the geo 600 detector andreas freise for the geo 600 team max-planck-institute for gravitational...

The GEO 600 Detector

Andreas Freise for the GEO 600 Team

Max-Planck-Institute for Gravitational PhysicsUniversity of Hannover

May 20, 2002

May 20, 2002 Andreas Freise

Network of Interferometric Detectors

LIGO

ACIGA

TAMAVIRGO

GEO

East Arm 600 m

North Arm 600 m

clean roomgallery in the central building

central area

trench with vacuum tube


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)


GEO 600 Sensitivity

broadband configurationnarrowband configuration


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


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


Monolithic Suspension

Silicate (Hydroxy- Catalysis) Bonding

Weld


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


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


Laser

Light Power


Output Mode Cleaner

Mode Cleaners

10 W 5 W

~ 5 kW

~ 4 mW (carrier) + ~ 100 mW (modulation sidebands)

1 W

10 kW atBeam Splitter


Status May 2002 (II)


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


Automated Control

control loops made of analog electronics

supervised by digital electronics

controlled by distributedvirtual instruments (LabView)


Length and Frequency Control


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


Mode Cleaners

Output Mode Cleaner

Michelson Length Control


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


Test Mass Actuators

Reaction Pendulum:

3 coil-magnet actuators at intermediate mass

Electrostatic actuation on test mass


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)


Alignment Control (II)

Light on the main photo detector


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


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 subtracted430 hours of continuous data taking ~ 0.9 TB of data recorded

Engineering run 28.12.2001 - 14.01.2002

Coincidence Run with LIGO


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


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


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

the geo 600 detector andreas freise for the geo 600 team max-planck-institute for gravitational...

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