dpg spring meeting, march 2011
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DPG spring meeting, March 2011
The AEI 10m Prototype InterferometerTobias Westphal for the AEI 10 m Prototype team
http://10m-prototype.aei.uni-hannover.de
Why to build another PT
Maximal overlap with GEO-HF subsystems• Develop and prove as many of the techniques needed for gravitational wave detector
upgrades as possible (e.g. laser, digital control infrastructure)•Provide training for people who will install upgrades to and run GEO-HF
2
Ultra-low displacement-noise test environment• To probe at and beyond the Standard Quantum Limit (SQL)
equivalent Heisenberg limit for 100 g test masses• Thermal noise interferometer•Other experiments within QUEST (for e.g. LISA or GRACE follow on)•Entanglement of macroscopic test masses (a bit further down the road…)
What is the SQL
3
SQL interferometer layout
4
Frequency reference cavity
Length: 12 mFinesse: ca. 7500
Triple pendulum suspensionMirror mass: 860 g
10 m Fabry-Perot arm cavityFinesse ca. 700
100 g Mirrorsmonolithic silica suspensions
~8 W @ 1064 nm fiber coupled
Optional:Power recycling
Optional:Signal recycling
Anti-resonantFabry-Perot cavity
as compound end mirror
Tap off~130 mW
5
Squeeze-in tanks
Learn from experience!
Earlier days (GEO600 design):• Not very versatile• REALLY uncomfortable
to work in
6
Walk-in tanks
600 mm flangesto fit viewports
100 mm flangesto fit feed throughs
100 mm flangesto fit feed throughs
Walk-in door
Ultra-high vacuum system
Tanks:3.4 m tall
3 m �
Tubes:1.5 m Ø
7
10-6mbar after about 12 hours
• 100 m³ Volume• 22 t stainless steel
• 170 l/s screw pump (roughing)• 2x 2000 l/s turbo pump (main)• 2x scroll pump (backing & differential)
• Metal gaskets below 600 mm• Double O-ring differentially pumped
Sliced open
• Optical benches in the tanks• Passive seismic isolation• Active inter table stabilisation
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Table subsystems
Inverted pendulum
Base plate
Optical table
Filter support
LVDT / Actuator
Vertical motorized blade
Horizontal motorized blade
Accelerometer
Tilt stabilisation
Geometricantispring
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GAS filter (vertical isolation)
10
Top view Side view
Featuring• very soft potential → large isolation• Huge loading capabilities
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Estimated motion
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
10-2 10-1 100 101 102
Frequency [Hz]
Dis
plac
emen
t [m
/√H
z]
GroundHorizontalVertical
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
10-2 10-1 100 101 102
Frequency [Hz]
Dis
plac
emen
t [m
/√H
z]D
ispl
acem
ent [
m/√
Hz]
GroundHorizontalVertical
GroundHorizontalVertical
60 dB
micro-seismic
anthropogenic
70 dB
Vertical isolation (measured)
12
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
1 10 100
Tran
sfer
func
tion
[dB
]
Frequency [Hz]
Reference Measurement
Single Magic Wand (SiC)
7 dB
← GAS-resonance frequency ca. 440 mHz
off-centered accelerometer
shaker structure
without magic wand
GAS filter shaker
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GAS filter in action
14
15
Estimated differential motion
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
10-2 10-1 100 101 102
Frequency [Hz]
Dis
plac
emen
t [m
/√H
z]
GroundHorizontalVertical
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
10-2 10-1 100 101 102
Frequency [Hz]
Dis
plac
emen
t [m
/√H
z]D
ispl
acem
ent [
m/√
Hz]
GroundHorizontalVertical
GroundHorizontalVertical
Inter table
Passiveisolatio
n
Active isolation
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Low freqency active isolation
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
10-2 10-1 100 101 102
Frequency [Hz]
Dis
plac
emen
t [m
/√H
z]
GroundHorizontalVertical
10-5
10-6
10-7
10-8
10-9
10-10
10-11
10-12
10-13
10-14
10-2 10-1 100 101 102
Frequency [Hz]
Dis
plac
emen
t [m
/√H
z]D
ispl
acem
ent [
m/√
Hz]
GroundHorizontalVertical
GroundHorizontalVertical
Stabilized inter table
Passiveisolatio
n
Active isolation
Accelerometers
LVDT`s
SPI
Suspension platform interferometer
Goal:• Stabilize inter table motion• 100 pm/√Hz, 10 nrad/√Hz
@ 10 mHz
Based on LISA Pathfinder experience:• Heterodyne Mach-Zehnder
interferometer with unequal arm length (by 23 m)
• Iodine-stabilised Nd:YAG (frequency noise)
• Optics bonded onto low CTE plate (thermal drifts)
• Digital signal processing (FPGAs)
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Digital control system
• Based on realtime LINUX• Runs EPICS software
18
ExperimentSensors & actuators Fieldboxes
Signal conditioningAA/AI filters
ADC/DAC6 x 32channel
PCI-XDA/AD & DIO
Front-endDigital filters
Analog world Digital world• Gives error signals• Carries actuation out
• Changes• Get data
GPStiming
Storage
Frame builder
Workstation
User world
/4
/2
N PR O
Isolator
N d:YVOcrysta ls
4
pum poptics
Laser: 35 W @ 1064 nmCrystals: • 3 x 3 x 10 mm3 Nd:YVO4 • 8 mm 0,3 % doped, 2 mm endcap
Frequency [FSR]
24 W measurement TEM00 model
No
rmal
ized
po
wer
Pump diode:• 808 nm, 45 W• 400 µm Ø fiber coupled, NA=0,22
Amplifier: • 38 W for 2 W seed and 150 W pump
19
99% in TEM00
Mirror suspensions
Frequency reference cavity:• Three horizontal, two vertical stages• 850 g per stage (mirror 10 cm x 5 cm)• Steel wires, last stage 55 µm Ø • Local control and alignment control at
uppermost stage(fast alignment is done at steering mirrors)
Interferometer optics:• Three horizontal stages, two vertical stages• 100 g per stage (mirror ca. 2“ x 1“)• All silica last stage, 4 filaments of 20 µm Ø
20
Sensitivity w/o Khalili cavities
21
High reflective coatings have lots of coating layers(1) Few layers medium R, low CTN(2) Many layers high R, high CTN
Let‘s separate reflectivity and losses!
Where does coating noise appear?
22
N
Coating noise
N
Reflectivity
Khalili cavity
23
EETMIETM
One HR mirror two mirrors:1. Medium reflectivity: ca. 50 % (IETM)
2. High reflectivity: 99.99 % (EETM)
(2n+1) l/2
Factor 1.6 reduction of coating thermal noise
Sensitivity w/o Khalili cavities
24
Sensitivity with Khalili cavities
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Sensitivity with doping & Khalili
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Titanium
The team
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Ken Strain: Scientific leaderStefan Goßler: CoordinatorGerhard Heinzel: LISA/LPF related experimentsYanbei Chen, Kentaro Somiya, Stefan Danilishin: Experiment design, noise analysisRoman Schnabel: Squeezing and QND experimentsHarald Lück: Vacuum system and GEO 600 related experimentsHartmut Grote: Electronics and GEO 600 related experimentsGEO operators: Filter design and construction, environmental monitoring Andreas Weidner: Electronics designKasem Mossavi: Vacuum system and pumps controlJens Breyer: Mechanical designBenno Willke, Jan Hendrik Pöld, Christina Bogan: High power laserGerrit Kühn, Michael Born, Martin Hewitson: Real time control systemAlessandro Bertolini, Alexander Wanner: Isolation tablesKatrin Dahl: SPIFumiko Kawazoe: Frequency reference cavityStefan Hild, Sabina Huttner, Christian Gräf: Interferometric sensing & controlGiles Hammond, Tobias Westphal: Monolithic suspensionsGerald Bergmann: Commissioning
http://10m-prototype.aei.uni-hannover.de See poster Christian Gräf
Q57.83 16:30
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