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
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
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
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 ?
9. July 2003 Hartmut Grote
Modecleaner Autoalignment
Bandwidth: 1kHz
9. July 2003 Hartmut Grote
Modecleaner Reflected Power
Time [s]
Ref
lect
ed p
ower
[A
rb.]
Pitch DWS feedback
... and yaw DWS feedback
9. July 2003 Hartmut Grote
PR und MI Autoalignment
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
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
9. July 2003 Hartmut Grote
Intermediate Mass Actuator
Alignment transfer function
Frequency [Hz]
Am
plit
ude
[Abs
.]
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
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
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
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
9. July 2003 Hartmut Grote
PR and MI Autoalignment
Matrix diagonalizationfor 4 dimensions
9. July 2003 Hartmut Grote
Computer Control
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]
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
9. July 2003 Hartmut Grote
9. July 2003 Hartmut Grote
9. July 2003 Hartmut Grote
Detect angle between wavefronts in “near-“ and “far“ field
Sensitivity typically 10 p rad / sqrt(Hz)
Differential Wavefront Sensing
9. July 2003 Hartmut Grote
Modelliertes Alignment am PR MI
9. July 2003 Hartmut Grote
Michelson Error Signal
A larger mismatch in the radii of curvature makes the system more sensitive to misalignment.
9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
Differential wavefrontsensing
Orthogonalization< 1/10
Bandwith 0.2 or 6 Hz
9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
Local beam centeringservos
Bandwidth ~ 1kHz
9. July 2003 Hartmut Grote
Autoalignment
Experimental setupfor 1 cavity
Spot position control
9. July 2003 Hartmut Grote
Autoalignment setup
PR + MI cavity
9. July 2003 Hartmut Grote
Misalignment eines Resonators
Messe Winkel zwischen Wellenfronten an zwei verschiedenen Positionen
Achse der Eigenmode
Achse des eintretenden Strahls