1. MC radiation pressure effects
S.HEBRI
S.Hebri
Detector meeting 05/04/2006

2. Motivation
Instabilities on the Thx open loop, and oscillation at 3.6Hz.
Prediction
Change of the mechanical resonance frequency.
S.Hebri
Detector meeting 05/04/2006

3. Thx OL TF with AA in low noise mode
Black RFC locked
Purple RFC unlocked
Resonance at 1.95Hz??? must be at 2.13HZ
3.6HZ
Oscillations seen at 3.6Hz are understood
S.Hebri
Detector meeting 05/04/2006

4. Thx OL TF with local control
Black MC locked
Purple MC unlocked
Strange behavior of the phase???
1.95Hz Hz
Change of the mechanical resonance due to the power in the cavity
S.Hebri
Detector meeting 05/04/2006

5. ThY OL TF with local control
Purple MC unlocked
Red MC locked
Black MC locked with 60% of power
Change of the frequency resonance function of the power
S.Hebri
Detector meeting 05/04/2006

6. Geometrical considerations
ThX
shift +x
ThY
shift -4x
© F. Bondu
Angular restoring force changes with shift of spot position
S.Hebri
Detector meeting 05/04/2006

7. Siesta simulation results
Sc_IB_TraMC~ 8W3.25KW
Plaser(simulation)=10W3.18KW
S.Hebri
Detector meeting 05/04/2006

8. Beam position Beam off- centred by 4mm
The resonance frequency doesn’t change as a function of the off-centering of the beam
S.Hebri
Detector meeting 05/04/2006

9. Conclusion
-The resonance frequency moves as a function of the power in the cavity.
-the ThX resonance frequency decreases, and Thy increases due to the geometry of the cavity.
- good corresponding between the simulation and the reality.
S.Hebri
Detector meeting 05/04/2006