate sideband of sideband :done DRMI locked with carrier resonance using dither for Michelson DOF. :done DRMI locked with sideband resonance using Double Demodulation(DDM) :done Off-resonant lock of signal arm cavity with DRMI :done Off-resonant lock of both arm cavities with DRMI :done Full carrier resonant of single arm with DRMI :done 25 Full RSE :in progress Arm lock is really really difficult! LIGO- G5195--R LSC meeting at LLO, March 25 3

4 DRMI lock with Unbalanced sideband by detuned cavity August 24 DRMI locked with carrier resonance (like GEO configuration) November 24 DRMI locked with sideband resonance (Carrier is anti resonant preparing for RSE.) Carrier 33MHz 166MHz ITMy Carrier BS ITMx Unbalanced 166MHz PRM DDM PD 33MHz DDM PD SRM OSA DDM PD Belongs to next carrier Belongs to next carrier Lock acquisition After lock: MICH : 12 Hz DDM@AP PRC : 33MHz@SP DDM@SP SRC : DDM@PO DDM@PO LIGO- G5195--R LSC meeting at LLO, March 25 4 Typical lock acquisition time : ~1sec Longest lock:2.5hour

5 Abs +/-33 off-resonant +/-33 resonant +166resonant Design Lock point SP33 Lock point.56 degree (1.7nm) LIGO- G5195--R LSC meeting at LLO, March 25 5

6 m Original design of SP DDM resonance 25 Double Demodulation at SP Abs -.4 dc= l+ l- ls : off-resonant -33 : off-resonant +166: resonant -166 : anti-resonant resonance SP33 Lock point.56degree Design Lock point 1 Demodulation Phase of f2 l + and l s plot separated Difficult to find PRM position without carrier LSC meeting at LLO, March 25 6 Demodulation Phase of f1 LIGO- G5195--R

7 Offset l deg, l s +.56 deg Abs Double Demodulation at SP dc= l+ l- ls resonance : resonant -33 : resonant +166: resonant -166 : anti-resonant resonance SP33 Lock point.56degree Design Lock point Demodulation Phase of f2 l + and l s plot overlapping DC line changed Easy to find PRM position using 33MHz resonance LikeAdLIGO configuration Carrier would be off resonant LSC meeting at LLO, March 25 7 Demodulation Phase of f1 LIGO- G5195--R

8 4m vs. Ad-LIGO 4m x6 x1.5 x3 Ad-LIGO x2 x8 x17 LIGO- G5195--R LSC meeting at LLO, March 25 8

9 Struggling lock acquisition for Arms Problems 1. Sideband resonance on arm cavities 2. Resonant point shift due to detuned SRC 3. 16kHz sampling rate is too slow for 4m. 4. Coupling between X arm and Y arm LIGO- G5195--R LSC meeting at LLO, March 25 9

10 Which is first? DRMI lock or Arms lock? DRMI first Shutter PRM ETMy ITMy BS DDM ITMx ETMx Carrier 33MHz 166MHz Shutter PRM ETMy Sideband resonance ITMy BS ITMx Carrier flash does not matter because DRMI is locked by DDM (beat of sidebands). Sideband flash matters. Can keep locking ~1sec with lower gain. ETMx Shutter SRM SRM Shutter Arms first ETMy ITMy Normalized by PRC power ETMy ITMy PRFPMI : succeeded RSE : not succeeded!»because of resonant point shift due to detuned SRC PRM BS ITMx ETMx PRM BS ITMx ETMx SRM LIGO- G5195--R SRM LSC meeting at LLO, March 25 1

11 Abs Resonant point shift Normalized transmitted power as input [W] 6x Resonant point shift Full RSE DRMI + X arm Resonant point shifts in single arm lock because of carrier phase change in detuned SRC CARM (XARM) [1-9 m] LIGO- G5195--R LSC meeting at LLO, March 25 11

12 Abs Digital sampling for 4m RSE configuration Normalized power as input[w] 1.x Digital sampling with arm transmitted light for RSE Full RSE Digital sampling points with 3x1-6 Due to large seismic motion, 3x1-6 m at 1Hz assumed here Due to very high combined finesse of arm and PRC ~18. Night is about 1 times better but still not enough. Needs wider linear error signal Mirror position [1-9 m]» Normalization technique to widen linear range» Slower mirror motion LIGO- G5195--R LSC meeting at LLO, March 25 12

13 Off-resonant lock scheme for arm cavity Error signal is produced by transmitted light as 1 Transmitted power + offset Off-resonant Lock point Resonant Lock 1. to avoid coupling through carrier in central part, 2. to widen linear range. LIGO- G5195--R LSC meeting at LLO, March 25 13

14 Off resonant Arm lock with DRMI DRMI with single arm lock Not so difficult Last ~1 min Lock acquisition time ~1 min Switched to POX/POY signal normalized by transmitted light Full carrier was stored in each arm cavity separately. Arm power Error signal Yarm lock Xarm lock Both arms lock with DRMI Off-resonant carrier on arm cavities Last < 1 min Locked only 2 times Ideal lock point Offset lock Offset lock LIGO- G5195--R LSC meeting at LLO, March 25 14

15 Coupling between L x and L y Common of arms(carm) : L + =( L x + L y ) / 2 Differential of arms(darm) : L = L x L y Power recycling cavity : l + =( l x + l y ) / 2 Michelson : l = l x l y Signal recycling cavity : l s =( l sx + l sy ) / 2 ETMy CARM/DARM lock Port Dem. Freq. L + L l + l l s SP f E-9-1.2E-3-1.3E-6-2.3E-6 AP f 2-4.8E E-8 1.3E-3-1.7E-8 SP f 1 f 2-1.7E-3-3.E E-2-1.E-1 AP f 1 f 2-6.2E-4 1.5E-3 7.5E E-2 PO f 1 f 2 3.6E-3 2.7E-3 4.6E-1-2.3E-2 1 Laser POY PRM l y L y l sy ITMy BS ITMx ETMx POX/POY lock Port Dem. Freq. L x L y l + l l s SP f E-1-1.2E-3-1.3E-6-2.3E-6 AP f 2 9.4E E-8 1.3E-3-1.7E-8 l x SP PO LIGO- G5195--R l sx SRM AP POX L x SP f 1 f 2-1.7E-3-3.E E-2-1.E-1 AP f 1 f 2-6.2E-4 1.5E-3 7.5E E-2 PO f 1 f 2 3.6E-3 2.7E-3 4.6E-1-2.3E-2 1 Coupling is 94% when carrier is resonant.» Off-resonant lock for arms LSC meeting at LLO, March 25 15

16 The way to RSE Arm lock first with offset using transmitted light DRMI lock first using DDM Resonant point shift Both arms lock with offset using transmitted light Clear sampling Problem and linear range problem Switch to POX/POY signal with the offset Switch to CARM/DARM signal with the offset Coupling between L x and L y Reduce offset Full RSE lock LIGO- G5195--R LSC meeting at LLO, March 25 16

17 Abs Way from off-resonant lock to com/diff lock 1-1 RSE vs FPMI Normalized transmitted power as input [W] Off-resonant Lock point +/-.2nm Full RSE FPMI(PRC,SRC misaligned) CARM (XARM) [1-9 m] LIGO- G5195--R LSC meeting at LLO, March 25 17

18 Abs Normalized SP166 for CARM Normalized transmitted power as input [W] Dem.phase accuracy ~1degre for 166MHz ~.1degree for 33MHz LIGO- G5195--R Full RSE FPMI(PRC,SRC misaligned) Raw error signal of SP166 SP166 normalized by (TrX + TrY) SP166 normalized by PRC power Off-resonant Lock point Normarized SP166 +/-.2nm CARM (XARM) [1-9 m] LSC meeting at LLO, March

19 e2e SIMULATION: 4Om/AdvLIGO package optical configuration IFO with Arms IFO Central part ETMY ETMX ITMY ITMX PRM BS SRM LIGO- G5195--R LSC meeting at LLO, March 25 19

20 e2e SIMULATION: 4Om/AdvLIGO package E2Evalidation of DC fields comparing with TWIDDLE results: good agreement! E2E transfer functions simulations (and comparison with TWIDDLE ones) of DOF at SP, AP and PO shaking the end mirrors with white noise at different demodulation frequencies : (33,133,166,199) MHz I signal E2E TWIDDLE E2E TWIDDLE Q signal Example: AP 166 MHz TWIDDLE and E2E comparison LIGO- G5195--R