alignment control of geo 600
DESCRIPTION
Alignment Control of GEO 600. Hartmut Grote for the GEO600 team Institut für Atom- und Molekülphysik University of Hannover Max-Planck-Institut für Gravitationsphysik 9. July 2003. Autoalignment: Why ?. Superimpose beam axes Maximize light power Stabilze optical gain - PowerPoint PPT PresentationTRANSCRIPT
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Alignment Control
of GEO 600
Hartmut Grotefor the GEO600 team
Institut für Atom- und MolekülphysikUniversity of Hannover
Max-Planck-Institut für Gravitationsphysik
9. July 2003
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9. July 2003 Hartmut Grote
Autoalignment: Why ?
Superimpose beam axes
Maximize light power
Stabilze optical gain
Center beam spots on mirrors
Minimize angular to longitudinal noise coupling
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9. July 2003 Hartmut Grote
Differrential wavefront sensing
(analog feedback for 14 DOF in GEO)
Spot position sensing
(digital feedback for 20 DOF in GEO)
Autoalignment: How ?
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9. July 2003 Hartmut Grote
Modecleaner Autoalignment
Bandwidth: 1kHz
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9. July 2003 Hartmut Grote
Modecleaner Reflected Power
Time [s]
Ref
lect
ed p
ower
[A
rb.]
Pitch DWS feedback
... and yaw DWS feedback
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9. July 2003 Hartmut Grote
PR und MI Autoalignment
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9. July 2003 Hartmut Grote
3 mm
Blades
Stack
Mirror
Magnet-CoilActuatorRange: 100 µm,Typ. DC-10 Hz
Intermediatemass
ElektrostaticActuatorRange: 1 µm (DC), Typ. 10-100 Hz
Double – Triple Pendulum
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9. July 2003 Hartmut Grote
Processing square root with analog electronics
Peak force: 30 µNNeeded for acquisition
Maximal mirror speed with PR gain 300 is100 nm/s
Electrostatic Drive
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9. July 2003 Hartmut Grote
Intermediate Mass Actuator
Alignment transfer function
Frequency [Hz]
Am
plit
ude
[Abs
.]
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9. July 2003 Hartmut Grote
Michelson Power Levels
Time [s]
Time [s]
Lig
ht p
ower
[A
rb.]
Lig
ht p
ower
[A
rb.]
Dark port
PR cavity
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9. July 2003 Hartmut Grote
Spectral Density of MI-DWS
Frequency [Hz]
Dif
fere
ntia
l MC
e/M
Cn
alig
nmrn
t [ra
d/sq
rt(H
z)]
Error signal
Feedback
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9. July 2003 Hartmut Grote
DWS Feedback Noise
Noise coupling by spot position deviations
Angular noise in GW band(e.g. caused by DWS feedback)
RMS angular noise
RMS deviationfrom center of pitch / yaw
Induced length noise
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9. July 2003 Hartmut Grote
Michelson Strain Sensitivity
S1
Sqrt-noise
HV-amplifier noise
Michelson DWS feedback noise (1mm)
Frequency [Hz]
Str
ain
sens
itivi
ty [
1/sq
rt(H
z)]
Noise limit
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9. July 2003 Hartmut Grote
PR and MI Autoalignment
Matrix diagonalizationfor 4 dimensions
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9. July 2003 Hartmut Grote
Computer Control
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9. July 2003 Hartmut Grote
Operation during S1
98% duty cycle, almost no human interaction required
Time
Time [days]
Time [days]
Tem
p. [
Deg
. C]
BS
pitc
h F
B [
µra
d]
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9. July 2003 Hartmut Grote
Summary and Outlook
Autoalignment for modecleaners and power recycled Michelson complete (14 DOF DWS, 20 DOF spot pos.)
Long term stable operation achieved (~98% duty cycle during S1, longest lock >121 hours)
Michelson DWS feedback needs 10-20dB more gain at 0.5-2 Hz (reach 10nradRMS for MI arms)
Signal recycling DWS feedback in near future
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9. July 2003 Hartmut Grote
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9. July 2003 Hartmut Grote
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9. July 2003 Hartmut Grote
Detect angle between wavefronts in “near-“ and “far“ field
Sensitivity typically 10 p rad / sqrt(Hz)
Differential Wavefront Sensing
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9. July 2003 Hartmut Grote
Modelliertes Alignment am PR MI
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9. July 2003 Hartmut Grote
Michelson Error Signal
A larger mismatch in the radii of curvature makes the system more sensitive to misalignment.
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9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
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9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
Differential wavefrontsensing
Orthogonalization< 1/10
Bandwith 0.2 or 6 Hz
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9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
Local beam centeringservos
Bandwidth ~ 1kHz
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9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
Spot position control
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9. July 2003 Hartmut Grote
Autoalignment setup
PR + MI cavity
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9. July 2003 Hartmut Grote
Misalignment eines Resonators
Messe Winkel zwischen Wellenfronten an zwei verschiedenen Positionen
Achse der Eigenmode
Achse des eintretenden Strahls