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L ocal S uspension P oint I nterferometer for CLIO. University of Tokyo, ICRR A , AIST B Takanori Saito , Souichi Telada B , Takashi Uchiyama A , Shinji Miyoki A , Osamu Miykawa A , Masatake Ohashi A and CLIO Collaborators. Outline. Motivation LSPI CLIO suspension system - PowerPoint PPT Presentation
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Local Suspension Point Interferometer for CLIO
University of Tokyo, ICRRA, AISTB
Takanori Saito, Souichi TeladaB, Takashi UchiyamaA,
Shinji MiyokiA, Osamu MiykawaA, Masatake OhashiA
and CLIO Collaborators
1GWADW at Hearton Hotel Kyoto2010/05/17
1. Motivation2. LSPI
CLIO suspension system Tandem Interferometer
3. LSPI Installation in CLIO CLIO in Kamioka mine Experimental setup
4. Experiment and result5. Summary
GWADW at Hearton Hotel Kyoto 22010/05/17
Outline
1. Motivation
3GWADW at Hearton Hotel Kyoto2010/05/17
Experiences from CLIO experimentLocking FP cavity is difficult in cryogenic temperature.
No damping resonant peaks of CLIO suspension effectively.Problems on present eddy current damping system
Damping force strongly depends on temperature. Because the damping force depends on resistance of a mass. The resistance is drastically changed from the room temperature to the
cryogenic temperature.
Needed a new damping system.Solution: active damping system
Damping resonant peaks of CLIO suspension. No large magnets. Adjustable damping force and frequency range. Low noise sensor if using interferometer.
2. Current Suspension system
4GWADW at Hearton Hotel Kyoto2010/05/17
6 stages suspension system.Upper 3 stages in room temperature part Lower 3 stages in cryogenic temperature part
Eddy current damping is being applied to the cryo-base by some magnets on damping stage.
Existing eddy current damping system will be replaced by active damping system in future.
Sensing and actuation point: cryo-base (not the test mass) Local Suspension Point
Main FP cavity will be used as a sensor to see the damping effect.
We call it Local Suspension Point Interferometer.
Cryo-Base
Test Mass
Cryogenic Temperature part
Room Temperature part
CLIO Suspension
3-stages vibration isolation system
Damping Stage
Upper Mass
Cryostat
5GWADW at Hearton Hotel Kyoto2010/05/17
PD
PBS1
PBS2
QWP1
QWP3
HWP2
PBS3
HWP1
PD
Electrical objects (actuators, PD, Laser source) don’t work in cryogenic temperature.
They are placed in room temp. part.To align the optics in cryogenic
temperature part is difficult. Not using simple Michelson
interferometer. Aligned from the room temperature
part remotely.
Avoid reconstructing the vacuum tank of CLIO.
Room arms
Cryogenicarms
Mirror1
Mirror2
Mirror4
QWP2
QWP4
S-wave
P-wave
Laser
2. Polarized Tandem InterferometerRoom
Temperature part
Cryogenic Temperature part
Mirror3
6GWADW at Hearton Hotel Kyoto2010/05/17
PD
PBS1
PBS2
QWP1
QWP3
HWP2
PBS3
HWP1
PD
Tandem interferometer Compensating optical path
length difference at cryogenic part by room temperature part.
Compact structure in the cryogenic temperature part.
Polarized interferometer. High contrast interferometer
Sensing pendulum motion of the cryo-base.
Room arms
Cryogenicarms
Mirror1
Mirror2
Mirror4
QWP2
QWP4
S-wave
P-wave
Laser
2. Polarized Tandem InterferometerRoom
Temperature part
Cryogenic Temperature part
Mirror3
History of LSPI experiment2008: Table-top experiment at Kashiwa Lab..2009-2010: First LSPI Installation in CLIO. Installation of optics in perpendicular arm end
suspension. Control test with existing eddy current damping Using aLIGO type digital system as servo Verified damping effect by LSPI.
Future Work Control test without the eddy current damping. Cryogenic test. Installation of second LSPI in other suspensions. Cooling all the test mass with LSPI systems.
3. LSPI Installation in CLIO
GWADW at Hearton Hotel Kyoto 72010/05/17
Per-arm End Suspension
CLIO Overview
GWADW at Hearton Hotel Kyoto 82010/05/17
3. Schematic of LSPI for CLIO
Two interferometers are installed for 2 DOFs
damping pendulum and yaw motion no big motion on pitch.
Two laser sources.Two corner cube mirrors (CCM)
are attached on the cryo-base.
Cryo-Base
UpperMass
TestMass
Cryogenicarms
PD
Laser Room arms
Essentially sensingthis length
Overview
Cryo-BaseUpperMass
TestMass
Cryogenicarms
PD
Laser
Essentially sensingthis length
Room arms
GWADW at Hearton Hotel Kyoto 92010/05/17
Overview
3. Schematic of LSPI for CLIO
Feedback points for length control.1. Cryo-base Damping the suspension system. Control in low frequency range (< 2Hz)
2. Active mirrors Control in high frequency range (2 ~ 20Hz)
Feedback the high frequency component to Active mirrorsavoids spoiling current CLIO sensitivity
Activemirrors
3. LSPI Setup (Room Temp.)
GWADW at Hearton Hotel Kyoto 102010/05/17
M3PBS3
PD
Active mirrors
Laser tank
Wave length: 633nmPower: 0.9mW
Into cryo.temp. part
From cryo.temp. part
PBS
Fixedmirror
3. LSPI Setup (Cryo. Temp.)
GWADW at Hearton Hotel Kyoto 112010/05/17
Reference mass
PBSQWP
Mirror
Coil-magnet actuators
From roomtemp. partInto room
temp. part
CCM
Mirror
115
Pendulum Second Mode(1.18Hz)
4. Damping test of LSPI
122010/05/17
Frequency [Hz]
Arb
itrar
y U
nit
13.5
Pendulum First Mode(0.48Hz)
GWADW at Hearton Hotel Kyoto
Transfer function of CLIO suspension
Measurement: 1. Excite test mass of main
100m FP cavity with/without LSPI lock during FP cavity locked.
2. Measure transfer function from excitation point to main mirror motion shown at the feedback signal of FP cavity control.
CLIO sensitivity with LSPI
GWADW at Hearton Hotel Kyoto 132010/05/17
We can expect that a suitable filter to the cryo-base loop can avoid to spoil the CLIO best sensitivity.
Frequency [Hz]
Dis
plac
emen
t [m
/rtH
z]
Two loops control. Cryo-base and active mirrors.
Add the 6Hz LPF only to cryo-base loop.
Improving CLIO sensitivity.
LSPI (Local Suspension Point Interferometer) is Local control system that has two polarized tandem interferometers
to damp the fluctuation of cryo-base. Installed to 1 of 4 main suspensions.
We succeeded in damping the resonant frequency of CLIO pendulum (0.48Hz, 1.18Hz) using LSPI.
Feeding back low frequency signal to cryo-base and high frequency signal to active mirror successfully avoided spoiling CLIO sensitivity around 20Hz.
GWADW at Hearton Hotel Kyoto 142010/05/17
6. Summary