Sensing and Controlsfor
Power-Recycling of TAMA300
Koji AraiandTAMA collaboration
National Astronomical Observatory,
Dept. of Phys., Univ. of Tokyo, ICRR, Univ. of Tokyo,
Dept of Adv. Mat. Sci, Univ. of Tokyo, ERI, Univ. of Tokyo,
Miyagi Univ. of Edu. , UEC, KEK
2001/7/12
4th Edoardo Amaldi conferenceIntroductionl Power recycling for TAMA300
Experiment begins this autumn.

This Talk:
Motivation for TAMA300 recycling
Length sensing/control system
Lock acquisitionPurpose of recycling on TAMA300 (1)l Why no power recycling up to now
Earlier operation as a gravitational wave detector~ We could start the operation in 1999 Spring
Every system for FPMI is strongly related with the recycled version~ Length control with frontal modulation=> subset of the recycled version~ Calibration method
Making development easier~ Noise hunting~ Longer lock duration~ Simpler diagnoses/analyses

Purpose of recycling on TAMA300 (2)l Scientific motivation
Power recycling improves the senstivity of TAMA
~ not only substantiallybut also practicallyl Technical challenge
Integrating the experiences~ past recycled prototypes and non-recycled TAMA
Investigating behaviours of IFO under power recycling~ detector diagnoses / data quality evaluation
Experiencing power-recycling with longer arms
~ prospect to LCGTIncreasing SNR with power recycling
l Reduction of read-out noise
Even with the current level of technical noises,
power-recycling is expected to improve SNR to NS binary coalescence

SNR for NS binary @ 10kpc

80
TAMA300 2001/6/2
Recycling (gain=4)
Recycling (gain=10)

60

40

20

1.4 Msolar
NS binary

0-1

102

34 5 6 70210m1 [Msolar]3

4 5 6 71012

Experience on power recycling
l Recycling gain~ achieved in past prototypes in Japan and planned for TAMA300
1512 *

10Recyclinggain
5082NAO20m

10TAMA300(planned)*25.4

2.9 *1

1997

3.8

1998

Univ. of Tokyo
3m
1999

2000

4.6

2001

2002

Power recycling for TAMA300 ~ within our experiences except for its length*1 M. Ando, et al, Phys. Lett. A 248 (1998) 145*2 S. Sato, et al, Appl. Opt. 39 (2000) 25, 4616

Strategyl Divided into two phases ~ low gain and high gain
1st step: Low gain recycling(RRM~48%, G~4.6)

Target: Easier lock acquisition=> Possibility of earlier full operation / observation=> Feeding back information to design of high gain recycling=> Establishing techniques for detector diagnoses / data analyses
2nd step: High gain recycling(RRM~90%, G~10)

Target:Optimization of optical parameters / control system
Improvement of the detector toward ultimate performances

Length sensing
Frontal modulation + 3rd harmonic demodulation
I Q
Phase
ShifterLASER

3fm
demodulation
fm

fx3

I
3fm

δl+ δl−frequency
triplerQ3fm

LP

Faraday
Isolator

EOM

fx3

L−=LP−LI
L+=LP+LI
l− = lP−lIl+ = lP+lI

SYlPPOlIASIQLIfmQδl−

δL+ δL−K. Arai, et al, Phys. Lett. A 273 (2000) 15

3rd harmonic demodulation
lPhotocurrent at the 3fm ~ beating of SB2 and SB-1
modulation
sidebands

3fm

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

frequency
ofelectric fieldlRobust extraction of δl+ and δlContribution of carrier audio-sidebands (mainly by δL+)
ReducedAmplitudes and signs
Less dependent on the couplings of CA and SB1

Extracted signal
lWell-diagnalized signals
PortDemod PhaseLDarkfm
Q
1
Pick-offfm
I
1.5e-4Bright3fm
Q
1.0e-2Brightfm
Q
1.5e-2Bright3fm
I
1.5e-4lShot noise limitPort(low gain recycling)L+ll+
3.0e-43.0e-31.0e-61
2.4e-75.0e-52.3e-21
3.6e-26.2e-11
1.6e-36.5e-21.2e-31(low gain recycling)
Shotnoise level (m/Hz1/2)

Demod Phase

Dark

fm

Q

L-

1.2 x 10-19 =4.0 x 10-22 1/Hz-1/2

Pick-offfmIL+

1.2 x 10-18 =1.0 x 10-6 Hz/Hz-1/2

Bright3fm

Ql-

1.4 x 10-14

for lock

Brightfm

Ql-

2.0 x 10-16

for operation

Bright3fm

Il+

2.8 x 10-15

Control topology
δL-:
δL+:
δl-:
δl+:

Front mirrors ~ differential
MC length & MC loop
Beamsplitter
Recycling Mirror
δLy3fm

δlδL+

δl+

δLx

δLδL-, δL+

drift compensation~ active isolator

Lock acquisitionl Procedure 1~ Standard (LIGO like)State 1

SB1
CA

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

Drastic increase of the inner power
Change of the couplings to the IFO=> change in optical gains and signal signState 2CA G0=0.18, under-coupled
SB1 G1=4.4, over-coupled

State 3

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

State 4

CA G0=4.6, over-coupled
SB1 G1=4.4, over-coupledGain variation / Sign flip (Recycling1)
3fm signals

1.0
RecycledMichelson

Optical gain

0.5

0.0

RecycledMichelson+
One arm-0.5

2x 0.82

dl-x 0.46
fm signals

Recycled
Fabry-Perot
Michelson

-1.0

dl+

3Statedl+x −0.023

dl-x −0.76

4No sign flip and less gain changes with 3fm signals~ no need of adaptive servo system (variable gain adj., dynamic sign change)

Lock acquisitionl Procedure 2 ~ Using pick-off signal (Pound-Drever-Hall technique like)
This technique worked fine in the prototypes,
particularly when the recycling gain was low.

Mixing of arm PDH signalsl Recycling makes arm length signals mixed
at the last moment of the acquisition
mixing of...

0%

two PDH signals are independent

100%
...

two PDH signals become equivalent

TAMA Recycling1 (G=4.6)
mixing = 50%

still independent in some extent

TAMA Recycling2 (G=10)
mixing = 85%

need careful treatment

Summaryl Power-recycling for TAMA300
Motivation
Expected to improve the sensitivity to NS binaries
Integrate our experiences with TAMA and the prototypes
2 step strategy: low gain (G~4.6) and high gain (G~10)
Expect earlier full operation
Chance to optimize the system
Length sensing: 3rd harmonic demodulation scheme
Robust extraction of dl+ and dlLock acquisition: try 2 different procedures
Using frontal modulation signals
Using arm reflections with pick-off mirrors