harald lückfor the geo600 comissioning team 1ilias meeting, palma, oct. 2005 title geo 600...

Harald Lück for the GEO600 Comissioning team 1 ILIAS Meeting, Palma, Oct. 2005

Title

GEO 600Commissioning Status

Based on a talk of Stefan Hild for the WG1 meeting in Perugia

Max-Planck-Institut für Gravitationsphysik(Albert-Einstein-Institut)

Harald Lück for the GEO600 Comissioning team ILIAS meeting Palma, Oct. 2005


GEO 600 layout

1.5-2 kW

0.09


Tuning signal recycling to 300 Hz

Better knowledge of IFO parameters:

more accurate parameter predictions from simulations

downtuning to 200 Hz realized

Fixed instability of MI auto-alignment by setting up a new telescope for DWS.

We will stay at 330 Hz !


GEO 600 design sensitivity


RF setup

OLD setup

New setup:

• Using a less noisy splitter(0/90°)

• Using a cable as phaseshifter

NEW setup

Old setup:

• Dominated by phase noise in the LO path (phaseshifter and splitter(0/90°)

• Due to this noise Q was mixed into P quadrature.


Shot noise

Green line is the shot noise level calculated from the DC current of the photodiode.

We are within a factor sqrt(2) shot noise limited above 1kHz !


Next step in RF setup (next week)

Proposed by Rana and others

GOALS: • Using only high quality hardware • Guaranteeing high RF levels in all components


Noise projections 21st of july


Noise in the SR-long loop

Noise in the detection band is entirely limited by front-end-noise (shot noise from the detector).Limits sensitivity from 100 to 500 Hz

PROBLEM

• Large locking range• OLG of 10^6 at 0.1 Hz• No feedback noise above100 Hz

Requirements

1. Servo has a locking mode and a running mode2. Lowering UGF to get less gain in detection band3. Using lowpass filter with very steep roll off above UGF

(implemeted digitally using a dSPACE system)

Solution


Analog SR electronics

Red = acq amp, green = acq phaDark blue = run amp, brown = run phaseLight blue = run2 amp, pink = run2 pha


Signal Recycling digital

Phase @18 Hz = -147 deg


SR feedback: analog vs. digital


Sensitivity improvement July to August

High frequency improvements: reduction of RF phase noiseLow frequency improvements: reduction of Signal recycling feedback noise


PR-bench

Historically grown layout of PR-bench not optimal !

• beam clipping• too many

transmissive optical components

• too many polarizing components

• acoustic coupling

Goal:Shorten and simplify the HPD path


Sensitivity after PR bench work

Removed resonance structures between 100 and 200 Hz.


Noise projections 4th of August


Michelson length control

< 0.1Hz


< 10 Hz

< 0.1Hz


Reaction Pendulum:

3 coil-magnet actuators at intermediate mass, range ~ 100µm


< 10 Hz

> 10 Hz

< 0.1Hz


Reaction Pendulum:

3 coil-magnet actuators at intermediate mass, range ~ 100µm

Electrostatic actuation on test mass bias 630V, range 0-900V= 3.5µm


Using ESD as actuator

• Force is proportional to square of applied voltage.

• high voltages are needed

• for bipolar actuation a bias voltage needs to be applied

Noise is introduced:

• loop electronics

• sqrt circuits

• intrinsic HV amplifier noise


Sqrt circuits in MI loop

ESD: F U^2

Sqrt circuits are necessary to give full linear force range for acquisition.

Drawback: sqrt circuits are noisy 1µV/sqrt(Hz)(=100µV/sqrt(Hz) @ ESD)


ESD: F U^2

Sqrt circuits are necessary to give full linear force range for acquisition.

Drawback: sqrt circuits are noisy 1µV/sqrt(Hz)(=100µV/sqrt(Hz) @ ESD)

Bypassing sqrt circuits after lock is acquired.

Sqrt circuits in MI loop


Noise in MI loop

HVA noise = 100nV/sqrt(Hz) (=10µV/sqrt(Hz) @ ESD)

HV-amplifier noise can be reduced by decreasing bias voltage or active noise suppression.

Suppressing noise introduced by loop electronics needs whitening


MI loop whitening / dewhitening

dewhiten

dewhiten

dewhiten

Whiten

Whitening right after mixer:zero 3.5 Hzpole 35 Hz

Dewhitening for both split passes

Passive dewhit-ening done in HV path (0-1kV)


Sensitivity after fixing noise from MI loop


Noise Projections 6th of October: Excess noise @ 200Hz


Current sensitivity vs. Design sensitivity

102

103

10-24

10-23

10-22

10-21

10-20

10-19

10-18

10-17

Freq. [Hz]

ASD

[h/ H

z]GEO600 Theoretical Noise Budget

SeismicSuspension TNSubstrate TNCoating TNThermorefractiveShot 350HzTotalShot Sept 1 h(t) Sept 1


Laser Improvements

• Exchanged master laser and slave laser pump diodes for new ones (13.3W from Laser)

• Improved optical path

• Cleaned components on laser bench

→ max. 9.2 W @ MC1


Burst events; Start-of-the-second glitches


Start-of-the-second glitches: A cal. issue


New MI longitudinal loop: reduce longitudinal dark fringe deviations

Old

NewMuch more gain @ low f

Overall gain

Overall gain


Low Frequency EP Reduction

10-1

100

101

102

103

104

10-7

10-6

10-5

10-4

10-3

10-2

10-1

100

Frequency (Hz)

Am

plitu

de (

Vrm

s /

Hz1/

2 )

nfft/fs = 10.00 : navs = 30 : enbw = 0.15 : nsecs = 300

G1:LSC_MID_EP-P_HPfs = 16384 : 2005-09-26 09:08:28

Optional:

Digital IM Feedback

= analog + res. @ 2.5Hz


MI AA digital (dSpace) servo 14th Sept.

Digital

Analog

Added res. gain stages


MI AA digital (dSpace) servo 8th Oct.

Tilt (Pitch) Rotation (Yaw)

Digital filter TFs contain resonant gain stages for suspension resonances


Reducing Noise in MI AA Loop 19th Oct.

• Optimization of gain distribution in MI AA loop reduced FB noise

Camera dark noise

BeforeAfter

BeforeAfter

Feedback noise

BeforeAfter

BeforeAfter

Rotation (Yaw) Tilt (Pitch)


Stationarity / GaussianityL

og(N

)Histograms of BLRMS


Current work / next steps

• Non stationary noise (already partly? cured)

• Decrease low frequency EP deviations for most loops, i.e. increase gain (partly done)

• Improve RF set-up

• Enhance to full input power

• Join S5. First in overnight/weekend mode– When close to design sensitivity join in 24/7 mode


Sensitivity improvement of GEO

102

103

10-21

10-20

10-19

10-18

10-17

Frequency [Hz]

h(t

) [H

z-1/2

]

Jan 02

Aug 02 (S1)

Jan 04 (S3)

Sept 05

Feb 05 (S4)

Aug 04


¿Preguntas? Translation Alta Vista Babelfish

Sunset in Ruthe

harald lückfor the geo600 comissioning team 1ilias meeting, palma, oct. 2005 title geo 600...

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