1. 1 Detector meeting, October 4 th 2006 M Laval Thermal effects and PR 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. 2 Detector meeting, October 4 th 2006 M Laval Thermal 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. 3 Detector meeting, October 4 th 2006 M Laval Comparisons of the recycling gains between Virgo and optical simulations (DarkF) Values measured by Virgo: At the beginning of the lock : G(carrier)=40G(sidebands)=30 After the thermal stabilization :G(carrier)=41-42G(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. 4 Detector meeting, October 4 th 2006 M Laval Shape of the dark fringe on B1p Virgo locked at step 12DarkF 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:

5. 5 Detector meeting, October 4 th 2006 M Laval Effects of a tilt of PR on the recycling gains (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. 6 Detector meeting, October 4 th 2006 M 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. 7 Detector meeting, October 4 th 2006 M 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): MirrorMapCurvature radiusRMS flatness NEHigh reflectivity coating3583.1m2.83nm WEHigh reflectivity coating3623.6m3.63nm NIHigh reflectivity coating73.9km1.73nm NITransmission68.6km1.62nm WIHigh reflectivity coating189,1km1.15nm WITransmission108.3km1.19nm PRHigh reflectivity coating-1351.0km0.89nm BSHigh reflectivity coating142.2km1.20nm 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. 8 Detector meeting, October 4 th 2006 M Laval Addition of the thermal effects Carrier Lower sideband Upper sideband

9. 9 Detector meeting, October 4 th 2006 M 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. 10 Detector meeting, October 4 th 2006 M Laval Conclusion  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. 11 Detector meeting, October 4 th 2006 M Laval To 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. 12 Detector meeting, October 4 th 2006 M Laval More details for the Carrier

13. 13 Detector meeting, October 4 th 2006 M Laval More details for the Lower Sideband

14. 14 Detector meeting, October 4 th 2006 M Laval More details for the Upper Sideband

15. 15 Detector meeting, October 4 th 2006 M Laval Shape of the dark fringe (1/3) Without thermal effects

16. 16 Detector meeting, October 4 th 2006 M Laval Shape of the dark fringe (2/3) With the absorption losses measured by the SMA of Lyon

17. 17 Detector meeting, October 4 th 2006 M Laval Shape of the dark fringe (3/3) With the absorption losses calculated by M Punturo

18. 18 Detector meeting, October 4 th 2006 M Laval Recycled beams (1/3) Without thermal effects

19. 19 Detector meeting, October 4 th 2006 M Laval Recycled beams (2/3) With the absorption losses measured by the SMA of Lyon

20. 20 Detector meeting, October 4 th 2006 M Laval Recycled beams (3/3) With the absorption losses calculated by M Punturo

21. 21 Detector meeting, October 4 th 2006 M Laval Beam reflected to the laser (1/3) Without thermal effects

22. 22 Detector meeting, October 4 th 2006 M Laval Beam reflected to the laser (2/3) With the absorption losses measured by the SMA of Lyon

23. 23 Detector meeting, October 4 th 2006 M Laval Beam reflected to the laser (3/3) With the absorption losses calculated by M Punturo