Power recycling
experimentforTAMA300
National Astronomical Observatory

Koji AraiTAMA300 Recycling

K. Arai
02/02/06
2nd TAMA Sympol Recycling experiment began in Oct., 2001l Purpose:

To improve SNR to NS binaries
To integrate the technical achievements of the R&D

l Current status:

Full lock has been achieved
Recycling gainContinuous lock~4(designed: 4.6)
~ 46minLength control with the frontal modulation scheme
Alignment control for the test masses

Purposel Scientific motivation
w To perform observations
with improved SNR to NS binaries

l 1st step: Low gain recycling(RRM~48%, G~4.6)

w Target: Faster realization of the full lock
> Earlier full operation / observation> Feeding back information to design of high gain recycling> Establishing techniques for diagnoses / analyses

l 2nd step: High gain recycling (RRM~90%, G~10)
w Target: Optimizing the detector performancePast recycling R&Ds in Japanl 3m prototype(Gachieved: 2.9~5.5)

w Demonstration of recycling for suspended FPMI *1
w Investigation of length sensing/control schemes> Sideband elimination technique *2 *3> 3rd harmonic demodulation technique *4

l 20m prototype(Gachieved: 8~12)

w Evaluation of the TAMA optics *5
w Investigation of length/alignment control
for high recycling gain
*1 M. Ando, et al, Phys. Lett. A 248 (1998) 145*2 M. Ando, et al, Phys. Lett. A 237 (1997) 13*3 M. Ando, et al, Phys. Lett. A 268 (2000) 268*4 K. Arai, et al, Phys. Lett. A 273 (2000) 15*5 S. Sato, et al, Appl. Opt. 39 (2000) 25, 4616

Optical configuration
Laser
Nd:YAGInnolight 1W

Recycling
Pick-offMirror(Rec. Cav.)
R=0.48R=0.01300m arm
Finesse ~500
Pick-offs(arm)
R=0.006

OpticalIsolator
Modulators

10m MC
Finnese~ 1700

δL−:
δL+:
δl−:
δl+:

Arm length differential
Arm length common
Michelson fringe
Recycling cavity length

Lock acquisition (1)l Lock acquisition procedure
5J=JA
SB1
CA

CA G0~0, under-coupled
SB1 G1~0, under-coupled

Drastic increase of the internal power
Change of the couplings to the IFO=> change in optical gains and signal sign
5J=JA

CA G0=0.18, under-coupled
SB1 G1=4.4, over-coupled

5J=JA!

CA G0=0.51, under-coupled
SB1 G1=4.4, over-coupled

5J=JA"CA G0=4.6, over-coupled
SB1 G1=4.4, over-coupled

Lock acquisition (2)l Length sensing for the lock acquisition

signals
fromarm Pick-offs

I Q
Phase
Shifter

LASER & MC

EOM

δ L2

Faraday
Isolator

δ l+
δ l−
fx3 fx3

frequency
triplers

3fm demodulation

δ L1

Lock acquisition (3)l 3rd harmonic demodulation for δl+ and δl−w Photocurrent at the 3fm ~ beating of SB2 and SB-1
modulation
sidebands

3fm

SB-3 SB-2 SB-1 CarrierSB1 SB2 SB3

frequencyofelectric fieldw Robust extraction of δl+ and δl-Contribution of carrier audio-sidebands (mainly by δL+)
ReducedAmplitudes and signs
Less dependent on the couplings of CA and SB1

Lock acquisition (4)l Signals from arm pick-offs
w Similar to Pound-Drever-Hall techniquew Power recycling mixes the informationof the arms each other> Ratio of the mixing is 50% at most(for RRM=48%, G~4.6).

Lock acquisition (4)l Time-series data of a lock acquisition
Almost stays at State3.
Always trying to lock the other arm.
Lock attempt failed
Locked!

Alignment control (1)l Wave Front Sensing for the test masses
I Q
Phase
ShifterLASEREOMFaraday
Isolator

w Currently the signals weretaken from the PO ports
w Eventually it will be replaced to thecommon differential control

QPDs
Gouy phasetelescopes

Alignment control (2)l Stabilizing gain fluctuation by WFS
w Without WFS

w With WFS

w The alignment servos were activatedeven during the lock acquisition

Operating model Length sensing for the operation
w Frontal modulation scheme
I Q
Phase
Shifter

LASER & MC

EOM

FaradayIsolator

δ l+
δ l−
δ L+

fx3

δ L−

Stabilityl 46 min. of continuous lockw Current most longest lock stretch

46.5 minSensitivityl Displacement sensitivity

1x10-17 m/sqrtHz ~ 7 times worse than the FPMI best

Plans for improvementl Drift control
w Optical axes controll Alignment
w Common-differential sensing/control
w Sensing matrix diagonalizing

l More power in the arm
w Introducing high power laser to the IFO
w Characterizations for the high gain recyclingl Noise issue

Summaryl The recycling experimentw began 4 months agol The full lock has already been achieved
w Arm lock by auxiliary length signals
w 3rd harmonic demodulationl Stability ~ 46min continuous lockw The stability was much improvedby the alignment controll Sensitivity ~ under investigationw Still x7 worse than the best