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1 Detector meeting, October 4th 2006M Laval
Thermal effects and PR Thermal effects and PR misalignments misalignments
Virgo simulations with the input mirror absorption losses calculated by Michele Punturo.
Effects of a PR tilt on the recycling gains (carrier and sidebands)•Without thermal effects (mirror map influences)•With thermal effects
Tools: • The optical simulation code DarkF (fortran90)Authors: -Jean Yves Vinet (OCA/ARTEMIS)
-Mikael Laval (OCA/ARTEMIS)
Approximation: No maps used for the beam splitter
2 Detector meeting, October 4th 2006M Laval
Thermal effects on the recycling gainsThermal effects on the recycling gains
• Initial absorption losses measured at the SMA of Lyon :NI : 1.25ppm Rc(thermal lens) = -58.7km (map fit with dx=1.56mm)WI : 1.38ppm Rc(thermal lens) = -53.2km (map fit with dx=1.56mm)
• Absorption losses calculated by Michele Punturo :
NI: 5ppm Rc(thermal lens) = -14.7km (map fit with dx=1.56mm)WI: 13.8ppm Rc(thermal lens) = -5.3km (map fit with dx=1.56mm)
The absorption losses of the input mirror high reflectivity coating determine the main thermal effects in Virgo but with time (and a possible pollution of the mirror surfaces) they have probably changed with respect to the measured values at the SMA of Lyon. Main effect = input mirror substrates become a converging lens
What are the absorption losses of the input mirrors?
The values of Rc are calculated for a power of 5kW in the long arms.
3 Detector meeting, October 4th 2006M Laval
Comparisons of the recycling gains between Virgo and optical simulations (DarkF)
Values measured by Virgo:
At the beginning of the lock : G(carrier)=40 G(sidebands)=30
After the thermal stabilization : G(carrier)=41-42 G(sidebands)=11
Values simulated by DarkF (sampling step=1.56mm ; injected power=7W):
Without thermal effects :
With thermal effects (LY):
With thermal effects (MP):
G(C)=45.2 G(LSB)=43.5 G(USB)=32.2
G(C)=45.2 G(LSB)=42.6 G(USB)=43.0
G(C)=45.0 G(LSB)=3.4 G(USB)=11.3
Nomenclature: C=Carrier ; LSB=Lower Sideband ; USB=Upper sideband
LY = with absorption losses measured by Lyon
MP = with absorption losses calculated by Michele Punturo
4 Detector meeting, October 4th 2006M Laval
Shape of the dark fringe on B1p
Virgo locked at step 12 DarkF
The absorption parameters have an important effect on the recycling gains of the sidebands. The results between Virgo and DarkF seems to confirm the absorption parameters calculated by Michele Punturo.
Conclusion:Conclusion:
5 Detector meeting, October 4th 2006M Laval
Effects of a tilt of PR on the recycling gainsEffects of a tilt of PR on the recycling gains(suggested by Julien Marque)(suggested by Julien Marque)
Impact of the mirror maps on the recycling gains:
There are some unstable cases (the carrier does not converge):•without mirror maps: θy= ± 0.7 μrad ; θy= ± 0.8 μrad
•with end mirror maps and input mirror transmission maps (only):
θy= -1.3 μrad ; θy= -1.4 μrad ; θy= ± 0.7 μrad
6 Detector meeting, October 4th 2006M Laval
The mirror maps (high reflectivity coating and transmission) have a big impact on the recycling gain of the carrier and of the upper sideband. The cause (residual curvature or flatness) will have to be determined.
Impact of the mirror maps on the recycling gains (2/3)
7 Detector meeting, October 4th 2006M Laval
Impact of the mirror maps on the recycling gains (3/3)
Mirror surfaces parameters (fits weighted by a centered gaussian beam on maps given by Lyon with dx=0.35mm):
Mirror Map Curvature radius RMS flatness
NE High reflectivity coating 3583.1m 2.83nm
WE High reflectivity coating 3623.6m 3.63nm
NI High reflectivity coating 73.9km 1.73nm
NI Transmission 68.6km 1.62nm
WI High reflectivity coating 189,1km 1.15nm
WI Transmission 108.3km 1.19nm
PR High reflectivity coating -1351.0km 0.89nm
BS High reflectivity coating 142.2km 1.20nm
Coating maps: always seen in front view (substrate behind the coating) Rc>0 concave mirror
transmission maps: Rc>0 diverging lens
Why PR has an impact on the upper sideband recycling gain (to be done)?
8 Detector meeting, October 4th 2006M Laval
Addition of the thermal effects
CarrierLower sidebandUpper sideband
9 Detector meeting, October 4th 2006M Laval
Ratio between sideband recycling gains
Some results of the scanning Fabry Perot showed a dissymmetry between both sidebands but in the last ones, the dissymmetry had disappeared. A different alignment of PR could explain these different results.
10 Detector meeting, October 4th 2006M Laval
ConclusionConclusion
The simulation seems to confirm the input mirror coating absorptions calculated by Michele Punturo.
Mirror maps are very important to simulate the thermal effects. They can not be neglected.
Variation of the PR alignment could explain the variations between sideband amplitudes on the scanning Fabry Perot.
11 Detector meeting, October 4th 2006M Laval
To be doneTo be done
To determine the effects of a new increase of the injected power in Virgo for the sidebands.
To explain the dissymmetry between both sidebands in the recycling cavity.
What is the most important factor for the flat mirrors:flatness or residual curvature?
What are the effects of the Beam splitter?
12 Detector meeting, October 4th 2006M Laval
More details for the Carrier
13 Detector meeting, October 4th 2006M Laval
More details for the Lower Sideband
14 Detector meeting, October 4th 2006M Laval
More details for the Upper Sideband
15 Detector meeting, October 4th 2006M Laval
Shape of the dark fringe (1/3)
Without thermal effects
16 Detector meeting, October 4th 2006M Laval
Shape of the dark fringe (2/3)
With the absorption losses measured by the SMA of Lyon
17 Detector meeting, October 4th 2006M Laval
Shape of the dark fringe (3/3)
With the absorption losses calculated by M Punturo
18 Detector meeting, October 4th 2006M Laval
Recycled beams (1/3)
Without thermal effects
19 Detector meeting, October 4th 2006M Laval
Recycled beams (2/3)
With the absorption losses measured by the SMA of Lyon
20 Detector meeting, October 4th 2006M Laval
Recycled beams (3/3)
With the absorption losses calculated by M Punturo
21 Detector meeting, October 4th 2006M Laval
Beam reflected to the laser (1/3)
Without thermal effects
22 Detector meeting, October 4th 2006M Laval
Beam reflected to the laser (2/3)
With the absorption losses measured by the SMA of Lyon
23 Detector meeting, October 4th 2006M Laval
Beam reflected to the laser (3/3)
With the absorption losses calculated by M Punturo
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