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The GEO 600 Detector. Andreas Freise and the GEO 600 Team University of Hannover May 20, 2002. GEO. LIGO. VIRGO. TAMA. ACIGA. Location of GEO 600. the gallery in the central building. the clean room. t he cen t ral area. North Arm 600 m. the trench with vacuum tube. East Arm - PowerPoint PPT Presentation
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The GEO 600 Detector
Andreas Freise and the GEO 600 Team
University of Hannover
May 20, 2002
May 20, 2002 Andreas Freise
Location of GEO 600
LIGO
ACIGA
TAMAVIRGO
GEO
East Arm 600 m
North Arm 600 m
the clean roomthe gallery in the central building
the central area
the trench with vacuum tube
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 0.1 mring cavity
Laser
14 W
Mode Cleaners
triangular 8 m ringcavities
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 1m diametertubes : 110-8 mbar main tanks : 510-8 mbar
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 insidevacuum tanks is mounted onthree Stacks:
Triple Pendulum Suspension
May 20, 2002 Andreas Freise
Monolithic Suspension
Silicate (Hydroxy- Catalysis) Bonding
Weld
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
May 20, 2002 Andreas Freise
Slave
Master
Master
Slave
enter 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
May 20, 2002 Andreas Freise
Laser
Light Power
Michelson Interferometer
Output Mode Cleaner
Mode Cleaners
10 W 5 W
~ 5 kW
~ 50 mW
1 W
10 kW atBeam Splitter
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 91% 92%
Power-Recycled Michelson:
MPR T=1.5%
Gain 200
Contrast 4000
MPR
final optics
test optics
May 20, 2002 Andreas Freise
Three types of control tasks:
1) Local control: damping of pendulum resonances, active seismic isolation, temperature control
2) Global control of longitudinal degrees of freedom of optical systems: length and frequency stabilisation
3) Global control of alignment of optical components: Automatic alignment system
Automated Control
control loops made of analog electronics
supervised by digital electronic(digital potentiometers, CMOSswitches, mico-controller, AD
converter)
controlled by distributed LabViewvirtual instruments
(digital bus, read ~1000 controlchannels, lock automation)
May 20, 2002 Andreas Freise
Length and Frequency Control
MichelsonInterferometer
Output Mode Cleaner
Laser
Mode Cleaners
the laser frequency is locked to thelength of the first mode cleanerthe length of the first mode cleaneris locked to the length of the second
the now pre-stabilised laser frequency is locked to the common mode of the power-recycled Michelson interferometer
25 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
May 20, 2002 Andreas Freise
Frequency Noise
Required frequency stability at the input of the final interferometer: 10 Hz/sqrt(Hz)
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:
a separate modulation frequency
reflected beam from AR coating
May 20, 2002 Andreas Freise
Reaction Pendulum:
3 coil-magnet actuators at intermediate mass
Electrostatic actuation on test mass
Test Mass Actuators
May 20, 2002 Andreas Freise
Alignment Control (I)
DC: beam positions are defined by reference marks, spot position control, below 0.1 Hz
around the resonance frequencies of the suspension pendulums the beam follows the input beam from the laser bench, differential wave-front sensing, 0.1 Hz to 10 Hz
no active control at the expected signal frequencies, the two mode cleaners suppress geometry fluctuations by ~106
May 20, 2002 Andreas Freise
Alignment Control (II)
differential wave-front sensing
spot position control
4 degrees of freedom for MC 1
+4 for MC 2+4 for MI common mode+2 for MI differential mode+2 for signal recycling
16 + 32 = 48
Status May 2002: Complete (except for the not yet installed signal recycling mirror)
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
May 20, 2002 Andreas Freise
Data Storage and Transfer
May 20, 2002 Andreas Freise
Coincidence Run with LIGO
Engineering run 28.12.2001 - 14.01.2002
• 430 hours of continous data taking
• Duty cycle (> 10mins) ~ 75%
• 98% for the last 24h.
• Longest lock: 3h:38min
• ~ 0.9 TB of data recorded
0
10
20
30
40
50
60
70
80
90
100
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
Pe
rce
nta
ge
of
time
in lo
ck
Daily overall duty cycles, maintenanceperiods not subtracted
May 20, 2002 Andreas Freise
Strain Sensitivity
May 20, 2002 Andreas Freise
Automated Control
Laser-mode-cleaner system with longitudinal control and auto alignment runs continuously since December 2000
Total time for relocking the injection locked laser and the two mode cleaners is typically < 40 sec
Continuous lock of the auto-aligned mode cleaner system: 48 hours
Locked 1200 m cavity without any re-alignment of the cavity mirrors for 36 hours
Continuous lock of the entire system: 10 hours