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

9

GAS filter (vertical isolation)

10

Top view Side view

Featuring• very soft potential → large isolation• Huge loading capabilities

11

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

13

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

16

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)

17

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

25

Sensitivity with doping & Khalili

26

Titanium

The team

27

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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