stefan hild 1ilias wg1 meeting, sep 2005, perugia title geo 600 commissioning progress...
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Stefan Hild 1 Ilias WG1 meeting, Sep 2005, Perugia
Title
GEO 600Commissioning progress
Max-Planck-Institut für Gravitationsphysik(Albert-Einstein-Institut)
Stefan Hild Ilias WG1 meeting, Sep 2005
Stefan Hild 2 Ilias WG1 meeting, Sep 2005, Perugia
GEO 600 layout
1.5-2 kW
0.09
Stefan Hild 3 Ilias WG1 meeting, Sep 2005, Perugia
Tuning signal recycling to 300 Hz
Better knowledge of IFO parameters:
more accurate prediction 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 !
Stefan Hild 4 Ilias WG1 meeting, Sep 2005, Perugia
GEO 600 design sensitivity
Stefan Hild 5 Ilias WG1 meeting, Sep 2005, Perugia
Calibration and demod phase @ 300 Hz
Using signal recycling
GW signal is split in P and Q quadrature
P-response independant of demod phase
Q-response only for larger than 20 to 30 deg demod phase compatible with current calibration(zero + complex pole)
Decided to use 40 deg for time being.
Drawback: ‚P‘ used for MI servo is not really only ‚P‘
Stefan Hild 6 Ilias WG1 meeting, Sep 2005, Perugia
High RF on HPD / Q-compensation
Observations:
• Found huge RF level after MI diode (1 Volt)
• Large DC level in Q after mixing.
Q-compensation:
Injected RF directly into resonance circuit of the HPD to make Q DC level zero.
Improved sensitivity above 700 Hz
Q-comp OFFQ-comp ON
Stefan Hild 7 Ilias WG1 meeting, Sep 2005, Perugia
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 from Q was mixed into P quadrature.
• That is why Q-compensation worked.
Stefan Hild 8 Ilias WG1 meeting, Sep 2005, Perugia
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 !
Stefan Hild 9 Ilias WG1 meeting, Sep 2005, Perugia
Future RF setup
Proposed by Rana and others
GOALS: • Using only high quality hardware • Guaranteeing high RF levels in all components
Stefan Hild 10 Ilias WG1 meeting, Sep 2005, Perugia
Noise projections 21st of july
Stefan Hild 11 Ilias WG1 meeting, Sep 2005, Perugia
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 using a dSPACE system)
Solutions
Stefan Hild 12 Ilias WG1 meeting, Sep 2005, Perugia
Analog SR electronics
Red = acq amp, green = acq phaDark blue = run amp, brown = run phaseLight blue = run2 amp, pink = run2 pha
Stefan Hild 13 Ilias WG1 meeting, Sep 2005, Perugia
Signal Recycling digital
Phase @18 Hz = -147 deg
Stefan Hild 14 Ilias WG1 meeting, Sep 2005, Perugia
SR feedback: analog vs. digital
Stefan Hild 15 Ilias WG1 meeting, Sep 2005, Perugia
SR loop filter future design
Bode Diagram
Frequency (Hz)
Phase (
deg)
Magnitude (
dB
)
10-3
10-2
10-1
100
101
102
103
-360
-270
-180
-90
0
90
180
270
To:
long s
tage 3
-150
-100
-50
0
50
100
150From: Input Point
To:
long s
tage 3
Filter not used at the moment. Can be implemented when more gain is needed around pendulum resonances
Four complex integrators:2.25 (2x),1.3, 0.56 Hz
Stefan Hild 16 Ilias WG1 meeting, Sep 2005, Perugia
Sensitivity improvement July to August
High frequency improvements: reduction of RF phase noiseLow frequency improvements: reduction of Signal recycling feedback noise
Stefan Hild 17 Ilias WG1 meeting, Sep 2005, Perugia
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
Stefan Hild 18 Ilias WG1 meeting, Sep 2005, Perugia
Sensitivity after PR bench work
Removed resonance structures between 100 and 200 Hz.
Stefan Hild 19 Ilias WG1 meeting, Sep 2005, Perugia
Noise projections 21st of july
Stefan Hild 20 Ilias WG1 meeting, Sep 2005, Perugia
Michelson length control
< 0.1Hz
Stefan Hild 21 Ilias WG1 meeting, Sep 2005, Perugia
< 10 Hz
< 0.1Hz
Michelson length control
Reaction Pendulum:
3 coil-magnet actuators at intermediate mass, range ~ 100µm
Stefan Hild 22 Ilias WG1 meeting, Sep 2005, Perugia
< 10 Hz
> 10 Hz
< 0.1Hz
Michelson length control
Reaction Pendulum:
3 coil-magnet actuators at intermediate mass, range ~ 100µm
Electrostatic actuation on test mass bias 630V, range 0-900V= 3.5µm
Stefan Hild 23 Ilias WG1 meeting, Sep 2005, Perugia
Using ESD as actuator
• Force is proportional to square of applied voltage.
• high voltages are needed
• for bipolar acting a bias voltage needs to be applied
Noise is introduced:
• loop electronics
• sqrt circuits
• intrinsic HV amplifier noise
Stefan Hild 24 Ilias WG1 meeting, Sep 2005, Perugia
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)
Stefan Hild 25 Ilias WG1 meeting, Sep 2005, Perugia
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
Stefan Hild 26 Ilias WG1 meeting, Sep 2005, Perugia
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
Stefan Hild 27 Ilias WG1 meeting, Sep 2005, Perugia
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)
Stefan Hild 28 Ilias WG1 meeting, Sep 2005, Perugia
Sensitivity after fixing noise from MI loop
Stefan Hild 29 Ilias WG1 meeting, Sep 2005, Perugia
Michelson servo design
Stefan Hild 30 Ilias WG1 meeting, Sep 2005, Perugia
MI loop gain problem
Strange observations:
• We are not able to increase the low frequency loop gain, even though it should work from loop model (oscillation around 8 Hz)
• OLG measurements show that there is nearly no gain around 8 to 10 Hz.
• We needed to turn down the MI crossover gain continiously for the last few months
Findings:
• Influence of MI AA gain on maximum cross over frequency (AA-tilt , cross over possible.
• phase margin of crossover, can crossover frequency, but adding integrator still causes 8Hz oscillation
• IM gain ( crossover frequency), less noise in servo 4 to 8 Hz.
• IM gain, still low gain around 8 to 10 Hz (low gain can‘t be caused by IM)
Stefan Hild 31 Ilias WG1 meeting, Sep 2005, Perugia
Injecting LF noise in MI loop
Injected noise from 5 to 11 HzBetween 6 and 7 Hz the noise is not suppressed !
Stefan Hild 32 Ilias WG1 meeting, Sep 2005, Perugia
Measurement of open loop gain (PRMI)
Resonance structureis clearly visible
Very low gain around 9 Hz
Design gain: 7 @ 15 Hz 20 @ 10 Hz 80 @ 6 Hz
Stefan Hild 33 Ilias WG1 meeting, Sep 2005, Perugia
Mi servo design detail
Stefan Hild 34 Ilias WG1 meeting, Sep 2005, Perugia
TF: Alignment to longitudinal
Tilt couples a factor of 10 stronger than rot @ 10 Hz.
(IM-FF tilt2long)
Why are the two rot-TF so different?
Stefan Hild 35 Ilias WG1 meeting, Sep 2005, Perugia
How to go on with the MI loop gain problem
Measure MI loop gain for various conditions to decouple crossover and AA-tilt.
Implementing digital AA control to be more flexible (nearly done).
Measure tilt2long for single suspensions, with the goal of setting up a FF system.
Investigate possible advantages of using the ESDs for angular alignment.
....
Stefan Hild 36 Ilias WG1 meeting, Sep 2005, Perugia
Segmented ESD for alignment
Stefan Hild 37 Ilias WG1 meeting, Sep 2005, Perugia
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
Stefan Hild 38 Ilias WG1 meeting, Sep 2005, Perugia
Latest noise projections
Stefan Hild 39 Ilias WG1 meeting, Sep 2005, Perugia
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
Stefan Hild 40 Ilias WG1 meeting, Sep 2005, Perugia
Discussion
Michelson loop gain problem:
• What experience exists in VIRGO with angular to longitudinal and longitudinal to angular couplings ?
• Is somewhere gain lost ?
• ...
Digital filtering:
• What kind of filters are used within VIRGO for steep roll off?
Stefan Hild 41 Ilias WG1 meeting, Sep 2005, Perugia
E n d
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