the geo 600 detector andreas freise for the geo 600 team max-planck-institute for gravitational...
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![Page 1: The GEO 600 Detector Andreas Freise for the GEO 600 Team Max-Planck-Institute for Gravitational Physics University of Hannover May 20, 2002](https://reader035.vdocuments.site/reader035/viewer/2022062422/56649e6a5503460f94b671f9/html5/thumbnails/1.jpg)
The GEO 600 Detector
Andreas Freise for the GEO 600 Team
Max-Planck-Institute for Gravitational PhysicsUniversity of Hannover
May 20, 2002
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May 20, 2002 Andreas Freise
Network of Interferometric Detectors
LIGO
ACIGA
TAMAVIRGO
GEO
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East Arm 600 m
North Arm 600 m
clean roomgallery in the central building
central area
trench with vacuum tube
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May 20, 2002 Andreas Freise
GEO 600 - Optical Layout
Michelson Interferometer with Dual-Recycling
folded arms with an opticalpath length of 2400 m
Output Mode Cleaner
triangular ring cavity
Laser
14 W
Mode Cleaners
2 triangular ringcavities (8 m opticalpath length)
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May 20, 2002 Andreas Freise
GEO 600 Sensitivity
broadband configurationnarrowband configuration
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May 20, 2002 Andreas Freise
MichelsonInterferometer
Output Mode Cleaner
Laser
Mode Cleaners
Vacuum Enclosure
400 m3 volume / 4000 m2 surface600 m long tubes, 60 cm diameter2 m tall tanks with 1 m diametertubes : 110-8 mbar main tanks : 510-8 mbar
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May 20, 2002 Andreas Freise
Seismic Isolation
g e o p ho n z
g e o p ho n x
g e o p ho n y
PZT
rub b e r la ye r
fla ng e
b e llo w
x
yz
The mechanical structure insideeach vacuum tank is mounted onthree Stacks:
Triple Pendulum Suspension
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May 20, 2002 Andreas Freise
Monolithic Suspension
Silicate (Hydroxy- Catalysis) Bonding
Weld
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May 20, 2002 Andreas Freise
Status May 2002 (I)
Michelson Interferometer
Laser
Mode Cleaners
final optics
test optics
Laser + Mode Cleaners complete
Power-Recycled Michelson with low finesse
Two main mirrors with monolythic suspension
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May 20, 2002 Andreas Freise
Slave
Master
Master
Slave
entrance to vacuum system
Laser System
Master Laser:
Nd:YAG NPRO (non-planar ring
oscillator) 800mW @ 1064 nm
Slave Laser:
Nd:YAG injection-locked ring
cavity 14 W @ 1064nm less than 5% in higher
modes
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May 20, 2002 Andreas Freise
Laser
Light Power
Michelson Interferometer
Output Mode Cleaner
Mode Cleaners
10 W 5 W
~ 5 kW
~ 4 mW (carrier) + ~ 100 mW (modulation sidebands)
1 W
10 kW atBeam Splitter
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May 20, 2002 Andreas Freise
Status May 2002 (II)
Michelson Interferometer
Laser
Mode Cleaners
2 W 1 W
~ 50 mW
200 W atBeam Splitter
Mode Cleaners:
Troughput 80% 72%
Finesse 2700 1900
Visibility 96% 92%
MPR
final optics
test optics
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May 20, 2002 Andreas Freise
Automated Control
control loops made of analog electronics
supervised by digital electronics
controlled by distributedvirtual instruments (LabView)
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May 20, 2002 Andreas Freise
Length and Frequency Control
MichelsonInterferometer
Output Mode Cleaner
Laser
Mode Cleaners25 MHz13 MHz37 MHz
Laser Frequency Stabilisation:
no rigid reference cavity
laser is directly stabilised to suspended cavities
3 sequential Pound- Drever-Hall control loops
common mode of the Power-Recycled Michelson
serves as frequency reference
Measured in-loop stability at the main interferometer input :0.1 mHz/sqrt(Hz) @ 100 Hz
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May 20, 2002 Andreas Freise
Mode Cleaners
Output Mode Cleaner
Michelson Length Control
MichelsonInterferometer
Laser
15 MHz
10 MHz
Differential arm length:(gravitational wave signal)
heterodyne detection Schnupp modulation
Signal-Recycling control:
separate modulation frequency
reflected beam from beam splitter AR coating
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May 20, 2002 Andreas Freise
Test Mass Actuators
Reaction Pendulum:
3 coil-magnet actuators at intermediate mass
Electrostatic actuation on test mass
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May 20, 2002 Andreas Freise
Alignment Control (I)
differential wave-front sensing
spot position control
4 degrees of freedom at MC 1
+4 at MC 2+4 at MI (common mode)+2 at MI (differential mode)+2 at Signal-Recycling cavity
16 + 20 = 36
Status May 2002: Complete (except for Signal- Recycling mirror)
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May 20, 2002 Andreas Freise
Alignment Control (II)
Light on the main photo detector
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May 20, 2002 Andreas Freise
Data Acquisition
Data acquisition uses 3 Data Collecting Units (DCUs)with (in total) :
64 channels @ 16384 Hz
64 channels @ 512 Hz
~ 1000 channels @ 1Hz
Possible data rate:
600kB/sec
~ 50 GB/day
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May 20, 2002 Andreas Freise
0
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31.12.01 02.01.02 04.01.02 06.01.02 08.01.02 10.01.02 12.01.02 14.01.02
Date
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rce
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ge
of
time
in lo
ck
Daily overall duty cycles, maintenanceperiods not subtracted430 hours of continuous data taking ~ 0.9 TB of data recorded
Engineering run 28.12.2001 - 14.01.2002
Coincidence Run with LIGO
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May 20, 2002 Andreas Freise
Detector Improvement (I)
Detector characterisation groups analyse data from coincidence run
Example: analysis of detector data for all times at which the Michelson interferometer left its normal operating point:
36 lock losses (on 10.01.2002)
9Not identified
7Acquisition failure
12Spike in laser channel
2Spot position event
2Stack movement
2Seismic event
2Manual alignment
NoCause of loss of lockChecked wiring of the laserelectronics, found and removed ground loops.
duration of continuous locking of the mode cleaner section improved from ~4 hours to up to 100 hours
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May 20, 2002 Andreas Freise
Detector Improvement (II)
Experimental optimisation period:
electronics for Michelson servo loops are being completed
Michelson automatic alignment is completed
losses inside interferometer have been reduced(PR gain improved from 15 to 200)
known problem with beam splitter suspension has beenfixed
sensitivity has been improved from 10-17 1/sqrt(Hz) to 10-18 1/sqrt(Hz) @ ~ 300 Hz
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May 20, 2002 Andreas Freise
Future steps
Optimisation (Michelson) June 02 Coincidence run with LIGO (S1) July 02 Implementation of Signal-Recycling end of July 02 Optimisation (Dual-Recycling) Aug.-Oct. 02 Installation of final subsystems starting Nov. 02 Coincidence run with LIGO (S2) end of Nov. 02